[GLIMS] Terra drifting orbits--unique science?

[Jeffrey Kargel]

Dear GLIMS colleagues,
As you may know, Terra (hence, also ASTER)  is entering its end-of-life period. NASA has a call (just a Request for Information--no money involved) on observations and possible unique science that a drifting orbit could achieve. The spacecraft is drifting to earlier morning equator crossings. I think the drift so far has been about 15 minutes earlier equator crossings, and this will get progressively earlier. If unique science is not identified, I suspect that Terra will be decommissioned earlier than if we do identify unique science. From a GLIMS/glacier perspective, do you see unique science potential (meaning, not simply a continuation of what we have been doing with ASTER and MODIS, but actual newly enabled science)?
I have one suggestion, but let me know what you think of it. Is it worth doing, would it achieve anything highly useful, would it be unique, and do you want to re-dedicate some ASTER resources  to achieving the following? If not, then is there something else that can be proposed? I believe they are looking for 1-page descriptions, so it should not be painful at this stage. Presumably there would be work to do if Terra is budgeted to remain operational and the unique science idea is accepted.  First, the announcement:

https://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=896712/solicitationId=%7B19F4296E-5280-3996-3149-42CB166328DC%7D/viewSolicitationDocument=1/NNH22ZDA018L_TAA_workshop_RFI.pdf

Now, the idea: Earlier equator crossings also mean earlier in the morning for all morning imaging. And it means earlier in the evening (for instance, greater dusk twilight in areas that have dusk twilight, or with a higher sun if it is a polar area where there is sunshine in the evening). I'll focus on the morning, but keep in mind also the descending node evening imaging possibilities and what new could be done, if anything useful. So, for morning, earlier times mean longer shadows, in general. Maybe that's a bad thing, but in ice plateau and ice cap areas, there would be greater definition of subtle details. There would also be fewer clouds in areas where late morning clouds normally build up after spectacularly m]clear early and mid mornings (such as in Nepal), though where morning fogs are common, as in many fjords, it would be the opposite. So there's good and bad with going to earlier morning. My experience in Nepal says that even 15 minutes, but certainly when it gets to 30-45 minutes earlier, there will be a substantially increased chance of clear skies. What about during the monsoon? I have very limited experience in the mountains during the monsoon; does anybody from the Himalayan region (or elsewhere) know whether the monsoon period commonly has clearer sky in the mid morning (say, 9 or 9:30 a.m. versus late (like the 10:30 nominal mission imaging time)?

What about in Alaska, or anywhere else? Does 15 minutes to an hour (or more) earlier imaging help in terms of having clear skies?

What about longer shadows and higher differential illumination to catch subtle details on low-sloping snowy surfaces?

Recall that ASTER's last remaining best unique aspect is its stereo imaging, but is there something about NOT being in the A-train orbit and going to earlier morning imaging  that helps even in terms of topographic DEM development?

What about thermal differences for earlier morning and earlier evening imaging? Is there any unique science that imaging at the modified times of day could help with?

Or should we let ASTER finally sleep after a life well lived?

Cheers,
Jeff Kargel
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