
Schiaparelli descent data: decoding underway - kartikkumar
http://exploration.esa.int/mars/58475-schiaparelli-descent-data-decoding-underway/
======
acqq
A statistics from a few years ago:

[http://www.popsci.com/science/article/2012-08/mars-rover-
cur...](http://www.popsci.com/science/article/2012-08/mars-rover-
curiosity%E2%80%99s-biggest-challenge-mars-itself)

"In the decades since humans started sending spacecraft to Mars, the Red
Planet has outscored us handily; humans have only about a .411 batting average
overall -- not great for missions that cost billions of dollars and countless
time to build. Seventeen landers have been sent, and just seven made it to the
surface safely, each of them with varying degrees of success."

Afterwards, Curiosity rover luckily succeeded, under much harder constraints
then these now (being huge but sensitive), so that is at least 8 from 18. With
this one, 8 from 19 (giving, interestingly, 0.42). I don't know which the real
ratio now is, am I missing something?

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TravelTechGuy
I especially liked this sentence: > the module had successfully completed most
steps of its 6-minute descent through the martian atmosphere

Completing "most steps" in a landing, but not the last one (I.e. Safe
touchdown) is equal to a crash.

~~~
david-given
That's unfair.

Schiaparelli was never a science mission. It was a technology demonstrator to
see whether the landing system worked. Even if it had landed intact, it had a
tiny set of science instruments and would only have lasted a few hours.

Well, we now know that there are a few bugs --- but we also know that _most of
the landing system works_ , including hibernation, terminal guidance, reentry,
heatshield deployment, the parachute... all of which is hugely valuable data.
Knowing that the last few stages _didn 't_ work is even more valuable,
particularly as it's returned telemetry on what happened.

Focusing only on the fact that the last couple of steps failed and it crashed
is doing the mission a huge disservice. Schiaparelli did precisely the job it
was designed for.

~~~
forketta
_Schiaparelli, the ExoMars Entry, descent and landing Demonstrator Module
(EDM) will provide Europe with the technology for landing on the surface of
Mars with a controlled landing orientation and touchdown velocity. The design
of Schiaparelli maximises the use of technologies already in development
within the ExoMars programme. These technologies include: special material for
thermal protection, a parachute system, a radar Doppler altimeter system, and
a final braking system controlled by liquid propulsion._

 _Schiaparelli is expected to survive on the surface of Mars for a short time
by using the excess energy capacity of its batteries._

[http://exploration.esa.int/mars/46124-mission-
overview/](http://exploration.esa.int/mars/46124-mission-overview/)

------
mattystowe
Its an expensive CI process!! Next iteration is in 2 years! ;-)

~~~
dogma1138
Next one needed data from this one so it might be pushed back.

It's another strike, it's actually weird how much success the US had at
landing on mars. The Russians have constantly failed at doing so.

~~~
GFK_of_xmaspast
> it's actually weird how much success the US had at landing on mars

Meanwhile in this universe :
[https://en.wikipedia.org/wiki/Mars_Climate_Orbiter](https://en.wikipedia.org/wiki/Mars_Climate_Orbiter)
[https://en.wikipedia.org/wiki/Mars_Polar_Lander](https://en.wikipedia.org/wiki/Mars_Polar_Lander)
[https://en.wikipedia.org/wiki/Deep_Space_2](https://en.wikipedia.org/wiki/Deep_Space_2)
[https://en.wikipedia.org/wiki/Mars_Observer](https://en.wikipedia.org/wiki/Mars_Observer)

~~~
jandrese
Some of it may come from a different engineering culture. There is an argument
that the Russians have better launch vehicles and engines because they were
willing to take a more rapid prototype approach and blow up a relatively large
number of engines to get the kinks worked out. The US took a more conservative
approach with fewer but more highly engineered engines that ended up being
less efficient than some Russian designs.

The problem is that you can't do rapid prototyping on Mars landers, each
iteration is just too expensive. This is where the US approach works better.

As for the ESA, I have no idea. Hopefully they got enough data out of the
lander before it crashed to figure out what went wrong exactly.

~~~
pinewurst
I'm not sure I agree with that argument. At least comparing specific impulses
of Proton and Soyuz vehicle engines with (older, pre-Russian engined) Delta
and Atlas shows the latter are often significantly higher.

That's not to say the Russians haven't done good engines but RD180 for example
is derived from the Energia engines which didn't have (at least publicly) lots
of trials/failures.

------
jonnys1
I am bit uninformed, can someone explain we what happened?

~~~
camiller
Euros sent a probe/lander to Mars, it crashed. The orbiter it traveled with,
which has it's own mission to analyze trace gasses in Mars outer atmosphere(I
think) is working fine.

Earth is 25-29 against Mars.

~~~
kobeya
A currency sent a probe to Mars?

~~~
camiller
Well.... Yeah it probably took a bunch of them.

Sorry, I was in a hurry and shortened Europeans to Euros. Probably could have
said ESA.

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fasteo
tl;dr;

Schiaparelli has crashed

~~~
tremon
The more interesting question is why it crashed, or rather:

\- why did it eject its parachute too soon?

\- why did the brake thrusters activate for a shorter time than planned?

Does anyone here know if the landing steps were timing-driven or telemetry-
driven? Was it supposed to eject its parachute after N seconds, or when
reaching M meters above the surface?

~~~
kartikkumar
The radar was only activated after the front shield was ejected, so there was
no altitude data prior to that event. It could be that accelerometers on board
sensed the dynamic pressure, so that parachute deployment was not purely open-
loop. I'll try to dig through publications to find out what the EDL (Entry-
Descent-Landing) strategy was.

EDIT: Here are some papers worth persuing:

[1]
[https://solarsystem.nasa.gov/docs/Bayle_ExoMars_EDM_Overview...](https://solarsystem.nasa.gov/docs/Bayle_ExoMars_EDM_Overview-
Paper.pdf)

[2] [http://ippw2016.jhuapl.edu/docs/abstracts/Missions-
abstracts...](http://ippw2016.jhuapl.edu/docs/abstracts/Missions-
abstracts.pdf#page=3)

[3]
[http://arc.aiaa.org/doi/abs/10.2514/6.2011-6341](http://arc.aiaa.org/doi/abs/10.2514/6.2011-6341)
(behind journal paywall)

~~~
tremon
Thanks! So it looks like the entire descent was telemetry-based (source [1],
section 3.4):

 _The functions of the EDM GNC [Guidance, Navigation and Control system] are
(1) to detect the conditions adequate for the deployment of the parachute and
(2) to command and control the final powered descent phase. The GNC sensors
aboard the EDM are the Inertial Measurement Unit (IMU) and the Radar Doppler
Altimeter (RDA). A main challenge for the EDM GNC relates to the fact that the
EDM needs to go into a hibernation mode during the 3-day long coast phase.
During this phase, the inertial reference of the IMU is lost and an additional
sensor is necessary in order to rebuild the inertial attitude shortly before
entry._

