16 Psyche is the heaviest known M-type asteroid, and is thought to be the exposed iron core of a protoplanet, the remnant of a violent collision with another object that stripped off its outer crust. Radar observations of the asteroid from Earth indicate an iron–nickel composition. On 4 January 2017, the Psyche mission was selected for NASA's Discovery #14 mission.
Psyche was submitted as part of a call for proposals for NASA's Discovery Program that closed in February 2015. It was shortlisted on 30 September 2015, as one of five finalists and awarded US$3 million for further concept development. One aspect of selection was enduring the "site visit" in which about 30 NASA personnel come and interview, inspect, and question the proposers and their plan.
On 4 January 2017, Lucy and Psyche were selected for the 13th and 14th Discovery missions, respectively, with launch for Psyche set for 2023. In May 2017, the launch date was moved up to target a more efficient trajectory, launching in July 2022 aboard a SpaceXFalcon Heavy launch vehicle and arriving on 31 January 2026 with a Mars gravity assist on 23 May 2023.
Data shows asteroid 16 Psyche to have a diameter of 222 km (138 mi). Scientists think that 16 Psyche could be the exposed core of an early planet that could have been as large as Mars and lost its surface in a series of violent collisions.
Its composition and density match mesosiderite meteorites and it is likely their parent body.
It was proposed that the rocket launch might be shared with a separate mission named Athena, that would perform a single flyby of asteroid 2 Pallas, the third-largest asteroid in the Solar System. In May 2020, it was announced that the Falcon Heavy carrying Psyche would include two smallsat secondary payloads to study the Martian atmosphere and binary asteroids, named EscaPADE (Escape and Plasma Acceleration and Dynamics Explorers) and Janus respectively, but in September 2020, the EscaPADE Mars atmosphere probe was removed from the plan.
The science questions this mission will address are:
Is 16 Psyche the stripped core of a differentiated planetesimal, or was it formed as an iron-rich body? What were the building blocks of planets? Did planetesimals that formed close to the Sun have very different bulk compositions?
If 16 Psyche was stripped of its mantle, when and how did that occur?
If 16 Psyche was once molten, did it solidify from the inside out, or the outside in?
The Psyche's electric propulsion system uses SPT-140 Hall-effect thrusters powered by its solar panels. An early SPT-140 Hall-effect thruster used for ground testing is shown in the top right of this picture.
This mission will use the model SPT-140 engine, a Hall-effect thruster utilizing solar electric propulsion, where electricity generated from solar panels is transmitted to an electric, rather than chemically powered, rocket engine. The thruster is nominally rated at 4.5 kW operating power, but it will also operate for long durations at about 900 watts. Psyche will be the first mission to use Hall-effect thrusters beyond lunar orbit.
The SPT-140 (SPT stands for Stationary Plasma Thruster) is a production line commercial propulsion system  that was invented in Russia by OKB Fakel and developed by NASA's Glenn Research Center, Space Systems Loral, and Pratt & Whitney since the late 1980s. The SPT-140 thruster was first tested in U.S. as a 3.5 kW unit in 2002 as part of the Air Force Integrated High Payoff Rocket Propulsion Technology program. Using solar electric thrusters will allow the spacecraft to arrive at 16 Psyche (at 3.3 astronomical units) much faster while consuming only 10% of the propellant it would need using conventional chemical propulsion.
Electricity will be generated by bilateral solar panels in an X-shaped configuration, with five panels on each side. Prior to the mission being moved forward with a new trajectory, the panels were to be arranged in straight lines, with only four panels on each side of the spacecraft.
Launch and trajectory
The launch is planned for August 2022 on a Falcon Heavy vehicle. The cost of the launch, including secondary payloads, is US$117 million. Psyche will be launched on a trajectory that will perform a gravity assist maneuver past Mars on 23 May 2023, toward the asteroid belt, and intercept the asteroid Psyche.
Psyche will encounter 16 Psyche asteroid and enter orbit on 31 January 2026. The spacecraft would orbit at decreasing altitudes or regimes. Its first regime, Orbit A, will see the spacecraft enter a 700 km (430 mi) orbit for magnetic field characterization and preliminary mapping for a duration of 56 days. It will then descend to Orbit B, set at 290 km (180 mi) altitude for 76 days, for topography and magnetic field characterization. It will then descend to Orbit C, at 170 km (110 mi) altitude for 100 days to perform gravity investigations and continue magnetic field observations. Finally, the orbiter will enter Orbit D, set at 85 km (53 mi) to determine the chemical composition of the surface using its gamma-ray and neutron spectrometers. It will also acquire continued imaging, gravity, and magnetic field mapping. The mission is planned to orbit the asteroid for at least 21 months.
^ ab"FY 2021 President's Budget Request Summary" (PDF). NASA. 10 February 2020. p. 437–439. This article incorporates text from this source, which is in the public domain.
^ abcdLord, Peter W.; van Ommering, Gerrit (2015). Evolved Commercial Solar Electric Propulsion: A Foundation for Major Space Exploration Missions(PDF). 31st Space Symposium, Technical Track, 13-14 April 2015, Colorado Springs, Colorado.
^ abcFoust, Jeff (28 February 2020). "Falcon Heavy to launch NASA Psyche asteroid mission". SpaceNews.
^ abChang, Kenneth (6 January 2017). "A Metal Ball the Size of Massachusetts That NASA Wants to Explore". The New York Times.
^ abElkins-Tanton, L. T.; et al. (2014). Journey to a Metal World: Concept for a Discovery Mission to Psyche(PDF). 45th Lunar and Planetary Science Conference. March 17–21, 2014. The Woodlands, Texas. 1253. Bibcode:2014LPI....45.1253E. LPI Contribution No. 1777.
^Shepard, Michael K. (January 2017). "Radar observations and shape model of asteroid 16 Psyche". Icarus. 281: 388–403. Bibcode:2017Icar..281..388S. doi:10.1016/j.icarus.2016.08.011.
^Grush, Loren (4 January 2017). "In the 2020s NASA will launch spacecraft to study Jupiter's asteroids, and another made of metal". The Verge.
^Brown, Dwayne C.; Cantillo, Laurie (30 September 2015). "NASA Selects Investigations for Future Key Planetary Mission". NASA. Retrieved 1 October 2015. This article incorporates text from this source, which is in the public domain.
^ abValentine, Karin (20 December 2016). "Journey to a metal world". ASU Now. Arizona State University.
^ abBrown, Dwayne C.; Cantillo, Laurie (4 January 2017). "NASA Selects Two Missions to Explore the Early Solar System". NASA. This article incorporates text from this source, which is in the public domain.
^ abMathewson, Samantha (2 March 2020). "NASA picks SpaceX Falcon Heavy to launch Psyche mission to metal asteroid in 2022". Space.com. Retrieved 22 May 2020.
^ abcAgle, D. C.; Russell, Jimi; Cantillo, Laurie; Brown, Dwayne (28 September 2017). "NASA Glenn Tests Thruster Bound for Metal World". NASA. This article incorporates text from this source, which is in the public domain.
^ abKane, Van (19 February 2014). "Mission to a Metallic World: A Discovery Proposal to Fly to the Asteroid Psyche". The Planetary Society.
^Wampler, Stephen (4 November 2015). "Lab-Johns Hopkins team tapped to work on possible NASA effort to explore asteroid". Lawrence Livermore National Laboratory. This article incorporates text from this source, which is in the public domain.
^Ferrais et al. (2020) 'Asteroid (16) Psyche's primordial shape: A possible Jacobi ellipsoid?, Astronomy and Astrophysics 638, L15. https://doi.org/10.1051/0004-6361/202038100
^Lewis, Wendy (26 October 2015). "SSL is JPL Industrial Partner for NASA Asteroid Exploration Mission Opportunity". SSL (company).
^Dorminey, Bruce (10 March 2019). "Proposed NASA SmallSat Mission Could Be First To Visit Pallas, Our Third Largest Asteroid". Forbes.
^The EscaPADE smallsat mission to study the Martian atmosphere has passed PDR, but won't launch with Psyche as originally planned; will be remanifested on a future flight. Jeff Foust, SpaceNews, 14 September 2020
^ abDavid, Leonard (18 October 2017). "Deep Space Communications via Faraway Photons". NASA / Jet Propulsion Laboratory. This article incorporates text from this source, which is in the public domain.
^Greicius, Tony (14 September 2017). "Psyche Overview". NASA. This article incorporates text from this source, which is in the public domain.
^ abHall, Loura, ed. (18 October 2017). ""Lighten Up" – Deep Space Communications via Faraway Photons". NASA. This article incorporates text from this source, which is in the public domain.
^Myers, Roger. "Solar Electric Propulsion: Introduction, Applications and Status" (PDF). Aerojet Rocketdyne.
^ abcJohnson, Ian K.; Kay, Ewan; Lee, Ty; Bae, Ryan; Feher, Negar (2017). New Avenues for Research and Development of Electric Propulsion Thrusters at SSL(PDF). 35th International Electric Propulsion Conference. October 8–12, 2017. Atlanta, Georgia. IEPC-2017-400. Archived from the original (PDF) on 7 January 2018. Retrieved 6 January 2018.
^"Development of the Psyche Mission for NASA's Discovery Program" (PDF). Archived from the original (PDF) on 24 June 2018.
^ abCole, Michael (9 October 2017). "NASA Glenn tests solar electric propulsion thruster for journey to metal world". Spaceflight Insider.
^DeFelice, David (18 August 2015). "NASA – Ion Propulsion". NASA. Retrieved 20 January 2018. This article incorporates text from this source, which is in the public domain.
^ ab"T-140". University of Michigan Plasmadynamics & Electric Propulsion Laboratory. Retrieved 6 January 2018.
^ abcOh, David Y.; Collins, Steve; Goebel, Dan; Hart, Bill; Lantoine, Gregory; Snyder, Steve; Whiffen, Greg; Elkins-Tanton, Linda; Lord, Peter; Pirkl, Zack; Rotlisburger, Lee (2017). Development of the Psyche Mission for NASA's Discovery Program(PDF). 35th International Electric Propulsion Conference, 8-12 October 2017, Atlanta, Georgia. IEPC-2017-153. Archived from the original (PDF) on 24 June 2018. Retrieved 7 January 2018.
^"Native Electric Propulsion Engines Today" (in Russian). Novosti Kosmonavtiki. 1999. Archived from the original on 6 June 2011.
^Delgado, Jorge J.; Corey, Ronald L.; Murashko, Vjacheslav M.; Koryakin, Alexander I.; Pridanikov, Sergei Y. (2014). Qualification of the SPT-140 for use on Western Spacecraft. 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, 28-30 July 2014, Cleveland, Ohio. doi:10.2514/6.2014-3606. AIAA 2014–3606.
^Agle, D. C.; Valentine, Karin; Cantillo, Laurie; Brown, Dwayne C. (24 May 2017). "NASA Moves Up Launch of Psyche Mission to a Metal Asteroid". NASA. This article incorporates text from this source, which is in the public domain.
Wikimedia Commons has media related to Psyche (spacecraft).
Mission website at NASA.gov
Mission website by Arizona State University
Boyle, Alan (10 September 2020). "First Mode wins US$1.8 million contract to build hardware for Psyche mission to asteroid". geekwire.com. Retrieved 28 October 2020.