[GLIMS] ASTER Update: when to decommission ASTER?

[Jeffrey Kargel]

Bruce,

I will send the PDF separately to you, but it can be posted for general GLIMS access. It is an updated presentation relative to what you may have been able to snag from an ASTER team meeting site. I am really pleased to see a small outpouring of support for keeping ASTER going for as long as we can keep it alive.

New gain calculations would help a lot, especially for the gains of the coming GLIMS STAR, planned to start January 1. Until now the drifting orbit and equator crossing time has been a bit of a minor matter, but next year it will likely require new gain settings in many cases. I will send you the STARs as the exist, and notify the ASTER Mission Ops that we want to generate new gains. The STARs evolved significantly for the presently active cycle, resulting in much better coverage of the Himalaya region; and last year, which resulted in much better Alaska coverage after the mysterious "exclusion zone" was lifted over Alaska.

 I have an experimental Science Team acquisition request (xAR) in the system which already has acquired data, to go all the way with low sun with grazing incidence and other very low sun angle (high off-nadir incidence). It is called ASTER xIm; I think that name is for ASTER Experimental Imaging. It was a result of a Drifting Orbits proposal, and that was actually one of three that ASTER submitted to NASA to justify keeping the mission going. ASTER was extended on the basis of those proposals, albeit with a 50% budget cut. ASTER xIm low-sun acquisitions was, therefore, a chief basis for approving ASTER and Terra for continued operation during the drifting orbits final years. If you'll recall, the novel drifting orbits proposals has to be something new, not just a continuance of what has been going on. The philosophy for ASTER xIm low-sun imaging is "if you can't beat them, then join them" in going for full-blown low-sun imaging, but over snowy surfaces only.

The processing backlog is just now starting to catch those acquisitions, which were made over Antarctica last December and Greenland in February-March, and Alaska in March. The last two slides show the browse images captured for one of those acquisitions over Alaska.  If somebody out there wants to work with me on a super-secret (hahaha) miniproject that will result in a paper, come forward with your volunteerism. It will be worth your while. I will do a special photoclinometry method adapted from something I developed for planet Mercury (and it works!). There's no money in it, just the glory of a new analysis method. If we can prove its worth, then I will be able to get an expanded set of low-sun special acquisitions. Currently, I have no technical support at all (and no money to speak of), so that's why I say there's no money involved. We would have to publish in a. free journal.

--Jeff



________________________________
From: GLIMS <glims-bounces at nsidc.org> on behalf of Bruce Raup <braup at colorado.edu>
Sent: Tuesday, September 12, 2023 4:05 PM
To: GLIMS Mailing List <glims at nsidc.org>
Subject: Re: [GLIMS] ASTER Update: when to decommission ASTER?

Hi Jeff,

Thanks for these updates from the ASTER Science Team meeting.  I certainly
vote for the latest date of decommissioning.

The original equator crossing time, as you know, was 10:30 local
(descending node; 22:30 for ascending).  1.5 hours is quite a lot of drift.
If ASTER remains operational into 2026, is there need, and opportunity, for
adjusting the GLIMS data acquisition requests in response to the orbit
drift?

I haven't done any calculations to assess the effect.  The ASTER gain
tool at https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.glims.org%2Ftools%2Faster_gain%2F&data=05%7C01%7C%7Ccfaac2032b104e670df908dbb3aa2b73%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638301315699619769%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=S9OnqpB5h2t7nvh8iyrql8RQH%2BW5sZdbT%2FPVodxq9qo%3D&reserved=0<http://www.glims.org/tools/aster_gain/> still works but has the
10:30 equator crossing time built into it.  I could think about updating
that tool.  Have you calculated the difference in sun angle for any cases?
Someone could also do a comparison of imagery from early in the mission to
recent imagery over the same target with similar atmospheric and
ground-cover conditions.

Cheers,
Bruce


2023-09-11, 17:02:  Jeffrey Kargel wrote:

> Dear GLIMS colleagues:
> I have a further clarification about ASTER's future (and that of MODIS and MISR onboard Terra). There are two separate dates being floated for decommissioning. One is Sep. 30, 2026—the last day of funding for ASTER and Terra mission
> operations under the funding (with a 50% cut) that is to begin on October 1, 2023. September 2026 is the decommissioning time that I mentioned yesterday. There is another possibility, and that is December 2025. That is the month when Terra's
> morning equator crossing will have shifted to 9 a.m. local time. The 9 a.m. is a bit of an arbitrary cutoff, but  it was thought a couple years ago that by that point the signal observed by VNIR will have decreased enough that it warrants
> turning ASTER off.
> I have pointed out that over snow and ice targets, there is still plenty of signal. If for nothing else, imaging of snow and ice targets would be very rewarding for GLIMS and any other cryospheric studies. There presently is not a lot of
> enthusiasm in ASTER Mission Ops to terminate ASTER that early. So, I suspect that Sep. 30, 2026 will stick. It would be possibly helpful, and certainly would not hurt, if we had a chorus of ASTER users to press for as late as possible of a
> decommissioning. ASTER is still a go-to resource for topographic studies, and that use should not end as the orbit drifts further. Thermal is also an underutilized part of ASTER, but there are people using it for glacier and glacier lake
> studies, so that is another key use that would benefit from a later decommissioning.
> There is an outside hope (far outside) that with a groundswell of support for new funding and operating ASTER and Terra beyond September 30, 2026, we might be able to continue into 2027. That is me talking, not ASTER Mission Ops. A lot
> depends on solar activity, since the solar wind and EUV fluffs up the atmosphere, which creates drag, and that impacts the orbit drift rate and the potential lifetime of Terra and ASTER.
> So.... I am looking for emails, individually, or if groups of you want to write letters, address them to me, and I will compile the responses. You can express how you have used ASTER data (or other Terra data) and whether you feel that
> extracting more lifetime out of ASTER, MODIS, or MISR will have a significant impact on science.
> Please reply with "ASTER" somewhere in the subject line.
> Cheers,
> Jeff Kargel
>
>

--
Bruce H. RAUP
National Snow and Ice Data Center
University of Colorado
cires.colorado.edu/~braup/
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