Quote from: Mattoco on 08/06/2012 07:55 am 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?



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If 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.