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Posted by: Jeff7 Nov 14 2005, 11:49 PM

Or Genesis. I seem to remember reading somewhere that the gravity sensor that would have told the parachute to deploy was put in upside down.


Ah, found a link. http://www.washingtonpost.com/wp-dyn/articles/A36645-2004Oct15.html.



Oops.
Also of note, this was after MCO "buried," as Robin Williams put it.

Posted by: djellison Nov 14 2005, 11:52 PM

BUT - Genesis worked - most of the samples, and all of the critical ones, survived fine. There was a delay to, but no loss of science.

Minerva was a last minute thing iirc - given that JPL was devloping a rover for Muses C but cancelled on them.

Doug

Posted by: Jeff7 Nov 15 2005, 12:04 AM

Really? Good to hear - I admit, I hadn't checked up on that project for quite some time. The website had gone months without any updates, other than to basically say "we found a few more large fragments, but they might be contaminated too." Checking the page now, well, it confirms what you said.
Still though, really - say one of the MER's had had this problem. (Polar Lander's issue perhaps?) Full speed right into the ground. Though the thought of the lander trying to deploy itself while buried in the center of a fresh crater is a bit amusing. It's a fairly important part though and it's in backwards. MSL would really suck if they put the Skycrane's retro-rockets in upside down.

Posted by: deglr6328 Nov 15 2005, 01:33 AM

eeeh? I don't know, have any papers even been published yet?

Posted by: Sedna Nov 15 2005, 02:36 AM

I think Genesis worked okay, but failed in a very important point: to get the samples back flawlessly!! All the thing with the helicopters was "funny" while the proble hitted the ground, as a scientist I would have just dropped the whole thing into the rubbish bin (what a pain!). Now, they are trying to "save something" while they should know by now many conclusions about the samples...

Posted by: elakdawalla Nov 15 2005, 03:18 AM

I think the scientists feel thankful every day that their samples survived an event that should have destroyed all hopes for any successful result from the mission. The Huygens Doppler Wind Experiment scientists feel the same way. It's heartbreaking to consider what they could have had, if their receiver had only been turned on aboard Cassini. Yet, thanks to some incredibly hard work, they do have a data set, and one that's sufficient to accomplish most of the stated goals of their experiment (though of course not everything they could have done if everything had gone right). I am sure the Genesis folks, while feeling rueful about the arduous task that they face, are eternally grateful that they've got data at all.

By the way, there are both http://www.agu.org/cgi-bin/sessions5?meeting=fm05&part=SH32A&maxhits=200 and http://www.agu.org/cgi-bin/sessions5?meeting=fm05&part=SH33A&maxhits=200 sessions of Genesis mission results planned for the 2005 Fall Meeting of the American Geophysical Union in San Francisco.

--Emily

Posted by: mcaplinger Nov 15 2005, 04:30 AM

Gee, it must be nice to be infallible.

Calling it the "english vs metric unit thing" is something of an oversimplification. You might want to read
ftp://ftp.hq.nasa.gov/pub/pao/reports/1999/MCO_report.pdf before being so casually dismissive of those of us who spent several years on the MS98 project (not that I had anything to do with the nav error.)

Posted by: The Messenger Nov 15 2005, 05:06 AM

Yes, there were three, or at least two-and-a-half navigation solutions, they ALL indicated the MCO should have been on a survivable track, and only one-of-the three contained the conversion error. The final chapter on Mars mission landing failures can't be written - not until there are better explanations for the thin upper atmosphere, hard landings, and harmonic gravitational degeneracies.

Posted by: odave Nov 15 2005, 02:33 PM

Yes, I'm aware that it was a much more complex problem, but I was trying to keep the post short by summarizing, and that often gets me in trouble. I apologize for my harsh tone. I was in a surly mood yesterday and normally keep my mouth shut when I'm feeling like that, but alas...so I'll wear the hairshirt today

Still, the navigation error was an unfortunate oversight - one that would get those responsible at least a reprimand, if not a demotion, in many companies.

I don't work on spacecraft, but I do work on projects that require a lot of creative energy and long, toiling hours. I know how badly I feel when something I've worked so hard on goes down the tubes, and no doubt you all on the MCO team felt like you were kicked in the stomach. I'm sorry for any hurt feelings my post may have caused.

What I should have said is that the most important thing is *not* to point the finger and kick the dog, it's to make sure that a lesson was learned and processes put in place to make sure it does not happen again.

Posted by: Analyst Nov 15 2005, 02:42 PM

Galileo had a spinning part with the f&p instruments, RTG and Mag booms and the engine/probe section and an unspun part with the HGA and pointed instruments. I don't see any use for reaction wheels on a (partly) spinner. Are you talking about the gyros (used for measuring the position in space instead of changing it)? The science runs on Galileo were compromised by safe mode entries because of cosmic ray hits in various subsystems (computer memory, camera...). I doubt Galileo had any reaction wheels. Cassini has four (one backup).

Analyst

Posted by: ljk4-1 Nov 15 2005, 03:14 PM

Is there anything more efficient and less prone to problems that reactions wheels that future probes could use?

Posted by: The Messenger Nov 15 2005, 03:45 PM

Yes, I tend to look at reaction wheels as gyros-on-steroids, but I shouldn't lump them together.


This may or may not be true; Reading through the Galileo event logs, NASA was having a tough time with Galileo hiding in her shell on close approach to Jupiter's moons - Near IO, this was blamed upon the intense EM Field, but most of the time the shutdowns were atributed to Cosmic Rays.

As I mentioned before, I have a problem with this simplistic explanation, because the probe invariably clammed up on closest-approaches to Jupiter's moons, then responded more or less normally while 'coasting' between them. This is why I suspect an ESD component, or something that we do not quite have a handle on.

It would be interesting to know precisely where and when Cassini has experienced reaction wheel problems, because I would like to be able to rule-out a scenario similar to what I just descibed.

Posted by: ljk4-1 Nov 15 2005, 04:12 PM

I wonder how we are ever going to have probes explore the inner Galilean moons without their being fried by the radiation and not have to bring a ridiculously heavy amount of shielding with them?

Posted by: Bob Shaw Nov 15 2005, 05:00 PM

The answer - once adequate power sources are available - will be some form of active EM shielding, essentially a mini-magnetosphere within which the vehicle resides. Obviously, it'll play silly buggers with particles and fields experiments, but them's the breaks!

There was some coverage of a sort of 'inside out' ion drive which could provide both propulsion and shielding several years ago - it was being proposed under one of NASA's 'blue-sky' programmes for looking at unorthodox - but perhaps buildable - engines (etc).

Bob Shaw

Posted by: Phil Stooke Nov 15 2005, 05:51 PM

I think this discussion needs to be moved!

Phil

Posted by: Bill Harris Nov 15 2005, 05:53 PM

"Aye, Cap'tn Kirk, I canna make the shields hol out much longa..."

Sorry, I couldn't help this one.

I've heard of that as a magnetic field around a superconducting coil.

--Bill

Posted by: BruceMoomaw Nov 15 2005, 07:36 PM

Galileo had no reaction wheels -- but its "dual-spin" design, which was supposed to be simple, ended up giving them cat-fits during the initial design period, and JPL has since sworn "never again". (They had particular trouble transferring electrical signals properly between the two sections of the craft, largely due to tiny bits of debris getting into the electrical brushes -- and indeed that problem caused resets periodically during the flight itself.)

Posted by: tasp Nov 15 2005, 07:39 PM

Having a Galileo II craft travel in an inclined path around Jupiter would help. The radiation seems to increase in the equatorial plane.

Having a probe cross the equatorial plane in the 'radiation shadow' {of a major moon} would help too.

{IIRC, the shadow won't necessarily be where you think it is }


Edit: clarified where to find radiation shadows, sorry for omission.

Posted by: The Messenger Nov 15 2005, 08:19 PM

Thanks, Bruce, this is a question I have been trying to get a reasonable answer to, for a very long time: Dirty brushes I can understand, cosmic rays that lurk near moons? - I don't think so.

Posted by: Sedna Nov 16 2005, 03:26 AM

Good to hear, we'll have then the chance to discuss and learn with that folks

Posted by: hendric Nov 16 2005, 04:23 AM

It wasn't that simple... You couldn't tell externally which way was down. You had to X-ray the sensor! Like, hadn't these guys heard the story of the Claymore mine? "THIS SIDE TO ENEMY"! They had two pairs of two sensors, I don't understand why they didn't have one of each pair flipped WRT the other, then this wouldn't even have been an issue. They did say Stardust won't have this issue, maybe that's what they did?

Posted by: hendric Nov 16 2005, 04:30 AM

So,, any bets on the next time we'll see a deployable HGA on a probe? I think the Galileo idea was a good one, it just got screwed by Challenger. Looking at the amount of data we're getting back from Cassini, I'm both saddened and awed at what Galileo accomplished.

Posted by: djellison Nov 16 2005, 08:36 AM

Well the TDRS sat's launch with deployable HGA's - but I'm not sure if their design would be applicable for deep space applications instead of GEO.

Doug

Posted by: BruceMoomaw Nov 16 2005, 09:19 AM

Galileo's antenna WAS an exact copy of the TDRS ones, which is why everyone was so confident that it would work. No one ever dreamed of truck vibrations as a cause of trouble.

At the COMPLEX meeting the suggestion was made that Europa Orbiter could easily increase its bit rate with an unfolding antenna. Universal groans followed; "Been there, done that," somebody muttered. I think this is unfair -- you just have to design the damn thing with more excess unfolding power.

Posted by: The Messenger Nov 16 2005, 03:13 PM

It is good to hear that most of the samples are/have been recovered. So what is the sun made out of, besides that light stuff we can see?

The Utah- Nevada Desert that Genesis crashed in, is a remarkable area for artifacts. Here is a great story:

A few years ago, my (former) wife was running a desert field survey near the Utah/Nevada boarder with a crew of archeological techs, and came across a crashed UFO.

No, really, an honest to God, saucer-like vessal about the size of a motor boat that had pancaked and broken into the sand. They were about a mile away (and spread out, because they were surveying), but she was closest, and her crew kept asking over the headphones what in the hell it was, and looking through the bonoculars the only thing that she could say is that 'It looks like nothing other than a crashed UFO'.

She promised the crew they would go back and check it out, after lunch, but that proved unnecessary: One of the marques on a local hotel said "Welcome: Crew of Independence Day." Nice prop. By the time they returned, the 'ship' had disappeared and returned to Hollywood...or hidden in Area 51, if you are into that kind of thing.

Posted by: mike Nov 16 2005, 04:04 PM

Thank goodness for movies like 'Independence Day'.. There just aren't enough stories about aliens blowing up the planet.

Posted by: ljk4-1 Nov 16 2005, 04:11 PM

How about an inflatable antenna?

How goes it on the plans for an interplanetary communications network?

Posted by: ljk4-1 Nov 16 2005, 04:14 PM

Some of the reasons given for the infamous Roswell saucer stories included the air drop tests of the Voyager and Viking Mars probe heat shields in the 1960s and 1970s, which looked an awful lot like a typical saucer-shaped UFO.

See the images at the end of this page:

http://www.af.mil/library/roswell/

The Roswell Air Force Base has one of the actual Voyager heat shields on display, or at least they did when I saw it in 1995.

Posted by: The Messenger Nov 16 2005, 07:29 PM

We have experimented a lot with using low density foams to build space structures, and they work very well in low pressure, low G environments. This would be another good use for the ISS, experimenting with large-scale expanding Tinker Toys.

Posted by: Bob Shaw Nov 16 2005, 10:25 PM

Now that's a helluva link - I didn't know *any* Voyager hardware was built, let alone flown (that's the *original* Voyager, chaps - the twin-payload Saturn V Mars mission!).

Bob Shaw