Author Topic: ESA-Roscosmos: ExoMars 2016 updates and discussion  (Read 232056 times)

Offline Svetoslav

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1000 on: 05/30/2017 06:55 PM »

Answer in bold.


So, we're probably more critical to government agencies, while at the same time more  generous to private companies?

Perhaps that's right. We admire private enterpreneurs and tend to forgive them even when they're not doing things in a public way. Both Vector and Rocket Lab refused to stream their first launches live. Both companies didn't report the maximum altitude of the rockets reached.

Government agencies use tax dollars and are sometimes more risk-averse, they also tend to exaggerate their achievements in order to justify money spent. They're also more public (or, at least NASA and ESA try to be public).

I'm a fan of government agencies and private companies and think that both of the models about how we should do things in space have a future.

But I try to judge the missions on equal ground.
« Last Edit: 05/30/2017 06:56 PM by Svetoslav »

Offline Star One

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1001 on: 05/30/2017 07:50 PM »
...the private company Rocket Lab launched its first Electron rocket on a test flight....

So why isn’t Schiaparelli judged on the same ground? ..
Answer in bold.

Good writeup though.

One thing that cannot be said is that GNC design team didn't have enough time to work this out: the lander GNC architecture was in development for almost a decade.

That's a rather simplistic and partisan response.

Offline baldusi

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1002 on: 05/30/2017 11:34 PM »
Personally, I think that Schiaparelli's landing was a failure because of the botched sw engineering process. The sort of mistakes in the guidance software are problems that speak bad of the engineers.
They simply didn't managed corner cases, didn't made a best effort to recover the integrated vector on a sensor saturation condition. But what's worse is that then the selection o valid input was inconsistent and totally wrong. It's like the Progress failure on Soyuz-2.1a, the failure was of fundamental engineering practices.
Failures from lack of experience is fine. From single obscure mistake, is fine. From fundamental handling of high reliability programming, it's not.

Offline LouScheffer

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1003 on: 05/31/2017 03:06 PM »
Personally, I think that Schiaparelli's landing was a failure because of the botched sw engineering process.
[...]
Failures from lack of experience is fine. From single obscure mistake, is fine. From fundamental handling of high reliability programming, it's not.
Agreed, especially since super analytic skills were not needed to see this problem coming.  Parachutes on Mars have been tried perhaps a dozen times, and are known to be tricky.  So even naive specifications, coding, and tests should call for the software to work no matter what the parachute does, provided only it opens and slows down the craft enough.

Online savuporo

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1004 on: 05/31/2017 03:53 PM »
..Failures from lack of experience is fine. From single obscure mistake, is fine. From fundamental handling of high reliability programming, it's not.

Just a small nitpick: technically the issue wasn't with programming. The software development contractor apparently took the modeled design and implemented as is. Design error, rather than implementation, but it doesn't change the point. This is not how you design high reliability avionics.
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Offline baldusi

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1005 on: 05/31/2017 05:19 PM »
..Failures from lack of experience is fine. From single obscure mistake, is fine. From fundamental handling of high reliability programming, it's not.

Just a small nitpick: technically the issue wasn't with programming. The software development contractor apparently took the modeled design and implemented as is. Design error, rather than implementation, but it doesn't change the point. This is not how you design high reliability avionics.

I'm sorry, but I have a certain background in security and even with botched designs, you can't tolerate unhandled corner cases. A sensor saturation condition, even if the models say it won't happen, is a corner case to be handled correctly. Else, just abort the program. Since they did program something in the sensor saturation case, then they should have handled it correctly.
If they had aborted on sensor saturation, because it was specified as a non defined condition, I would have classified it as a specification/design problem alone. But they did take the input and kept going. So it's design/specification, programming and integration problems. All failed processes.

Offline eeergo

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1006 on: 06/29/2017 05:00 PM »

http://blogs.esa.int/rocketscience/2017/06/28/tgo-short-summer-break/


Quote
On 25 June, the Trace Gas Orbiter (TGO) will suspend its aerobraking campaign until the end of August due to Mars' conjunction with the Sun.

[...]

Upon arrival at Mars on 19 October last year, the TGO orbit was 33,000 x 205 km, the goal of the approximately 11-month-long aerobraking campaign is to bring this to a 370 x 420 km quasi-circular orbit.

From March to June this year, the orbit duration was reduced from 24 to approximately 14 hours using this aerobraking technique. The target is to reach an orbit that lasts about two hours for the science phase of the mission. As the orbit duration is gradually reduced, the more frequent orbits will require constant communication with the spacecraft – from January 2018 on, deep space antennas from ESA Estrack and NASA DSN will connect to TGO, 24 hours a day, 7 days a week.

[...]

In May, TGO was a little behind with its descent plan because of  this 'safety first' approach. This cautious tactic has helped the team to understand more accurately any possible failures and evolve ways to successfully avoid them. Since this slower beginning (aerobrakign began in full in March), the approach has gradually been made more aggressive, and as a result the craft has caught up to the original plan, and is now slightly ahead of schedule.
« Last Edit: 06/29/2017 05:00 PM by eeergo »
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Online savuporo

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1007 on: 08/16/2017 06:43 AM »
Tons of abstracts posted re ExoMars and specifically Shiaparelli

esaconferencebureau.com/docs/default-source/17c12-docs/ippw14_abstracts_low_res.pdf
Quote
EXOMARS 2016 POST FLIGHT MISSION ANALYSIS OF SCHIAPARELLI COASTING, ENTRY, DESCENT AND LANDING
For the ExoMars2016 Mission, Thales Alenia Space Italia acted as prime contractor, leading the Spacecraft Composite development and verification (including the system design and verification of the EDM and key GNC/EDL technologies). DEIMOS Space has been involved in the Exomars Programme (2016 and 2020 missions) since 2004 providing more than 10 years of technical activities in the areas of End to End (from launch to landing) Mission Engineering and GNC. In particular, for the 2016 mission DEIMOS Space was responsible in Phase E of the Mission Anal- ysis of the Schiaparelli mission, from separation from the TGO to landing on Mars, covering the pre-flight trajectory predictions and performance analysis [1] and the post flight analyses presented here.

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ATMOSPHERIC MARS ENTRY AND LANDING INVESTIGATIONS & ANALYSIS (AMELIA) BY THE EXOMARS 2016 SCHIAPARELLI MODULE
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PRELIMINARY ANALYSIS OF ENTRY AND DESCENT RADIO COMMUNICATIONS OF EXOMARS 2016 SCHIAPARELLI.

Quote
ACHIEVEMENTS OF THE COMARS+ INSTRUMENTATION PACKAGE DURING THE ENTRY FLIGHT PHASE OF THE EXOMARS SCHIAPARELLI LANDER

etc
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Offline plutogno

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Re: ESA-Roscosmos: ExoMars 2016 updates and discussion
« Reply #1008 on: 08/29/2017 07:25 AM »
AEROBRAKING: BACK TO THE FUTURE

After an approximately 11-week pause due to Mars conjunction and a major software update, ESA’s ExoMars Trace Gas Orbiter (TGO) will restart its aerobraking campaign in September.

http://blogs.esa.int/rocketscience/2017/08/26/aerobraking-back-to-the-future/

Tags: Mars Exomars