[X] My Assistant

[Redstone]

MRO has shifted from the cruise phase to Approach phase. Apparently, the trajectory is so good that TCM-3 was cancelled. This is good news for the prospects for a long life for MRO supporting future missions. TCM-4 is on Feb 28, and MOI on March 10. Only 5 weeks away!

[djellison]

Given the addition of some post-moi-pre-aerobraking imaging, at what appears to be between about 0000 and 0600 on the 15th of March - any idea on a nadir target for that sort of time?

Doug

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[jmknapp]

Given the addition of some post-moi-pre-aerobraking imaging, at what appears to be between about 0000 and 0600 on the 15th of March - any idea on a nadir target for that sort of time?

Doug

Looks like it's the north polar ice cap. Here's the view midway in that interval (+ marks the nadir point):



Note that the FOV above is 5 degrees. CTX has an FOV 0f 6 degrees; HiRISE 1.14 degrees.

[mcaplinger]

Looks like it's the north polar ice cap. Here's the view midway in that interval (+ marks the nadir point):

Try looking (hint, hint) closer to 6:00 UTC.

[jmknapp]

Try looking (hint, hint) closer to 6:00 UTC.

Hmmm... here is the view at 0600:



Wondering what you are hinting at--perhaps this is targeted after one of the proposed Phoenix landing sites? The subpoint above is 75N 141W.

[mcaplinger]

Wondering what you are hinting at--perhaps this is targeted after one of the proposed Phoenix landing sites? The subpoint above is 75N 141W.

I think your software is confused, or ours is. What SPICE kernel are you using?

[jmknapp]

I think your software is confused, or ours is. What SPICE kernel are you using?

Could be. Here are the kernels I'm using:

CK:
'$KROOT/ck/DESAT_MOI_sc_20060103171803.bc',

SPK:
'$KROOT/spk/spk_c_tcm1-od006_050812_060315_p-v1.bsp',
'$KROOT/spk/spk_moi_lowperf_t2_051123_060320_p-v1.bsp',
'$KROOT/spk/spk_moi_ideal_051123_060320_p-v1.bsp',
'$KROOT/spk/spk_moi_highperf_t1_051123_060320_p-v1.bsp',

I notice there's a big difference whether highperf, ideal or lowperf is used, so maybe that's the difference. The projection above uses highperf (since it's the last listed in the config file).

[mcaplinger]

I notice there's a big difference whether highperf, ideal or lowperf is used, so maybe that's the difference. The projection above uses highperf (since it's the last listed in the config file).

We were doing this planning several weeks ago, so the kernel I used was from mid-January. In those kernels, we were near periapsis at 6:00 UTC. Looks like we're looking at some replanning if the MOI performance makes this much difference. I would try rerunning with ideal and see what that looks like.

BTW, what software are you using for this?

[jmknapp]

We were doing this planning several weeks ago, so the kernel I used was from mid-January. In those kernels, we were near periapsis at 6:00 UTC. Looks like we're looking at some replanning if the MOI performance makes this much difference. I would try rerunning with ideal and see what that looks like.

BTW, what software are you using for this?

Hmmm... using the "ideal" kernel gives periapsis on 15MAR2006 at 06:24UTC, 399km, at 67S 28E, although it's on the night side so the picture is dark. Pretty big difference there.

The software I'm using is a C program that I wrote to use the CSPICE library--so there could be a bug or three there. The same program works pretty well with Cassini, but at least in that case I have actual images to compare against for testing. Choice of kernels seems to be a big factor.

One kernel tells a cautionary tale:

spk_nomoi_051123_060320_p-v1.bsp

No MOI--gulp! That pessimistic kernel gives this view on 15MAR:

[mcaplinger]

Hmmm... using the "ideal" kernel gives periapsis on 15MAR2006 at 06:24UTC, 399km, at 67S 28E, although it's on the night side so the picture is dark. Pretty big difference there.

The software I'm using is a C program that I wrote to use the CSPICE library--so there could be a bug or three there. The same program works pretty well with Cassini, but at least in that case I have actual images to compare against for testing. Choice of kernels seems to be a big factor.

That result sounds pretty close to ours, so I'd say your code is working well. Those kernels just appeared on the NAIF website and I don't know what sort of burn performance differences they represent; it would surprise me if plausible burn variations would change the orbit timing so much.

[Bob Shaw]

That result sounds pretty close to ours, so I'd say your code is working well. Those kernels just appeared on the NAIF website and I don't know what sort of burn performance differences they represent; it would surprise me if plausible burn variations would change the orbit timing so much.

Guys, can you *please* work out whoever is right, you're beginning to (gulp) worry me! MOI has already eaten several pretty toys...

Bob Shaw

[Guest_AlexBlackwell_*]

Guys, can you *please* work out whoever is right, you're beginning to (gulp) worry me! MOI has already eaten several pretty toys...

You think Mike might be using metric figures, while jmknapp is using English units?

Hmm. That sounds vaguely familiar.

[mcaplinger]

You think Mike might be using metric figures, while jmknapp is using English units?

Very funny, Alex. If it makes anyone feel better, I don't have anything to do with planning MOI.

jmknapp has performed a valuable public service by highlighting that those three kernels produce significant orbital timing changes; I hadn't appreciated that the MOI performance could induce that large a change, but now we're prepared. We weren't given any context about what those kernels might mean -- they just showed up on the NAIF website. They may be for training purposes, or they may be physically realistic.

[Guest_AlexBlackwell_*]

Very funny, Alex. If it makes anyone feel better, I don't have anything to do with planning MOI.

I couldn't resist the tweak, Mike, especially since I know the way the MCO/MPL/DS2 losses were reported has grated on you. It's not the same, though, as needling Bruce. Now that is fun

jmknapp has performed a valuable public service by highlighting that those three kernels produce significant orbital timing changes; I hadn't appreciated that the MOI performance could induce that large a change, but now we're prepared. We weren't given any context about what those kernels might mean -- they just showed up on the NAIF website. They may be for training purposes, or they may be physically realistic.

Is this similar to the slight differences between MSSS-generated and JPL-designed targeting boxes that were evident early in MOC campaign? If I remember correctly, sometimes your orbit predicts disagreed with JPL's.

[djellison]

It's not the same, though, as needling Bruce. Now that is fun

Now that's actually a requirement for membership here, it's not a matter of humour - it's part of the process

Doug