Author Topic: NASA - MSL Updates  (Read 70047 times)

Offline ugordan

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Re: NASA - MSL Updates
« Reply #40 on: 12/02/2011 08:41 PM »
Makes me wonder though if there are any bumps in deployment of the bridle that could inadvertently cause a slack reading?

After Mars Polar Lander, I'm pretty sure that's one failure mode you won't be seeing in the near future.

Offline Jim

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Re: NASA - MSL Updates
« Reply #41 on: 12/02/2011 09:20 PM »
Makes me wonder though if there are any bumps in deployment of the bridle that could inadvertently cause a slack reading?

After Mars Polar Lander, I'm pretty sure that's one failure mode you won't be seeing in the near future.

Early post mentions persistence check

Offline Nomadd

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Re: NASA - MSL Updates
« Reply #42 on: 12/02/2011 09:34 PM »
Makes me wonder though if there are any bumps in deployment of the bridle that could inadvertently cause a slack reading?

After Mars Polar Lander, I'm pretty sure that's one failure mode you won't be seeing in the near future.

 I'd imagine the reduced thrust would have to agree with the altimeter reading to cut loose, or go to an alternate law if the two didn't jive.
 I imagine some pretty strange stuff though.
« Last Edit: 12/04/2011 03:36 AM by Nomadd »

Offline Bogeyman

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Re: NASA - MSL Updates
« Reply #43 on: 12/05/2011 06:01 PM »
I have heard that there were or have been computer problems with MSL. What's the story about that because I have not seen or read anything else than this English text so far in the German space forum?

Quote quoted from German Forum 'Raumcon':
"The spacecraft experienced a computer reset on Tuesday apparently related to star-identifying software in the attitude control system. The reset put the spacecraft briefly into a precautionary safe mode. Engineers restored it to normal operational status for functions other than attitude control while planning resumption of star-guided attitude control."

Regards, Chris

Offline Jim

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Re: NASA - MSL Updates
« Reply #44 on: 12/05/2011 06:28 PM »
I have heard that there were or have been computer problems with MSL. What's the story about that because I have not seen or read anything else than this English text so far in the German space forum?

Quote quoted from German Forum 'Raumcon':
"The spacecraft experienced a computer reset on Tuesday apparently related to star-identifying software in the attitude control system. The reset put the spacecraft briefly into a precautionary safe mode. Engineers restored it to normal operational status for functions other than attitude control while planning resumption of star-guided attitude control."

Regards, Chris

it isn't a problem with the computers but a star tracker issue.

Offline Bogeyman

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Re: NASA - MSL Updates
« Reply #45 on: 12/05/2011 06:56 PM »
it isn't a problem with the computers but a star tracker issue.

So what is the consequence of that? MSL can't navigate anymore? Can they fix it?

Offline Jim

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Re: NASA - MSL Updates
« Reply #46 on: 12/05/2011 07:05 PM »
it isn't a problem with the computers but a star tracker issue.

So what is the consequence of that? MSL can't navigate anymore? Can they fix it?

No, they are looking at it.  It isn't a big deal.

Offline iamlucky13

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Re: NASA - MSL Updates
« Reply #47 on: 12/06/2011 05:39 PM »
"........As planned, MSL does not have a direct means of sensing Rover touchdown; a software logic is employed instead.

No, the sensors detect the weight on the bridle which determines landing

Can both of these be correct in some way I'm not seeing?

Yes. The load on the bridle is the key part of the software logic, and this is an indirect parameter. It doesn't have a touchdown switch on the bottom of the rover or anything like that.

Ok so if I understand this correctly what actually causes the bridle cut is that the DS senses a difference in thrust requirement based on the when the lander touches the surface it is no longer carrying that load, correct?

Makes me wonder though if there are any bumps in deployment of the bridle that could inadvertently cause a slack reading? Of course I am sure they have covered all anomalies, still would love to a ton more about the systems development.

It's been a while since I read the papers, but I'm almost certain the bridle tension is measured directly by a load cell, and the logic for cutting the bridle doesn't care what the DS thrust is.

A bump during deploy wouldn't be a problem - simply don't allow the bridle to be cut until the deployment sequence is complete.

A complete loss of thrust would cause a slack reading, but in that case, Curiosity is probably screwed anyways.

Offline TheFallen

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Re: NASA - MSL Updates
« Reply #48 on: 12/07/2011 04:56 AM »
You can now view MSL's current position in space on JPL's Solar System Simulator

http://space.jpl.nasa.gov/

Offline mrhuggy

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Re: NASA - MSL Updates
« Reply #49 on: 12/09/2011 02:48 PM »
A little interesting news on MSL, looks like they will try to image MSL hanging of the Skycrane using the HiRISE camera on MRO.

Mars Orbiters Will Attempt To Take Pictures Of Curiosity As It Lands

If the pull it off, it could be the best picture ever.
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Online kevin-rf

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Re: NASA - MSL Updates
« Reply #50 on: 12/09/2011 03:23 PM »
Will wonders never cease, wow!
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Offline ugordan

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Re: NASA - MSL Updates
« Reply #51 on: 12/09/2011 03:25 PM »
It won't top Phoenix under its parachute simply because of the resolution and contrast (big white/red parachute against the background vs a small hunk of metal).

Online rcoppola

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Re: NASA - MSL Updates
« Reply #52 on: 12/09/2011 03:56 PM »
I wonder how much bigger they can scale up the decent -sky crane method of landing mass on the surface. Supply runs for a future mission perhaps...
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Offline Robotbeat

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Re: NASA - MSL Updates
« Reply #53 on: 12/09/2011 05:04 PM »
A little interesting news on MSL, looks like they will try to image MSL hanging of the Skycrane using the HiRISE camera on MRO.

Mars Orbiters Will Attempt To Take Pictures Of Curiosity As It Lands

If the pull it off, it could be the best picture ever.
Awesome!
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Offline Robotbeat

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Re: NASA - MSL Updates
« Reply #54 on: 12/09/2011 05:15 PM »
It won't top Phoenix under its parachute simply because of the resolution and contrast (big white/red parachute against the background vs a small hunk of metal).
It might be possible to get both the parachute and MSL doing the skycrane maneuver. The parachute isn't going to disappear instantly, and the field of view is necessarily large.

Not only that, but the MSL parachute ought to be almost twice the diameter as the Phoenix parachute (>3 times the area). And the hunks of metal should also be bigger.

I wonder also if they would be able to slew the spacecraft quickly and take more than one picture. Did they take more than one for Phoenix?
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Offline hyper_snyper

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Re: NASA - MSL Updates
« Reply #55 on: 12/09/2011 07:09 PM »
Are hydrazine rocket plumes transparent?  I guess they would be too small to see them from orbit anyways.

Offline ugordan

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Re: NASA - MSL Updates
« Reply #56 on: 12/09/2011 07:16 PM »
It won't top Phoenix under its parachute simply because of the resolution and contrast (big white/red parachute against the background vs a small hunk of metal).
It might be possible to get both the parachute and MSL doing the skycrane maneuver. The parachute isn't going to disappear instantly, and the field of view is necessarily large.

Not only that, but the MSL parachute ought to be almost twice the diameter as the Phoenix parachute (>3 times the area). And the hunks of metal should also be bigger.

The parachute would be prominent, there's no question about that. They might get both the parachute+backshell and descent stage in a single "frame", but my point was the descent stage alone would be much less obvious than the parachute (which Phoenix was under at the time of its image). Phoenix' dropped heatshield was barely detectable on the other hand.

Offline iamlucky13

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Re: NASA - MSL Updates
« Reply #57 on: 12/09/2011 09:09 PM »
It won't top Phoenix under its parachute simply because of the resolution and contrast (big white/red parachute against the background vs a small hunk of metal).

There's also the awesome coincidence of the huge background crater that made the Phoenix shot inspiring.

It was all the more awesome, because it's one of the first photographs we've actually seen of Mars taken at an angle across the landscape (62 degrees) to appreciate as a familiar perspective, instead of staring nearly straight down to maximize resolution.

At the same time, this means Phoenix was roughly twice as far away as the minimum (about 640km instead of 300 km straight down). Depending how things work out, they could be closer (more resolution, but looking straight down at the parachute) or further away (more interesting angle)


I wonder also if they would be able to slew the spacecraft quickly and take more than one picture. Did they take more than one for Phoenix?

I don't think they easily can. Remember, HiRise is a pushbroom camera. It scans a row of pixels continuously across the surface, matched to the motion of the spacecraft to build up a large image.

They might be able to make one sweep, end the image, and then make another sweep, but there's a tradeoff between the size of the area they cover (likelihood of actually spotting the spacecraft) and the number of sweeps they can make.

The field of ground view of HirRISE at a 60 degree angle is about 12 km. The landing ellipse is 20 km. That presents a good argument for simply scanning a single long frame instead of scanning multiple passes over a smaller area.

Offline iamlucky13

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Re: NASA - MSL Updates
« Reply #58 on: 12/09/2011 10:01 PM »
By the way, Emily Lakdawalla had a great article on the challenge of capturing Phoenix on HiRISE, along with some some detailed information about the camera system from one of the HiRISE optical engineers:

http://www.planetary.org/blog/article/00001547/

Offline ChrisC

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Re: NASA - MSL Updates
« Reply #59 on: 12/10/2011 01:50 AM »
By the way, Emily Lakdawalla had a great article on the challenge of capturing Phoenix on HiRISE, along with some some detailed information about the camera system from one of the HiRISE optical engineers:

http://www.planetary.org/blog/article/00001547/

I was going to post this same thing.  For anyone excited about the prospect of imaging MSL during the descent, Emily's excellent piece about how they made it work with Phoenix is frankly required reading.
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