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Emily LakdawallaNovember 23, 2016

Schiaparelli investigation update; crash site in color from HiRISE

ESA issued an update on the Schiaparelli landing investigation today, identifying a problem reading from an inertial measurement unit as the proximate cause of the crash. The landing had proceeded nominally through the deployment of the parachute and release of the heat shield, but then the problem with the gyroscope made Schiaparelli think it had already landed. ESA's statement elaborates:

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.

Meanwhile, ExoMars Trace Gas Orbiter is operating its science instruments for the first time this week. I can't wait to see the first CASSIS images!

The two Mars Reconnaissance Orbiter HiRISE images of the landing site taken after the crash are now available in their calibrated form. Together they form a stereo pair covering the landing site.

I worked with the second image in order to produce high-resolution color views of the lander and parachute. Usually, when you work with HiRISE data, it's best to work with map-projected images because then north is up and the scale is fixed and known. But map projection, like any other rotation and scaling operation on digital images, blurs the original data somewhat. So when you're interested with features on the scale of individual pixels, it's worth it to work with the "non-map" data, which represents the pixels as they came off the camera detector. Here is the best I could do at revealing detail at the Schiaparelli landing site. You can see the impact crater that it made. I measure it at 11 pixels across -- as the original data have a resolution of 27.8 centimeters per pixel, that's just about exactly 3 meters.

Schiaparelli backshell and parachute landing location from HiRISE in color

NASA / JPL / UA / Emily Lakdawalla

Schiaparelli backshell and parachute landing location from HiRISE in color
The parachute and backshell as seen on November 1, 2016, about two weeks after the crash. The parachute is bright white and slightly folded; the conical shape of the backshell is visible. Image scale is 27.8 cm/pixel; the whole image is 234 meters square. Inset at lower left shows the same image enlarged by a factor of 5, preserving original HiRISE pixels.
Schiaparelli lander crash site from HiRISE in color

NASA / JPL / UA / Emily Lakdawalla

Schiaparelli lander crash site from HiRISE in color
The landing site as seen on November 1, 2016, about two weeks after the crash. Color and grayscale data have been combined to emphasize the shape of the impact crater, dark ejecta from the impact/explosion, and bright fragments of the lander. Image scale is 27.8 cm/pixel; the whole image is 234 meters square.
Schiaparelli crash site (300% enlarged detail)

NASA / JPL / UA / Emily Lakdawalla

Schiaparelli crash site (300% enlarged detail)
Original HiRISE data has been enlarged with nearest-neighbor sampling, so individual pixel edges are still visible. Original pixels are 27.8 centimeters across.

Read more: pretty pictures, pics of spacecraft in space, amateur image processing, mission status, ExoMars TGO, Mars, Mars Reconnaissance Orbiter

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Emily Lakdawalla

Senior Editor and Planetary Evangelist for The Planetary Society
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