Psyche (spacecraft)

Artist's illustration depicting the metal-rich asteroid Psyche.

Shape model of asteroid Psyche, with some of the observed surface features indicated.

Differentiation is a fundamental process in shaping many asteroids and all terrestrial planets, and direct exploration of a core could greatly enhance understanding of this process. The Psyche mission aims to characterize 16 Psyche's geology, shape, elemental composition, magnetic field, and mass distribution. It is expected that this mission will increase the understanding of planetary formation and interiors.

Instruments onboard of the spacecraft:[30]
1. Hall-effect thrusters
2. Optical telecommunications system
3. Star trackers
4. Low-gain antenna
5. Sun sensor
6. X-band High-gain antenna
7. Neutron spectrometer
8. Gamma-ray spectrometer
9. Cold gas thrusters
10. -Y Panel
11. Magnetometer
12. Top deck
13. +Y Panel
14. Multispectral imagers (x2)

Specifically, the science goals for the mission are:[31]

• Understand a previously unexplored building block of planet formation: iron cores.
• Look inside terrestrial planets, including Earth, by directly examining the interior of a differentiated body, which otherwise could not be seen.
• Explore a new type of world, made of metal.

The science questions this mission aims to address are:[19][31]

• 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?
• Did 16 Psyche produce a magnetic dynamo as it cooled?
• What are the major alloy elements that coexist in the iron metal of the core?
• What are the key characteristics of the geologic surface and global topography? Does 16 Psyche look radically different from known stony and icy bodies?
• How do craters on a metal body differ from those in rock or ice?

SPT-140 Hall-effect thrusters undergoing testing at NASA's Jet Propulsion Laboratory.

The spacecraft uses ion propulsion. It has four SPT-140 engines, which are Hall-effect thrusters using solar electric propulsion, where electricity generated from solar panels is transmitted to an electric, rather than chemically powered, rocket engine.[23][36][37] The thruster is nominally rated at 4.5 kW operating power,[38] but it will also operate for long durations at about 900 watts.[36] Psyche is the first interplanetary mission to use Hall-effect thrusters, although not the first to use electric thrusters in general.[39]

The SPT-140 (SPT stands for Stationary Plasma Thruster) is a production line commercial propulsion system[3] that was invented in the USSR by OKB Fakel and developed by NASA's Glenn Research Center, Space Systems Loral, and Pratt & Whitney since the late 1980s.[40][41] The SPT-140 thruster was first tested in the US at the Plasmadynamics and Electric Propulsion Laboratory in 1997,[42] and later as a 3.5 kW unit in 2002 as part of the Air Force Integrated High Payoff Rocket Propulsion Technology program.[38][3]

Using solar electric thrusters will allow the spacecraft to arrive at 16 Psyche (located 3.3 astronomical units from Earth) much faster, while consuming less than 10% of the propellant it would need using conventional chemical propulsion.[43]

One of two solar arrays on the spacecraft partially deployed (only horizontally) in JPL's clean room.

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.[44]

DSOC's flight transceiver can be identified by its large tube-like sunshade on the Psyche spacecraft, as seen here inside a clean room at JPL.

The spacecraft will also test an experimental laser communication technology called Deep Space Optical Communications (DSOC).[45] It is hoped that the device will increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means.[45][46] The DSOC experiment is NASA's first demonstration of optical communications beyond the Earth-Moon system. DSOC is a system that consists of a flight laser transceiver, a ground laser transmitter, and a ground laser receiver. New technologies have been implemented in each of these elements. The transceiver is mounted on the Psyche spacecraft. The DSOC technology demonstration will begin shortly after launch and continue as the spacecraft travels from Earth to its gravity-assist flyby of Mars. DSOC operations are planned for one year after launch, with extended-mission opportunities to be evaluated. Palomar Observatory's Hale Telescope will receive the high-rate data downlink from the DSOC flight transceiver.[47][48]

The Discovery program solicitation offered mission projects an extra $30 M if they would host and test the 25 kg DSOC unit, which needs about 75 Watts.[49] It is hoped to advance DSOC to technology readiness level 6.[48] DSOC tests should begin about 60 days after launch. The test-runs of the laser equipment will occur over distances of 0.1 to 2.5 astronomical units (AU) on the outward-bound probe.[48]

The DSOC flight laser transceiver will feature a near-infrared laser transmitter to send high-rate data to the ground system, and a sensitive photon-counting camera to receive a ground-transmitted laser. The transceiver's 8.6-inch (22-centimeter) aperture telescope is mounted on an assembly of struts and actuators that stabilizes the optics from spacecraft vibrations. The flight hardware is fitted with a sunshade and protrudes from the side of the spacecraft, making it one of Psyche's easily identifiable features.[47]

A high-power near-infrared laser transmitter at JPL's Table Mountain facility near Wrightwood, California, will uplink a modulated laser beam to the flight transceiver and demonstrate the transmission of low-rate data. The uplink laser will also act as a beacon for the flight transceiver to lock onto. The downlink data sent back by the DSOC transceiver on Psyche will be collected by the 200-inch (5.1-meter) Hale Telescope at Caltech's Palomar Observatory in San Diego County, California, using a sensitive superconducting nanowire photon-counting receiver to demonstrate high-rate data transfer.[47]

A Falcon Heavy launches Psyche at 10:19 EDT, Oct. 13, 2023

Psyche's launch period opened at October 5, 2023, with instantaneous launch windows every day until October 25.[50] On 28 September, NASA announced that the launch would be delayed by a week due to issues found with the spacecraft's thrusters, moving the launch date from October 5 to October 12.[51] The launch was delayed an additional day to October 13 due to bad weather.[52]

Psyche launched on October 13, 2023, at 10:19 am EDT, on a Falcon Heavy rocket from Launch Pad 39A at Kennedy Space Center.[53][17][15][5] This was the eighth Falcon Heavy launch, and the first one for NASA. The two side boosters used in the mission made their fourth flight; they landed back at Cape Canaveral a few minutes after liftoff, and will be reused on future flights, including the launch of Europa Clipper in 2024. The core stage of the rocket was expended. The Psyche spacecraft was released from the upper stage of the rocket about an hour after liftoff.[54][55] A carrier wave signal from the spacecraft was received by ground controllers just after separation, providing information on spacecraft status prior to solar array deployment.[56] Full communication with the spacecraft was established at 11:50 am EDT. The spacecraft then began a 100-day commissioning phase, during which all systems and instruments are tested and calibrated.[53]

The cost of the launch was US$117 million.[7] Psyche will conduct a gravity assist maneuver at Mars in 2026, which will position the spacecraft for arrival at the target asteroid in August 2029.[1]

Mission plan of Psyche

The approach sequence will begin in May 2029, when the first navigation images and measurements of 16 Psyche will be taken, the asteroid still just a few pixels wide. The spacecraft will then use its electric propulsion system to position itself to be captured by the asteroid's gravity, which is expected to occur in late July 2029. At this point, the first close-up images of 16 Psyche will be taken, with the asteroid appearing about 500 pixels across. Over the next 20 days the spacecraft will maneuver itself to enter the first of four science orbits.[50]

Psyche is scheduled to enter orbit around 16 Psyche in August 2029.[1] The spacecraft will orbit the asteroid at four different altitudes, which are named alphabetically from highest (A) to lowest (D). In the original mission plan, the spacecraft would progress through the orbits sequentially from highest to lowest.[39] After the 2022 launch delay, the mission plan was updated to reflect the new 2029 arrival date, which meant the spacecraft would arrive at the asteroid at a different point in its orbit around the Sun. In the new mission plan, Psyche will initially enter Orbit A, then descend to Orbit B1, then Orbit D, back out to Orbit C, and finally it will move out to Orbit B2 (the second portion of Orbit B). This redesign ensures that the asteroid's surface is correctly illuminated by the Sun during Orbit B.[57][58]

Orbital operations of Psyche

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 303 km (188 mi) altitude for 92 days, for topography and magnetic field characterization. It will then descend to Orbit D, which is the lowest orbit at 75 km (47 mi) and is also uniquely inclined to allow direct view of the asteroid's equator (compared to the other orbits that go around its poles), for 100 days to determine the chemical composition of the surface using its gamma-ray and neutron spectrometers. After that it will ascend to Orbit C at 190 km (120 mi) altitude for 100 days to perform gravity investigations and continue magnetic field observations. Finally, the orbiter will return to Orbit B for 100 days, to finish mapping the portion of the asteroid's surface that was under darkness during the first portion of Orbit B. It will also acquire continued imaging, gravity, and magnetic field mapping. In total, the prime mission is expected to last 26 months, ending in November 2031. At the end of the mission, the spacecraft will be left in orbit around the asteroid.[59][50][39][60]

Animation of Psyche

Around the Sun

Around 16 Psyche

   Psyche  ·    16 Psyche ·    Earth ·    Mars ·    Sun

The laser beams from the spacecraft will be received by a ground telescope at Palomar Observatory in California.[48] Laser beams to the spacecraft will be sent from a smaller telescope at JPL Table Mountain Facility.[48]

Psyche's thruster integration underway

Testing began on the spacecraft in December 2021. These tests included but were not limited to electromagnetic testing and TVAC, or thermal vacuum chamber testing. The electromagnetic testing was conducted to ensure that the electronics and magnetic components that make up the spacecraft will not interfere with each other while conducting the mission. The TVAC testing was conducted inside the 85- by 25-foot vacuum chamber at JPL's facility in Southern California, which replicates the lack of air in space. This allows for the engineers and scientist to observe the effects of the space environment on the orbiter. Inside the TVAC, the JPL employees can observe how well the spacecraft reacts to harsh conditions. Without air surrounding the spacecraft, the heating and cooling of the unit is affected. The spacecraft will be hot in the hours after launch, while it is still close to Earth and facing the Sun, especially with its electronics running, and later, when the spacecraft gets farther from the Sun, it faces intense cold, especially when flying in 16 Psyche's shadow. Vibration tests of the spacecraft by scientists and engineers ensure it can survive the extreme conditions of the rocket launch. They also performed shock testing to ensure the spacecraft could survive the shock of separation from the rocket's second stage. Finally, they performed acoustic testing on the craft. The sound of the launch can be so violent that it can damage the hardware, so intense acoustic testing was performed to ensure mission success.[61]