Arizona Researchers Turn Mars Orbiter Upside Down To Study Phobos
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The Mars Odyssey orbiter has been observing the Red Planet since October 2001.
Now, Arizona researchers are making it do backflips to observe Mars's largest moon, Phobos.
Jonathan Hill is a mission planner at Arizona State University's space flight facility, where he tells ASU's visible and infrared camera, THEMIS (Thermal Emission Imaging System), what to do each day.
Hill said putting the orbiter through such tricky maneuvers to view Phobos and Deimos, Mars's smaller moon, was definitely not part of Odyssey's original plan.
"But after a decade and a half, really, in orbit around Mars, NASA was pushing us to come up with some new and different science," he said.
The flip, which requires six weeks to calculate, was programmed by Lockheed Martin in Denver and driven by Jet Propulsion Laboratory in Southern California, which leads the Mars Odyssey mission.
It involves not only photographing an object moving perpendicular to Odyssey's orbit, but also arranging for the orbiter to pass the moon at just the right speed.
"The THEMIS camera works on the assumption that it's orbiting over Mars, and it actually uses its velocity past Mars to build up images. So when we look at something like Phobos, we actually have to get Odyssey to rotate past it at the same angular speed as we go over the surface of Mars," said Hill.
The team previously had observed Phobos during its eight-hour day cycle.
By pointing THEMIS at Phobos during different eclipse phases, when the 16-mile-wide moon swings rapidly between 81 and -189 Fahrenheit, researchers hoped to better understand its composition and possibly learn whether it broke off Mars or was captured.
Hill says that meant analyzing its makeup, which they now know shares a trait with Earth's moon: dust.
"When the Apollo astronauts were walking around, they were kicking up that really fine powdery dust. So Phobos is very similar on the surface," he said.
Christopher Edwards of Northern Arizona University led the processing and analysis of the Phobos images.
In a release, Edwards called the moon's origins "enigmatic," explaining that its orbital position and instability have led some to suggest it has repeatedly been destroyed and reformed.
Phobos's orbit seems to conflict with the capture hypothesis, though, so some have proposed it was blasted from Mars's surface by a meteorite. Once in orbit, the bits and pieces clumped together to form Phobos.
In coming months, Odyssey will observe Phobos's crescent phases to gain a fuller sense of its heating characteristics as it rotates.
Thereafter, the mission faces a financially uncertain future. Hill says the White House budget for fiscal year 2021 provides just enough funding to close out the mission and keep Odyssey in a stable orbit, but little else.
