Spacecraft

Psyche combines brains built by NASA with off-the-shelf components used in Earth-orbiting commercial satellites: The main computer, flight software, fault-protection systems, and most of the telecommunications systems come from NASA’s Jet Propulsion Laboratory in Southern California, while a Palo Alto, California, division of Colorado-based Maxar Technologies provided the main body of the spacecraft and most of its engineering hardware systems.

The body, or spacecraft bus, has a rectangular, panel-box construction supported by an internal central cylinder of graphite composite. It is an enhanced, modified version of Maxar’s 1300 satellite bus from a family of long-lasting, powerful communications satellites that have been sent into Earth orbit for more than 30 years but have never gone to deep space.

For this mission, to enable the Maxar bus to support the payload and travel to the cold and dark of the asteroid belt, the spacecraft’s temperature is regulated with thermal blanketing, embedded heat pipes, multilayer insulation, heaters, about 300 temperature sensors, and thermal louvers over the radiator surfaces that open and close like Venetian blinds to release heat and limit cooling.

The full flight system, including the spacecraft’s twin five-panel solar arrays, is about the size of a singles tennis court: 81 feet (24.76 meters) long by 24 feet (7.34 meters) wide. The bus is about 16.1 feet (4.9 meters) tall, including the 6.6-foot (2-meter) booms for two of the instruments; 7.1 feet (2.2 meters) wide; and 7.8 feet (2.4 meters) deep.

Excluding propellant, Psyche is expected to weigh up to 3,563 pounds (1,616 kilograms) at launch.

Propulsion

Similar to NASA’s past Dawn and Deep Space 1 missions, Psyche uses solar electric propulsion, which relies on large solar arrays to generate power for the entire flight system, including the spacecraft’s thrusters. Those thrusters employ a combination of electric and magnetic fields to accelerate and expel charged atoms, or ions, of xenon gas that in turn create thrust as they accelerate rapidly away from the craft, emitting a brilliant blue glow.

Inert and easily ionized, the chemical element xenon exists in the air we breathe in tiny amounts, and it is commonly used in car headlights and plasma TVs. Psyche will carry seven roughly 22-gallon (82-liter) tanks of xenon propellant, totaling 2,392 pounds (1,085 kilograms) – more xenon than any previous space mission.

Compared with conventional chemical propulsion, Psyche’s incredibly efficient solar electric propulsion system uses a much smaller amount of propellant and produces a lower amount of thrust, meaning Psyche’s acceleration toward its target will be slow. Since the thrusters work nearly continuously during the cruise to Psyche, the speed of the spacecraft will continue to increase – to up to 124,000 mph (200,000 kph) relative to Earth – and can exceed what chemical propulsion systems are capable of. Psyche consumes just 0.35 kilograms to 1.3 kilograms of xenon a day, depending on the thruster power level, and the mission will get the equivalent of nearly 10 million miles to the gallon on its long journey.

Psyche will be the first spacecraft to use Hall-effect thrusters beyond lunar orbit. (Dawn and Deep Space 1 used ion thrusters; Psyche’s thrusters are simpler and more powerful.) The four thrusters are located in two pairs on the bottom of the spacecraft bus. Only one thruster will operate at a time, providing up to 240 millinewtons of thrust – about the amount of force that one AA battery would exert on the palm of your hand. Psyche will spend most of its flight time thrusting toward its target. Once at the asteroid, the orbiter will rely on the thrusters to propel itself through four orbits (one of which has two parts) around the asteroid for the mission’s science investigations.

Psyche also has 12 smaller thrusters fueled by a nitrogen cold gas system to help with momentum management around the asteroid and for use when the Hall-effect thrusters aren’t fully functional, like when the spacecraft separates from the rocket, when the solar arrays are deploying, and when the spacecraft is in “safe mode” (a precautionary standby status). The spacecraft will carry three 22-gallon (82-liter) tanks of pressurized nitrogen propellant, or about 101 pounds (46 kilograms).

Spacecraft power is provided by twin five-panel, cross-shaped solar arrays that deploy from opposite sides of the spacecraft and spin around a central axis to point at the Sun. To generate sufficient power when Psyche is more than three times farther from the Sun than Earth is, the arrays must be large: about 800 square feet (75 square meters). Each array measures 37.1 feet (11.3 meters) long and 24 feet (7.3 meters) wide.

The arrays power everything on board, including the science instruments. Near Earth, they will generate 21 kilowatts. But after arriving at Psyche, when the asteroid is farthest from the Sun, they’ll produce about 2.3 kilowatts – a little more than what’s needed to power a hair dryer.

The underlying technology isn’t much different from solar panels installed on a home, but Psyche’s 22,730 ZTJ triple-junction photovoltaic cells, provided by SolAero Technologies of Albuquerque, New Mexico, are hyper-efficient, lightweight, radiation resistant, and able to provide more power with less sunlight.

For more on the solar array deployment timeline after launch, go to the mission overview section.

The spacecraft also carries a 144 amp-hour, 13-cell lithium-ion battery that can supply power when the arrays aren’t in sunlight or when power needs exceed what’s available from the arrays.

Telecommunications

Psyche will communicate with Earth via its four antennas: one 6.5-foot (2-meter) fixed high-gain antenna provided by Maxar and three small low-gain antennas designed and manufactured by JPL. Together, the antennas will provide nearly full sky coverage. Only one antenna can be used at a time.

Like all NASA interplanetary missions, Psyche will send data and receive commands via the agency’s Deep Space Network (DSN), which has three ground stations equidistant around Earth to talk with and track spacecraft. Psyche will rely on the DSN’s 111-foot-wide (34-meter-wide) antennas, communicating in the X-band frequency range, which is on the radio portion of the electromagnetic spectrum. The DSN then routes the data back to Psyche mission controllers through a ground data system at JPL.

While cruising toward the asteroid Psyche, the spacecraft will communicate at least once per week with the DSN. Much more frequent communication will occur as the spacecraft gathers science data and images while orbiting the asteroid.

All Psyche data – navigation, science, and both spacecraft and instrument engineering telemetry – will be transmitted through its antennas to DSN facilities.

Attached to one side of the spacecraft, the Deep Space Optical Communications (DSOC) technology demonstration will send only test data – optical signals that will go to other Earth ground stations. DSOC is physically aligned with the high-gain antenna on the spacecraft so that Psyche can send its radio and DSOC’s optical signals at the same time. More information about DSOC can be found in the DSOC section.