On Wednesday, October 19th, 2016, the European Space Agency (ESA) attempted, for them, a double first: placing a vehicle successfully in orbit around Mars (the Trace Gas Orbiter, or TGO) and landing a vehicle on the planet’s surface (the Schiaparelli demonstrator).
Launched in March 2016, TGO is the second European orbiter mission to Mars, the first being Mars Express, which has been operating around the red planet for 12 years. TGO’s mission is to perform detailed, remote observations of the Martian atmosphere, searching for evidence of gases which may be possible biological importance, such as methane and its degradation products. At the same time, it will to image Mars, and act as a communications for Europe’s planned 2020 Mar rover vehicle.
TGO’s primary mission won’t actually start until late 2017. However, October 19th marked the point at which the vehicle entered its preliminary orbit around Mars. Orbital insertion was achieved following a 139-minute engine burn which slowed the vehicle sufficiently to place it in a highly elliptical, four-day orbit around Mars. Early next year, the spacecraft will begin shifting to its final science orbit, a circular path with an altitude of 400 km (250 mi), ready to start its main science mission.
On Sunday, October 16th, prior to orbital insertion, TGO had bid farewell to the 2-metre diameter Schiaparelli Entry, Descent and Landing Demonstrator Module (EDM), which it had carried to Mars. The EDM was specifically designed to gather data on entry into, and passage through, the Martian atmosphere and test landing systems in preparation for ESA’s 2020 rover mission landing.
Once separated from TGO, Schiaparelli travelled ahead of the orbiter, entering the Martian atmosphere at a speed of 21,000 km/h (13,000 mph; 5.8 km/s / 3.6 mi/s), at 14:42 UT on October 19th. After using the upper reaches of the Martian atmosphere to reduce much of its velocity, Schiaparelli should have proceeded to the surface of Mars using a mix of parachute and propulsive descent, ending with a short drop to the ground, cushioned by a crushable structure designed to deform and absorb the final touchdown impact. Initially, everything appeared to go according to plan. Data confirmed Schiaparelli had successfully entered the Martian atmosphere and dropped low enough for the parachute system to deploy. Then things went awry.
Analysis of the telemetry suggests Schiaparelli prematurely separated from its parachute, entering a period of free fall before the descent motors fired very briefly, at too high an altitude and while the lander was moving too fast. Shortly after this, data was lost. While attempts were made to contact the EDM using ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter (MRO) it was not until October 20th that Schiaparelli’s fate became clear.
Images taken by MRO of Schiaparelli’s landing zone revealed a new 15x40m (49x130ft) impact crater, together with a new bright object about 1 kilometre south of it. The crater is thought to be Schiaparelli’s impact point, and the latter the lander’s parachute and aeroshell.
In releasing the NASA images on October 21st, the European Space Agency stated,”Estimates are that Schiaparelli dropped from a height of between 2 and 4 km (1.4-2.4 mi), impacting at a speed greater than 300 km/h (186 mph). It is also possible that the lander exploded on impact, as its thruster propellant tanks were likely still full.”
While the lander carried a small suite of science instruments which would have been used to monitor the environment around it for a few days following the landing, the major part of the mission was to gather data atmospheric entry and the use of parachute and propulsive descent capabilities. ESA believe this part of the mission to have been a success, even with minimal data gathered on the propulsive element of the descent.
In the meantime, TGO is currently on a 101,000 km x 3691 km orbit (with respect to the centre of the planet). It is fully functional, and will undertake instrument calibration operations in November, prior to commencing the gentle aerobraking manoeuvres designed to reduce and circularise its orbit around Mars.