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#580 by Beckler on 06 Aug, 2012 17:09
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This is an amazing image! I've always wished for external images of missions; they're rare. I think video of the entire landing sequence could have been possible too: just before landing (a min. or so?) shoot out a small camera that embeds or otherwise lands into the soil. Then it tracks and records video--imagine seeing the whole thing in HD. Would have been incredible, not to mention extremely useful for capturing general public interest...
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#581 by rdale on 06 Aug, 2012 17:10
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Not sure the camera would make it down before the lander, nor would it have a good focused shot, plus it'd be tough to find it afterwards and retrieve and then download the data.
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#582 by robertross on 06 Aug, 2012 17:12
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RTG operates as a 'trickle charger'. We run off the bateries during the day but recharge the batteries at night. The heat from the RTG gets pumped around the rover to keep everything warm.
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#583 by robertross on 06 Aug, 2012 17:16
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And in case anyone missed it:
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#584 by Lars_J on 06 Aug, 2012 17:16
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Was there any word during the presser about what the altitude of MSL above Mars was when the MRO image was taken?
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#585 by Pheogh on 06 Aug, 2012 17:20
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140kg of fuel was left over. Touchdown speed reported by spacecraft was .75m/s which was intended velocity. But will take more analysis to get true velocity.
If the hydrazine was going to be a possible issue why didn't they just pre-command the descent stage to expend all prop and crash ballistically? -
#586 by rdale on 06 Aug, 2012 17:25
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My guess is there is always residual... Plus as mentioned afterwards - they have no intention of sending the rover north, so that's where they sent the stage.
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#587 by Halidon on 06 Aug, 2012 17:26
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If the hydrazine was going to be a possible issue why didn't they just pre-command the descent stage to expend all prop and crash ballistically?
That appears to be essentially what they did, and there would still be residual hydrazine in the wreckage. -
#588 by marsman2020 on 06 Aug, 2012 17:27
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Rear hazcam: some dust on lens but otherwise alright and survived pyro event. A ridge on the horizon (crater rim?), looking into sun causing some saturation on the image.
Would that lens dust be from blowing the cover too early, or just the blowing itself?QuoteIf pyros look like pyros, they're probably oversized. The animation clearly shows a spring on the cover, but it was likely restrained by some sort of catch severed by a pyro. It could alternatively have been solenoid released like a pop-up flash on a camera, but usually a pyro is the lightest, simplest, and most reliable way. It could be as simple as thin wire coated in a little bit of powder that creates enough gas pressure to push a pin out of a slot or burns through a severable link.
Well, since I was the cognizant engineer on these now-world-famous dust covers, I guess I can stop lurking and talk about them a little bit.
The covers are indeed are restrained by a metal rod, which was cut by a dual NSI pyro cable cutter. The cutter is massive overkill for the job, but....
These dust covers were one of the last things added to the rover. The MSL HazCams are build-to-print copies of the MER HazCams. On MER, the cameras were protected inside the lander, and in over 10 rover-years on the ground they haven't seen dust building up enough to be worrysome. The Skycrane system was supposed to reduce the plume ground pressure during landing to the point where dust wouldn't be an issue for MSL.
But after Phoenix landed and everyone saw the pictures of pebbles *on top of* the pads on the bottom of the lander legs, and the legs themselves coated with a sticky looking layer of dust, some concerned folks looked at the issue more closely. It turned out there is a core flow in the Mars Lander Engines on the descent stage that stays strong all the way to the surface, even hanging at the end of the skycrane. And that can kick up a lot of dust+reaction products during the skycrane maneuver, some of which would go back towards the rover. There was a review of hardware in danger of being coated with "sticky" dust; everything was determined to be dust tolerant *except* the HazCams.
Oh, but the HazCams were already done, and so were their mounting interfaces onto the rover, and the mounting hardware was already built....
I was given the task of working around all the geometric constraints of were the cameras needed to be to do their job, carving out a volume for the covers to open, making sure they end up above the belly pan of the rover so they don't impede mobility after they are open, etc (just finding room for the covers to swing with the vehicle design where it was in late 2009 was....fun). The covers were a "do no harm" best effort - the idea was not to impact the existing HazCams. Some of the constraints in that area meant they couldn't be 100% sealed, hence the dust particles that got past them. But the front images from last night especially showed a LOT of caked-on dust blocking a significant amount of the images - and that's what we were really trying to protect against - caked on dust or impacts from small pebbles damaging the coating on the cameras.
Another consequence of being a late addition to the design was that we didn't have time to procure a custom mini-cable-cutter, and we had to fire something with the same electrical characteristics as a NASA Standard Initiator. The cutters I used had been ordered for another part of MSL and then went unused because of a design change in that other subsystem.
The cover flips open (in 10-20ms depending on if it's the front or the rear) into a honeycomb energy absorber that bring it to stop with a constant deceleration. The honeycomb absorbers I used had been fabricated 10 years ago as flight spares for the TES mission and kept in their purge/baked out bags with all the certifications by the engineer who built them. I went to review my absorber design with him one day, showed him the size and shape, and he said - "I already built that, I have 60 flight certified units in storage". Once the covers are open, the spring force from the torsion springs holds it in place against ever moving again. Because the springs are oversized to meet design practices for moving mechanism torque margins, they have plenty of torque to simply hold the covers open forever. No latches or other mechanism needed.
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#589 by JohnFornaro on 06 Aug, 2012 17:29
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Nathan Moeller has just tweeted this:
https://twitter.com/AstroN8/status/232496228464750592/photo/1/large
WOW.
That's pretty freaking amazing right there, on so many levels.
Yes indeed. The timing, the visual acuity. Knowing where to look. Pretty amazing. -
#590 by Silmfeanor on 06 Aug, 2012 17:30
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Well, since I was the cognizant engineer on these now-world-famous dust covers, I guess I can stop lurking and talk about them a little bit.
Thanks for the information
And good work, and congratulations!
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#591 by jnc on 06 Aug, 2012 17:35
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I was the cognizant engineer on these now-world-famous dust covers, I guess I can stop lurking and talk about them a little bit.
Thanks very much for taking the time to give us that detailed and authoritative account. Much appreciated...
Noel
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#592 by JBF on 06 Aug, 2012 17:43
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Nathan Moeller has just tweeted this:
https://twitter.com/AstroN8/status/232496228464750592/photo/1/large
WOW.
That's pretty freaking amazing right there, on so many levels.
Yes indeed. The timing, the visual acuity. Knowing where to look. Pretty amazing.
Here is the full shot.
http://mars.jpl.nasa.gov/msl/images/Milkovich_2_Parachute-w-inset-full.jpg -
#593 by marsman2020 on 06 Aug, 2012 17:45
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Also, I've moved on from JPL to another company, and when I left my understanding was the the first images *uplinked* would be with the covers open, and the images with the covers closed would be taken but uplinked later, much like the MARDI images.
I guess with the communications window from Odyssey being so tight, they decided to bin down and grab the images with closed covers right away, because the opening sequence might not have completed before the end of the comm window... So I had no idea my hardware was going to be so famous. They even made that cool press-release quality animation for the final pre-landing press conference yesterday.
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#594 by lucspace on 06 Aug, 2012 17:49
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SpaceflightNow in its landing story:
"... A sophisticated radar altimeter then began measuring altitude and velocity, feeding those data to the rover's flight computer while a high-definition camera began recording video of the remaining few minutes of the descent."
Any chance we will get to see that video? -
#595 by rdale on 06 Aug, 2012 17:50
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No.
That's not the sort of info they would keep private. Nothing big comes down until the mast is up. -
#596 by lucspace on 06 Aug, 2012 17:53
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Then what was the purpose of that video?
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#597 by Jim on 06 Aug, 2012 17:54
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This is an amazing image! I've always wished for external images of missions; they're rare. I think video of the entire landing sequence could have been possible too: just before landing (a min. or so?) shoot out a small camera that embeds or otherwise lands into the soil. Then it tracks and records video--imagine seeing the whole thing in HD. Would have been incredible, not to mention extremely useful for capturing general public interest...
Not feasible. The camera would be a lander itself and would require many services. -
#598 by ugordan on 06 Aug, 2012 17:56
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marsman2020, thanks for that great explanation about the covers. Answers my question about why some dust managed to sneak past the covers anyway.
Do you (by any chance) know how well-protected the scientific cameras are? -
#599 by ugordan on 06 Aug, 2012 17:58
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Any chance we will get to see that video?
Yes, but as has been pointed out several times, it's going to take many days if not weeks to get the whole thing on the ground in original resolution. What we are expected to receive in the next couple of hours are 18 selected *thumbnail* frames (192x144 pixels, color) from that imager.
And good work, and congratulations!
