Просмотр кода страницы Английская Википедия:Dawn (spacecraft)

{{Английская Википедия/Панель перехода}}
{{Short description|NASA mission to study main-belt asteroids via a robotic probe (2007–18)}}
{{Use mdy dates|date=May 2020}}
{{DISPLAYTITLE: ''Dawn'' (spacecraft)}}
{{Infobox spaceflight |auto=all

| name                  = ''Dawn''
| names_list            = 
| image                 = Dawn spacecraft model.png
| image_caption         = Illustration of the ''Dawn'' spacecraft
| image_size            = 300px

| mission_type          = Multi-target [[orbiter]]
| operator              = [[NASA]]{{\}}[[Jet Propulsion Laboratory|JPL]]
| COSPAR_ID             = 2007-043A
| SATCAT                = 32249
| website               = http://dawn.jpl.nasa.gov/
| mission_duration      = {{time interval|September 27, 2007, 11:34|November 1, 2018}} <ref name="NASA-20180907" /><ref name="GSpaceTimeline" /> 
| manufacturer          = {{hlist|[[Orbital Sciences Corporation|Orbital Sciences]]<ref>{{cite web|url=https://solarsystem.nasa.gov/missions/dawn/mission/the-team/mission-teams/|title=Dawn}}</ref>|[[Jet Propulsion Laboratory|JPL]]|[[University of California, Los Angeles|UCLA]]}}
| launch_mass           = {{convert|2684.6|lb|kg|order=flip|abbr=on}}<ref name="ceres.press.kit">{{cite web |url=https://solarsystem.nasa.gov/system/downloadable_items/2733_dawn-ceres.pdf |title=Dawn at Ceres |type=Press kit |publisher=NASA{{\}}Jet Propulsion Laboratory |date=March 2015}}</ref>
| dry_mass              = {{convert|1647.1|lb|kg|order=flip|abbr=on}}<ref name="ceres.press.kit" />
| dimensions            = {{convert|1.64|xx|19.7|xx|1.77|m|ft|sigfig=2|abbr=on}}<ref name="ceres.press.kit" />
| power                 = 10 kW at 1 AU<ref name="ceres.press.kit" /> <br /> 1.3 kW at 3 AU<ref name="Rayman 2006 605–616" />

| launch_date           = {{start-date|September 27, 2007, 11:34}}&nbsp;UTC<ref name="nssdc" />
| launch_rocket         = [[Delta II]] 7925H
| launch_site           = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Space Launch Complex 17|SLC-17B]]
| launch_contractor     = [[United Launch Alliance]]

| disposal_type         = Uncontrolled stable orbit
| deactivated           = 
| last_contact          = October 30, 2018<ref name="NYT-20181101" />
<!--orbit parameters-->
| orbit_epoch           = October 30, 2018, 00:00:00&nbsp;UTC<ref name="horizonseph">{{cite web|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&CENTER='500@2000001'&COMMAND='-203'&CSV_FORMAT='NO'&EL='1'&MAKE_EPHEM='YES'&OBJ_DATA='YES'&OUT_UNITS='KM-S'&REF_PLANE='ECLIPTIC'&REF_SYSTEM='J2000'&START_TIME='2018-10-30'&STEP_SIZE='1%20h'&STOP_TIME='2018-10-30%2000:00:00.01'&TABLE_TYPE='ELEMENTS'&VEC_DELTA_T='NO'&VEC_LABELS='NO'&VEC_TABLE='2x'&VECT_CORR='NONE'|title=Nasa Horizons Ephemeris – Target body name: Dawn (spacecraft) (-203)|publisher=NASA JPL|date=6 January 2022}}</ref>
| orbit_reference       = [[Ceres (dwarf planet)|Ceres]]
| orbit_regime          = [[Highly elliptical orbit|Highly elliptical]]
| orbit_semimajor       = {{convert|2475.1356|km|mi}}<ref name="horizonseph"/>
| orbit_periapsis       = {{convert|37.004|km|mi}}
| orbit_apoapsis        = {{convert|3973.866|km|mi}}
| orbit_eccentricity    = 0.7952&nbsp;<ref name="horizonseph"/>
| orbit_inclination     = 76.1042&nbsp;degrees<ref name="horizonseph"/>
| orbit_arg_periapsis   = 164.1014&nbsp;degrees<ref name="horizonseph"/>
| orbit_RAAN            = −79.4891&nbsp;degrees<ref name="horizonseph"/>
| orbit_period          = 1,628.68&nbsp;minutes<ref name="horizonseph"/>

|interplanetary         = 
 {{Infobox spaceflight/IP
  |type           = flyby
  |object         = [[Mars]]
  |arrival_date   = February 18, 2009, 00:27:58&nbsp;UTC<ref name="nssdc">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2007-043A |title=Dawn |work=[[National Space Science Data Center]] |publisher=NASA |access-date=November 20, 2016}}</ref>
  |distance       = {{convert|542|km|mi|abbr=on}}<ref name="nssdc" />
 }}
 {{Infobox spaceflight/IP
  |type           = orbiter
  |object         = [[4 Vesta]]
  |arrival_date   = July 16, 2011, 04:47&nbsp;UTC<ref name="nasa20110801">{{cite news |url=https://www.nasa.gov/mission_pages/dawn/news/dawn20110801.html |title=NASA's Dawn Spacecraft Begins Science Orbits of Vesta |publisher=NASA |first1=Dwayne C. |last1=Brown |first2=Priscilla |last2=Vega |date=August 1, 2011 |access-date=August 6, 2011 |archive-date=February 2, 2019 |archive-url=https://web.archive.org/web/20190202164311/https://www.nasa.gov/mission_pages/dawn/news/dawn20110801.html |url-status=dead }}</ref>
  |departure_date = September 5, 2012, 06:26&nbsp;UTC<ref name="nssdc" />
 }}
 {{Infobox spaceflight/IP
  |type           = orbiter
  |object         = [[Ceres (dwarf planet)|1 Ceres]]
  |arrival_date   = March 6, 2015, 12:29&nbsp;UTC<ref name="nssdc" />
  |departure_date = 
 }}

| instruments_list      = {{Infobox spaceflight/Instruments
  | acronym1 = FC | name1 = Framing Camera
  | acronym2 = VIR | name2 = Visible and Infrared Spectrometer
  | acronym3 = GRaND | name3 = Gamma Ray and Neutron Detector
 }}

| programme             = [[Discovery program]]
| previous_mission      = ''[[Deep Impact (spacecraft)|Deep Impact]]''
| next_mission          = ''[[Kepler (spacecraft)|Kepler]]''

| insignia              = Dawn logo.png
| insignia_caption      = ''Dawn'' [[mission patch]]
| insignia_size         = 160px
}}

'''''Dawn''''' is a retired [[space probe]] that was launched by [[NASA]] in September 2007 with the mission of studying two of the three known [[protoplanet]]s of the [[asteroid belt]]: [[4 Vesta|Vesta]] and [[Ceres (dwarf planet)|Ceres]].<ref name="NASA-20180907" /> In the fulfillment of that mission—the ninth in NASA's [[Discovery Program]]—''Dawn'' entered orbit around Vesta on July 16, 2011, and completed a 14-month survey mission before leaving for Ceres in late 2012.<ref name=5SepDepart>{{cite news |url=http://www.space.com/17119-nasa-dawn-asteroid-spacecraft-vesta.html |title=NASA's Dawn Spacecraft Hits Snag on Trip to 2 Asteroids |work=Space.com |date=August 15, 2012 |access-date=August 27, 2012}}</ref><ref name=Aug262012>{{cite web |title=Dawn Gets Extra Time to Explore Vesta |publisher=NASA |url=http://www.nasa.gov./mission_pages/dawn/news/dawn20120418.html |date=April 18, 2012 |access-date=April 24, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120421191416/http://www.nasa.gov/mission_pages/dawn/news/dawn20120418.html |archive-date=April 21, 2012 }}</ref> It entered orbit around Ceres on March 6, 2015.<ref name="NASA-20150306">{{cite web |last1=Landau |first1=Elizabeth |last2=Brown |first2=Dwayne |title=NASA Spacecraft Becomes First to Orbit a Dwarf Planet |url=http://www.jpl.nasa.gov/news/news.php?feature=4503 |date=March 6, 2015 |publisher=NASA |access-date=March 6, 2015}}</ref><ref name="Rayman2015.03.06">{{cite web |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150306-dawn-journal-ceres-orbit-insertion.html |title=Dawn Journal: Ceres Orbit Insertion! |publisher=[[Planetary Society]] |first=Marc |last=Rayman |date=March 6, 2015 |access-date=March 6, 2015}}</ref> In 2017, NASA announced that the planned nine-year mission would be extended until the probe's [[hydrazine]] fuel supply was depleted.<ref name="NASA-20171019">{{cite web |url=https://www.jpl.nasa.gov/news/news.php?feature=6980 |title=Dawn Mission Extended at Ceres |publisher=[[NASA]] |last=Landau |first=Elizabeth |date=October 19, 2017 |access-date=October 19, 2017}}</ref> On November 1, 2018, NASA announced that ''Dawn'' had depleted its hydrazine, and the mission was ended. The derelict probe remains in a stable orbit around Ceres.<ref>{{Cite news|url=https://www.nasa.gov/press-release/nasa-s-dawn-mission-to-asteroid-belt-comes-to-end|title=NASA's Dawn Mission to Asteroid Belt Comes to End|last=Northon|first=Karen|date=November 1, 2018|work=NASA|access-date=November 12, 2018|language=en}}</ref>

''Dawn'' is the first spacecraft to have orbited two extraterrestrial bodies,<ref name=siliconvalleyastrolecture>{{cite speech |title=Now Appearing At a Dwarf Planet Near You: NASA's Dawn Mission to the Asteroid Belt |first=Marc |last=Rayman |event=Silicon Valley Astronomy Lectures |location=Foothill College, Los Altos, CA |date=April 8, 2015 |url= https://www.youtube.com/watch?v=j_3jKyqAIqY |access-date= July 7, 2018}}</ref> the first spacecraft to have visited either Vesta or Ceres, and the first to have orbited a dwarf planet.<ref>{{cite book|url=https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf|title=Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016|page=2|last1=Siddiqi|first1=Asif A.|lccn=2017059404|isbn=9781626830424|publisher=NASA History Program Office|edition=second|year=2018|id=SP2018-4041|series=The NASA history series|location=Washington, D.C.}}</ref>

The ''Dawn'' mission was managed by NASA's [[Jet Propulsion Laboratory]], with spacecraft components contributed by European partners from Italy, Germany, France, and the Netherlands.<ref name="amspace20171008">{{cite news |url=http://www.americaspace.com/2017/10/08/complexity-and-challenge-dawn-project-manager-speaks-of-difficult-voyage-to-vesta-and-ceres/ |title=Complexity and Challenge: Dawn Project Manager Speaks of Difficult Voyage to Vesta and Ceres |work=AmericaSpace |first=Ben |last=Evans |date=October 8, 2017 |access-date=February 28, 2018}}</ref> It was the first NASA exploratory mission to use [[Ion thruster|ion propulsion]], which enabled it to enter and leave the orbit of two celestial bodies. Previous multi-target missions using rockets powered by [[Rocket engine|chemical engine]], such as the [[Voyager program|''Voyager'' program]], were restricted to [[Planetary flyby|flybys]].<ref name="Rayman 2006 605–616">{{cite journal |last=Rayman |first=Marc |author2=Fraschetti, Thomas C. |author3=Raymond, Carol A. |author4=Russell, Christopher T. |title=Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres |journal=Acta Astronautica |date=April 5, 2006 |volume=58 |pages=605–616 |url=http://dawn.jpl.nasa.gov/mission/Dawn_overview.pdf |access-date=April 14, 2011 |doi=10.1016/j.actaastro.2006.01.014 |issue=11 |bibcode=2006AcAau..58..605R}}</ref>

==Project history==

===Technological background===
[[File:SERT-1 spacecraft.jpg|thumb|150px|left|SERT-1: first [[ion engine]] NASA spacecraft;<ref>{{cite web |url=http://www.nasa.gov/centers/glenn/about/history/ds1.html |title=Glenn Contributions to Deep Space 1 |date=May 21, 2008 |publisher=NASA |access-date=March 18, 2015}}</ref> launched on July 20, 1964.<ref name = "Cybulski">{{cite web |first1=Ronald J.|last1=Cybulski |first2=Daniel M.|last2=Shellhammer |first3=Robert R.|last3=Lovell |first4=Edward J.|last4=Domino |first5=Joseph T.|last5=Kotnik |url=https://ntrs.nasa.gov/api/citations/19650009681/downloads/19650009681.pdf |title=Results from SERT I Ion Rocket Flight Test| id=NASA-TN-D-2718 |publisher=[[NASA]] |date=1965}}</ref>]]
The first working ion thruster in the US was built by [[Harold R. Kaufman]] in 1959 at NASA's [[Glenn Research Center]] in [[Ohio]]. The thruster was similar to the general design of a gridded electrostatic ion thruster with [[mercury (element)|mercury]] as its propellant. Suborbital tests of the engine followed during the 1960s, and in 1964 the engine was tested on a suborbital flight aboard the [[SERT-1 (spaceship)|Space Electric Rocket Test 1]] (SERT 1). It successfully operated for the planned 31 minutes before falling back to Earth.<ref name="Glenn">{{cite web |url=http://www.nasa.gov/centers/glenn/about/fs08grc.html |title=Innovative Engines – Glenn Ion Propulsion Research Tames the Challenges of 21st Century Space Travel |publisher=NASA |access-date=November 19, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070915023928/http://www.nasa.gov/centers/glenn/about/fs08grc.html |archive-date=September 15, 2007 }}</ref> This test was followed by an orbital test, SERT-2, in 1970.

[[Deep Space 1]] (DS1), which NASA launched in 1998, demonstrated the long-duration use of a [[xenon]]-propelled ion thruster on a science mission,<ref name="MD">{{cite journal |title=Mission design for deep space 1: A low-thrust technology validation mission |author=Rayman, M.D. and Chadbourne, P.A. and Culwell, J.S. and Williams, S.N. |journal=Acta Astronautica |volume=45 |issue=4–9 |pages=381–388 |year=1999 |url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/19098/1/98-0310.pdf |bibcode=1999AcAau..45..381R |doi=10.1016/s0094-5765(99)00157-5 |url-status=dead |archive-url=https://web.archive.org/web/20150509172350/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/19098/1/98-0310.pdf |archive-date=May 9, 2015 }}</ref> and validated a number of technologies, including the [[NASA Solar Technology Application Readiness|NSTAR]] [[electrostatic ion thruster]], as well as performing a flyby of an asteroid and a comet.<ref name="Dawn">{{cite web |url=http://descanso.jpl.nasa.gov/DPSummary/090924dawn-FinalCorrex--update5G.pdf |title=Dawn Telecommunications |author=Jim Taylor |publisher=NASA/JPL |date=August 2009 |access-date=March 18, 2015}}</ref> In addition to the ion thruster, among the other technologies validated by the DS1 was the [[Small Deep Space Transponder]], which is used on ''Dawn'' for long-range communication.<ref name="Dawn" />

===Discovery Program selection===
Twenty-six proposals were submitted to the [[Discovery Program]] solicitation, with budget initially targeted at US$300 million.<ref name="autogenerated3"/> Three semi-finalists were downselected in January 2001 for a phase-A design study: Dawn, Kepler, and INSIDE Jupiter.<ref>{{cite web |url=http://www.spacetoday.net/Summary/7 |title=NASA announces Discovery mission finalists |website=Spacetoday.net |date=January 4, 2001 |access-date=January 11, 2016}}</ref>   In December 2001 NASA selected the Kepler and the Dawn mission for the Discovery program.<ref name="autogenerated3">{{cite web |author=Susan Reichley |url=http://www.jpl.nasa.gov/releases/2001/release_2001_245.html |title=2001 News Releases - JPL Asteroid Mission Gets Thumbs Up from NASA |website=Jpl.nasa.gov |date=December 21, 2001 |access-date=January 11, 2016 |archive-date=May 1, 2017 |archive-url=https://web.archive.org/web/20170501104328/https://www.jpl.nasa.gov/releases/2001/release_2001_245.html |url-status=dead }}</ref> Both missions were initially selected for a launch in 2006.<ref name="autogenerated3"/>

===Cancellation and reinstatement===
The status of the ''Dawn'' mission changed several times. The project was cancelled in December 2003,<ref>{{cite news |last=Ambrosiano |first=Nancy |date=March 28, 2006 |title=NASA's Dawn mission is a go |publisher=Los Alamos National Laboratory |url=http://www.lanl.gov/news/index.php/fuseaction/nb.story/story_id/8140 |access-date=October 1, 2007 |archive-date=October 20, 2007 |archive-url=https://web.archive.org/web/20071020201844/http://lanl.gov/news/index.php/fuseaction/nb.story/story_id/8140 |url-status=dead }}</ref> and then reinstated in February 2004. In October 2005, work on ''Dawn'' was placed in "stand down" mode, and in January 2006, the mission was discussed in the press as "indefinitely postponed", even though NASA had made no new announcements regarding its status.<ref>{{cite news |url=http://www.space.com/missionlaunches/ap_060121_dawn_hold.html |title=NASA Asteroid Mission Won't Launch This Year |year=2006 |work=Space.com |access-date=March 4, 2006 |first=Alicia |last=Chang |archive-date=February 13, 2006 |archive-url=https://web.archive.org/web/20060213020557/http://www.space.com/missionlaunches/ap_060121_dawn_hold.html |url-status=dead }}</ref> On March 2, 2006, ''Dawn'' was again cancelled by NASA.<ref>{{cite web |url=http://www.spaceflightnow.com/news/n0603/03dawn/ |title=Probe built to visit asteroids killed in budget snarl |year=2006 |publisher=SpaceflightNow.com |access-date=March 4, 2006 |first=Stephen |last=Clark}}</ref>

The spacecraft's manufacturer, [[Orbital Sciences Corporation]], appealed NASA's decision, offering to build the spacecraft at cost, forgoing any profit in order to gain experience in a new market field. NASA then put the cancellation under review,<ref>{{cite news |url=http://www.cnn.com/2006/TECH/space/03/16/asteroid.mission.ap/index.html |title=NASA reviewing canceled mission |date=March 16, 2006 |publisher=CNN.com |access-date=March 27, 2006 |archive-url=https://web.archive.org/web/20060321081642/http://www3.cnn.com/2006/TECH/space/03/16/asteroid.mission.ap/index.html |archive-date=March 21, 2006}}</ref> and on March 27, 2006, it was announced that the mission would not be cancelled after all.<ref>{{cite web |url=http://www.nasa.gov/pdf/145511main_Dawn_letter.pdf |title=Dawn Mission Reclama |first=Rex |last=Geveden |year=2006 |access-date=March 27, 2006 |archive-date=June 25, 2006 |archive-url=https://web.archive.org/web/20060625233756/http://www.nasa.gov/pdf/145511main_Dawn_letter.pdf |url-status=dead }}</ref><ref>{{cite news |url=http://space.com/news/060327_dawn_mission.html |title=NASA Reinstates Cancelled Asteroid Mission |first=Tariq |last=Malik |date=March 27, 2006 |work=Space.com |access-date=March 27, 2006}}</ref> In the last week of September 2006, the ''Dawn'' mission's instrument payload integration reached full functionality. Although originally projected to cost US$373 million, cost overruns inflated the final cost of the mission to US$446 million in 2007.<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2007-043A |title=Dawn |publisher=NASA – National Space Science Data Center |access-date=July 16, 2011}}</ref> [[Christopher T. Russell]] was chosen to lead the ''Dawn'' mission team.

==Scientific background==
[[File:Ceres and Vesta, Moon size comparison.jpg|thumb|200px|Scale comparison of Vesta, Ceres, and the Moon]]
The ''Dawn'' mission was designed to study two large bodies in the [[asteroid belt]] in order to answer questions about the formation of the [[Solar System]], as well as to test the performance of its [[ion thruster]]s in deep space.<ref name="NASA-20180907">{{cite web |last1=McCartney |first1=Gretchen |last2=Brown |first2=Dwayne |last3=Wendel |first3=JoAnna |title=Legacy of NASA's Dawn, Near the End of its Mission |url=https://www.jpl.nasa.gov/news/news.php?feature=7231 |date=September 7, 2018 |work=[[NASA]] |access-date=September 8, 2018}}</ref> Ceres and Vesta were chosen as two contrasting [[protoplanet]]s, the first one apparently "wet" (i.e. icy and cold) and the other "dry" (i.e. rocky), whose [[Accretion (astrophysics)|accretion]] was terminated by the formation of [[Jupiter]]. The two bodies provide a bridge in scientific understanding between the formation of [[terrestrial planet|rocky planets]] and the icy bodies of the Solar System, and under what conditions a rocky planet can hold water.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/goal_index.asp |title=DAWN Mission Objectives |publisher=NASA |access-date=February 28, 2017 |archive-url=https://web.archive.org/web/20130214195648/http://dawn.jpl.nasa.gov/mission/goal_index.asp |archive-date=February 14, 2013 |url-status=dead }}</ref>

The [[International Astronomical Union]] (IAU) adopted a new [[IAU definition of planet|definition of planet]] on August 24, 2006, which introduced the term "[[dwarf planet]]" for [[Hydrostatic equilibrium|ellipsoidal]] worlds that were too small to qualify for planetary status by [[Clearing the neighbourhood|"clearing their orbital neighborhood"]] of other orbiting matter. ''Dawn'' is the first mission to study a dwarf planet, arriving at Ceres a few months before the arrival of the ''[[New Horizons]]'' probe at [[Pluto]] in July 2015.

[[File:PIA19547-Ceres-DwarfPlanet-Dawn-RC3-AnimationFrame25-20150504.jpg|thumb|200px|left|''Dawn'' image of Ceres from 13,600 km, May 4, 2015]]
Ceres comprises a third of the total mass of the asteroid belt. Its spectral characteristics suggest a composition similar to that of a water-rich [[carbonaceous chondrite]].<ref>{{Cite journal |title=Ceres: Evolution and current state |journal=Journal of Geophysical Research |volume=110 |issue=E5 |pages=E05009 |author1=Thomas B. McCord |author2=Christophe Sotin |year=2005 |doi=10.1029/2004JE002244|bibcode=2005JGRE..110.5009M |doi-access=free }}</ref> Vesta, a smaller, water-poor [[achondrite|achondritic]] [[asteroid]] comprising a tenth of the mass of the asteroid belt, has experienced significant heating and [[Igneous differentiation|differentiation]]. It shows signs of a metallic [[Planetary core|core]], a Mars-like density and lunar-like basaltic flows.<ref name=SolarViewsCalvin>{{cite web |url=http://www.solarviews.com/eng/vesta.htm |title=Vesta |author=Calvin J. Hamilton |access-date=January 6, 2013}}</ref>

Available evidence indicates that both bodies formed very early in the history of the Solar System, thereby retaining a record of events and processes from the time of the formation of the terrestrial planets. [[Radionuclide]] dating of pieces of meteorites thought to come from Vesta suggests that Vesta differentiated quickly, in three million years or less. Thermal evolution studies suggest that Ceres must have formed some time later, more than three million years after the formation of [[Ca-Al-rich inclusions|CAI]]s (the oldest known objects of Solar System origin).<ref name=SolarViewsCalvin/>

Moreover, Vesta appears to be the source of many smaller objects in the Solar System. Most (but not all) [[Vestoid|V-type]] [[near-Earth asteroid]]s, and some outer main-belt asteroids, have [[spectrum|spectra]] similar to Vesta, and are thus known as ''vestoids''. Five percent of the meteoritic samples found on Earth, the [[HED meteorite|howardite–eucrite–diogenite]] (HED) meteorites, are thought to be the result of a collision or collisions with Vesta.

It is thought that Ceres may have a differentiated interior;<ref name="Thomas">{{cite journal |doi=10.1038/nature03938 |bibcode=2005Natur.437..224T |pmid=16148926 |title=Differentiation of the asteroid Ceres as revealed by its shape |year=2005 |last1=Thomas |first1=P. C. |last2=Parker |first2=J. Wm. |last3=McFadden |first3=L. A. |last4=Russell |first4=C. T. |last5=Stern |first5=S. A. |last6=Sykes |first6=M. V. |last7=Young |first7=E. F. |journal=Nature |volume=437 |issue=7056 |pages=224–226|s2cid=17758979 }}</ref> its oblateness appears too small for an undifferentiated body, which indicates that it consists of a rocky core overlain with an icy [[Mantle (geology)|mantle]].<ref name=Thomas/> There is a large collection of potential samples from Vesta accessible to scientists, in the form of over 1,400 HED meteorites,<ref name="Meteoritical Bulletin Database">{{cite web |url=http://www.lpi.usra.edu/meteor/metbull.php |title=Meteoritical Bulletin Database |access-date=November 27, 2014}}</ref> giving insight into Vesta geologic history and structure. Vesta is thought to consist of a metallic iron–nickel core, an overlying rocky [[olivine]] mantle and crust.<ref>{{cite journal |doi=10.1006/icar.1998.5956 |title=A Thermal Model for the Differentiation of Asteroid 4 Vesta, Based on Radiogenic Heating |year=1998 |last1=Ghosh |first1=A |journal=Icarus |volume=134 |issue=2 |pages=187–206 |bibcode=1998Icar..134..187G |last2=McSween |first2=Harry Y.}}</ref><ref name="Sahijpal2007">{{cite journal |doi=10.1111/j.1945-5100.2007.tb00589.x |author=Sahijpal, S. |author2=Soni, P. |author3=Gagan, G. |title=Numerical simulations of the differentiation of accreting planetesimals with <sup>26</sup>Al and <sup>60</sup>Fe as the heat sources |journal=Meteoritics & Planetary Science |volume=42 |issue=9 |pages=1529–1548 |year=2007 |bibcode=2007M&PS...42.1529S|doi-access=free }}</ref><ref name="Gupta2010">{{cite journal |author=Gupta, G. |author2=Sahijpal, S. |title=Differentiation of Vesta and the parent bodies of other achondrites |journal=[[J. Geophys. Res. Planets]] |volume=115 |issue=E8 |pages=E08001 |year=2010 |doi=10.1029/2009JE003525 |bibcode=2010JGRE..115.8001G |doi-access=free }}</ref>
{{Gallery|align=center |width=700
|File:PIA19063-Ceres-DwarfPlanet-DawnMission-March2015.jpg|The first color map of Ceres by ''Dawn'' (exaggerated color, March 2015)
}}

==Objectives==
[[File:Animation of Dawn trajectory.gif|thumb|right|Animation of '' Dawn''{{'s}} trajectory from September 27, 2007, to October 5, 2018<br>{{legend2|magenta| ''Dawn'' }}{{·}}{{legend2|Royalblue|[[Earth]]}}{{·}}{{legend2|Gold|[[Mars]]}}{{·}}{{legend2|Cyan|[[4 Vesta]] }}{{·}}{{legend2|lime|[[Ceres (dwarf planet)|1 Ceres]]}}]]
[[File:Dawn trajectory as of September 2009-en.svg|thumb|upright=1.25|''Dawn''{{'s}} approximate flight trajectory]]
The ''Dawn'' mission's goal was to characterize the conditions and processes of the Solar System's earliest eon by investigating in detail two of the largest protoplanets remaining intact since their formation.<ref name="NASA-20180907" /><ref name="Objectives">{{cite news |title=Mission Objectives |year=2006 |url=http://dawn.jpl.nasa.gov/mission/goal_index.asp |publisher=[[JPL]] – NASA |access-date=March 23, 2013 |archive-url=https://web.archive.org/web/20130214195648/http://dawn.jpl.nasa.gov/mission/goal_index.asp |archive-date=February 14, 2013 |url-status=dead }}</ref>

Although the mission has finished, the data analyses and interpretations will continue for many years. The primary question that the mission addresses is the role of size and water in determining the evolution of the planets.<ref name="Objectives"/> Ceres and Vesta are highly suitable bodies with which to address this question, as they are two of the most massive of the protoplanets. Ceres is geologically very primitive and icy, while Vesta is evolved and rocky. Their contrasting characteristics are thought to have resulted from them forming in two different regions of the early Solar System.<ref name="Objectives"/>

There are three principal scientific drivers for the mission. First, the ''Dawn'' mission can capture the earliest moments in the origin of the Solar System, granting an insight into the conditions under which these objects formed. Second, ''Dawn'' determines the nature of the building blocks from which the terrestrial planets formed, improving scientific understanding of this formation. Finally, it contrasts the formation and evolution of two small planets that followed very different evolutionary paths, allowing scientists to determine what factors control that evolution.<ref name="Objectives"/>

==Instruments==
[[File:PIA19559-Ceres-DwarfPlanet-Dawn-OpNav8-image1-20150516-crop.jpg|thumb|200px|Framing camera view of the [[Bright spots on Ceres|Ceres bright spots]]]]
NASA's Jet Propulsion Laboratory provided overall planning and management of the mission, the flight system and scientific payload development, and provided the [[ion propulsion system]]. Orbital Sciences Corporation provided the spacecraft, which constituted the company's first interplanetary mission. The [[Max Planck Institute for Solar System Research]] and the [[German Aerospace Center]] (DLR) provided the framing cameras, the [[Italian Space Agency]] provided the mapping [[spectrometer]], and the [[Los Alamos National Laboratory]] provided the [[gamma ray]] and [[neutron]] spectrometer.<ref name="Rayman 2006 605–616" />

*'''Framing camera (FC)'''&nbsp;– Two redundant framing camera were flown. Each used a f/7.9 refractive optical system with a focal length of 150&nbsp;mm.<ref name="Dawn Spacecraft and Instruments">{{cite web |title=Dawn Spacecraft and Instruments |url=http://www.nasa.gov/mission_pages/dawn/spacecraft/instruments.html |access-date=August 17, 2014 |archive-date=January 1, 2012 |archive-url=https://web.archive.org/web/20120101212028/http://www.nasa.gov/mission_pages/dawn/spacecraft/instruments.html |url-status=dead }}</ref><ref name=sierks>{{cite conference |url=https://indico.cern.ch/event/43007/contributions/1065032/attachments/927899/1313759/Poster_Gutierrez.pdf |title=Dawn Framing Camera: A Telescope En Route To The Asteroid Belt |conference=1st EIROforum School of Instrumentation. May 11–15, 2009. Geneva, Switzerland. |first1=H. |last1=Sierks |first2=K.-M. |last2=Aye |first3=I. |last3=Büttner |first4=R. |last4=Enge |first5=W. |last5=Goetz |first6=P. |last6=Gutierrez-Marques |first7=H. |last7=Hartwig |first8=I. |last8=Hejja |first9=H. U. |last9=Keller |first10=W. |last10=Kühne |first11=T. |last11=Maue |first12=A. |last12=Nathues |first13=M. |last13=Richards |first14=R. |last14=Schäfer |first15=S. |last15=Schröder |first16=M. |last16=Sperling |first17=I. |last17=Szemerey |first18=S. |last18=Mottola |first19=T. |last19=Behnke |first20=U. |last20=Carsenti |first21=R. |last21=Jaumann |first22=M. |last22=Tschentscher |first23=B. |last23=Fiethe |first24=F. |last24=Bubenhagen |first25=H. |last25=Michalik |first26=K.-U. |last26=Reiche |display-authors=5 |date=2009}}</ref> A frame-transfer [[charge-coupled device]] (CCD), a Thomson TH7888A,<ref name=sierks /> at the focal plane has 1024 × 1024 sensitive 93-μrad pixels, imaging a 5.5° x 5.5° [[field of view]]. An 8-position filter wheel permits [[panchromatic]] (clear filter) and spectrally selective imaging (7 narrow band filters). The broadest filter allows imaging at wavelengths from 400 to 1050&nbsp;nm. The FC computer is a custom [[Radiation hardening|radiation-hardened]] [[Xilinx]] system with a [[LEON2]] core and 8 [[GiB]] of memory.<ref name=sierks /> The camera offered  resolutions of 17 m/pixel for Vesta and 66 m/pixel for Ceres.<ref name=sierks /> Because the framing camera was vital for both science and navigation, the payload had two identical and physically separate cameras (FC1 & FC2) for redundancy, each with its own optics, electronics, and structure.<ref name="Rayman 2006 605–616" /><ref>{{cite journal |doi=10.1007/s11214-011-9745-4 |title=The Dawn Framing Camera |year=2011 |last1=Sierks |first1=H. |last2=Keller |first2=H. U. |last3=Jaumann |first3=R. |last4=Michalik |first4=H. |last5=Behnke |first5=T. |last6=Bubenhagen |first6=F. |last7=Büttner |first7=I. |last8=Carsenty |first8=U. |last9=Christensen |first9=U. |display-authors=8 |journal=Space Science Reviews |bibcode=2011SSRv..163..263S |volume=163 |issue=1–4 |pages=263–327|s2cid=121046026 }}</ref>
*'''Visible and [[infrared]] [[spectrometer]] (VIR)'''&nbsp;– This instrument is a modification of the visible and infrared thermal-imaging spectrometer used on the [[Rosetta spacecraft|''Rosetta'']] and ''[[Venus Express]]'' spacecraft. It draws its heritage from the [[Saturn]] orbiter [[Cassini–Huygens|''Cassini''{{'}}s]] visible and infrared mapping spectrometer. The spectrometer's VIR spectral frames are 256 (spatial) × 432 (spectral), and the slit length is 64 [[Angular mil|mrad]]. The mapping spectrometer incorporates two channels, both fed by a single grating. A CCD yields frames from 0.25 to 1.0 μm, while an array of HgCdTe photodiodes cooled to about 70 K spans the spectrum from 0.95 to 5.0 μm.<ref name="Rayman 2006 605–616" /><ref>{{cite journal |doi=10.1007/s11214-010-9668-5 |title=The VIR Spectrometer |year=2011 |last1=de Sanctis |first1=M. C. |last2=Coradini |first2=A. |last3=Ammannito |first3=E. |last4=Filacchione |first4=G. |last5=Capria |first5=M. T. |last6=Fonte |first6=S. |last7=Magni |first7=G. |last8=Barbis |first8=A. |last9=Bini |first9=A. |display-authors=8 |journal=Space Science Reviews |bibcode=2011SSRv..163..329D |volume=163 |issue=1–4 |pages=329–369|s2cid=121295356 }}</ref>
*'''Gamma Ray and Neutron Detector (GRaND)'''<ref>T.H. Prettyman [http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2231.pdf Gamma Ray and Neutron Spectrometer for Dawn], Lunar and Planetary Science XXXVII (2006), abstract 2231</ref>&nbsp;– This instrument is based on similar instruments flown on the [[Lunar Prospector]] and [[Mars Odyssey]] space missions. It had 21 sensors with a very wide field of view.<ref name="Dawn Spacecraft and Instruments" /> It was used to measure the abundances of the major rock-forming elements (oxygen, magnesium, aluminium, silicon, calcium, titanium, and iron) and potassium, thorium, uranium, and water (inferred from hydrogen content) in the top 1 m of the surface of Vesta and Ceres.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/technology/index.asp |title=Science Payload |access-date=March 21, 2010 |publisher=NASA |url-status=dead |archive-url=https://web.archive.org/web/20100527113905/http://dawn.jpl.nasa.gov/technology/index.asp |archive-date=May 27, 2010  }}</ref><ref>{{cite web |url=http://dawn.jpl.nasa.gov/technology/GRaND.asp |title=GRaND science instrument moves closer to launch from Cape |access-date=March 21, 2010 |publisher=NASA |url-status=dead |archive-url=https://web.archive.org/web/20110521184228/http://dawn.jpl.nasa.gov/technology/GRaND.asp |archive-date=May 21, 2011 }}</ref><ref>{{cite journal |doi=10.1111/j.1945-5100.1997.tb01582.x |bibcode=1997M&PS...32..929R |title=A magma ocean on Vesta: Core formation and petrogenesis of eucrites and diogenites |year=1997 |last1=Righter |first1=Kevin |pages=929–944 |last2=Drake |first2=Michael J. |journal=Meteoritics & Planetary Science |volume=32 |issue=6|s2cid=128684062 |doi-access=free }}</ref><ref>{{cite journal |doi=10.1111/j.1945-5100.2001.tb01892.x |bibcode=2001M&PS...36..501D |year=2001 |last1=Drake |pages=501–513 |first1=Michael J. |journal=Meteoritics & Planetary Science |volume=36 |issue=4 |title=The eucrite/Vesta story|doi-access=free }}</ref><ref>{{cite journal |doi=10.1117/12.578551 |title=Proceedings of SPIE{{snd}}Mapping the elemental composition of Ceres and Vesta: Dawn's gamma ray and neutron detector |year=2004 |last1=Prettyman |first1=Thomas H. |volume=5660 |page=107 |journal=Instruments, Science, and Methods for Geospace and Planetary Remote Sensing|s2cid=119514228 |url=https://zenodo.org/record/1235604 }}</ref><ref>{{cite journal |doi=10.1109/TNS.2003.815156 |bibcode=2003ITNS...50.1190P |title=Gamma-ray and neutron spectrometer for the Dawn mission to 1 Ceres and 4 Vesta |journal= IEEE Transactions on Nuclear Science|date=August 2003 |volume=50 |issue=4 |pages=1190–1197 |first=T.H. |last=Prettyman|s2cid=122574914 |url=https://zenodo.org/record/1232255 }}<!--|access-date=July 9, 2013 --></ref>

A [[magnetometer]] and laser [[altimeter]] were considered for the mission, but were not ultimately flown.<ref>{{cite news |first1=James |last1=Oberg |date=September 27, 2007 |title=Spacecraft's ion drive gets its day in the sun |work=NBC News |url=http://www.nbcnews.com/id/21014201/ns/technology_and_science-space/t/spacecrafts-ion-drive-gets-its-day-sun/ |access-date=November 25, 2018}}</ref>

==Specifications==
[[File:Dawn at Launch Pad.jpg|thumb|upright|''Dawn'' prior to encapsulation at its launch pad on July 1, 2007]]

===Dimensions===
With its [[solar array]] in the retracted launch position, the ''Dawn'' spacecraft is {{convert|2.36|m|ft}} wide. With its solar arrays fully extended, ''Dawn'' is {{convert|19.7|m|ft|abbr=on}} wide.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/dawn/spacecraft/ |title=Dawn Mission Overview |publisher=NASA |access-date=August 17, 2014 |archive-date=December 4, 2011 |archive-url=https://web.archive.org/web/20111204160818/http://www.nasa.gov/mission_pages/dawn/spacecraft/ |url-status=dead }}</ref> The solar arrays have a total area of {{convert|36.4|m2|abbr=on}}.<ref>{{cite web |url=http://www.lpi.usra.edu/opag/nov_2007_meeting/presentations/solar_power.pdf |title=Solar Power for Outer Planets Study |publisher=NASA |author=Scott W. Benson |date=November 8, 2007 |access-date=November 27, 2014}}</ref> The main antenna is five feet (1.24 metres) in diameter.<ref name=siliconvalleyastrolecture />

===Propulsion system===
The ''Dawn'' spacecraft was propelled by three [[xenon]] [[ion thruster]]s derived from [[NASA Solar Technology Application Readiness|NSTAR]] technology used by the ''Deep Space 1'' spacecraft,<ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/spacecraft.asp |title=Dawn Mission |publisher=NASA – JPL |access-date=July 18, 2011}}</ref> using one at a time. They have a [[specific impulse]] of 3,100 s and produce a [[thrust]] of 90&nbsp;mN.<ref>{{cite web |title=Dawn, Ion Propulsion |publisher=NASA |url=http://dawn.jpl.nasa.gov/mission/ion_prop.asp |access-date=September 28, 2007}}</ref> The whole spacecraft, including the ion propulsion thrusters, was powered by a 10&nbsp;kW (at 1&nbsp;[[astronomical unit|AU]]) [[multijunction photovoltaic cell|triple-junction]] [[gallium arsenide]] [[Photovoltaic module|photovoltaic]] solar array manufactured by Dutch Space.<ref>{{cite web |title=Dawn, Spacecraft |publisher=NASA |url=http://dawn.jpl.nasa.gov/mission/spacecraft.asp |access-date=September 28, 2007}}</ref><ref>{{cite web |url=http://www.dutchspace.nl/pages/business/content.asp?id=234&LangType=1033 |title=Dawn Solar Arrays |access-date=July 18, 2011 |year=2007 |publisher=Dutch Space}}</ref> ''Dawn'' was allocated {{convert|247|kg|lb|0|abbr=on}} of xenon for its Vesta approach, and carried another {{convert|112|kg|lb|0|abbr=on}} to reach Ceres,<ref name="GarnerEtAl">{{cite conference |url=https://trs.jpl.nasa.gov/handle/2014/44151 |title=Ion propulsion: An enabling technology for the Dawn Mission |last1=Garner |first1=Charles E. |last2=Rayman |first2=Mark M. | last3=Whiffen | first3=Greg J. | last4=Brophy | first4=John R. | last5=Mikes | first5=Steven C. |date=February 10, 2013 |publisher=Jet Propulsion Laboratory, National Aeronautics and Space Administration |location=Kauai, Hawaii |conference=23rd AAS/AIAA Spaceflight Mechanics Meeting |hdl=2014/44151 }}</ref> out of a total capacity of {{convert|425|kg|lb|abbr=on}} of on-board [[propellant]].<ref>{{cite web |last=Watanabe |first=Susan |date=July 5, 2007 |url=http://www.nasa.gov/mission_pages/dawn/spacecraft/ |title=Dawn: Spacecraft & Instruments |publisher=NASA |access-date=August 10, 2006 |archive-date=December 4, 2011 |archive-url=https://web.archive.org/web/20111204160818/http://www.nasa.gov/mission_pages/dawn/spacecraft/ |url-status=dead }}</ref> With the propellant it carried, ''Dawn'' was able to perform a [[Delta-v|velocity change]] of approximately 11&nbsp;km/s over the course of its mission, far more than any previous spacecraft achieved with onboard propellant after separation from its launch rocket.<ref name="GarnerEtAl"/> However, the thrust was very gentle; it took four days at full throttle to accelerate ''Dawn'' from zero to 60&nbsp;mph (96&nbsp;km/h).<ref name=siliconvalleyastrolecture /> 
''Dawn'' is NASA's first purely exploratory mission to use ion propulsion engines.<ref>{{cite web |title=Dawn Lifts Off |publisher=National Geographic Society |url=http://news.nationalgeographic.com/news/2007/09/photogalleries/wip-week48/ |archive-url=https://web.archive.org/web/20071021041049/http://news.nationalgeographic.com/news/2007/09/photogalleries/wip-week48/ |url-status=dead |archive-date=October 21, 2007 |access-date=September 28, 2007}}</ref> The spacecraft also has twelve 0.9 N [[hydrazine]] thrusters for [[Spacecraft attitude control|attitude control]] (orientation), which were also used to assist in orbital insertion.<ref>{{cite web |title=NSSDC – Spacecraft – Details |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2007-043A |year=2007 |publisher=NASA |access-date=January 22, 2015}}</ref>

The Dawn spacecraft was able to achieve a record-breaking level of propulsion from its ion engine.<ref>{{Cite web|url=https://dawn.jpl.nasa.gov/mission/|title=Dawn Mission {{!}} Mission|website=dawn.jpl.nasa.gov|language=en|access-date=November 24, 2018}}</ref> NASA noted three specific areas of excellence:<ref>{{Cite web | url=https://dawn.jpl.nasa.gov/mission/ | title=Overview &#124; Dawn}}</ref> 
*First to orbit two different astronomical bodies (not including Earth).
*[[Solar electric propulsion|Solar-electric propulsion]] record, including a velocity change in space of 25,700&nbsp;mph (11.49&nbsp;km/s). This is 2.7 times the velocity change by solar-electric ion drive than the past record.
*Achieved 5.9 years of ion engine runtime by September 7, 2018. This amount of runtime equates to 54% of Dawn's time in outer space.

===Outreach microchip===
''Dawn'' carries a memory [[Integrated circuit|chip]] bearing the names of more than 360,000 space enthusiasts.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/DawnCommunity/index.asp |title=All Aboard the Dawn Spacecraft |date=May 20, 2007 |publisher=JPL – NASA |access-date=May 21, 2007}}</ref> The names were submitted online as part of a public outreach effort between September 2005 and November 4, 2006.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/DawnCommunity/Sendname2asteroid/index_asteroid_blt.aspx |title=Send Your Name to the Asteroid Belt |date=November 4, 2006 |publisher=JPL.NASA.gov |access-date=June 21, 2007 |archive-url=https://web.archive.org/web/20070411054822/http://dawn.jpl.nasa.gov/DawnCommunity/Sendname2asteroid/index_asteroid_blt.aspx <!-- Bot retrieved archive --> |archive-date=April 11, 2007}}</ref> The microchip, which is two centimetres in diameter, was installed on May 17, 2007, above the spacecraft's forward ion thruster, underneath its [[high-gain antenna]].<ref>{{cite web |url=http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=32165 |title=Kennedy Media Gallery |date=May 17, 2007 |publisher=NASA |access-date=June 21, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20071021000520/http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=32165 |archive-date=October 21, 2007 }}</ref> More than one microchip was made, with a back-up copy put on display at the 2007 Open House event at the [[Jet Propulsion Laboratory]] in Pasadena, California.

==Mission summary==

===Launch preparations===
On April 10, 2007, the spacecraft arrived at the Astrotech Space Operations subsidiary of [[Spacehab|SPACEHAB, Inc.]] in [[Titusville, Florida]], where it was prepared for launch.<ref>{{cite web |url=http://www.spaceflightnow.com/news/n0704/10dawnarrival/ |title=Dawn arrives in Florida |publisher=Spaceflight Now |date=April 2007 |access-date=June 28, 2013}}</ref><ref>{{cite web |url=http://www.space.gs/11-apr-2007-dawn.html |title=Dawn at Astrotech's Payload Processing Facility |publisher=Space and Astronautics News |date=April 11, 2007 |access-date=June 28, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20070927205639/http://www.space.gs/11-apr-2007-dawn.html |archive-date=September 27, 2007 }}</ref> The launch was originally scheduled for June 20, but was delayed until June 30 due to delays with part deliveries.<ref>{{cite web |url=https://www.newscientist.com/article/dn12215-launch-of-dawn-asteroid-mission-postponed-again.html |title=Launch of Dawn asteroid mission postponed again |work=New Scientist |year=2007 |access-date=June 28, 2013}}</ref> A broken crane at the launch pad, used to raise the [[solid rocket booster]]s, further delayed the launch for a week, until July 7; prior to this, on June 15, the second stage was successfully hoisted into position.<ref>{{cite web |url=http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070618.html |title=Expendable Launch Vehicle Status Report |date=June 18, 2007 |access-date=June 28, 2013 |publisher=NASA}}</ref> A mishap at the Astrotech Space Operations facility, involving slight damage to one of the solar arrays, did not have an effect on the launch date; however, bad weather caused the launch to slip to July 8. Range tracking problems then delayed the launch to July 9, and then July 15. Launch planning was then suspended in order to avoid conflicts with the [[Phoenix (spacecraft)|''Phoenix'' mission]] to Mars, which was successfully launched on August 4.

===Launch===
[[File:Dawn ignition.jpg|thumb|upright|''Dawn'' launching on a [[Delta II]] rocket from [[Cape Canaveral Air Force Station Space Launch Complex 17]] on September 27, 2007]]
The launch of ''Dawn'' was rescheduled for September 26, 2007,<ref>{{cite web |url=http://www.nasa.gov/mission_pages/dawn/news/HQ_07150_Dawn_postpone_Sep.html |title=NASA Mission to Asteroid Belt Rescheduled for September Launch |date=July 7, 2007 |publisher=NASA |access-date=November 9, 2013}}</ref><ref>{{cite web |url=http://www.nasa.gov/missions/highlights/schedule.html |title=Dawn Launch Date |work=NASA launch schedule |access-date=September 1, 2007}}</ref><ref>{{cite book |title=The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres |editor1-first=Christopher |editor1-last=Russell |editor2-first=Carol |editor2-last=Raymond |publisher=Springer Science+Business Media |location=New York |isbn=978-1-4614-4903-4 |doi=10.1007/978-1-4614-4903-4 |year = 2012|bibcode=2012dmmp.book.....R |s2cid=132296936 }}</ref> then September 27, due to bad weather delaying fueling of the second stage, the same problem that delayed the July 7 launch attempt. The launch window extended from 07:20–07:49 EDT (11:20–11:49 [[GMT]]).<ref>{{cite web |url=http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070907.html |title=Expendable Launch Vehicle Status Report |date=September 7, 2007 |publisher=NASA |access-date=November 9, 2013}}</ref> During the final built-in hold at T&minus;4 minutes, a ship entered the exclusion area offshore, the strip of ocean where the rocket boosters were likely to fall after separation. After commanding the ship to leave the area, the launch was required to wait for the end of a collision avoidance window with the [[International Space Station]].<ref>{{cite web |url=http://www.nasa.gov/mission_pages/dawn/launch/launch-blog.html |title=NASA's Launch Blog |date=September 27, 2007 |publisher=NASA |access-date=November 9, 2013 |archive-date=June 30, 2017 |archive-url=https://web.archive.org/web/20170630183958/http://www.nasa.gov/mission_pages/dawn/launch/launch-blog.html |url-status=dead }}</ref> ''Dawn'' finally launched from [[Cape Canaveral Air Force Station Space Launch Complex 17|pad 17-B]] at the [[Cape Canaveral Air Force Station]] on a [[Delta II|Delta 7925-H]] rocket<ref>{{cite web |url=http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070511.html |title=Expendable Launch Vehicle Status Report |date=May 11, 2007 |publisher=NASA |access-date=November 9, 2013 |archive-date=June 23, 2017 |archive-url=https://web.archive.org/web/20170623162426/http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070511.html |url-status=dead }}</ref> at 07:34 EDT,<ref>{{cite web |url=http://www.ulalaunch.com/images/product_sheet/Delta_Product_Sheet_FINAL.pdf |title=ULA—One Team for Assured Access to Space |publisher=ulalaunch.com |access-date=November 9, 2013 |archive-url=https://web.archive.org/web/20070928093124/http://www.ulalaunch.com/images/product_sheet/Delta_Product_Sheet_FINAL.pdf <!-- Bot retrieved archive --> |archive-date=September 28, 2007}}</ref><ref>{{cite web |url=http://www.nasa.gov/mission_pages/dawn/launch/index.html |title=NASA's Launch Coverage |date=September 27, 2007 |publisher=NASA |access-date=November 9, 2013 |archive-date=June 24, 2017 |archive-url=https://web.archive.org/web/20170624120420/https://www.nasa.gov/mission_pages/dawn/launch/index.html |url-status=dead }}</ref><ref>{{cite web |url=http://www.nasa.gov/mission_pages/dawn/news/dawn-20070927.html |title=Dawn Spacecraft Successfully Launched |publisher=NASA |date=September 27, 2007 |access-date=November 9, 2013 |archive-date=May 15, 2017 |archive-url=https://web.archive.org/web/20170515230530/http://www.nasa.gov/mission_pages/dawn/news/dawn-20070927.html |url-status=dead }}</ref> reaching escape velocity with the help of a [[Spin-stabilized satellite|spin-stabilized]] solid-fueled third stage.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/journal_9_12_07.asp#assembly |title=Dawn Journal |date=September 12, 2007 |access-date=July 21, 2014 |website=Jet Propulsion Laboratory }}</ref><ref>{{cite web |url=http://www-ssc.igpp.ucla.edu/dawn/DawnJournal_24August08.html |title=Dear Dawnivores |date=August 24, 2008 |access-date=November 9, 2013 |first=Marc D. |last=Rayman |archive-date=May 30, 2012 |archive-url=https://archive.today/20120530164742/http://www-ssc.igpp.ucla.edu/dawn/DawnJournal_24August08.html |url-status=dead }}</ref> Thereafter, ''Dawn's'' ion thrusters took over.

===Transit to Vesta===
After initial testing, during which the [[ion thruster]]s accumulated more than 11 days 14 hours of operation, ''Dawn'' began long-term cruise propulsion on December 17, 2007.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/journal_12_17_07.asp |title=Dawn Journal: December 17, 2007 |last=Rayman |first=Marc D. |publisher=JPL |access-date=November 9, 2013}}</ref> On October 31, 2008, ''Dawn'' completed its first thrusting phase to send it on to [[Mars]] for a [[gravity assist]] flyby in February 2009. During this first interplanetary cruise phase, ''Dawn'' spent 270 days, or 85% of this phase, using its thrusters. It expended less than 72 kilograms of xenon propellant for a total change in velocity of 1.81&nbsp;km/s. On November 20, 2008, ''Dawn'' performed its first [[trajectory]] correction maneuver (TCM1), firing its number 1 thruster for 2 hours, 11 minutes.
[[File:Mars image by Dawn probe.jpg|thumb|Greyscale NIR image of Mars (northwest [[Tempe Terra]]), taken by ''Dawn'' during its 2009 flyby]]
''Dawn'' made its closest approach (549&nbsp;km) to [[Mars]] on February 17, 2009, during a successful gravity assist.<ref>{{cite web |url=http://www.planetary.org/blog/article/00001755/ |title=Dawn Journal: Aiming away from a bull's eye at Mars |access-date=November 9, 2013 |first=Marc D. |last=Rayman |publisher=The Planetary Society |archive-url=https://web.archive.org/web/20110716023248/http://www-ssc.igpp.ucla.edu/dawn/DawnJournal_24August08.html |archive-date=July 16, 2011}}</ref><ref>{{cite news |url=http://www.space.com/missionlaunches/090218-dawn-asteroid-mars.html |title=Asteroid-Bound Probe Zooms Past Mars |work=Space.com |first=Tariq |last=Malik |date=February 18, 2009 |access-date=November 9, 2013}}</ref> This flyby slowed Mars's orbital velocity by about {{convert|1|in|cm|abbr=on|order=flip}} per 180 million years.<ref name=siliconvalleyastrolecture /> On this day, the spacecraft placed itself in [[Safe mode (spacecraft)|safe mode]], resulting in some data acquisition loss. The spacecraft was reported to be back in full operation two days later, with no impact on the subsequent mission identified. The [[root cause analysis|root cause]] of the event was reported to be a software programming error.<ref name=jplstatus>{{cite web |url=https://dawn.jpl.nasa.gov/mission/status_2009.html |date=February 28, 2009 |access-date=January 9, 2018 |title=Dawn Receives Gravity Assist from Mars |publisher=NASA/JPL}}</ref>

To cruise from Earth to its targets, ''Dawn'' travelled in an elongated outward spiral trajectory. The actual Vesta chronology and estimated{{update inline|date=June 2017}} Ceres chronology are as follows:<ref name=GSpaceTimeline>{{cite web |url=http://planetary.org/explore/topics/dawn/ |title=GSpace Topics: Dawn |publisher=Planetary Society |access-date=November 9, 2013}}</ref>
*September 27, 2007: launch
*February 17, 2009: Mars [[gravity assist]]
*July 16, 2011: Vesta arrival and capture
*August 11–31, 2011: Vesta survey orbit
*September 29 – November 2, 2011: Vesta first high altitude orbit
*December 12, 2011 – May 1, 2012: Vesta low altitude orbit
*June 15 – July 25, 2012: Vesta second high altitude orbit
*September 5, 2012: Vesta departure
*March 6, 2015: Ceres arrival
*June 30, 2016: End of primary Ceres operations
*July 1, 2016: Beginning of Ceres extended mission<ref name="sfnow20160702">{{cite news |url=https://spaceflightnow.com/2016/07/02/pluto-probes-extended-mission-approved-but-new-dawn-destination-denied/ |title=Pluto probe's extended mission approved, but new Dawn destination denied |work=Spaceflight Now |first=Stephen |last=Clark |date=July 2, 2016 |access-date=June 21, 2017}}</ref>
*November 1, 2018: End of Mission

===Vesta approach===
As ''Dawn'' approached Vesta, the Framing Camera instrument took progressively higher-resolution images, which were published online and at news conferences by NASA and MPI.
<gallery class="center">
File:Vesta image by Dawn probe.jpg|June 14, 2011<br />{{convert|265,000|km|mi|abbr=on}}
File:Dawn-image-062411.jpg|June 24, 2011<br />{{convert|152,000|km|mi|abbr=on}}
File:Vesta 20110701 cropped.jpg|July 1, 2011<br />{{convert|100,000|km|mi|abbr=on}}
File:Dawn-image-070911.jpg|July 9, 2011<br />{{convert|41,000|km|mi|abbr=on}}
</gallery>
On May 3, 2011, ''Dawn'' acquired its first targeting image, 1,200,000&nbsp;km from Vesta, and began its approach phase to the asteroid.<ref>[http://www.nasa.gov/mission_pages/dawn/news/dawn20110511.html "NASA's Dawn Captures First Image of Nearing Asteroid"] {{Webarchive|url=https://web.archive.org/web/20120807223545/http://www.nasa.gov/mission_pages/dawn/news/dawn20110511.html |date=August 7, 2012 }}. NASA. May 11, 2011. Retrieved September 1, 2012.</ref> On June 12, ''Dawn's'' speed relative to Vesta was slowed in preparation for its orbital insertion 34 days later.<ref>{{cite web |url=http://www.nasa.gov/home/hqnews/2011/aug/HQ_11-254_Dawn_Image.html |title=NASA'S Dawn Spacecraft Begins Science Orbits Of Vesta |publisher=NASA |date=August 1, 2011 |access-date=August 7, 2014 |archive-date=November 22, 2013 |archive-url=https://web.archive.org/web/20131122164137/http://www.nasa.gov/home/hqnews/2011/aug/HQ_11-254_Dawn_Image.html |url-status=dead }}</ref><ref>[https://web.archive.org/web/20090322131458/http://neo.jpl.nasa.gov/orbits/fullview4.jpg "View of Vesta from Dawn"]. NASA/JPL MYSTIC simulator (updated periodically). Retrieved September 1, 2012.</ref>

''Dawn'' was scheduled to be inserted into orbit at 05:00 UTC on July 16 after a period of thrusting with its ion engines. Because its antenna was pointed away from the Earth during thrusting, scientists were not able to immediately confirm whether or not ''Dawn'' successfully made the maneuver. The spacecraft would then reorient itself, and was scheduled to check in at 06:30 UTC on July 17.<ref>{{cite news |last=Wall |first=Mike |title=NASA Spacecraft Now Orbiting Huge Asteroid Vesta&nbsp;... Hopefully |url=http://www.space.com/12306-dawn-vesta-asteroid-orbit-arrival.html |work=[[Space.com]] |date=July 16, 2011 |access-date=July 17, 2011}}</ref> NASA later confirmed that it received telemetry from ''Dawn'' indicating that the spacecraft successfully entered orbit around Vesta, making it the first spacecraft to orbit an object in the asteroid belt.<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-14160135 |date=July 17, 2011 |title=Dawn probe orbits asteroid Vesta |first=Jonathan |last=Amos |publisher=BBC |access-date=January 22, 2015}}</ref><ref>{{cite book|url=https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf|title=Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016|page=2|last1=Siddiqi|first1=Asif A.|lccn=2017059404|isbn=9781626830424|publisher=NASA History Program Office|edition=second|year=2018|id=SP2018-4041|series=The NASA history series|location=Washington, D.C.}}</ref> The exact time of insertion could not be confirmed, since it depended on Vesta's mass distribution, which was not precisely known and at that time had only been estimated.<ref>{{cite news |last1=Vega |first1=Priscilla |last2=Brown |first2=Dwayne |title=NASA's Dawn Spacecraft Enters Orbit Around Asteroid Vesta |url=http://www.nasa.gov/mission_pages/dawn/news/dawn20110716.html |publisher=NASA |date=July 16, 2011 |access-date=July 17, 2011 |archive-date=June 19, 2012 |archive-url=https://web.archive.org/web/20120619102718/http://www.nasa.gov/mission_pages/dawn/news/dawn20110716.html |url-status=dead }}</ref>

===Vesta orbit===
After being captured by Vesta's gravity and entering its orbit on July 16, 2011,<ref name="sciencemag.org">{{cite journal |title=Dawn at Vesta: Testing the Protoplanetary Paradigm |journal=[[Science (journal)|Science]] |first1=C. T. |last1=Russell |last2=Raymond |first2=C. A. |last3=Coradini |first3=A. |last4=McSween |first4=H. Y. |last5=Zuber |first5=M. T. |last6=Nathues |first6=A. |last7=De Sanctis |first7=M. C. |last8=Jaumann |first8=R. |last9=Konopliv |first9=A. S. |last10=Preusker |first10=F. |last11=Asmar |first11=S. W. |last12=Park |first12=R. S. |last13=Gaskell |first13=R. |last14=Keller |first14=H. U. |last15=Mottola |first15=S. |last16=Roatsch |first16=T. |last17=Scully |first17=J. E. C. |last18=Smith |first18=D. E. |last19=Tricarico |first19=P. |last20=Toplis |first20=M. J. |last21=Christensen |first21=U. R. |last22=Feldman |first22=W. C. |last23=Lawrence |first23=D. J. |last24=McCoy |first24=T. J. |last25=Prettyman |first25=T. H. |last26=Reedy |first26=R. C. |last27=Sykes |first27=M. E. |last28=Titus |first28=T. N. |display-authors=5 |volume=336 |issue=6082 |pages=684–686 |date=May 11, 2012 |doi=10.1126/science.1219381 |bibcode=2012Sci...336..684R |pmid=22582253|s2cid=206540168 }}</ref> ''Dawn'' moved to a lower, closer orbit by running its xenon-ion engine using solar power. On August 2, it paused its spiralling approach to enter a 69-hour survey orbit at an altitude of {{convert|2750|km|mi|abbr=on}}. It assumed a 12.3-hour high-altitude mapping orbit at {{convert|680|km|mi|abbr=on}} on September 27, and finally entered a 4.3-hour low-altitude mapping orbit at {{convert|210|km|mi|abbr=on}} on December 8.<ref name="status2011">{{cite web |url=http://dawn.jpl.nasa.gov/mission/status_2011.html |title=Mission Status Updates |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=2011}}</ref><ref>{{cite journal |title=The Dawn Mission to Vesta and Ceres |journal=[[Space Science Reviews]] |first1=C. T. |last1=Russell |first2=C. A. |last2=Raymond |volume=163 |issue=1–4 |pages=3–23 |date=December 2011 |doi=10.1007/s11214-011-9836-2 |bibcode=2011SSRv..163....3R|s2cid=121717060 }}</ref><ref>{{cite conference |url=http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2011index/IEPC-2011-326.pdf |title=The Dawn of Vesta Science |conference=32nd International Electric Propulsion Conference. September 11–15, 2011. Wiesbaden, Germany. |first1=Charles E. |last1=Garner |first2=Marc D. |last2=Rayman |first3=John R. |last3=Brophy |first4=Steven C. |last4=Mikes |date=2011 |id=IEPC-2011-326 |access-date=May 6, 2012 |archive-date=November 9, 2013 |archive-url=https://web.archive.org/web/20131109124425/http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2011index/IEPC-2011-326.pdf |url-status=dead }}</ref>
[[File:Animation of Dawn trajectory around 4 Vesta.gif |400px|thumb |center|Animation of Dawn{{'s}} trajectory around [[4 Vesta]] from July 15, 2011, to September 10, 2012<br/>{{legend2|magenta| Dawn}}{{·}}{{legend2| Lime |[[4 Vesta]]}}]]
<gallery class="center">
File:Vesta from Dawn, July 17.jpg|July 17, 2011<br />{{convert|16,000|km|mi|abbr=on}}
File:Vesta from Dawn, July 18.jpg|July 18, 2011<br />{{convert|10,500|km|mi|abbr=on}}
File:Vesta darkside.jpg|July 23, 2011<br />{{convert|5,200|km|mi|abbr=on}}
File:Vesta Full-Frame.jpg|July 24, 2011<br />{{convert|5,200|km|mi|abbr=on}}
</gallery>

In May 2012, the ''Dawn'' team published preliminary results of their study of Vesta, including estimates of the size of Vesta's metal-rich core, which is theorized to be {{convert|220|km|mi|abbr=on}} across. The scientists stated that they think that Vesta is the "last of its kind" – the only remaining example of the large planetoids that came together to form the rocky planets during the formation of the Solar System.<ref name="sciencemag.org" /><ref>{{cite news |url=https://www.bbc.com/news/science-environment-18027933 |title=Asteroid Vesta is 'last of a kind' rock |work=BBC News |first=Jonathan |last=Amos |date=May 11, 2012 |access-date=January 20, 2015}}</ref> In October 2012, further ''Dawn'' results were published, on the origin of anomalous dark spots and streaks on Vesta's surface, which were likely deposited by ancient asteroid impacts.<ref>{{cite journal |title=Delivery of dark material to Vesta via carbonaceous chondritic impacts |journal=[[Icarus (journal)|Icarus]] |last1=Reddy |first1=Vishnu |last2=Le Corre |first2=Lucille |last3=O'Brien |first3=David P. |last4=Nathues |first4=Andreas |last5=Cloutis |first5=Edward A. |last6=Durda |first6=Daniel D. |last7=Bottke |first7=William F. |last8=Bhatt |first8=Megha U. |last9=Nesvorny |first9=David |last10=Buczkowski |first10=Debra |last11=Scully |first11=Jennifer E.C. |last12=Palmer |first12=Elizabeth M. |last13=Sierks |first13=Holger |last14=Mann |first14=Paul J. |last15=Becker |first15=Kris J. |last16=Beck |first16=Andrew W. |last17=Mittlefehldt |first17=David |last18=Li |first18=Jian-Yang |last19=Gaskell |first19=Robert |last20=Russell |first20=Christopher T. |last21=Gaffey |first21=Michael J. |last22=McSween |first22=Harry Y. |last23=McCord |first23=Thomas B. |last24=Combe |first24=Jean-Philippe |last25=Blewett |first25=David |display-authors=5 |volume=221 |issue=2 |pages=544–559 |date=November–December 2012 |doi=10.1016/j.icarus.2012.08.011 |bibcode=2012Icar..221..544R |arxiv=1208.2833|s2cid=37947646 }}</ref><ref>{{Cite journal |title=Dark material on Vesta from the infall of carbonaceous volatile-rich material |journal=[[Nature (journal)|Nature]] |first1=T. B. |last1=McCord |last2=Li |first2=J.-Y. |last3=Combe |first3=J.-P. |last4=McSween |first4=H. Y. |last5=Jaumann |first5=R. |last6=Reddy |first6=V. |last7=Tosi |first7=F. |last8=Williams |first8=D. A. |last9=Blewett |first9=D. T. |last10=Turrini |first10=D. |last11=Palomba |first11=E. |last12=Pieters |first12=C. M. |last13=De Sanctis |first13=M. C. |last14=Ammannito |first14=E. |last15=Capria |first15=M. T. |last16=Le Corre |first16=L. |last17=Longobardo |first17=A. |last18=Nathues |first18=A. |last19=Mittlefehldt |first19=D. W. |last20=Schröder |first20=S. E. |last21=Hiesinger |first21=H. |last22=Beck |first22=A. W. |last23=Capaccioni |first23=F. |last24=Carsenty |first24=U. |last25=Keller |first25=H. U. |last26=Denevi |first26=B. W. |last27=Sunshine |first27=J. M. |last28=Raymond |first28=C. A. |last29=Russell |first29=C. T. |display-authors=5 |volume=491 |issue=7422 |pages=83–86 |date=November 2012 |doi=10.1038/nature11561 |bibcode=2012Natur.491...83M |pmid=23128228|s2cid=2058249 }}</ref><ref>{{cite news |url=http://www.latinospost.com/articles/6285/20121031/nasas-dawn-spacecraft-probes-proto-planet-vesta.htm |title=NASA's Dawn Spacecraft Probes Proto-Planet Vesta, Discovers Deposits that Give Scientists Insight into the Origins of the Solar System |work=Latinos Post |first=James |last=Paladino |date=October 31, 2012 |access-date=November 28, 2012}}</ref> In December 2012, it was reported that ''Dawn'' had observed gullies on the surface of Vesta that were interpreted to have been eroded by transiently flowing liquid water.<ref>{{cite conference |url=http://www.hou.usra.edu/meetings/lpsc2014/pdf/1796.pdf |title=Sub-Curvilinear Gullies Interpreted as Evidence for Transient Water Flow on Vesta |conference=45th Lunar and Planetary Science Conference. March 17–21, 2014. The Woodlands, Texas. |first1=J. E. C. |last1=Scully |first2=C. T. |last2=Russell |first3=A. |last3=Yin |first4=R. |last4=Jaumann |first5=E. |last5=Carey |first6=H. Y. |last6=McSween |first7=J. |last7=Castillo-Rogez |first8=C. A. |last8=Raymond |first9=V. |last9=Reddy |first10=L. |last10=Le Corre |display-authors=5 |date=2014 |bibcode=2014LPI....45.1796S}}</ref><ref>{{cite news |url=https://www.bbc.com/news/science-environment-20582704 |title=Dawn probe spies possible water-cut gullies on Vesta |work=BBC News |first=Jonathan |last=Amos |date=December 6, 2012 |access-date=December 8, 2012}}</ref> More details about the ''Dawn'' mission's scientific discoveries at Vesta are included on the [[4 Vesta|Vesta]] page.

''Dawn'' was originally scheduled to depart Vesta and begin its two and a half year journey to Ceres on August 26, 2012.<ref name="Aug262012" /> However, a problem with one of the spacecraft's [[reaction wheel]]s forced ''Dawn'' to delay its departure from Vesta's gravity until September 5, 2012.<ref name="5SepDepart" /><ref name="NewSci2012">{{cite news |url=https://www.newscientist.com/blogs/shortsharpscience/2012/09/asteroid-hopping-spacecraft-ma.html |title=Dawn departs Vesta to become first asteroid hopper |work=New Scientist |series=Short sharp Science |first=Jacob |last=Aron |date=September 6, 2012 |access-date=November 9, 2013 |archive-date=September 7, 2012 |archive-url=https://web.archive.org/web/20120907134311/http://www.newscientist.com/blogs/shortsharpscience/2012/09/asteroid-hopping-spacecraft-ma.html |url-status=dead }}</ref><ref>{{cite web |url=http://dawn.jpl.nasa.gov/feature_stories/engineers_assess_reaction_wheel.asp |title=Dawn Engineers Assess Reaction Wheel |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Jia-Rui C. |last=Cook |date=August 18, 2012 |access-date=January 22, 2015 |archive-url=https://web.archive.org/web/20150315131809/http://dawn.jpl.nasa.gov/feature_stories/engineers_assess_reaction_wheel.asp |archive-date=March 15, 2015}}</ref><ref name="DawnDepartedVesta">{{cite web |url=http://dawn.jpl.nasa.gov/feature_stories/dawn_departs_vesta.asp |title=Dawn has departed the giant asteroid Vesta |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Jia-Rui C. |last=Cook |date=September 5, 2012 |archive-url=https://web.archive.org/web/20150414203658/http://dawn.jpl.nasa.gov/feature_stories/dawn_departs_vesta.asp |archive-date=April 14, 2015}}</ref><ref name="Yahoo Dawn Departs Vesta">{{cite news |url=https://www.yahoo.com/news/nasas-dawn-spacecraft-says-goodbye-giant-asteroid-vesta-205041936.html |title=NASA's Dawn Spacecraft Says Goodbye to Giant Asteroid Vesta |work=Space.com via Yahoo! News |date=September 5, 2012 |access-date=September 6, 2012}}</ref>

<gallery class="center">
File:Central Mound at the South Pole on the asteroid Vesta image of NASA’s Dawn spacecraft 14f2 311811321 detail.jpg|Central Mound at the South Pole on the asteroid Vesta on August 12, 2011
File:Vesta Snowman craters close-up.jpg|The [[snowman]] shaped craters on Vesta
File:Vesta Cratered terrain with hills and ridges.jpg|Craters and ridges of Vesta
</gallery>

{| class="wikitable" style="margin:0.5em auto; width:600px;"
! Geologic map of Vesta based on ''Dawn'' data<ref name="Williams2014">{{cite journal |title=Introduction: The geologic mapping of Vesta |journal=[[Icarus (journal)|Icarus]] |first1=David A. |last1=Williams |first2=R. Aileen |last2=Yingst |first3=W. Brent |last3=Garry |volume=244 |pages=1–12 |date=December 2014 |doi=10.1016/j.icarus.2014.03.001 |bibcode=2014Icar..244....1W |hdl=2286/R.I.28071 |url=https://repository.asu.edu/attachments/144882/content/ND_I_Williams_etal_2014_preprint.pdf |hdl-access=free |access-date=September 24, 2019 |archive-date=August 31, 2021 |archive-url=https://web.archive.org/web/20210831111836/https://repository.asu.edu/attachments/144882/content/ND_I_Williams_etal_2014_preprint.pdf |url-status=dead }}</ref>
|-
| style="font-size:88%; text-align:center;" |[[File:PIA18788-VestaAsteroid-GeologicMap-DawnMission-20141117.jpg|600px]]
The most ancient and heavily cratered regions are brown; areas modified by the [[Veneneia]] and [[Rheasilvia]] impacts are purple (the Saturnalia Fossae Formation, in the north)<ref name="Scully2014">{{Cite journal |title=Geomorphology and structural geology of Saturnalia Fossae and adjacent structures in the northern hemisphere of Vesta |journal=Icarus |last1=Scully |first1=J. E. C. |last2=Yin |first2=A. |last3=Russell |first3=C. T. |last4=Buczkowski |first4=D. L. |last5=Williams |first5=D. A. |last6=Blewett |first6=D. T. |last7=Ruesch |first7=O. |last8=Hiesinger |first8=H. |last9=Le Corre |first9=L. |last10=Mercer |first10=C. |last11=Yingst |first11=R. A. |last12=Garry |first12=W. B. |last13=Jaumann |first13=R. |last14=Roatsch |first14=T. |last15=Preusker |first15=F. |last16=Gaskell |first16=R. W. |last17=Schröder |first17=S. E. |last18=Ammannito |first18=E. |last19=Pieters |first19=C. M. |last20=Raymond |first20=C. A. |display-authors=5 |volume=244 |pages=23–40 |date=December 2014 |doi=10.1016/j.icarus.2014.01.013 |bibcode=2014Icar..244...23S|hdl=2286/R.I.28070 |url=https://elib.dlr.de/90161/1/1809.pdf |hdl-access=free }}</ref> and light cyan (the Divalia Fossae Formation, equatorial),<ref name = "Williams2014"/> respectively; the Rheasilvia impact basin interior (in the south) is dark blue, and neighboring areas of Rheasilvia ejecta (including an area within Veneneia) are light purple-blue;<ref name="Schäfer2014">{{Cite journal |title=Imprint of the Rheasilvia impact on Vesta – Geologic mapping of quadrangles Gegania and Lucaria |journal=Icarus |last1=Schäfer |first1=M. |last2=Nathues |first2=A. |last3=Williams |first3=D. A. |last4=Mittlefehldt |first4=D. W. |last5=Le Corre |first5=L. |last6=Buczkowski |first6=D. L. |last7=Kneissl |first7=T. |last8=Thangjam |first8=G. S. |last9=Hoffmann |first9=M. |last10=Schmedemann |first10=N. |last11=Schäfer |first11=T. |last12=Scully |first12=J. E. C. |last13=Li |first13=J. Y. |last14=Reddy |first14=V. |last15=Garry |first15=W. B. |last16=Krohn |first16=K. |last17=Yingst |first17=R. A. |last18=Gaskell |first18=R. W. |last19=Russell |first19=C. T. |display-authors=5 |volume=244 |pages=60–73 |date=December 2014 |doi=10.1016/j.icarus.2014.06.026 |bibcode=2014Icar..244...60S|hdl=2286/R.I.28060 |hdl-access=free }}</ref><ref name="Kneissl2014">{{Cite journal |title=Morphology and formation ages of mid-sized post-Rheasilvia craters – Geology of quadrangle Tuccia, Vesta |journal=Icarus |last1=Kneissl |first1=T. |last2=Schmedemann |first2=N. |last3=Reddy |first3=V. |last4=Williams |first4=D. A. |last5=Walter |first5=S. H. G. |last6=Neesemann |first6=A. |last7=Michael |first7=G. G. |last8=Jaumann |first8=R. |last9=Krohn |first9=K. |last10=Preusker |first10=F. |last11=Roatsch |first11=T. |last12=Le Corre |first12=L. |last13=Nathues |first13=A. |last14=Hoffmann |first14=M. |last15=Schäfer |first15=M. |last16=Buczkowski |first16=D. |last17=Garry |first17=W. B. |last18=Yingst |first18=R. A. |last19=Mest |first19=S. C. |last20=Russell |first20=C. T. |last21=Raymond |first21=C. A. |display-authors=5 |volume=244 |pages=133–157 |date=December 2014 |doi=10.1016/j.icarus.2014.02.012 |bibcode=2014Icar..244..133K|hdl=2286/R.I.28058 |hdl-access=free }}</ref> areas modified by more recent impacts or mass wasting are yellow/orange or green, respectively.
|}

===Transit to Ceres===
{| class="wikitable floatright"
|+Imaging dates (2014–2015) and resolution<ref>{{cite web |url=http://dawnblog.jpl.nasa.gov/2015/02/25/dawn-journal-february-25/#table |archive-url=https://web.archive.org/web/20150227143103/http://dawnblog.jpl.nasa.gov/2015/02/25/dawn-journal-february-25/#table |url-status=dead |archive-date=February 27, 2015 |title=Dawn Journal February 25 |publisher=NASA |date=February 25, 2015 |access-date=March 1, 2015}}</ref>
|-
!Date	||distance <br />(km)	||diameter <br />(px)	||resolution <br />(km/px)	||portion of disk<br />illuminated
|-
|December 1	||1,200,000	||9	||112	||94%
|-
|January 13	||383,000	||27	||36	||95%
|-
|January 25	||237,000	||43	||22	||96%
|-
|February 3	||146,000	||70	||14	||97%
|-
|February 12	||83,000	||122	||7.8	||98%
|-
|February 19	||46,000	||222	||4.3	||87%
|-
|February 25	||40,000	||255	||3.7	||44%
|-
|March 1	||49,000	||207	||4.6	||23%
|-
|April 10	||33,000	||306	||3.1	||17%
|-
|April 15	||22,000	||453	||2.1	||49%
|}
During its time in orbit around Vesta, the probe experienced several failures of its reaction wheels. Investigators planned to modify their activities upon arrival at Ceres for close range geographical survey mapping. The ''Dawn'' team stated that they would orient the probe using a "hybrid" mode utilizing both reaction wheels and ion thrusters. Engineers determined that this hybrid mode would conserve fuel. On November 13, 2013, during the transit, in a test preparation, ''Dawn'' engineers completed a 27-hour-long series of exercises of said hybrid mode.<ref>{{cite web |url=http://dawn.jpl.nasa.gov/feature_stories/Dawn_Fills_Out_Ceres_Dance_Card.asp |title=Dawn Fills out its Ceres Dance Card |publisher=NASA/JPL |date=December 3, 2013 |access-date=March 18, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150415025503/http://dawn.jpl.nasa.gov/feature_stories/Dawn_Fills_Out_Ceres_Dance_Card.asp |archive-date=April 15, 2015 }}</ref>

On September 11, 2014, ''Dawn''{{'s}} ion thruster unexpectedly ceased firing and the probe began operating in a triggered safe mode. To avoid a lapse in propulsion, the mission team hastily exchanged the active ion engine and electrical controller with another. The team stated that they had a plan in place to revive this disabled component later in 2014. The controller in the ion propulsion system may have been damaged by a [[high-energy particle]]. Upon exiting the safe mode on September 15, 2014, the probe's ion thruster resumed normal operation.<ref name=SafeMode2014>{{cite web |url=http://dawn.jpl.nasa.gov/feature_stories/Dawn_operated_normally.asp |title=Dawn Operating Normally After Safe Mode Triggered |publisher=NASA/JPL |date=September 16, 2014 |access-date=March 18, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20141225012242/http://dawn.jpl.nasa.gov/feature_stories/Dawn_operated_normally.asp |archive-date=December 25, 2014}}</ref>

Furthermore, the ''Dawn'' investigators also found that, after the propulsion issue, ''Dawn'' could not aim its main communications antenna towards Earth. Another antenna of weaker capacity was instead temporarily retasked. To correct the problem, the probe's computer was reset and the aiming mechanism of the main antenna was restored.<ref name=SafeMode2014/>

===Ceres approach===
''Dawn'' began photographing an extended disk of Ceres on December 1, 2014,<ref name=dawnjournal1214>{{cite web |url=http://dawnblog.jpl.nasa.gov/2014/12/29/dawn-journal-december-29/ |archive-url=https://web.archive.org/web/20150101091612/http://dawnblog.jpl.nasa.gov/2014/12/29/dawn-journal-december-29/ |url-status=dead |archive-date=January 1, 2015 |title=Dawn Journal |publisher=NASA/JPL |date=December 29, 2014 |access-date=January 21, 2015}}</ref> with images of partial rotations on January 13 and 25, 2015 released as animations.
Images taken from ''Dawn'' of Ceres after January 26, 2015, exceeded the resolution of comparable images from the [[Hubble Space Telescope]].<ref>{{cite web |url=http://dawnblog.jpl.nasa.gov/2014/10/31/dawn-journal-october-31/#sthash.OPRlufJs.dpuf |title=Dawn Journal October 31 |publisher=NASA |date=October 31, 2014 |access-date=January 18, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150120120112/http://dawnblog.jpl.nasa.gov/2014/10/31/dawn-journal-october-31/#sthash.OPRlufJs.dpuf |archive-date=January 20, 2015  }}</ref>

<div align="center">'''Progression of images of Ceres taken by ''Dawn'' between January and March 2015'''</div>
<gallery class="center">
File:Ceres OpNav 2 single frame by Dawn, 25 January 2015.jpg|January 25, 2015<br />{{convert|237,000|km|mi|abbr=on}}
File:PIA19179-Ceres-DawnSpacecraft-20150204.jpg|February 4, 2015<br />{{convert|145,000|km|mi|abbr=on}}
File:Ceres RC1 single frame by Dawn, 12 February 2015.jpg|February 12, 2015<br />{{convert|80,000|km|mi|abbr=on}}
File:Ceres RC2 single frame by Dawn, 19 February 2015.jpg|February 19, 2015<br />{{convert|46,000|km|mi|abbr=on}}
</gallery>

Because of the failure of two reaction wheels, ''Dawn'' made fewer camera observations of Ceres during its approach phase than it did during its Vesta approach. Camera observations required turning the spacecraft, which consumed precious hydrazine fuel. Seven optical navigation photo sessions (OpNav 1–7, on January 13 and 25, February 3 and 25, March 1, and April 10 and 15) and two full rotation observation sessions (RC1–2, on February 12 and 19) were planned{{update inline|date=December 2015}} before full observation begins with orbital capture. The gap in March and early April was due to a period when Ceres appears too close to the Sun from ''Dawn''{{'s}} vantage point to take pictures safely.<ref>{{cite web |url=http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/ |archive-url=https://web.archive.org/web/20150202001407/http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/ |url-status=dead |archive-date=February 2, 2015 |title=Dawn Journal January 29 |publisher=NASA |date=January 29, 2015 |access-date=February 13, 2015}}</ref>

===Ceres orbit===
[[File:Animation of Dawn trajectory around Ceres.gif |center|400px|thumb |Animation of ''Dawn''{{'s}} trajectory around [[Ceres (dwarf planet)|Ceres]] from February 1, 2015, to February 1, 2025<br>{{legend2|magenta| ''Dawn''}}{{·}}{{legend2| Lime |[[Ceres (dwarf planet)|Ceres]]}}]]

{| class="wikitable center"
|+ Mapping orbits and resolution<ref name="NASA-20150331">{{cite web |url=http://dawnblog.jpl.nasa.gov/2015/03/31/dawn-journal-march-31-2/#table |title=Dawn Journal March 31 [2015] |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=March 31, 2015 |access-date=September 9, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150905091717/http://dawnblog.jpl.nasa.gov/2015/03/31/dawn-journal-march-31-2/#table |archive-date=September 5, 2015  }}</ref> – [[Commons:Category:Photos of Ceres by Dawn|Photos of Ceres by Dawn on Commons]]
|-
! Orbit phase || No. || Dates<ref name="PS-20150730">{{cite web |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150730-dawn-journal-descent-to-hamo.html |title=Dawn Journal: Descent to HAMO |work=[[The Planetary Society]] |first=Marc |last=Rayman |date=July 30, 2015 |access-date=September 9, 2015}}</ref>	|| Altitude<br />(km; mi)<ref>Distance from surface, not radius of the orbit</ref> || Orbital period || Resolution<br />(km/px) || Improvement<br />over ''Hubble'' || Notes
|-
| [[Commons:Category:Dawn Ceres RC3 phase|RC3]]|| 1st || April 23 – May 9, 2015 || {{convert|13,500|km|mi|abbr=on}} || 15&nbsp;days || 1.3	|| 24× ||
|-
| [[Commons:Category:Dawn Ceres Survey phase|Survey]]|| 2nd || June 6–30, 2015	|| {{convert|4,400|km|mi|abbr=on}} || 3.1&nbsp;days || 0.41	|| 73× ||
|-
| [[Commons:Category:Dawn Ceres HAMO phase|HAMO]]|| 3rd || August 17 – October 23, 2015 || {{convert|1,450|km|mi|abbr=on}}	|| 19&nbsp;hours || 0.14 (140&nbsp;m) || 217× ||
|-
| [[Commons:Category:Dawn Ceres LAMO phase|LAMO/XMO1]] || 4th || December 16, 2015 – September 2, 2016 || {{convert|375|km|mi|abbr=on}}|| 5.5&nbsp;hours	|| 0.035 (35&nbsp;m) || 850× ||
|-
| [[Commons:Category:Dawn Ceres XMO2 phase|XMO2]]|| 5th || October 5 – November 4, 2016 || {{convert|1480|km|mi|abbr=on}} || 19&nbsp;hours || 0.14 (140&nbsp;m) || 217× || <ref>{{cite web |url=http://photojournal.jpl.nasa.gov/catalog/PIA21221 |title=PIA21221: Dawn XMO2 Image 1 |publisher=NASA{{\}}Jet Propulsion Laboratory |date=November 7, 2016 |access-date=November 20, 2016}}</ref><ref name="Dawn Mission Status Updates" /><ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/journal_11_28_16.html |title=Dawn Journal: November 28, 2016 |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=November 28, 2016 |access-date=December 30, 2016}}</ref>
|-
|[[Commons:Category:Dawn Ceres XMO3 phase|XMO3]]|| 6th || December 5, 2016 – February 22, 2017 || {{convert|7520|-|9350|km|mi|abbr=on|disp=br()}} || ≈8&nbsp;days || 0.9 (est) || 34× (est) || <ref name="Dawn Mission Status Updates"/><ref>{{cite web |url=http://dawn.jpl.nasa.gov/mission/journal_12_29_16.html |title=Dawn Journal: December 29, 2016 |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=December 29, 2016 |access-date=December 30, 2016}}</ref>
|-
| XMO4 || 7th || April 22 – June 22, 2017 || {{convert|13830|-|52800|km|mi|abbr=on|disp=br()}} || ≈29&nbsp;days || || || <ref name="status2017">{{cite web |url=http://dawn.jpl.nasa.gov/mission/status_2017.html |title=2017 Mission Status Updates |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=2017}}</ref>
|-
| XMO5 || 8th || June 30, 2017 – April 16, 2018 || {{convert|4400|-|39100|km|mi|abbr=on|disp=br()}} || 30&nbsp;days || || || <ref name="status2017" /><ref name="plansoc20180525">{{cite web |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20180525-dawn-journal-getting-elliptical.html |title=Dawn Journal: Getting Elliptical |publisher=The Planetary Society |first=Marc |last=Rayman |date=May 25, 2018 |access-date=June 5, 2018}}</ref><ref name="nasa20180320">{{cite web |url=https://www.jpl.nasa.gov/blog/2018/3/dear-vernal-dawnquinoxes |title=Dear Vernal Dawnquinoxes |publisher=NASA |first=Marc |last=Rayman |date=March 20, 2018 |access-date=June 5, 2018}}</ref>
|-
|[[Commons:Category:Dawn Ceres XMO6 phase|XMO6]] || 9th || May 14–31, 2018 || {{convert|440|-|4700|km|mi|abbr=on|disp=br()}} || 37&nbsp;hours || || || <ref name="status2018">{{cite web |url=https://dawn.jpl.nasa.gov/mission/status_2018.html |title=2018 Mission Status Archive |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=2018}}</ref>
|-
| [[Commons:Category:Dawn Ceres XMO7 phase|XMO7 (FINAL)]] || 10th || June 6, 2018 – present || {{convert|35|-|4000|km|mi|abbr=on|disp=br()}} || 27.2&nbsp;hours || || || <ref name="MissionStatus2018">{{cite web |last=Rayman |first=Marc |title=Dawn – Mission Status |url=https://dawn.jpl.nasa.gov/mission/status_2018.html |date=August 9, 2018 |work=[[NASA]] |access-date=September 12, 2018 }}</ref><ref name="SFN-20180615">{{cite web |last=Clark |first=Stephen |title=Dawn spacecraft flying low over Ceres |url=https://spaceflightnow.com/2018/06/15/dawn-spacecraft-flying-low-over-ceres/ |date=June 15, 2018 |work=SpaceFlightNow.com |access-date=June 16, 2018 }}</ref><ref name="sfi20180602">{{cite news |url=http://www.spaceflightinsider.com/missions/solar-system/dawn-will-enter-lowest-ever-orbit-around-ceres/ |title=Dawn will enter lowest ever orbit around Ceres |work=Spaceflight Insider |first=Laurel |last=Kornfeld |date=June 2, 2018 |access-date=June 5, 2018}}</ref><ref name="nasa20180429">{{cite web |url=https://www.jpl.nasa.gov/blog/2018/4/dear-isaac-newdawn-charles-dawnwin-albert-einsdawn-and-all-other-science-enthusiasts |title=Dear Isaac Newdawn, Charles Dawnwin, Albert Einsdawn and all other science enthusiasts |publisher=NASA |first=Marc |last=Rayman |date=April 29, 2018 |access-date=June 5, 2018}}</ref>
|}
<gallery class="center">
File:PIA19546-Ceres-DwarfPlanet-Dawn-RC3-image12-20150504.jpg|April 23, 2015<br />'''1st Map Orbit – RC3'''<br />{{convert|13600|km|mi|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres RC3 phase|view on commons]])}}
File:PIA19578-Ceres-DwarfPlanet-Dawn-2ndMappingOrbit-image10-20150614.jpg|June 6, 2015<br />'''2nd Map Orbit – SRVY'''<br />{{convert|4400|km|mi|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres Survey phase|view on commons]])}}
File:PIA19888-Ceres-DwarfPlanet-Dawn-3rdMapOrbit-HAMO-image12-20150821.jpg|August 17, 2015<br />'''3rd Map Orbit – HAMO'''<br />{{convert|915|mi|km|order=flip|sigfig=3|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres HAMO phase|view on commons]])}}
File:PIA20653-Ceres-DwarfPlanet-Dawn-4thMapOrbit-LAMO-image113-20160326.jpg|December 10, 2015<br />'''4th Map Orbit – LAMO'''<br />{{convert|385|km|mi|sigfig=2|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres LAMO phase|view on commons]])}}
File:PIA21248 - Dawn XMO2 Image 28.jpg|October 5, 2016<br />'''5th Map Orbit – XMO2'''<br />{{convert|1480|km|mi|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres XMO2 phase|view on commons]])}}
File:PIA22526-DwarfPlanetCeres-Dawn-OccatorCraterLandslides-20180609.jpg|June 9, 2018<br />'''10th Map Orbit – XMO7'''<br />{{convert|35|km|mi|abbr=on}}<br />{{small|([[Commons:Category:Dawn Ceres XMO7 phase|view on commons]])}}
</gallery>

''Dawn'' entered Ceres orbit on March 6, 2015,<ref name="nbcnews3615">{{cite news |url=http://www.nbcnews.com/science/space/dawn-spacecraft-slips-quietly-orbit-around-dwarf-planet-ceres-n318371 |title=Dawn Spacecraft Slips Quietly Into Orbit Around Dwarf Planet Ceres |work=NBC News |first=Alan |last=Boyle |date=March 6, 2015 |access-date=March 11, 2015}}</ref> four months prior to the arrival of ''New Horizons'' at Pluto. ''Dawn'' thus became the first mission to study a dwarf planet at close range.<ref name="NasaDawn">{{cite web |url=http://www.jpl.nasa.gov/news/news.php?release=2013-347 |title=NASA's Dawn Fills out its Ceres Dance Card |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Jia-Rui |last=Cook |date=December 3, 2013 |access-date=December 8, 2013}}</ref><ref name="Ceresintroduction">{{cite book |chapter=Ceres: Its Origin, Evolution and Structure and Dawn's Potential Contribution |title=The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres |publisher=Springer New York |first1=Thomas B. |last1=McCord |first2=Julie |last2=Castillo-Rogez |first3=Andy |last3=Rivkin |pages=63–76 |date=2012 |doi=10.1007/978-1-4614-4903-4_5 |isbn=978-1-4614-4902-7}}</ref> ''Dawn'' initially entered a [[polar orbit]] around Ceres, and continued to refine its orbit. It obtained its first full topographic map of Ceres during this period.<ref>{{cite web |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/03191629-lpsc-2015-dawn-at-ceres.html |title=LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes |publisher=The Planetary Society |first=Emily |last=Lakdawalla |date=March 19, 2015 |access-date=March 21, 2015}}</ref>

From April 23 to May 9, 2015, ''Dawn'' entered an RC3 orbit (Rotation Characterization 3) at an altitude of {{convert|13,500|km|mi|abbr=on}}. The RC3 orbit lasted 15 days, during which ''Dawn'' alternated taking pictures and sensor measurements and then relayed the resulting data back to Earth.<ref>{{cite web |url=http://dawnblog.jpl.nasa.gov/2014/02/28/dawn-journal-february-28-2014/ |archive-url=https://web.archive.org/web/20140311065323/http://dawnblog.jpl.nasa.gov/2014/02/28/dawn-journal-february-28-2014/ |url-status=dead |archive-date=March 11, 2014 |title=Dawn Journal February 28 |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc |last=Rayman |date=February 28, 2014 |access-date=February 13, 2015}}</ref> On May 9, 2015, ''Dawn'' powered its ion engines and began a month-long spiral descent down to its second mapping point, a Survey orbit, three times closer to Ceres than the previous orbit. The spacecraft stopped twice to take images of Ceres during its spiral descent into the new orbit.

On June 6, 2015, ''Dawn'' entered the new Survey orbit at an altitude of {{convert|4,430|km|mi|abbr=on}}. In the new Survey orbit, ''Dawn'' circled Ceres every three Earth days.<ref>{{Cite web |url=http://www.jpl.nasa.gov/news/news.php?feature=4582 |title=Ceres Animation Showcases Bright Spots |publisher=NASA{{\}}Jet Propulsion Laboratory |last=Landau |first=Elizabeth |date=May 11, 2015 |access-date=May 13, 2015}}</ref> The Survey phase lasted 22 days (7 orbits), and was designed to obtain a global view of Ceres with ''Dawn''{{'s}} framing camera, and generate detailed global maps with the visible and infrared mapping spectrometer (VIR).

On June 30, 2015, ''Dawn'' experienced a software glitch when an anomaly in its orientation system occurred. It responded by going into [[Safe mode (spacecraft)|safe mode]] and sending a signal to engineers, who fixed the error on July 2, 2015.  Engineers determined the cause of the anomaly to be related to the mechanical gimbal system associated with one of ''Dawn's'' ion engines.  After switching to a separate ion engine and conducting tests from July 14 through July 16, 2015, engineers certified the ability to continue the mission.<ref>{{Cite web |url=http://www.jpl.nasa.gov/news/news.php?feature=4659 |title=Dawn Maneuvering to Third Science Orbit |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Elizabeth |last=Landau |date=July 17, 2015 |access-date=July 20, 2015}}</ref>

On August 17, 2015, ''Dawn'' entered the HAMO orbit (High-Altitude Mapping Orbit).<ref>{{Cite web |url=http://www.vofoundation.org/blog/dawn-mission-enters-high-altitude-mapping-orbit-over-ceres |title=Dawn Mission Enters High Altitude Mapping Orbit Over Ceres |work=The Catholic Astronomer |publisher=[[Vatican Observatory]] |first=Bob |last=Trembley |date=August 21, 2015 |access-date=August 28, 2015}}</ref> ''Dawn'' descended to an altitude of {{convert|1,480|km|mi|abbr=on}}, where in August 2015 it began the two-month HAMO phase. During this phase, ''Dawn'' continued to acquire near-global maps with the VIR and framing camera at higher resolution than in the Survey phase. It also imaged in [[Stereoscopy|stereo]] to resolve the surface in 3D.

On October 23, 2015, ''Dawn'' began a two-month spiral toward Ceres to achieve a LAMO orbit (Low-Altitude Mapping Orbit) at a distance of {{convert|375|km|mi|abbr=on}}. Since reaching this fourth orbit in December 2015, ''Dawn'' was scheduled to acquire data for the next three months with its gamma-ray and neutron detector (GRaND) and other instruments that identified the composition at the surface.<ref name="Dawn Mission Status Updates">{{Cite web |url=http://dawn.jpl.nasa.gov/mission/status.html |title=Dawn Mission Status Updates |publisher=NASA{{\}}Jet Propulsion Laboratory |date=October 16, 2015 |access-date=October 17, 2015}}</ref>

Having surpassed its mapping objectives, ''Dawn'' climbed to its fifth science orbit of {{convert|1460|km|mi|abbr=on}} beginning on September 2, 2016, to complete additional observations from a different angle.<ref name="nasa20160831">{{cite web |url=http://www.jpl.nasa.gov/news/news.php?feature=6608 |title=Dawn Sets Course for Higher Orbit |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Elizabeth |last=Landau |date=August 31, 2016 |access-date=November 20, 2016}}</ref> ''Dawn'' began raising its altitude to its sixth science orbit of {{convert|7200|km|mi|abbr=on}} on November 4, 2016, with a goal of reaching it by December 2016. The return to a higher altitude allowed for a second set of data at this altitude, which improves the overall science quality when added to the first batch. However, this time the spacecraft was placed where it was not spiraling and was orbiting in the same direction as Ceres, which reduced propellant consumption.<ref name="nasa20161118">{{cite web |url=http://www.jpl.nasa.gov/news/news.php?feature=6678 |title=New Ceres Views as Dawn Moves Higher |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Elizabeth |last=Landau |date=November 18, 2016 |access-date=November 20, 2016}}</ref>

==Mission conclusion==
A flyby of the asteroid [[2 Pallas]] after the completion of the Ceres mission was suggested but never formally considered; orbiting Pallas would not have been possible for ''Dawn'' due to the high inclination of Pallas's orbit relative to Ceres.<ref>{{cite web |url=http://dawnblog.jpl.nasa.gov/2014/12/29/dawn-journal-december-29/#comment-7392 |archive-url=https://web.archive.org/web/20150101091612/http://dawnblog.jpl.nasa.gov/2014/12/29/dawn-journal-december-29/#comment-7392 |url-status=dead |archive-date=January 1, 2015 |title=Dawn Journal December 29 |publisher=NASA/JPL |date=January 11, 2015 |access-date=March 10, 2015}}</ref>

In April 2016, the ''Dawn'' project team submitted a proposal to NASA for an extended mission that would have seen the spacecraft break orbit from Ceres and perform a flyby of the asteroid [[145 Adeona]] in May 2019,<ref name="ExtendedMission">{{cite news |url=https://www.newscientist.com/article/2085288-nasas-dawn-probe-may-visit-third-asteroid-after-ceres-and-vesta/ |title=NASA's Dawn probe may visit third asteroid after Ceres and Vesta |work=New Scientist |first=Govert |last=Schilling |date=April 20, 2016 |access-date=April 24, 2016}}</ref> arguing that the science gained from visiting a third asteroid might outweigh the returns from staying at Ceres.<ref name="sfnow20160702" /> NASA's Planetary Mission Senior Review Panel, however, declined the proposal in May 2016.<ref name="pmsr2016">{{cite web |url=https://solarsystem.nasa.gov/docs/PMSR2016_Report_Final.pdf |title=Report for Planetary Mission Senior Review 2016 |publisher=NASA |first=J. Douglas |last=McCuistion |date=June 17, 2016 |access-date=June 22, 2017 |archive-url=https://web.archive.org/web/20161222114712/https://solarsystem.nasa.gov/docs/PMSR2016_Report_Final.pdf |archive-date=December 22, 2016 |url-status=dead }}</ref><ref name="verge20160701">{{cite news |url=https://www.theverge.com/2016/7/1/12085358/nasa-ceres-dawn-probe-mission-extension-asteroid-adeona |title=NASA's Dawn spacecraft won't be leaving dwarf planet Ceres |work=The Verge |first=Loren |last=Grush |date=July 1, 2016 |access-date=June 19, 2017}}</ref> A one-year mission extension was approved, but the review panel ordered that ''Dawn'' remain at Ceres, stating that the long-term observations of the dwarf planet, particularly as it approached [[perihelion]], would potentially yield better science.<ref name="sfnow20160702" />

The one-year extension expired on June 30, 2017.<ref name="sfnow20170617">{{cite news |url=https://spaceflightnow.com/2017/06/17/dawn-mission-managers-await-nasa-decision-on-spacecrafts-future/ |title=Dawn mission managers await NASA decision on spacecraft's future |work=Spaceflight Now |last=Clark |first=Stephen |date=June 17, 2017 |access-date=June 19, 2017}}</ref><ref name="nasadawn20170927">{{cite web |url=https://dawn.jpl.nasa.gov/mission/journal_09_27_17.html |title=Dawn Journal |publisher=NASA{{\}}Jet Propulsion Laboratory |first=Marc D. |last=Rayman |date=September 27, 2017}}</ref> The spacecraft was placed in an uncontrolled but relatively stable orbit around Ceres, where it ran out of hydrazine propellant by October 31, 2018,<ref name="NYT-20181101" /> and where it will remain as a "monument" for at least 20 years.<ref name="NASA-20180906">{{cite web |last1=Brown |first1=Dwayne |last2=Wendel |first2=JoAnna |last3=McCartney |first3=Gretchen |title=The Legacy of NASA's Dawn, Near End of Mission |url=https://www.nasa.gov/feature/jpl/the-legacy-of-nasa-s-dawn-near-end-of-mission |date=September 6, 2018 |work=[[NASA]] |access-date=November 2, 2018 |archive-date=September 13, 2018 |archive-url=https://web.archive.org/web/20180913152025/https://www.nasa.gov/feature/jpl/the-legacy-of-nasa-s-dawn-near-end-of-mission/ |url-status=dead }}</ref><ref name="NASA-20181101-EndOfDawnMission">{{cite news |last1=Brown |first1=Dwayne |last2=Wendel |first2=JoAnna |last3=McCartney |first3=Gretchen |title=NASA's Dawn Mission to Asteroid Belt Comes to End |url=https://www.jpl.nasa.gov/news/news.php?feature=7275 |date=November 1, 2018 |work=[[NASA]] |access-date=November 2, 2018 }}</ref><ref name="NYT-20181101">{{cite news |last=Chang |first=Kenneth |title=NASA's Dawn Mission to the Asteroid Belt Says Good Night – Launched in 2007, the spacecraft discovered bright spots on Ceres and forbidding terrain on Vesta. |url=https://www.nytimes.com/2018/11/01/science/nasa-dawn-ceres-vesta-asteroids-end.html |date=November 1, 2018 |work=[[The New York Times]] |access-date=November 2, 2018 }}</ref>
{{multiple image|header=Ceres – some of the last views by the ''Dawn'' spacecraft (September 1, 2018)<ref name="NASA-20180906" /><ref name="NASA-20181101-EndOfDawnMission" /><ref name="NYT-20181101" /> |align=center |caption_align=center |width=400|image1=PIA22769-CeresDwarfPlanet-AhunaMons-LastLooks-20181101.jpg |caption1=[[Ahuna Mons]] |image2=PIA22485-CeresDwarfPlanet-OccatorCrater-LastLooks-20181101.jpg |caption2=[[Occator Crater]]}}

==Media==

===High-resolution image===
[[File:PIA21906-Ceres-DwarfPlanet-HighResolution-Dawn-20170920.jpg|thumb|center|600px|<div class="center">High-resolution view of Ceres taken during its Low-Altitude Mapping Orbit</div>]]

===Ceres atlas images===
{{multiple image |perrow=1/3 |align=center |caption_align=center |width= |direction=horizontal
|image1=PIA20014-Ceres-SurveyAtlas-Overall-June2015.jpg
|caption1=Overall
|width1=700
|image2=PIA20014-Ceres-SurveyAtlas-Kerwan-June2015.jpg
|caption2=Kerwan section<br />([http://photojournal.jpl.nasa.gov/archive/PIA20014_fig2_Kerwan.pdf PDF version])
|width2=200
|image3=PIA20014-Ceres-SurveyAtlas-AsariZadeni-June2015.jpg
|caption3=Asari-Zadeni section<br />([http://photojournal.jpl.nasa.gov/archive/PIA20014_fig1_Asari-Zadeni.pdf PDF version])
|width3=290
|image4=PIA20014-Ceres-SurveyMap-Occator-June2015.jpg
|caption4=Occator section<br />([http://photojournal.jpl.nasa.gov/archive/PIA20014_fig3_Occator.pdf PDF version])
|width4=200
}}

===Maps of Ceres===
<gallery class="center" widths="450px" heights="250px">
File:USGS-Ceres-Nomenclature-20161207.png|Map of Ceres feature names
File:PIA20918-Ceres-Dawn-GlobalMap-Annotated-20160926.jpg|Topographical map of Ceres
</gallery>

===Flyover videos===
<gallery class="center" widths="200px" heights="163px">
File:Video-FlyOver-DwarfPlanet-Ceres--Dawn-20150608.ogv|[[:File:Video-FlyOver-DwarfPlanet-Ceres--Dawn-20150608.ogv|Surface features exaggerated]]
File:PIA20182-Ceres-360Video-20151208.webm|[[:File:PIA20182-Ceres-360Video-20151208.webm|Focus on Occator Crater]]
File:Video-FlightOverDwarfPlanetCeres-20160129.WebM|[[:File:Video-FlightOverDwarfPlanetCeres-20160129.WebM|Flight over dwarf planet Ceres]]
File:CeresDwarfPlanet-OccatorCrater-DawnFlyover-20161215.webm|[[:File:CeresDwarfPlanet-OccatorCrater-DawnFlyover-20161215.webm|Flyover of Occator Crater]]
</gallery>

==See also==
{{Portal| Spaceflight }}
;Features on Ceres
* [[Ahuna Mons]], a mountain on Ceres
* [[Bright spots on Ceres]]
* [[List of geological features on Ceres]]
;Other asteroid missions
* [[List of minor planets and comets visited by spacecraft]]
* [[Chang'e 2]] {{ndash}} [[4179 Toutatis]] flyby
* [[Galileo (spacecraft)#Asteroid encounters|''Galileo'' probe]] {{ndash}} [[951 Gaspra]] and [[243 Ida]] flybys
* ''[[Hayabusa]]'' {{ndash}} [[25143 Itokawa]] rendezvous and sample return
* ''[[Hayabusa2]]'' {{ndash}} [[162173 Ryugu]] rendezvous and sample return
* [[NEAR Shoemaker]] {{ndash}} [[253 Mathilde]] flyby, orbited [[433 Eros]] from 2000 to 2001
* [[OSIRIS-REx]] {{ndash}} [[101955 Bennu]] sample return mission
* ''[[Rosetta (spacecraft)|Rosetta]]'' {{ndash}} [[2867 Šteins]] and [[21 Lutetia]] flyby

==References==
{{Reflist|30em}}

==External links==
{{Commons category|Dawn (spacecraft)}}
* [http://dawn.jpl.nasa.gov/ ''Dawn'' website] by [[Jet Propulsion Laboratory]]
* [https://www.nasa.gov/dawn ''Dawn'' website] by [[NASA]]
* [http://dawndata.igpp.ucla.edu/ ''Dawn'' public data archives] by [[UCLA]]
* [https://www.youtube.com/watch?v=Hth3nKGKTFc ''Dawn'' Legacy – Video (03:04)] by [[NASA]] (September 7, 2018).
* [https://pdssbn.astro.umd.edu/data_sb/missions/dawn/index.shtml ''Dawn Mission Archive''] at the NASA Planetary Data System, Small Bodies Node

; Instruments
* [http://www.mps.mpg.de/3889356/Kameras Framing Cameras] by the [[Max Planck Institute for Solar System Research]]
* [http://www.iaps.inaf.it/solarsystem/vir/ Visual and Infrared Spectrometer] {{Webarchive|url=https://web.archive.org/web/20150402161229/http://www.iaps.inaf.it/solarsystem/vir/ |date=April 2, 2015 }} by the [[Istituto Nazionale di Astrofisica]]
* [http://dawn.jpl.nasa.gov/technology/GRaND_inter.asp Gamma Ray and Neutron Spectrometer] by NASA ([http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2231.pdf journal paper])

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