BY NASA'S JET PROPULSION LABORATORYJULY 9, 2025

NASA's Mars Reconnaissance Orbiter has learned to pull off daring 120-degree rolls that give its SHARAD radar ten-times-stronger echoes, exposing hidden ice and geology more than a mile underground.

Engineers painstakingly schedule these flips to keep solar arrays powered and antennas linked while juggling five competing instruments. The fresh trick revives a 19-year-old spacecraft, even helping the Mars Climate Sounder stay in action after its pivot failed, and promises a richer view of the Red Planet's resources, climate, and past habitability.

After nearly 20 years of exploring Mars, NASA's Mars Reconnaissance Orbiter (MRO) is proving it still has a few surprises left. Engineers have recently taught the spacecraft a bold new move, rolling nearly upside down, to unlock a deeper view beneath the Martian surface. This new maneuver allows MRO to search even more effectively for signs of liquid and frozen water, along with other buried features that could reveal Mars' hidden history.

The breakthrough is highlighted in a new paper published in the Planetary Science Journal, which describes three of these dramatic "very large rolls" carried out between 2023 and 2024.

Teaching the Orbiter New Moves

"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 of the Planetary Science Institute in Tucson, Arizona.

MRO was originally built to roll up to 30 degrees in any direction, allowing it to aim its instruments at features like impact craters, ancient riverbeds, and potential landing sites. But now, engineers have pushed it even further.

"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 (JPL) in Southern California.

Coordinating Complex Spacecraft Rolls

The process for rolling 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 the other instruments may have a less-favorable view of Mars during the maneuver.

That's why each regular roll is planned weeks in advance, with instrument
teams negotiating who conducts science and when. Then, 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 (SHARAD), to have a deeper view of Mars than ever before.

Sharper Radar Insights Underground

Designed to peer from about half a mile to a little over a mile (1 to 2 kilometers) belowground, SHARAD allows scientists to distinguish between materials like rock, sand, and ice. The radar was especially useful in determining where ice could be found close enough to the surface that future astronauts might one day be able to access it. Ice will be key for producing rocket propellant for the trip home and is important for learning more about the climate, geology, and potential for life at Mars.

But as great as SHARAD is, the team knew it could be even better.

Overcoming Signal Interference

To give cameras like the High-Resolution Imaging Science Experiment (HiRISE) prime viewing at the front of MRO, SHARAD's two antenna segments were mounted at the back of the orbiter. While this setup helps the cameras, it also means that radio signals SHARAD pings onto the surface below encounter parts of the spacecraft, interfering with the signals and resulting in images that are less clear.

"The SHARAD instrument was designed for the near-subsurface, and there are 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 very large rolls to 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 is not pointed at Earth, and its solar arrays aren't able to track the Sun.

"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.

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.

Climate Sounder Adapts to Rolls

While SHARAD scientists are benefiting from these new moves, the team working with another MRO instrument, the Mars Climate Sounder, is making the most of MRO's standard roll capability.

The JPL-built instrument is a radiometer that serves as one of the most detailed sources available of information on Mars' atmosphere. Measuring
subtle changes in temperature over the course of many seasons, Mars Climate Sounder reveals the inner workings of dust storms and cloud formation. Dust and wind are important to understand: They are constantly reshaping the Martian surface, with wind-borne dust blanketing solar panels and posing a health risk for future astronauts.

Mars Climate Sounder was designed to pivot on a gimbal so that it can get views of the Martian horizon and surface. It also provides views of space, which scientists use to calibrate the instrument. But in 2024, the aging gimbal became unreliable. Now Mars Climate Sounder relies on MRO's standard rolls.

"Rolling used to restrict our science," said Mars Climate Sounder's
interim principal investigator, Armin Kleinboehl of JPL, "but we've incorporated it into our routine planning, both for surface views and calibration."

Reference: "SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft" by Nathaniel E. Putzig, Gareth A. Morgan, Matthew R. Perry, Bruce A. Campbell, Jennifer L. Whitten, Fabrizio Bernardini, Alessandro DiCarlofelice, Piero Tognolatti and Pierfrancesco Lombardo, 11 June 2025, The Planetary Science Journal.

NASA's Mars Reconnaissance Orbiter (MRO) is a long-running spacecraft mission dedicated to studying the Red Planet from orbit. Launched in 2005 and managed by NASA's Jet Propulsion Laboratory (JPL) in Southern California for the agency's Science Mission Directorate, MRO is part of NASA's broader Mars Exploration Program. It plays a key role in analyzing Mars' surface, atmosphere, and subsurface using a suite of advanced instruments.

One of MRO's standout tools is SHARAD (Shallow Radar), which probes beneath
the Martian surface to detect features like ice and rock layers. Provided by the Italian Space Agency and operated by Sapienza University of Rome, SHARAD is a collaborative effort analyzed by a joint U.S.-Italian science team, with U.S. participation led by the Planetary Science Institute in Tucson, Arizona.

Lockheed Martin Space, based in Denver, built the orbiter and continues to support its operations, ensuring the spacecraft's longevity and scientific productivity well into its second decade.

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