The Platform Atmospheric Characteristics Instrumentation Suite (PACIS) for sensing Mars's atmosphere during the entry, descent and landing of the ESA ExoMars Rosalind Franklin mission

In 2028 the ESA ExoMars mission will arrive on Mars and release the Rosalind Franklin rover to explore its landing site in Oxia Planum. The mission’s study of Mars, however, will begin before touchdown. Here, we present the Platform Atmospheric Characteristics Instrumentation Suite (PACIS) which will include a microphone, accelerometer, temperature and pressure sensor to measure the atmosphere during the descent phase of the ExoMars lander. The primary instrument objectives are:

• P1: To measure the vertical profile of the atmosphere at the ExoMars Rosalind Franklin mission's landing site
• P2: To record atmospheric activity and dynamics during descent
• P3: To record the sound of entry, descent and landing (EDL) operations including parachute release, retrorockets and landing.  

The microphone recording of the EDL sequence will be unique for Mars and it will allow the capture of high frequency activity experienced by the lander, particularly turbulence. The vertical profile from the accelerometer (prior to parachute deployment) pressure and temperature sensors will help determine the atmospheric structure and dynamics. Vertical atmospheric profiles of Mars are still scarce and are important for the success of future missions as well as improving our knowledge of the Martian atmosphere.

Once landed, the secondary objective of the PACIS instrument is:

• S1: To characterize the wind, pressure and temperature at the ExoMars landing site

The ExoMars lander is battery operated with no ability to recharge. As such, surface operations for PACIS will be limited to several hours owing to power constraints. Nevertheless, the PACIS instruments will about several hours worth of data post landing to act as a useful tie point to atmospheric models. This will aid future mission interpretations related to the atmosphere. Notably, there are few surface atmospheric measurements from existing missions near the Oxia Planum landing site.

As an additional instrument to the ExoMars landing module, PACIS technologies are based on heritage design from previous projects. The microphone is the same as the one used on the NASA Perseverance mission. The temperature sensor is based on the design from the DREAMS package from ExoMars Schiaparelli. Similarly, the pressure sensor is the flight model originally built as part of the MTK-L meteorology package on the Kazachok surface platform. Similar versions of this instrument have been flown on missions including Perseverance and Curiosity.

We will present the current design and status of the instrument just prior to its critical design review. In particular, we will demonstrate the concept of operations and highlight the potential scientific return.