All of ESA and NASA’s orbiters provide data relay services for surface missions, which currently comprises NASA’s Curiosity rover and Insight lander. The ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO) is a key provider, relaying around 60% of NASA’s Mars surface data to Earth. TGO will be the primary relay for the second ExoMars mission in 2021, which comprises a rover and a surface science platform.