Sensors Collect Crucial Data on Mars Landings With Arrival of Perseverance MEDLI2 Visible on Mars 2020 Heat Shield: The Mars 2020 spacecraft’s heat shield falls away as the aeroshell descends to Mars on Feb. 18, 2021. The orange cabling seen on the shield is part of a suite of sensors and electronics called MEDLI2, which collects data during the descent that will help engineers land future spacecraft on Mars. Credit: NASA/JPL-Caltech. Download image › MEDLI2 was one of the crucial technologies onboard the rover’s protective aeroshell that helped document the entry, descent, and landing of the spacecraft. “Tango Delta, touchdown confirmed, Perseverance safely on the surface of Mars, ready to begin seeking the signs of past life.” For more than six years, the Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) team has been waiting to hear those words.