June 26, 2025, TUCSON, Ariz. – After nearly 20 years of operations, NASA’s Mars Reconnaissance Orbiter, or MRO for short, is on a roll, performing a new maneuver to squeeze even more science out of the busy spacecraft as it circles the Red Planet.
Engineers have essentially taught the probe to roll over so that it’s nearly upside down. Doing so enables MRO to look deeper underground as it searches for liquid and frozen water, among other things. The new capability is detailed in a paper published in the Planetary Science Journal, documenting three “very large rolls,” as the mission calls them, performed in 2023 and 2024.
“Not only can you teach an old spacecraft new tricks, you can open up entirely new regions of the subsurface to explore by doing so,” said one of the paper’s authors, Gareth Morgan, a Planetary Science Institute senior scientist living in Washington, D.C.
The orbiter was designed to roll up to 30 degrees in any direction so that it can point its instruments at surface targets. This has enabled MRO to capture images and data on potential landing sites, impact craters and more.
“We’re unique in that the entire spacecraft and its software are designed to let us roll all the time,” said Reid Thomas, MRO’s project manager at NASA’s Jet Propulsion Laboratory in Southern California.
The process isn’t simple. The spacecraft carries five operating science instruments that have different pointing requirements. To target a precise spot on the surface with one instrument, the orbiter has to roll a particular way, which means other instruments may have a less-favorable view of Mars during the maneuver.
That’s why each regular roll has to be planned weeks in advance, with instrument teams negotiating who gets to conduct science and when. An algorithm checks MRO’s position above Mars and automatically commands the orbiter to roll so the appropriate instrument points at the correct spot on the surface. At the same time, the algorithm commands the spacecraft’s solar arrays to rotate and track the Sun and its high-gain antenna to track Earth to maintain power and communications.
Very large rolls, which are 120 degrees, require even more planning to maintain the safety of the spacecraft. The payoff is that the new maneuver enables one particular instrument, called the Shallow Radar, or SHARAD, to have a deeper view of Mars than ever before.
“Ideally, SHARAD’s radar antenna would be pointed toward the ground at all times, but because of concerns about interference with other instruments and limited space on the planet-facing side of the spacecraft, SHARAD was placed on an edge of the space-facing side. In that configuration we get decent signal, but when we roll, we get the spacecraft body out of the way and it greatly boosts our ability to see into the subsurface,” said paper lead author Nathaniel Putzig, PSI’s associate director and a senior scientist living in Golden, Colorado.
Bigger rolls, better science
Designed to peer a little over a mile below ground, SHARAD allows scientists to distinguish between materials like rock, sand and ice. The radar has been especially useful in determining where water ice can be found close enough to the surface that future astronauts might one day be able to dig it up. Ice is important for producing rocket propellant for the trip home as well as for learning more about the climate, geology and potential for life on Mars.
But as great as SHARAD is, the team knew it could be even better.
“The SHARAD instrument was designed for the near-subsurface, and there’s select regions of Mars that are just out of reach for us,” said Morgan, a co-investigator on the SHARAD team. “There is a lot to be gained by taking a closer look at those regions.”
In 2023, the team decided to try developing 120-degree rolls – the very large rolls – that rotate SHARAD’s antenna toward the planet and provide the radio waves an unobstructed path to the surface. What they found is that the maneuver can strengthen the radar signal by 10 times or more, offering a much clearer picture of the Martian underground.
But the roll is so large that the spacecraft’s communications antenna can’t point at Earth, and its solar arrays aren’t able to track the Sun. That’s because the antenna and panels, which rotate on gimbals, are not designed to move to that extent.
“The very large rolls require a special analysis to make sure we’ll have enough power in our batteries to safely do the roll,” Thomas said. “Because the solar panels’ edges could strike the spacecraft’s body, we park them during the roll, so it is very important to carefully plan the maneuver to ensure that there will be sufficient power.”
Given the time involved, the mission limits itself to one or two very large rolls a year. But engineers hope to use them more often by streamlining the process.
“MRO has been doing great science for nearly 20 years,” Putzig said. “Because the spacecraft is long-lived, we accomplished a lot of goals that the mission set out to do. Now, we’ve had the opportunity to propose new and different things we hadn’t done throughout the mission. This is just one of many things this veteran mission is doing that is having a demonstrable impact on science and our understanding of Mars.”
Putzig serves as the U.S. and Deputy Team Leader for SHARAD, which was provided to MRO by the Italian Space Agency, who operate it through a contract to Team Leader Pierfrancesco Lombardo at the Sapienza University of Rome. PSI research scientist Matthew Perry is another SHARAD co-investigator. PSI Senior Research Associate Fritz Foss is a SHARAD team member, as are PSI Research Associates Megan Russell and Aaron Russell.
NASA’s Jet Propulsion Laboratory in Southern California manages MRO for NASA’s Science Mission Directorate in Washington.
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