Psyche (spacecraft)

Psyche is a planned orbiter mission to explore the origin of planetary cores by studying the metallic asteroid of the same name.[7] Lindy Elkins-Tanton of Arizona State University is the principal investigator who proposed this mission for NASA's Discovery Program. NASA's Jet Propulsion Laboratory (JPL) will manage the project.

For other uses, see Psyche (disambiguation).

Psyche
An illustration of the Psyche spacecraft
Mission typeAsteroid orbiter
Operator
Website
Mission durationCruise: 5 years, 10 months (planned)[1]
Science: 21 months in orbit
Spacecraft properties
SpacecraftPsyche
ManufacturerMaxar Technologies[2]
Launch mass2,608 kg (5,750 lb) [3]
Dry mass1,648 kg (3,633 lb) [4]
Payload mass30 kg (66 lb)
Power4.5 kW
Start of mission
Launch dateOctober 5, 2023 (planned)[5]
RocketFalcon Heavy[6]
Launch siteKennedy Space Center, LC-39A
ContractorSpaceX
16 Psyche orbiter
Orbital insertionAugust 2029[1]

Psyche mission patch
 

16 Psyche is the heaviest known M-type asteroid, and was once thought to be the exposed iron core of a protoplanet,[8] the remnant of a violent collision with another object that stripped off its mantle and crust. Numerous recent studies have all but ruled that out.[9][10][11] Radar observations of the asteroid from Earth indicate an iron–nickel composition.[12] On January 4, 2017, the Psyche mission was selected for NASA's Discovery #14 mission,[13] and launch was scheduled for no earlier than September 20, 2022,[14] but the Psyche launch was postponed.[15] Psyche is scheduled to launch no earlier than October 5, 2023.[5]

History
Main article: Selection of Discovery Mission 13 and 14

Psyche was submitted as part of a call for proposals for NASA's Discovery Program that closed in February 2015. It was shortlisted on September 30, 2015, as one of five finalists and awarded US$3 million for further concept development.[7][16]

On January 4, 2017, Psyche was selected for the 14th Discovery mission, with launch set for 2023.[17] In May 2017, the launch date was moved up to target a more efficient trajectory, launching in July 2022 aboard a SpaceX Falcon Heavy launch vehicle and arriving on January 31, 2026, following a Mars gravity assist on May 23, 2023.[18]

In June 2022 NASA found that the late delivery of the testing equipment and flight software for the Psyche spacecraft did not give them enough time to complete the required testing, and decided to delay the launch, with future windows available in 2023 and 2024 to rendezvous with the asteroid in 2029 and 2030, respectively.[19]

On October 28, 2022, NASA announced that Psyche was targeting a launch period opening on October 10, 2023, which would correspond with an arrival at the asteroid in August 2029.[1]

On April 18, 2023, JPL's mission page for Psyche was updated to reflect a new launch date of October 5, 2023.[5]

An independent review of the delays at JPL reported in November 2022 found understaffing, insufficient planning, and communications issues among engineers and with management. The VERITAS Venus mission was delayed to free up staff to focus on Psyche.[20]

Mission overview

The Psyche spacecraft is designed with solar electric propulsion,[21][22] and the scientific payload includes a multispectral imager, a magnetometer, and a gamma-ray spectrometer.[22][23]

The mission is designed to perform 21 months of science. The spacecraft was built by NASA Jet Propulsion Laboratory (JPL) in collaboration with SSL (formerly Space Systems/Loral) and Arizona State University.[1][24]

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.[25] 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,[18] but in September 2020, the EscaPADE Mars atmosphere probe was removed from the plan.[26] Janus was later removed from the Psyche mission as well on November 18, 2022, after an assessment determined that it would not be on the required trajectory to meet its science requirements as a result of Psyche’s new launch period.[27]

Science goals and objectives
Illustration depicting the metal-rich asteroid Psyche.
Shape model of asteroid Psyche, with some of the observed surface features indicated.

Differentiation was 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:[28]
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:

  • 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 objectives are:

  • Determine whether 16 Psyche is a core, or if it is unmelted material.
  • Determine the relative ages of regions of 16 Psyche's surface.
  • Determine whether small metal bodies incorporate the same light elements as are expected in the Earth's high-pressure core.
  • Determine whether 16 Psyche was formed under conditions more oxidizing or more reducing than Earth's core.
  • Characterize 16 Psyche's topography.

The science questions this mission aims to address are:[8]

  • 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?

Instruments

Psyche will fly a payload of 30 kg (66 lb),[3] consisting of four scientific instruments:[29]

Spacecraft

The spacecraft bus is the Space Systems Loral (SSL) 1300 platform.[30] JPL added the command and data handling and telecom subsystems and all flight software.[30]

Propulsion
SPT-140 Hall-effect thrusters undergoing testing at NASA's Jet Propulsion Laboratory.
SPT-140Parameter/units [31][32]
TypeHall-effect thruster
Power [30]Max: 4.5 kW
Min: 900 watts
Specific impulse (Isp)1800 seconds
Thrust280 mN[32]
Thruster mass8.5 kg
Propellant mass922 kg of xenon[33]
Total impulse8.2 MN·s (for Psyche)

This mission will use four of 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.[21][34][35] The thruster is nominally rated at 4.5 kW operating power,[36] but it will also operate for long durations at about 900 watts.[34] Psyche will be the first mission to use Hall-effect thrusters beyond lunar orbit.[37]

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.[38][39] 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.[36][3]

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.

Power
One of two solar arrays on the spacecraft deployed in JPL's clean room.
Solar panelsParameter/units [31][32]
TypeTriple-Junction Solar Cells[30]
PowerSolar array performance: At Earth: 20 kW
At 16 Psyche: 2.3 kW [30]

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.[40]

Laser communications experiment
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).[41] It is hoped that the device will be able to increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means.[41][42] Deep Space Optical Communications (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.[43][44]

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.[45] It is hoped to advance DSOC to TRL 6.[44] 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.[44]

Flight hardware: 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.[43]

Ground systems: A high-power near-infrared laser transmitter at the Jet Propulsion Laboratory'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.[43]

Operations
Psyche mission plan: 1: launch (August 2022) 2: Beginning of tests of the DSOC experimental laser communication system (blue dots) 3: Gravitational assistance from Mars (May 2023) 4: and 5: Solar conjunction 6: Insertion into orbit around Psyche (January 2026) 7: Solar conjunction 8: End of the mission (October 2027)[46]

Launch and trajectory

As of April 2023, Psyche is scheduled to launch no earlier than October 5, 2023, on a Falcon Heavy vehicle.[5] The cost of the launch is US$117 million.[6] 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]

Orbit regimes
This illustration shows how the spacecraft will explore asteroid Psyche, starting with a high-altitude Orbit A and gradually lowering into Orbit D as it conducts its science investigation.

Psyche is scheduled to enter orbit around 16 Psyche in August 2029.[1] The spacecraft would orbit at decreasing altitudes or regimes.[37] Its first regime, Orbit A, would see the spacecraft enter a 700 km (430 mi) orbit for magnetic field characterization and preliminary mapping for a duration of 56 days. It would then descend to Orbit B, set at 290 km (180 mi) altitude for 76 days, for topography and magnetic field characterization. It would 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 expected to orbit the asteroid for at least 21 months.[37][47]

The laser beams from the spacecraft will be received by a ground telescope at Palomar Observatory in California.[44] Laser beams to the spacecraft will be sent from a smaller telescope at JPL Table Mountain Facility.[44]

Construction and pre-launch testing

Testing
Psyche's thruster integration underway

Testing began on the spacecraft in December 2021. These tests include but are not limited to electromagnetic testing and TVAC, or thermal vacuum chamber testing. The electromagnetic testing is 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, when it’s 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 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.[48]

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