MEDLI2 data shines light on Perseverance rover entry, descent, and landing

NASA's Perseverance rover was successfully placed on the surface of Mars on February 18, 2021. On that date, the rover began exploring Mars. One of the crucial technologies aboard the protective aeroshield that helped document the entry, descent, and landing (EDL) of the spacecraft is MEDLI2. All of the MEDLI2 data was stored on Perseverance for transmission to Earth after a successful landing.

MEDLI2's job was to collect critical data about the environment during entry into the planet's atmosphere. The system had three types of sensors, including thermocouples, heat flux sensors, and pressure transducers. Those sensors were designed to measure extreme heat and pressure during entry.

The system also had electronics and hardware for recording thermal and pressure loads experienced during entry and parachute deployment. MEDLI2 used measurements gathered to determine the heating and atmospheric forces that occurred on the heat shield and backshell. Together those components comprised the aeroshell that housed and protected the Perseverance rover during the trip to Mars and EDL.

Mission controllers powered MEDLI2 on five hours before the rover began the descent to the surface of Mars, known as "7 Minutes of Terror." Powering the systems on five hours ahead of entry allowed the electronics to stabilize temperature and measure internal conditions before entry. The system activated successfully, and the team was able to monitor incoming data throughout the five-hour coast phase before entry.

Most of the sensors and primary electronics were mounted to the Mars 2020 heatshield. About 10 seconds after the supersonic parachute was deployed, MEDLI2 was powered down for the last time with its job completed. MEDLI2 systems were turned off a few seconds before the heatshield separated to prevent any potential power issues from occurring. Three days after a successful landing, all remaining MEDLI2 data was transmitted back to Earth. Researchers are currently working on data analysis and performance reconstruction operations.