A defect sensor seems to have caused the crash of the ExoMars Schiaparelli on October 19, the European Space Agency (ESA) announced after the Italian Space Agency had accused a Romanian company of the missions’ failure.
The European Space Agency announced the preliminary conclusions of the investigation, blaming an inaccurate single-second inertial measurement for the unfortunate crash landing of its Schiaparelli lander.
The parachute deployed normally at an altitude of 12 km and a speed of 1730 km/h. The vehicle’s heatshield, having served its purpose, was released at an altitude of 7.8 km.
As Schiaparelli descended under its parachute, its radar Doppler altimeter functioned correctly and the measurements were included in the guidance, navigation and control system. However, saturation – maximum measurement – of the Inertial Measurement Unit (IMU) had occurred shortly after the parachute deployment. The IMU measures the rotation rates of the vehicle. Its output was generally as predicted except for this event, which persisted for about one second – longer than would be expected.
When merged into the navigation system, the erroneous information generated an estimated altitude that was negative – that is, below ground level. This in turn successively triggered a premature release of the parachute and the backshell, a brief firing of the braking thrusters and finally activation of the on-ground systems as if Schiaparelli had already landed. In reality, the vehicle was still at an altitude of around 3.7 km.
This behaviour has been clearly reproduced in computer simulations of the control system’s response to the erroneous information.
“This is still a very preliminary conclusion of our technical investigations,” says David Parker, ESA’s Director of Human Spaceflight and Robotic Exploration. “The full picture will be provided in early 2017 by the future report of an external independent inquiry board, which is now being set up, as requested by ESA’s Director General, under the chairmanship of ESA’s Inspector General.
“But we will have learned much from Schiaparelli that will directly contribute to the second ExoMars mission being developed with our international partners for launch in 2020.”
ESA released the preliminary conclusions after the Italian Space Agency had accused that the decisive tests for the Sciaparelli lander simulations had been entrusted to an organization “which hadn’t enough expertize”. It’s about Arca Space Romanian company, based in Las Cruces, USA, as La Repubblica reported.
In retort, the Arca Space Corporation manager, Dumitru Popescu warned the Italian space agency to be more careful, as they don’t have proves to support their accusations. “They could pay the price. We are at ease that we did all we could do: to run a specific test we should have flown very closely to the Russian base in Sevastopol. Russia has just annexed Crimea and we risked generating a conflict between the Russian Federation and NATO,” the Romanian manager argued.
The Schiaparelli mission was launched by the ESA in partnership with the Roscosmos Russian group, with technologies belonging to Russia and other European countries, including Italy.