robust and cater for any contingencies,” says flight
director Michel Denis.
Aerobraking proper will begin on 15 March with
a series of seven thruster firings, about one every
three days, that will steadily lower the craft’s alti-
tude at closest approach – from 200 km to about
114 km.
Flight dynamics experts at our ESOC operations
centre work on every ESA mission, from those in
very low orbits, like Swarm and CryoSat, to those
exploring our Solar System, like Rosetta and Exo-
Mars.
“Then the atmosphere can start its work, pull-
ing us down,” says Peter Schmitz. “If all goes as
planned, very little fuel will then be needed until
the end of aerobraking early in 2018, when final
firings will circularise the 400 km orbit.”
No date has been set, but science observations
can begin once the final orbit is achieved. In ad-
dition, the path will provide two to three overflights
of each rover every day to relay signals.
Overall, the spacecraft is in excellent health.
On 30 November, it received an updated ‘oper-
ating system’. To date, only one ‘safe mode’ has
been triggered, when a glitch caused the craft to
reboot and wait for corrective commands. That
happened during preliminary testing of the main
engine, when a faulty configuration was quickly
identified and fixed.
“We are delighted to be flying such an excellent
spacecraft,” says Michel. “We have an exciting
and challenging mission ahead of us.”
Why did Schiaparelli crash duri ng landing?
Contact with the ExoMars Schiaparelli lander
– longer than would be expected.
was lost during its attempt to make it to the sur-
When merged into the navigation system, the
face last October. It was later discovered that the
erroneous information generated an estimated
lander had crashed into the surface of the Red
altitude that was negative – that is, below ground
Planet.
level. This in turn successively triggered a prema-
A large volume
ture release of the
of data recovered
parachute and the
from the Mars lander
backshell, a brief fir-
shows that the at-
ing of the braking
mospheric entry and
thrusters and finally
associated braking
activation of the on-
occurred exactly
ground systems as if
as expected. The
Schiaparelli had al-
parachute deployed
ready landed. In real-
normally at an alti-
ity, the vehicle was
tude of 12 km and a
still at an altitude of
speed of 1730 km/h.
around 3.7 km.
The vehicle’s heat-
This behaviour has
shield, having served
been clearly repro-
its purpose, was re-
duced in computer
leased at an altitude
simulations of the
of 7.8 km.
control system’s re-
As Schiaparelli
sponse to the errone-
descended under its
ous information.
parachute, its radar
“This is still a very
Doppler altimeter
preliminary conclu-
Schiaparelli’s heat-scorched shield while descending through
functioned correctly
sion of our technical
the atmosphere of Mars. Credit: ESA/ATG medialab
and the measure-
investigations,” says
ments were included in the guidance, navigation
David Parker, ESA’s Director of Human Spaceflight
and control system.
and Robotic Exploration. “The full picture will be
However, saturation – maximum measurement
provided in early 2017 by the future report of an
– of the Inertial Measurement Unit (IMU) occurred
external independent inquiry board.
shortly after the parachute deployment. The
“But we will have learned much from Schia-
IMU measures the rotation rates of the vehicle.
parelli that will directly contribute to the second
Its output was generally as predicted except for
ExoMars mission being developed with our interna-
this event, which persisted for about one second
tional partners for launch in 2020.”
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