Magellan EDR/RAW Data |
Magellan EDR/RAW Data |
Sep 11 2020, 09:03 PM
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#1
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Member Group: Members Posts: 432 Joined: 18-September 17 Member No.: 8250 |
Just curious, has anyone gone spelunking in the Magellan SAR EDR (raw) dataset?
https://pds-imaging.jpl.nasa.gov/data/magellan/edr/ Looks like a set of 9-track mag tapes were copied to CD-ROMs for preservation, and at some point the CD files were put online in PDS. In starting to look at it, I realized that lack of knowledge of mag tape volume/label/file/record structure and terminology may impede younger explorers of this dataset. |
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Sep 11 2020, 10:38 PM
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#2
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Solar System Cartographer Group: Members Posts: 10256 Joined: 5-April 05 From: Canada Member No.: 227 |
I have used the mosaicked (tiled) data, not the raw 'noodle' data (long strip from one orbit). But I completely agree that much better access is needed, beginning with a good map-based search tool. I haven't checked for quite a while, though. Must be 10 years since I worked on Venus. I used to think I could do an atlas of Mercury and Venus exploration and I made a good start, but a lifetime isn't long enough to do everything I want to do.
One thing I did notice: USGS's Map-a-planet, which I used to use all the time until it was revamped and made less convenient, had 3 global mosaics corresponding to radar image cycles 1, 2 and 3. One mosaic often helped fill a gap in another. But where a gap still remained, occasionally on those CD-ROMs a later version of a mosaic would include a bit of extra coverage and fill the gap. But searching for that magic tile was a real pain. That's where a fully updated dataset with good map search capabilities would really help - show all products within the selected box. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Sep 11 2020, 11:31 PM
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#3
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
I have used the mosaicked (tiled) data, not the raw 'noodle' data (long strip from one orbit). The recollections of a recovering Magellan data processor: The noodle data came in two flavors: the really raw data that Brian is talking about, and the so-called F-BIDR (Full resolution basic image data record, https://pds-geosciences.wustl.edu/missions/...idr/dataset.cat -- map-projected noodles). Even during the mission, I didn't know anyone brave enough to look at the EDRs, and even using the F-BIDRs was considered pretty hard-core; not sure if going back to the EDR would really confer much benefit, but it would require a detailed knowledge of SAR processing. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jan 31 2022, 12:23 AM
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#4
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
this is an old thread but
For about the next week i will have on my G-drive a massive C1 Venus map it is 131072 x 65536 pixels and 8 Gig's in size see the celestia forum post on this https://celestia.space/forum/viewtopic.php?f=5&t=21899 |
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Jan 31 2022, 10:29 AM
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#5
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Member Group: Members Posts: 349 Joined: 20-June 07 From: Slovenia Member No.: 2461 |
I get this result when using Venus Magellan SAR FMAP Left Look Global Mosaic at 225m/px with 600m/px stereo-derived DEM overlayed. This version is 168976x76983 px weighing 13 GB. There is also a version at 75m/px available, but i haven's tried it yet. It's a huge download at 109 GB! And you need lots of RAM to open it. As you may noticed, I prefer white to black rendering of Magellan's data, which renders the surface in much more "photographic" way. |
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Mar 15 2023, 09:27 PM
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#6
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Solar System Cartographer Group: Members Posts: 10256 Joined: 5-April 05 From: Canada Member No.: 227 |
Hot off the press:
https://twitter.com/ThePlanetaryGuy/status/...066117344014343 Volcanic eruption/surface changes seen on Venus in old Magellan data. If you wonder why it took so long, this is a very small area on a big planet. It also points to the fact that there is no convenient way to get into Magellan data now the fine old USGS Map-a-planet has been replaced by the clumsy Map-a-planet 2. If Venus science is going to prosper it really really really needs a kind of Quickmap interface to all 3 cycles of Magellan data, plus earth-based radar imaging and the ability to add new mission data as it arrives. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Mar 15 2023, 09:44 PM
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#7
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
https://www.science.org/doi/10.1126/science.abm7735
"We therefore cannot exclude the possibility that the flows were present when the Cycle 1 image was taken, but were not apparent in the image, perhaps because the surface texture makes the flows more distinguishable at the lower incidence angle of Cycle 2." Seems like this is most likely a radar artifact to me. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Mar 15 2023, 11:56 PM
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#8
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Solar System Cartographer Group: Members Posts: 10256 Joined: 5-April 05 From: Canada Member No.: 227 |
That does indeed apply to the putative lava flow, but the change in the 2 km-wide caldera is, I think, incontestable.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Mar 16 2023, 12:11 AM
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#9
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
That does indeed apply to the putative lava flow, but the change in the 2 km-wide caldera is, I think, incontestable. Hmm. Well, I don't know. Google for "SAR layover". I worked on Magellan just enough to be very skeptical of changes in SAR data acquired with much different geometries. I would hope that the reviewers knew more about it than I do. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Mar 16 2023, 12:40 AM
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#10
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Solar System Cartographer Group: Members Posts: 10256 Joined: 5-April 05 From: Canada Member No.: 227 |
I know about layover, but the changes don't look like layover to me. But we will see.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Mar 16 2023, 04:18 AM
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#11
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Member Group: Members Posts: 254 Joined: 14-January 22 Member No.: 9140 |
What seems to be brightening marking both sides of the smaller, earlier version of the caldera do seem to be real topographical features that are substantially different in the later image. Of course, there's no possible limit to the weird interactions that could make terrain look different from different radar angles, but this would be a really insidious artifact if it is an artifact. I guess for anyone to evaluate it fully they'd have to add a study of what sorts of other apparent differences have been seen elsewhere on Venus to see how unique this apparent difference is.
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Mar 17 2023, 08:32 AM
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#12
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Member Group: Members Posts: 349 Joined: 20-June 07 From: Slovenia Member No.: 2461 |
For a little visual aid here is 3D view of the Maat Moons rendered at 4x vertical exaggeration , looking towards southeast, the area from the article is in the front. The Magellan DEM is really rough and blocky, producing kind of an artificial bench that is not really there, but it could possibly be a downward movement of lava that we are seeing. Unfortunately it will be a long wait until we get 250m/pixel DEM planned by the VERITAS mission for a better view. |
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Mar 18 2023, 02:35 AM
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#13
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Member Group: Members Posts: 254 Joined: 14-January 22 Member No.: 9140 |
And after a few years' more wait, EnVision will provide 60m spatial resolution topography.
However, if there was any significant change during just a year of Magellan's mission, it seems likely that some more significant change will be there to be discovered after ~35 years, unless, improbably, there's just one location on Venus where change occurs. |
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Mar 19 2023, 12:45 AM
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#14
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
" The Magellan DEM is really rough and blocky"
and that is a major under statement i have been able to clean it up a little bit bit not to much |
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Mar 19 2023, 07:16 PM
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#15
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Member Group: Members Posts: 254 Joined: 14-January 22 Member No.: 9140 |
The radar maps in Fig. 2 A and B are annoyingly misaligned, something that is easy to miss with the eye, but longitude lines offered as references above Fig. 2A don't even remotely align with the un-labeled lines that appear between 2A and 2B. When I try to overlay the figures in Photoshop and "blink" them, the differences are apparent and cannot be resolved in any way with a mere translation between them. It feels like the text talks past this issue, saying that "the black box in © indicates the extent of the unrectified images in panels A and B," but it is clear that those panels, while obviously matching approximately, differ by more than the sizes of the features being discussed. It's strange. I can't tell if the work is sloppy or if the artifacts produced by the different geometries is simply enormous, but one or the other seems to be in play.
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