NASA’s Psyche Spacecraft Uses Mars Flyby for Gravity Assist and Calibration

The Psyche spacecraft didn’t visit Mars to study the Red Planet, but it used the encounter to “steal” orbital energy. By utilizing Mars as a planet-sized slingshot, the probe increased its velocity without consuming any xenon propellant.

This navigation feat was a prerequisite for the mission’s ultimate goal.

Instrument Calibration and the Martian Bow Shock

While the primary goal was propulsion, the mission team spent a month of approach time treating Mars as a “stunt double” for the target asteroid. This allowed scientists to calibrate sensors under dynamic conditions, ensuring they would function when the craft finally reaches the asteroid belt.

The magnetometer, which has been active since the October 2023 launch, recorded its first celestial body signature during the flyby. It detected an intense uptick in the magnetic field corresponding to the bow shock region—the area where solar wind slams into a planet’s magnetic field. The flyby further calibrated sensors, offering a better look at Mars’ bow shock, which diverts particles around the planet.

This flyby calibration effort validated the instrument’s performance under dynamic conditions while also revealing the fascinating physics of planetary magnetism. — Ben Weiss, Psyche’s deputy principal investigator and the magnetometry investigation lead at Massachusetts Institute of Technology in Cambridge

Similarly, the gamma-ray and neutron spectrometer was put through its paces. This instrument will help scientists determine the chemical elements that make up the asteroid’s surface material by measuring emissions produced when high-energy cosmic rays bombard a planetary body. While the 2,864-mile altitude was too distant to detect gamma rays, the instrument successfully measured a count-rate enhancement of neutrons escaping the Martian surface.

David Lawrence, the science lead for Psyche’s spectrometer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, noted, Around the time of Mars closest approach, the neutron spectrometer detected a count-rate enhancement close to what we anticipated. It was very gratifying to see. He added, As expected, we didn’t detect gamma rays from Mars, but we put the instrument through its paces, and it performed excellently.

Multispectral Imaging of Huygens Crater and Polar Caps

The spacecraft’s multispectral imager captured a series of views that NASA has since processed into a time-lapse video. The sequence opens with the faint crescent of Mars growing steadily larger before gliding over the planet’s sweeping ocher vistas, showing the surface pockmarked with impact craters. Gleaming polar ice caps shine in the sun’s light.

• Huygens Crater: A double-ringed Huygens crater.
• South Polar Cap: Mars’ water-ice-rich, south polar cap, which spans some 700 kilometers.
• Martian Moons: The imager successfully picked out Phobos and Deimos from very far away.

Jim Bell, the Psyche imager instrument lead at Arizona State University, explained that identifying the moons was a part of a practice for the satellite search that we’ll use at the asteroid Psyche to look for any moonlets there.

The Path to a Metallic World in 2029

The spacecraft’s ultimate destination is an asteroid named Psyche, located in the asteroid belt between Mars and Jupiter. Astronomers announce that for the first time ever, we are exploring a world made not of rock or ice, but of metal. Scientists suspect this object may be the debris-blasted iron core of a planetesimal, the building block of planets.

The arrival is scheduled around August 2029 (with another mention of July 2029). During the May 15 flyby, the craft passed only around 4,600 kilometers (2,800 miles) from the red planet’s surface at more than 19,848 kilometers (12,000 miles) per hour.