ExoMars - Schiaparelli landing |
ExoMars - Schiaparelli landing |
Aug 12 2016, 07:07 PM
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#31
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Solar System Cartographer Group: Members Posts: 10184 Joined: 5-April 05 From: Canada Member No.: 227 |
Starting a new topic here - hopefully that's OK! Clearly there will be a lot of action around this in the next weeks and months with descent images and HiRISE views of the hardware.
I thought I had posted this map earlier but apparently not. This shows the various landing ellipses in this area. The original plan was for an ellipse oriented NW-SE, but it changed with the different launch date and is now nearly E-W. Note that the ellipse shown in the recent ESA release is the envelope of all ellipses over a given launch period, but the actual landing ellipse for the given launch date is smaller. Opportunity's final landing ellipse is shown for comparison. http://exploration.esa.int/mars/57445-exom...6-landing-site/ http://exploration.esa.int/mars/57446-exom...6-landing-site/ Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Oct 26 2016, 08:39 PM
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#32
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Member Group: Members Posts: 122 Joined: 19-June 07 Member No.: 2455 |
What a wonderful insight into the computer system on the Viking landers. Interesting that they say in there that a system could be run completely off preset timings but it was decided on that mission to allow the craft to fly itself a bit based on accelerometer input. Instead of using radar to decide altitude they basically used computed speed and timing which says to me that one can know fairly accurately where the craft is at any time without sophisticated add ons. Hindsight seems to say that radar is a wonderful addition that enhances the entry but nothing replaces the basic science and physics that can model the path and timings very precisely. I suppose there's a nerd factor that takes over when designing complex systems, a pull to reject simplicity. Sometimes, as in the case of the Curiosity sky crane, it all comes together but we all had nightmares about all the things that had to go exactly right. In many ways the real genius was shown in the very simplistic idea of the airbag delivery system, something that ESA could have certainly used for its first attempts since their lander was so light. I understand they wanted the base of the lander on the actual surface so once the airbag is deflated and retracted flip the thing off onto its head. Oh the ease of armchair quarterbacking. Laughs.
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Oct 26 2016, 08:50 PM
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#33
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
Instead of using radar to decide altitude... You are reading way too much into that basically non-technical history. Radar is essential for Viking or any Mars lander that has to do anything based on altitude, as the altitude relative to the ground can't be determined any other way. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Oct 27 2016, 12:43 PM
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#34
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Junior Member Group: Members Posts: 78 Joined: 20-September 14 Member No.: 7261 |
Radar is essential for Viking or any Mars lander that has to do anything based on altitude, as the altitude relative to the ground can't be determined any other way. There's always laser altimeters for altitude and doppler Lidar for relative velocity. Might be worth it for the 2020 surface platform to check into what's available, especially inhouse with ESA members and associates. OPTEL-D with AIM heritage comes to mind as a family of something that could possibly be further downsized to a sufficiently low footprint. |
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Oct 27 2016, 04:29 PM
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#35
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
There's always laser altimeters for altitude and doppler Lidar for relative velocity. Radar is an extremely robust and mature technology and the larger beam footprint and longer wavelength can be an advantage. The landing applications for lidar I know of are for terrain hazard avoidance, not altitude/velocity determination per se, for example https://www-robotics.jpl.nasa.gov/publicati...aejJGCD2002.pdf AFAIK, every successful Mars lander (and Moon lander, for that matter) has used radar. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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