Psyche (spacecraft)

Psyche is a NASA Discovery Program space mission launched on October 13, 2023 to explore the origin of planetary cores by orbiting and studying the metallic asteroid 16 Psyche beginning in 2029. NASA's Jet Propulsion Laboratory (JPL) manages the project.

The spacecraft will not land on the asteroid, but will orbit it from August 2029 through late 2031. Psyche uses solar-powered Hall-effect thrusters for propulsion and orbital maneuvering, the first interplanetary spacecraft to use that technology. It's also the first mission to use laser optical communications beyond the Earth-Moon system.

Asteroid 16 Psyche is the heaviest known M-type asteroid, and may be an exposed iron core of a protoplanet, the remnant of a violent collision with another object that stripped off its mantle and crust. On January 4, 2017, the Psyche mission was selected for NASA's Discovery #14 mission. It was launched atop a SpaceX Falcon Heavy rocket.

History
Psyche was submitted by Lindy Elkins-Tanton, a principal investigator at Arizona State University, 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.

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

In June 2022 NASA found that the late delivery of the testing equipment and Guidance, Navigation, and Control (GNC) 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.

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.

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.

On April 18, 2023, JPL's mission page for Psyche was updated to reflect a new launch date of October 5, 2023. On September 28, 2023, the launch was again delayed to no earlier than October 12, 2023, due to an unspecified issue with the spacecraft. After one additional delay due to bad weather, Psyche was launched successfully on October 13, 2023.

An update in May 2024 reported the spacecraft was in good health and on track to complete its mission on the planned timeline along with commencing fire of its xenon thrusters.

Target
16 Psyche is the heaviest known M-type asteroid with a mean diameter of 220 km, and may be an exposed iron core of a protoplanet, the remnant of a violent collision with another object that stripped off its mantle and crust.

Recent studies show that it is "a mixed metal and silicate world". Another study considers it to be either a metal core of a protoplanet or "a differentiated world with a regolith composition … peppered with localized regions of high metal concentrations". Radar observations of the asteroid from Earth indicate an iron–nickel composition.

The historical asteroid symbol for Psyche, a butterfly's wing topped by a star, may have influenced the mission insignia.

Mission overview
The Psyche spacecraft is designed with solar electric propulsion, and the scientific payload includes a multispectral imager, a magnetometer, and a gamma-ray spectrometer.

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.

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.

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.

Science goals and objectives
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.



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 questions this mission aims to 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?
 * 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
Payloads installed on Psyche are:

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

Propulsion


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. The thruster is nominally rated at 4.5 kW operating power, but it will also operate for long durations at about 900 watts. Psyche is the first interplanetary mission to use Hall-effect thrusters, although not the first to use electric thrusters in general.

The SPT-140 (SPT stands for Stationary Plasma Thruster) is a production line commercial propulsion system 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. The SPT-140 thruster was first tested in the US at the Plasmadynamics and Electric Propulsion Laboratory in 1997, and later 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 (located 3.3 astronomical units from Earth) much faster, while consuming less than 10% of the propellant it would need using conventional chemical propulsion.

Power


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.

Laser communications experiment


The spacecraft will also test an experimental laser communication technology called Deep Space Optical Communications (DSOC). It is hoped that the device will increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means. 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 will showcase its capabilities by sending data at up to 2 megabits per second, from distances beyond the orbit 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.

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. It is hoped to advance DSOC to technology readiness level 6. The test-runs of the laser equipment are planned to occur over distances of 0.1 to 2.5 astronomical units (AU) on the outward-bound probe. The first successful test of the system occurred on December 11, 2023 when a cat video of an employee's cat playing with a laser pointer was streamed back to Earth from a distance of 31 million kilometers. The video signal took 101 seconds to reach Earth, sent at the system's maximum bit rate of 267 megabits per second (Mbps). On the night of December 4, the project demonstrated downlink bit rates of 62.5 Mbps, 100 Mbps, and 267 Mbps, which is comparable to broadband internet download speeds. The team was able to download a total of 1.3 terabits of data during that time. As a comparison, NASA's Magellan mission to Venus downlinked 1.2 terabits during its entire mission from 1990 to 1994. During a test on April 8, 2024 the spacecraft transmitted data at a maximum rate of 25 Mbps. The project's goal was proving at least 1 Mbps was possible at the distance of 226 e6km.

Flight hardware
The DSOC flight laser transceiver features 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.

Ground systems
A high-power near-infrared laser transmitter at JPL's Table Mountain facility near Wrightwood, California, acts as an uplink by transmitting a modulated laser beam to the flight transceiver to demonstrate the transmission of low-rate data. The uplink laser also acts as a beacon for the flight transceiver to lock onto. The downlink data sent back by the DSOC transceiver on Psyche is 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.

Launch and trajectory
Psyche's launch period opened at October 5, 2023, with instantaneous launch windows every day until October 25. 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. The launch was delayed an additional day to October 13 due to bad weather.

Psyche launched on October 13, 2023, at 10:19 am EDT, on a Falcon Heavy rocket from Launch Pad 39A at Kennedy Space Center. 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. 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. 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.

The cost of the launch was US$117 million. 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.

Orbit regimes
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.

Psyche is scheduled to enter orbit around 16 Psyche in August 2029. 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. 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.

Its first regime, Orbit A, will see the spacecraft enter a 700 km 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 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 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 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.

Ground stations for laser link
The laser beams from the spacecraft will be received by a ground telescope at Palomar Observatory in California. Laser beams to the spacecraft will be sent from a smaller telescope at JPL Table Mountain Facility.

Testing
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.