Solar wings to fly to Psyche asteroid

The National Aeronautics and Space Administration March 7 reported the nearing launch of its 11-year Psyche project, with the assemblage of its massive solar panels that will power the spacecraft through its nearly four-year journey.

Scheduled to launch on Aug. 1, the Psyche spacecraft will travel 1.5 billion miles to a mysterious, metal-rich asteroid of the same name.

"Seeing the spacecraft fully assembled for the first time is a huge accomplishment; there's a lot of pride," said Brian Bone, lead on assembly, testing, and launch operations for the mission at NASA's Jet Propulsion Laboratory in Southern California. "This is the true fun part. You're feeling it all come together. You feel the energy change and shift."

At 800-square-feet (75-square-meters), the five-panel, cross-shaped solar arrays are the largest ever installed at JPL, which has built many spacecraft over the decades.

When these arrays fully deploy in flight, the spacecraft will be about the size of a single tennis court, and after a three and a half year solar-powered cruise, the craft will arrive in 2026 at the asteroid Psyche – a 173-mile- (280 kilometers) wide space rock thought to be unusually rich in metal. Once there, it will spend two years making increasingly close orbits of the asteroid to study it.

Venturing to the asteroid belt between Mars and Jupiter, far from the Sun, presents challenges for a mission of this magnitude, especially when considered its solar-powered propulsion.

Near Earth, the specialized solar arrays are able to generate upwards of 21 kilowatts – enough electricity to power three or four average U.S. homes. But once at Psyche, with such distant sunlight, they'll produce at most 2 kilowatts – sufficient for little more than a hairdryer.

"The underlying technology isn't much different from solar panels installed on a home, but Psyche's are hyper-efficient, lightweight, radiation-resistant, and able to provide more power with less sunlight," said Peter Lord, Psyche technical director at Maxar Technologies in Palo Alto, California, where the arrays and solar electric propulsion chassis were built. "These arrays are designed to work in low-light conditions, far away from the Sun," he added.

Only the three center panels on each five-panel, cross-shaped array can be deployed at JPL due to the limitations of the gravity-offload fixture and the opposing direction of rotation of the cross panels. Deployment of the two cross panels was previously performed at Maxar with different equipment.

After further spacecraft testing is completed at JPL, the arrays will be removed and returned to Maxar in order to repeat the cross-panel deployments, make any final repairs to the solar cells, and test overall performance. The arrays then get shipped from Maxar to NASA's Kennedy Space Center in Florida, where they will be reintegrated onto the spacecraft in preparation for launch in August.

About an hour after launch, Psyche will deploy the arrays sequentially, first unfolding the three lengthwise center panels, then the two cross panels on one wing before repeating the process with the other wing. Each array takes about seven and a half minutes to unfurl and latch into place.

Once deployed, the solar array will provide all the power for the journey to asteroid Psyche, as well as the power needed to operate the scientific instruments aboard: a magnetometer to measure any magnetic field the asteroid may have, imagers to photograph and map its surface, and spectrometers to reveal the composition of that surface.

What these instruments relay to scientists 1.5 billion miles back on Earth will help them better understand the nature of such a peculiar celestial body. Postulates regarding its makeup include the explanation that Psyche could very well have existed during the formation of the Solar System, either as a remnant core material from a planetesimal – one of the building blocks of rocky planets – or as primordial material that never melted during the Big Bang.

This mission aims to find out and help answer fundamental questions about Earth's own metal core and the formation of our universe.