[X] My Assistant

[Guest_AlexBlackwell_*]

Regarding the MARDI issue, I note today's entry on NASA Watch. I'm not sure about the testing for Phoenix but I thought MARDI had passed a similar test for MPL (i.e., confirmation of non-interference with the EDL sequence). Perhaps someone who was involved with the latter could clarify.

[mcaplinger]

Rather than give you the inside story, which I obviously don't have the authority to do, let me ask a question. The press release says this:

Tests of the assembled lander found that an interface card has a small possibility of triggering loss of some vital engineering data if it receives imaging data during a critical phase of final descent. That possibility is considered an unacceptable risk...

So the question: what probability of failure should be considered an "unacceptable risk"? The bug that caused the failure of MPL had a probability in the tens of percent, as I recall from the review board reports, so it was obviously unacceptable. But given that a PHX landing failure would result in no science data being returned, it might not take that large a probability to be judged unacceptable. I didn't have to make that call, and I don't know what the failure probability assessment was, but the press release implies it wasn't zero. Of course, in aerospace failure probabilities of zero don't come along very often.

Disclaimer: just my own opinions, no privileged information.

[monitorlizard]

I find myself agreeing with Rakhir on the MARDI issue. One descent image, taken at the optimum time, should be enough to help quickly locate Phoenix's landing spot in a later HiRISE image. Yes, some science will be lost, but it seems to me that ten or so descent images are most desired to create a "landing movie", which would be more for PR than science. It would be nice if MARDI could squeeze out two descent images, that would do a lot to provide context for the surface images.

Lockheed Martin has had more than their fair share of screw-ups in the last ten years, so I do share everyone's disappointment about this.

[belleraphon1]

All...

http://www.nasa.gov/home/hqnews/2007/jul/H...stpone_Sep.html

"NASA will hold a news briefing at 11:30 a.m. EDT on Monday, July 9, to preview the launch of the Phoenix Mars Lander. Prior to the Phoenix presentations, media will have the opportunity to learn in more detail about the rescheduled Dawn launch.[i][u] The briefing will originate from the NASA Headquarters auditorium, 300 E St., S.W., Washington. It will air live on NASA Television and be streamed online at: http://www.nasa.gov/ntv"

Craig

[edstrick]

Mardi for the 2001 Mars Lander was pre-pre-pre thinking about Mars Recon Orbiter and 29 cm/pixels from orbit. In the context of Global Surveyor images that were more than a bit noisy at full resolution (so that the noise could easily be higher than the actual contrast of small terrain features), and were much <most?> of the time taken with pixel-binning at lower resolution, MARDI was absolutely scientifically necessary.

It'd still be nice to have had a color landing-zoom movie, but it's no longer a critical mission capibility for geologic interpretation.

I expect they'll pick a frame size to get resolution between 5 and 10 cm per pixel, something better than Recon Orbiter's 25-29'ish cm/pixel, but still get decent area coverage.

(I'm still frustrated, 41 years later, that neither Surveyor 1 or 2 got descent image sequences at the moon)

[mcaplinger]

It'd still be nice to have had a color landing-zoom movie...

There seems to be some confusion about the color. MARDI/PHX ( http://www.msss.com/mars/surveyor/ms98/lan...t/abstract.html ) is panchromatic (black-and-white), though the images could be colorized via the usual methods. It's the MSL MARDI (completely different instrument, just the same name) that's color.

Question: if imaging from a moving, powered platform, would you rather take a single image or a series of images?

Disclaimer: just my opinions, public information only.

[djellison]

Exactly - I'm sure Dan's overdone it a bit on the EDL animation - but there's no guarentee with the thing pitching and rolling around that just one image, at almost any point during landing, will get the landing site itself into frame.

Doug

[monitorlizard]

I can't imagine any serious problem with HiRISE finding Phoenix after it lands, unless it wildly misses its target ellipse. At 29 cm/pixel, Phoenix should stand out like a sore thumb in a color image. If it should happen that the one mardi descent image doesn't capture the exact landing site, I don't think all that much science will be lost. The terrain should be geologically similar for an area much larger than the landing ellipse.

[tedstryk]

I have worried about the mission in the past. I mean, while we found out a likely reason for the MPL failure, we can only hope that there weren't other problems that were overlooked. While much time and money has been spent improving Phoenix, it still is, at its core, a spacecraft designed and built in the pre-MPL/MCO faster-cheaper-splat days. I won't have an comfortable feeling about it until it is safely on the surface (then again, the only mission I didn't feel that way about, given all the things that could go wrong, is Voyager at Neptune, and that was because I was 10 years old and too dumb to consider it).

[mcaplinger]

a spacecraft designed and built in the pre-MPL/MCO faster-cheaper-splat days...

As I have said many, many times before in this forum, any spacecraft can fail no matter how expensive it was. Neither MS98 failure had that much to do with money, and both designs were fundamentally sound IMHO.

[tedstryk]

As I have said many, many times before in this forum, any spacecraft can fail no matter how expensive it was. Neither MS98 failure had that much to do with money, and both designs were fundamentally sound IMHO.

That was what I was indicating by my parenthetical statement.

[Guest_Zvezdichko_*]

There's something I have missed. Is there a telemetry relay system onboard Phoenix so everything could be reviewed during descend?

[Jim from NSF.com]

It records the telemetry. Only tones (semaphores) are transmitted during descent

[centsworth_II]

Did I just hear on the Phoenix press briefing that MRO
was to try and image Phoenix "...on the way down."?!

[ElkGroveDan]

I wasn't listening, but they are probably talking about the entry trail. As I recall MGS attempted this (unsuccessfully) with one or both of the MERs.