Innovative Technology Reveals Martian Atmosphere

An antenna on ExoMars’ Trace Gas Orbiter has been repurposed to help researchers explore new areas of the Martian atmosphere. Using this modified equipment, a team including researchers from Imperial College London has investigated previously unreachable regions of Mars’ atmosphere. These areas, which can obstruct radio signals, are vital for future Mars habitation missions.

The ExoMars Trace Gas Orbiter (TGO) collaborated with another ESA spacecraft, Mars Express (MEX), to carry out this research. The two spacecraft maintain a radio link, allowing radio waves to penetrate the deeper layers of Mars’ atmosphere as one spacecraft moves behind the planet. Jacob Parrott, a PhD student from the Department of Physics at Imperial and lead author of the study, explained:

“The systems on MEX and TGO were not initially designed to do this – the radio antennas we used were made for communication between orbiters and rovers on the planet’s surface. We had to reprogramme them whilst inflight to carry out this new science.”

Parrott added, “This innovative technique is likely to be a game-changer for future missions, proving that mutual radio occultation between two orbiting spacecraft is an economical way to extract more scientific value from existing equipment.”

Mutual radio occultation offers several advantages over traditional methods of studying Mars’ atmosphere. First, it allows researchers to gather measurements at any time of day, rather than being limited to sunrise and sunset periods as is the case with Earth-based observations. This expanded window enables scientists to explore the atmospheric conditions around noon and midnight for the first time.

Additionally, mutual occultation is not constrained by the “occultation seasons” that impact measurements relying on a link to Earth stations. These seasons arise from the spacecraft’s orbit, restricting the periods when observations are feasible. For instance, Mars Express could only perform radio occultation for two months in 2022 due to such limitations.

By using the unique geometry of two orbiting spacecraft, mutual occultation overcomes these temporal restrictions, enabling more frequent and comprehensive atmospheric sampling. As Dr. Colin Wilson, Project Scientist for the ExoMars Trace Gas Orbiter and Mars Express at ESA, stated:

“ESA has now demonstrated the viability of this technique, which could be transformational for Mars science in the future. There are currently seven spacecraft orbiting Mars; as the number of spacecraft increases, as it will in coming decades, the number of radio occultation opportunities increases rapidly. Therefore, this technique will be an increasingly important tool for studying Mars.”

Furthermore, traditional radio occultation measurements are confined to specific locations relative to Earth’s movement, making it challenging to capture global atmospheric changes on Mars. In contrast, mutual occultation allows for exploration of the entire depth of Mars’ ionosphere, a charged layer of the upper atmosphere, providing a more comprehensive understanding of its atmospheric dynamics.