7 ms·

Schiaparelli descent data: decoding underway

114 points by kartikkumar 10y ago

fasteo 10y ago
tl;dr; Schiaparelli has crashed
- tremon 10y ago
  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 10y ago
    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-Paper.pdf https://solarsystem.nasa.gov/docs/Bayle_ExoMars_EDM_Overview... [2] http://ippw2016.jhuapl.edu/docs/abstracts/Missions-abstracts.pdf#page=3 http://ippw2016.jhuapl.edu/docs/abstracts/Missions-abstracts... [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 10y ago
      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.
mattystowe 10y ago
Its an expensive CI process!! Next iteration is in 2 years! ;-)
- dogma1138 10y ago
  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.
  - Sharlin 10y ago
    "Fortunately" the ExoMars rover was already pushed back to the next launch window in 2020 for unrelated reasons.
  - GFK_of_xmaspast 10y ago
    > 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
    - skykooler 10y ago
      Sure, there's been a bunch of failures. But we also landed 5 landers successfully. That's pretty successful, compared to other attempts.
    - jandrese 10y ago
      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.
jonnys1 10y ago
I am bit uninformed, can someone explain we what happened?
- DrNuke 10y ago
  Schiaparelli was a disk with a crumple designed to land on Mars. The disk interrupted its signal one minute before landing and scientists are trying to explain why: descense too fast, incorrect model, unexpected failure, anything else.
- camiller 10y ago
  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 10y ago
    A currency sent a probe to Mars?
    - camiller 10y ago
      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.
acqq 10y ago
A statistics from a few years ago: http://www.popsci.com/science/article/2012-08/mars-rover-curiosity%E2%80%99s-biggest-challenge-mars-itself http://www.popsci.com/science/article/2012-08/mars-rover-cur... "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?
TravelTechGuy 10y ago
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.
- cmg 10y ago
  Reminds me of a classic The West Wing scene, when a missile test misses its target by 137 miles. Yes, every step is important, but 6/7 is still not a success. LEO That nine out of ten criterion that the DOD lays down for success in these tests were met. BARTLET The tenth being? LEO They missed the target. BARTLET [with sarcasm] Damn! LEO Sir! BARTLET So close. LEO Mr. President. BARTLET That tenth one! See, if there were just nine...
- api 10y ago
  I think it's almost a tongue in cheek thing in aerospace. There's stuff like "RUD" which stands for "Rapid Unscheduled Disassembly" and means the rocket exploded, etc.
  - raverbashing 10y ago
    Well according to SpaceX it was an anomaly ;)
- fernandopj 10y ago
  In that same spirit, one could even say there was just a slight deviation from the expected lithobreaking landing phase - so all steps were indeed performed, just not to spec
- david-given 10y ago
  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.

114 points by kartikkumar 10y ago

fasteo 10y ago

tl;dr; Schiaparelli has crashed

tremon 10y ago
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 10y ago
  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-Paper.pdf https://solarsystem.nasa.gov/docs/Bayle_ExoMars_EDM_Overview... [2] http://ippw2016.jhuapl.edu/docs/abstracts/Missions-abstracts.pdf#page=3 http://ippw2016.jhuapl.edu/docs/abstracts/Missions-abstracts... [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 10y ago
    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.

mattystowe 10y ago

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

dogma1138 10y ago
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.
- Sharlin 10y ago
  "Fortunately" the ExoMars rover was already pushed back to the next launch window in 2020 for unrelated reasons.
- GFK_of_xmaspast 10y ago
  > 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
  - skykooler 10y ago
    Sure, there's been a bunch of failures. But we also landed 5 landers successfully. That's pretty successful, compared to other attempts.
  - jandrese 10y ago
    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.

jonnys1 10y ago

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

DrNuke 10y ago
Schiaparelli was a disk with a crumple designed to land on Mars. The disk interrupted its signal one minute before landing and scientists are trying to explain why: descense too fast, incorrect model, unexpected failure, anything else.
camiller 10y ago
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 10y ago
  A currency sent a probe to Mars?
  - camiller 10y ago
    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.

acqq 10y ago

A statistics from a few years ago: http://www.popsci.com/science/article/2012-08/mars-rover-curiosity%E2%80%99s-biggest-challenge-mars-itself http://www.popsci.com/science/article/2012-08/mars-rover-cur... "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?

TravelTechGuy 10y ago

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.

cmg 10y ago
Reminds me of a classic The West Wing scene, when a missile test misses its target by 137 miles. Yes, every step is important, but 6/7 is still not a success. LEO That nine out of ten criterion that the DOD lays down for success in these tests were met. BARTLET The tenth being? LEO They missed the target. BARTLET [with sarcasm] Damn! LEO Sir! BARTLET So close. LEO Mr. President. BARTLET That tenth one! See, if there were just nine...
api 10y ago
I think it's almost a tongue in cheek thing in aerospace. There's stuff like "RUD" which stands for "Rapid Unscheduled Disassembly" and means the rocket exploded, etc.
- raverbashing 10y ago
  Well according to SpaceX it was an anomaly ;)
fernandopj 10y ago
In that same spirit, one could even say there was just a slight deviation from the expected lithobreaking landing phase - so all steps were indeed performed, just not to spec
david-given 10y ago
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.