Artist's rendering of the Psyche spacecraft
|Mission type||Asteroid orbiter|
|Operator||NASA · ASU|
|Website||NASA: www.nasa.gov/psyche |
|Mission duration||Cruise: 3.5 years |
Science: 21 months in orbit (2026–2027)
|Launch mass||2,608 kg (5,750 lb)|
|Start of mission|
|Launch date||August 2022|
|Flyby of Mars|
|Closest approach||May 23, 2023|
|Distance||500 km (310 mi)|
|16 Psyche orbiter|
|Orbital insertion||January 31, 2026|
Psyche mission insignia
Psyche is a planned orbiter mission that will explore the origin of planetary cores by studying the metallic asteroid 16 Psyche. 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.
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 January 4, 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 September 30, 2015, as one of five finalists and awarded $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 January 4, 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 August 2022 and arriving in January 31, 2026 with a Mars gravity assist in May 23, 2023.
Data shows asteroid 16 Psyche to have a diameter of about 252 km (157 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.
The mission will launch in August 2022 and arrive in four years to perform 21 months of science. The spacecraft will be built by NASA JPL in collaboration with SSL (formerly Space Systems/Loral) and Arizona State University.
Science goals and objectives
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 will 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 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 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?
- 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?
- The Multispectral Imager will provide high-resolution images using filters to discriminate between metallic and silicate constituents.
- The Gamma-ray and Neutron Spectrometer will analyze and map the asteroid's elemental composition.
- The Magnetometer will measure and map the remnant magnetic field of the asteroid.
- The X-band Gravity Science Investigation will use the X-band (microwave) radio telecommunications system to measure the asteroid's gravity field and deduce its interior structure.
The spacecraft will also test an experimental laser communication technology called Deep Space Optical Communications. It is hoped that the device will be able to increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means. The laser beams from the spacecraft will be received by a ground telescope at Palomar Observatory in California.
|Power||Max: 4.5 kW|
Min: 900 W
At 16 Psyche: ≤ 1 kW
|Specific impulse (Isp)||1800 s|
|Total impulse||8.2 MN·s|
|Thrust||280 mN |
|Thruster mass||8.5 kg|
|Propellant mass||≈ 425 kg of xenon|
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.
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 US 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. Psyche will be launched on a trajectory for a flyby of Mars on May 23, 2023 to perform a gravity assist maneuver toward the asteroid belt, and intercept the asteroid Psyche.
Psyche will encounter 16 Psyche asteroid and enter orbit on January 31, 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.
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- Mission website at NASA.gov
- Mission website by Arizona State University