In 2016, the Entry, descent and landing Demonstration Module (EDM), called Schiaparelli, tested technologies required to land on Mars, using special thermal protection materials, a parachute system, a Doppler radar altimeter system and a final liquid-propulsion braking system. During the entry phase, Schiaparelli was to be slowed by atmospheric drag on its heatshield, after which its parachute would open to further brake its speed during the descent, and the parachute would then be jettisoned and a soft landing accomplished with retrothrusters.
On 19 October 2016, most of the six-minute descent sequence went according to plan: the module successfully entered the atmosphere, protected from the high temperatures by its heatshield. Sensors then acquired vital data on the probe and Mars’ atmosphere during this critical phase.
Things started to go wrong during the second phase of this sequence. After the parachute opening, the module began to experience unexpected lateral oscillation movements, causing its inertial measurement units (IMUs) to become saturated. This resulted in conflicting information being sent to the flight computer, which activated the planned sequence in the wrong order: the front heatshield was jettisoned, followed by the parachute and backshell, and the braking thrusters were fired and then shut off, leaving the module to fall 4,000 metres to the surface.
The sequence of events was precisely pieced together from the data returned by the module throughout the descent and right up to impact, notably during the last 19 seconds. The data transmitted by Schiaparelli were relayed by satellites already in Mars orbit.
Atmospheric braking, heatshield subjected to extreme heat flux.
The German space agency DLR developed a Combined Aerothermal and Radiometer Sensors instrument package (COMARS+). This system consisted of three COMARS sensors, each comprising a broadband radiometer and an electronic unit for analogue signal processing. The sensors simultaneously measured pressure and heat flux. CNES supplied the ICOTOM narrow-band radiometer to measure the temperature of CO2 plasma around the capsule. Each of the three sensors received the signal in two frequency bands. These data will be useful in designing future heatshields.
|Spectral bands||CO2 emission bands in infrared (2,7 µm ; 4,3 µm)|
|Size||12 mm x 50 mm|
|Power consumed||0 W|
|Total Mass||50 g (with cabling)|
The EDM was expected to survive on the surface of Mars for a short time (about 8 Martian days or ‘sols’), using the excess energy capacity of its batteries.
The EDM surface payload, named DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface), consisted of a suite of sensors to measure the wind speed and direction (MetWind), humidity (DREAMS-H), pressure (DREAMS-P), surface temperature (MarsTem), the transparency of the atmosphere (Solar Irradiance Sensor, SIS) and the electric fields on the planet's surface (Atmospheric Radiation and Electricity Sensor; MicroARES).