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'{{DISPLAYTITLE:''CAESAR'' (spacecraft)}} {{Infobox spaceflight |auto=all | name = ''CAESAR'' | names_list = | image = Caesar-sample return concept 2018.png | image_caption = Artist's concept of ''CAESAR'' obtaining a sample from comet 67P | image_size = 275px | mission_type = Sample return | operator = [[NASA]] | COSPAR_ID = | SATCAT = | website = | mission_duration = Planned: {{time interval|August 2024|November 2038|show=ym|sep=,}} | spacecraft_bus = | manufacturer = [[Orbital ATK]] | launch_mass = | landing_mass = | dry_mass = | payload_mass = | dimensions = | power = | launch_date = Planned: August 2024<ref name="SBAG18Squyres">{{cite conference |url=https://www.lpi.usra.edu/sbag/meetings/jan2018/presentations/3-15pm-Squyres.pdf |title=CAESAR: Project Overview |conference=18th Meeting of the NASA Small Bodies Assessment Group. 17-18 January 2018. Ames Research Center, California. |publisher=[[Lunar and Planetary Institute]] |first=Steve |last=Squyres |date=2018}}</ref> | launch_rocket = | launch_site = | launch_contractor = | landing_date = November 2038<ref name="SBAG18Squyres" /> | landing_site = [[Utah Test and Training Range]]<ref name="SBAG18Squyres" /> |interplanetary = {{Infobox spaceflight/IP |type = orbiter |object = Comet [[67P/Churyumov–Gerasimenko]] <!--body visited - e.g. Jupiter, Venus, etc--> |orbits = |arrival_date = January 2029<ref name="SBAG18Squyres" /> |departure_date = February 2032<ref name="SBAG18Squyres" /> |location = |sample_mass = {{convert|100|to|800|g|abbr=on}} }} | programme = [[New Frontiers program]] | previous_mission = [[OSIRIS-REx]] | next_mission = | insignia = | insignia_caption = | insignia_size = }} '''''CAESAR''''' ('''Comet Astrobiology Exploration Sample Return''') is a proposed [[sample-return mission]] to comet [[67P/Churyumov–Gerasimenko]]. The mission was proposed in 2017 to NASA's [[New Frontiers program]] mission 4, and on 20 December 2017 it was one of two finalists selected for further concept development. If selected in July 2019, it may launch between 2024 and 2025, with a capsule delivering a sample to Earth in 2038. The Principal Investigator is [[Steve Squyres]] of [[Cornell University]] in New York. ''CAESAR'' would be managed by NASA's [[Goddard Space Flight Center]] in Greenbelt, Maryland, and the spacecraft built by [[Orbital ATK]] of Dulles, Virginia. The ''CAESAR'' team chose comet 67P over other cometary targets in part because the data collected by the [[Rosetta (spacecraft)|''Rosetta'' mission]] that observed the comet from 2014 to 2016, allows the spacecraft to be designed to the conditions there, which in turn will increase the mission's chance of success.<ref name="nyt20171219">{{cite news |url=https://www.nytimes.com/2017/12/19/science/nasa-new-frontiers-finalists.html |title=Finalists in NASA's Spacecraft Sweepstakes: A Drone on Titan, and a Comet-Chaser |work=[[The New York Times]] |first=Kenneth |last=Chang |date=19 December 2017 |accessdate=8 January 2018}}</ref> The ''Rosetta'' mission also provides a vast scientific context for this mission's sample-return analysis. ==Overview== [[File:Comet 67P on 31 January 2015 - NAVCAM.jpg|thumb|Comet [[67P/Churyumov–Gerasimenko]] as seen by ''Rosetta'' in 2015; ''CAESAR''{{'s}} proposed target]] The two [[New Frontiers program]] mission 4 finalists, announced on 20 December 2017, are [[Dragonfly (spacecraft)|''Dragonfly'']] to Titan, and ''CAESAR''.<ref name="ibtimes">{{cite news |url=http://www.ibtimes.com/nasas-new-frontier-mission-will-search-alien-life-or-reveal-solar-systems-history-2631073 |title=NASA's New Frontier Mission Will Search For Alien Life Or Reveal The Solar System's History |work=International Business Times |first=Elana |last=Glowatz |date=20 December 2017}}</ref> Comet 67P was previously explored by the European Space Agency's [[Rosetta (spacecraft)|''Rosetta'']] probe and its lander [[Philae (spacecraft)|''Philae'']] during 2014-2015 to determine its origin and history. Squyres explained that knowing the existing conditions at the comet, it allows them to design systems that will dramatically improve the chances for success.<ref name="nyt20171219" /> The ''CAESAR'' and ''Dragonfly'' missions will receive {{US$|4 million}} funding each through the end of 2018 to further develop and mature their concepts.<ref name="nyt20171219" /> NASA plans to select one of these proposals in July 2019 to build and launch in 2024 or 2025.<ref name="ibtimes"/><ref name="nyt20171219" /> ===Background=== A comet sample return mission was one of the goals in a list of options for a New Frontiers mission in both the 2003 and 2011 [[Planetary Science Decadal Survey]], which were guiding surveys among those in the scientific community of what and where NASA should prioritize.<ref name="nasa-newfront">{{cite web |url=https://discoverynewfrontiers.nasa.gov/program/index.cfml |title=New Frontiers Program: Overview |publisher=NASA |archiveurl=https://web.archive.org/web/20170126051523/https://discoverynewfrontiers.nasa.gov/program/index.cfml |archivedate=26 January 2017}}</ref> Another comet mission proposal, ''[[Comet Hopper]]'', was one of three [[Discovery Program]] finalists that received {{US$|3 million}} in May 2011 to develop a detailed concept study, however it was not selected.<ref name='Taylor'>{{cite news |url=http://www.tgdaily.com/space-features/55816-nasa-picks-project-shortlist-for-next-discovery-mission |title=NASA picks project shortlist for next Discovery mission |work=Tech Guru Daily |first=Kate |last=Taylor |date=9 May 2011 |accessdate=28 October 2015}}</ref> NASA has launched several missions to comets in the late 1990s and 2000s; these missions include ''[[Deep Space 1]]'' (launched 1998), [[Stardust (spacecraft)|''Stardust'']] (launched 1999), ''[[CONTOUR]]'' (launched 2002 but failed after launch), and [[Deep Impact (spacecraft)|''Deep Impact'']] (launched 2005), as well as some participation on the [[Rosetta (spacecraft)|''Rosetta'']] mission. ===Astrobiology=== Some researchers have speculated that Earth may have been seeded with [[organic compound]]s early in its development by [[tholin]]-rich comets, providing the raw material necessary for [[abiogenesis|life to emerge]].<ref name= "sagan1979">{{cite journal |title=Tholins: organic chemistry of interstellar grains and gas |journal=Nature |first1=Carl |last1=Sagan |author1-link=Carl Sagan |first2=Bishun |last2=Khare |author2-link=Bishun Khare |last-author-amp=yes |volume=277 |issue=5692 |pages=102–107 |date=11 January 1979 |doi=10.1038/277102a0 |bibcode=1979Natur.277..102S}}</ref><ref name="cometary tholins">{{cite journal |title=Production and Chemical Analysis of Cometary Ice Tholins |journal=Icarus |first1=Gene D. |last1=McDonald |first2=Linda J. |last2=Whited |first3=Cynthia |last3=DeRuiter |first4=Bishun N. |last4=Khare |first5=Archita |last5=Patnaik |first6=Carl |last6=Sagan |display-authors=1 |volume=122 |issue=1 |pages=107-117 |date=July 1996 |doi=10.1006/icar.1996.0112 |bibcode=1996Icar..122..107M}}</ref> Tholins were detected by the [[Rosetta (spacecraft)|''Rosetta'']] mission to comet [[67P/Churyumov–Gerasimenko]].<ref>{{cite journal |title=OSIRIS observations of meter-sized exposures of {{chem2|H2O}} ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments |journal=Astronomy & Astrophysics |first1=A. |last1=Pommerol |first2=N. |last2=Thomas |first3=M. R. |last3=El-Maarry |first4=M. |last4=Pajola |first5=O. |last5=Groussin |display-authors=1 |volume=583 |at=A25 |date=November 2015 |doi=10.1051/0004-6361/201525977 |bibcode=2015A&A...583A..25P}}</ref><ref>{{cite journal |url=http://science.sciencemag.org/content/349/6247/aab0673.full |title=CHO-bearing organic compounds at the surface of 67P/Churyumov-Gerasimenko revealed by Ptolemy |journal=Science |first1=I. P. |last1=Wright |first2=S. |last2=Sheridan |first3=S. J. |last3=Barber |first4=G. H. |last4=Morgan |first5=D. J. |last5=Andrews |first6=A. D. |last6=Morse |display-authors=1 |volume=349 |issue=6247 |date=31 July 2015 |doi=10.1126/science.aab0673 |bibcode=2015Sci...349b0673W}}</ref> ==Sample return== The spacecraft will not land on the comet, but would momentarily contact the surface with its TAG (Touch-And-Go) robotic arm. The sampler mechanism on the arm would produce a burst of [[nitrogen]] gas to blow [[regolith]] particles in to the sampler head located at the end of the arm. ''CAESAR'' will collect a total of between {{convert|100|and|800|g|abbr=on}} of regolith from the comet. The maximum pebble size would be {{convert|4.5|cm|in|abbr=on}}.<ref name="SBAG18Squyres"/> The system would separate the [[volatiles]] from the solid substances and preserve the samples for the return trip. The spacecraft would head back to Earth and drop off the sample in a capsule, which would re-enter Earth's atmosphere and parachute down to the surface in 2038.<ref name="nyt20171219" /> A summary presentation by the Principal Investigator shows the spacecraft would perform a specimen collection procedure similar to what NASA's [[OSIRIS-REx]] mission will be doing on an asteroid, including raising the solar arrays into a Y-shaped configuration to minimize the chance of dust accumulation during contact and provide more ground clearance.<ref name="SBAG18Squyres"/> ==Propulsion== [[File:NASA NEXT Ion thruster.712983main NEXT LDT Thrusterhi-res full.jpg|thumb|NASA's Evolutionary Xenon Thruster (NEXT) operation in a vacuum chamber]] The propulsion system on ''CAESAR'' would be NASA's [[NEXT (ion thruster)|NEXT ion thruster]],<ref name="SBAG18Squyres"/> a type of [[solar electric propulsion]]. ==See also== *[[List of missions to comets]] ==References== {{reflist}} {{Astrobiology}} {{Comets}} {{Comet spacecraft}} {{New Frontiers program}} {{Use dmy dates|date=January 2018}} [[Category:Missions to comets]] [[Category:New Frontiers program proposals]] [[Category:Origin of life]] [[Category:Proposed NASA space probes]] [[Category:Proposed astrobiology space missions]]'