I'm pretty sure the answer to that is here in the forum, somewhere. I know I read about it online and I suspect it was in a set of posts here.

Short version, from my best memory of the thread (which is fair warning, as my best memory is, as we all know, fallible) the programming was originally to have the descent stage burn for a specified period of time during flyaway. Then someone decided it should just burn to fuel depletion, wanting to reduce the possibility of contaminating the surface with excess propellants. That person even tried showing that the amount of prop assumed to be left at start of flyaway would result in just about the same burn time as the timed-cutoff burn, but the prop remaining envelope was giving possible flyaway distances of up to 20 km on the burn-to-depletion plan. In the end, because they wanted to be able to characterize the crash site envelope as accurately as possible, they decided on the timed burn after all.

-the other Doug

And, while my theory isn't disproven by this, I see no indication of surface darkening between the rover and the descent stage crash point. However, based on what I know of the orientation of the rover, it looks to me like the descent stage flight and crash ought to have been right in the center of the rear hazcam's field of view. So, whatever caused the RHA, I'd have to say that the descent stage was definitely involved.

-the other Doug

Maybe, Mongo. Also, though, remember what the dynamics were supposed to be on the flyaway maneuver. At bridle cut confirmation the descent stage tilts over and begins to translate horizontally. During this period it will gain a little altitude and the trajectory turns into a long, slow arc with a high point between the rover's landing spot and the descent stage's crash location. Also, the slant angle of the rocket plumes to the surface becomes much greater during this maneuver than during vertical descent, such that the upper plumes may not even impinge on the surface at all. In fact, at the highest altitude achieved during the flyaway arc, it might be that the combination of slant angle and altitude could have greatly reduced the raising of a dust cloud during that part of the flight.

So, for example, the unmoving cloud may be a lot closer to the rover than the dynamic cloud, which could be the result of descent stage plume impingement as the stage descends towards its crash point. We just don't know how high the stage got during flyaway. We do know that at the initiation of the maneuver and at the end of the maneuver it ought to have been kicking up a good cloud of dust, if the MARDI sequence is anything to go by.

-the other Doug

If the descent stage kicked up a cloud of dust as it flew off into the sunset, that could also explain why Curiosity seems to be so dust-covered. Not only did we have a highly chaotic dust cloud through which Curiosity was lowered during the skycrane maneuver (caused by the interaction not only of the rocket plumes with the ground but with each plume's interaction with the other plumes), but also, if my theory is correct, as the descent stage flew away it pushed dust from down its flight path back towards the rover, adding a parting back-splash of dust as it departed. And considering the relative gas pressure of the rapidly-moving (and pointed back at the rover) cloud of exhaust vs. the ambient air pressure, the exhaust could have produced a localized wind that would have pushed such a dust cloud back towards the rover, as well, such that much of it settled out of the air on top of our now-dirty little girl.

In any event, it sounds like we could use a nice breeze to clean off after that landing...

-the other Doug

In regards the first rear hazcam images and what we actually see in the two frames, I think we need to determine what we know about what was happening at that moment, as well as what we don't know, and what we can find out later.

First off, the Rear Hazcam Anomaly (or RHA, I think I'll call it) appears in the same position in both the left and right hazcam images, so we know it's really unlikely to be artifact from dust clods hitting the dust covers.

The first bit of important data we can know right now but that I don't think we here at UMSF have in hand is the timing of the image captures. Considering how quickly we got these images down, I'd have to think that they were taken within a few seconds of touchdown. We now know from the MARDI sequence we saw yesterday that there was a rather large amount of dust still up in the air at touchdown, and we know from the Viking 1 first image sequence that such a dust cloud can take as much as a minute or two to settle out and the cloud fall back down to the ground and/or disperse into a non-detectable airborne haze. (The first V1 surface image shows a very rapidly changing illumination level from beginning to about one minute into the image capture, which has been supposed for decades to be the result of a strong tau influence from the settling dust cloud raised by the rockets during landing.)

Assuming the RHA images were taken within, say, five seconds of touchdown, we could be looking at nothing more than a localized thick spot in the dust cloud raised by the landing. The slight change in the shape of this dense part of the cloud between the two images could be either from the different look angle between the two hazcams, or from the cloud changing shape as it falls back down toward the ground in the time between when the first and second images were captured.

However, the more exciting possibility is that we are actually seeing the exhaust and/or the dust being blown up from the ground as the descent stage is actually performing its flyaway maneuver. After all, we know that there was significant dust impingement and movement on the surface from considerably higher than the height at which the skycrane maneuver was initiated, so even if the descent stage rose 10 meters between bridle cut and the highest point of its arc towards its crash point, the exhaust could still have been disturbing the surface throughout the flyaway maneuver.

We may be looking up the bells of the descent stage (not resolvable itself in these images due to the dust cover on the lens covers and of course the resolution limits of the hazcams). I doubt that the exhaust itself would be so dark (at least, with so much contrast against the sky) as what we see, though, so it just makes more sense to me that we're looking at the dust cloud being kicked up in a line along the path of the retreating descent stage.

Since the descent stage was, at flyaway initiation, supposed to tip over along one of its primary axes, and assuming there was no twisting on the bridle as the rover descended, it makes a lot of sense that the flyaway trajectory would be either directly to the rear, front or one of the sides of the rover. The most northward-facing trajectory away from the rover would have been directly to the aft, going west-northwest. So, if the images were captured quickly after touchdown, it would make sense that the descent stage, in flight, would be in the field of view of the rear hazcams.

I guess the most important thing, in figuring out what we're seeing, is an exact knowledge of the time after touchdown when these two images were captured. If it was within, say, two to five seconds after touchdown then I submit we can't be seeing the descent stage impact, since it would still be in flight. If it's still in flight, we're either seeing the engine exhaust itself (less likely) or the entrained dust cloud that even at that moment was being kicked up by the rocket engines.

What do y'all think?

-the other Doug

The "good" MRO passes in six and 12 days should give us a much better idea as to the current condition and location of the descent stage. I imagine if it exploded upon impact, we'll see plenty of evidence for that, too. I somehow doubt it would explode, though... the hydrazine, while not exactly stable, is only explosive when in contact with the catalyst beds, no?

However -- can you imagine what would have happened if they had left the fly-away programming to burn until fuel depletion? I get the image of the descent stage running headlong into the far wall of Gale, at speed.

-the other Doug

It was the dust-blowing sequence that really blew me away. The rockets really kicked up a little maelstrom, there. I hope they weren't assuming that the body of the rover would protect the mast cams from blowing dust, cause it looks like Curiosity descended into a rather energetically blowing cloud of dust there at the end.

-the other Doug

Oh. My. God.

-the other Doug

Interesting -- Google Chrome doesn't display this page properly. Ever since the wee hours when I first pulled this page up, in Chrome all I get are image placeholders and clicking on any of the placeholders just re-displays the same page with the placeholders.

Works just fine, as designed, when I access the site via Internet Explorer 9.

Just an FYI for y'all.

-the other Doug

That looks to be very close to the co-ordinates that were called out at the end of EDL last night and were mapped here at that time. Very close indeed.

-the other Doug

Based on a single 256-pixel hazcam, I can see that we have very few rocks around here. More like scattered gravel and stones. This looks more like what I expected Gusev to look like, more like an ancient lakebed.

Of course, any serious analysis will wait for better images.

-the other Doug

It's a thumbnail from a hazcam, but we have a hazy horizon and a wheel in the dirt.

Welcome to Mars, everyone.

-the other Doug

So, we don't expect to start getting bent-pipe UHF through MODY until a couple of minutes after entry begins, and it will be ratty at first, according to what I just heard in the controllers' round-up? I imagine that means the Eyes animation will only start reflecting actual circumstances at about that time?

-the other Doug

I was just in the middle of typing a post asking when we might get confirmation that Odyssey has completed its attitude change, when the NASA TV commentary announced they're in the middle of the turn, so I imagine we'll get some kind of a confirmation here in the next ten to twenty minutes. ***fingers and toes crossed***

However, I also note that the Navigation officer just called for a conference on a local loop, off the air. Hope nothing is wrong with any of assets at Mars or onboard the spacecraft.

-the other Doug

Thanks for the kind wishes, guys. Life just got real busy and complicated, and I needed time for some things that couldn't come from anywhere else but the hours I would spend on this forum every day. That doesn't mean I haven't been lurking from time to time -- after all, where else can I get my fix of high-quality images from the Martian surface? Really been enjoying the pictures from Oppy, especially the latest of her straddling Whim Creek.

As for de-lurking tonight, I decided I couldn't experience this night without sharing it with my like-minded friends.

Good to see all of you, too.

-the other Doug

As Toff Markin said to Darth Vader, "This had better work."



-the other Doug

According to the Eyes animation, Mars is presenting a truly iconic appearance to the approaching MSL, with Syrtis Major neatly centered in the rapidly swelling disk of the planet. Fine work by all involved, esp. Fearless Leader (aka JPL Visualization Engineer... ). You can truly place yourself right there.

-the other Doug

De-lurking for the evening to wish good luck and Godspeed to all those involved with tonight's landing. (As bkellysky noted, in the absence of a cheerleading thread, I decided to add my best wishes here.)

BTW -- anyone have a good timeline hack on when to open up my bag of mission peanuts? That would have been a good event to have on the EDL portion of the Eyes sim.

-the other Doug

Wow! That's a lot, Greg. Of course, MS has never been known to scrimp on salaries.

I guess I've just been figuring that the mean salary of an engineer is on the order of $50K a year. Doug has noted to me personally that it's likely a lot more -- something that surprises me, but then again, I only know about salary ranges for the companies I've worked for and that friends and acquantiances have worked for. (Not to say our intrepid JPLers don't deserve every penny they get, I was just, from my own work experience, vastly underestimating the salary ranges.)

So, please -- if anyone out there thinks I'm undervaluing the men and women at JPL, APL, Cornell, etc., etc., all I can plead is that the software and hardware engineers I know who work in the Minneapolis area seem to think that $50K is a great salary. Please forgive me for assuming that salary ranges where I live, for people who do different things than supporting space probes, are at all representative of salary ranges across the country. Mea culpa, mea culpa, mea maxima culpa....

-the other Doug

Again, sorry -- writing posts and getting interrupted at work and you're answering my questions before I can post them...

-the other Doug

Again, apologies. I'd still be very interested in seeing what the actual DSN costs are in these budgets, though. As I said to Mike, if about $20 million per year in extension funding isn't mostly DSN costs, I have to wonder how much it costs to keep 20 to 50 people employed, in office space, and with decent computer access these days...

-the other Doug

Thanks, Mike. I was going off of some discussions on a couple of other forums I read and sometimes post to, which were quoting DSN costs as as much as $15 to $20 million per year (if not more) for pretty much every spacecraft that uses it, and from what I was seeing from the publicly-available cost formulae at the time, these guesstimates didn't seem out of line.

If I'm wrong, I'm certainly more than willing to admit it. In the beginning here, I was just responding to concerns expressed and opinions given over the cost of yearly extended ops for the MERs, and was trying to determine where all of about $20 million a year was being spent to keep the old girls going. Not that I feel it's money poorly spent, just that, with the world economy in deep recession, I'm afraid that our wonderful planetary exploration vehicles, including the MERs, could be cut back or cut off entirely unless we figure out some way to operate them more cheaply.

For example, I recall that there was a "groundswell" campaign to collect money to keep the Viking landers going when Congress threatened to cut off their funding, and that the money collected wasn't really enough to pay for the DSN time, much less data analysis and storage. And that was nearly 30 years ago. That certainly reinforced the idea that DSN costs were a majority of the continuing operating expenses.

If Doug's numbers are right, then it would seem that we're paying something like $16 million a year for the rather limited staffing and facilities required to operate the MERs. Apologies, but that doesn't sound realistic, either.

-the other Doug

You typed your breakdown while I was typing my response, there, Doug. Those are much lower figures than I've seen on some other fora for DSN costs, and also your mentioning of ability to communicate with multiple spacecraft at one time through one dish is something that wasn't in the literature last time I looked through it (about 6 months ago).

And please, stop harping on the term "attack." It means, in this context, to aggressively seek resolution to what appears to be a valid concern. As I've explained, that's certainly how I meant it; I'd appreciate it if you can accept that.

-the other Doug

When I said "attack" I meant to aggressively investigate why the costs are so high, as in "we need to attack this problem and get it solved, people." (That is a perfectly acceptable use of the word, and not intended to imply violence or disrespect against the institution being discussed.) Is it intrinsically extremely expensive to operate these radio receivers? I grant you, they have to separate out extremely faint signals from background noise that fairly swamps them. But does the equipment needed to do so cost exorbitant amounts? Or does it require millions and millions of dollars a year in maintenance? These are the questions that were on my mind.

One thing that was on my mind, as well, is that the way supply-and-demand economics works, you can charge pretty much what you want to charge if you have no competition, and for the most part the DSN has no real competition. I guess I'm just wondering, in this age when electronics are so incredibly advanced over what they were when the DSN was designed and built, are there cheaper ways to accomplish what the DSN accomplishes? Even granted the initial outlays that would be required, the fact that the DSN is so time-limited by so many demands on its time, it would be quite useful to have a second or even third set of receivers active at (roughly) every DSN location around the globe (or, as has been suggested, though I think the cost would be really outrageous, place a new DSN into LEO). If a new network can be built that can be operated much more cheaply, with the same quality of data return, as the current DSN, has anyone contemplated how to get this done? *Can* it be done?

Those were the questions that were on my mind.

I certainly didn't mean to offend anyone. I just have run across several cases where DSN costs have been discussed as being very high, tens of millions of US dollars a year to support a single planetary probe. Everyone talks about ways to lower costs so we can fly more missions, but they seem to concentrate on launch vehicles and ASRGs and such, when over the course of a long, multiply-extended mission, it would appear that DSN costs are one of the really high-ticket items in the budget. And the DSN is getting to the point where we can't fly many more missions at one time than we have going right now; we seem to always be looking at trade-offs from one mission to the next based on which mission gets the DSN time at any given day and hour. (I know we've lost some Cassini data due to DSN conflicts, that's been mentioned here before.)

IIRC, one of the main DSN dishes is offline now (repairs that will take a couple of years to complete), and it is making the juggling of requests that much more difficult. We're now in a position, it appears, that if we lost another dish in the DSN, we may have seriously degraded our ability to operate the missions currently in flight. I'd say that calls for an expansion of the capability. And if the many millions (perhaps billions) of dollars US spent in total for DSN time every year underfunds the network, then how in the world are we going to expand it?

These were my concerns. I sincerely apologize if I offended anyone, I certainly didn't mean to. I just wanted to point out some concerns over planning expanded planetary exploration when the DSN seems to be a bottleneck, both in terms of cost and in terms of capability.

Forgiven?

-the other Doug

I would guess that the answer to how much of the MERs' extended mission costs are DSN costs incurred for uplinks and paid to the MODY /MRO project teams for their relay services lies in the detailed budget accounting. Is the detailed budget data (down to line item) for the MER extensions available publicly? That would be quite instructive, I would think.

It would also be good to see budget detail at that level for other missions, like Cassini, New Horizons and LRO (to name but a few) to see just what the percentage of operations costs commonly consist of DSN charges.

-the other Doug