My Assistant
| Posted on: Feb 2 2016, 02:53 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I dont believe those orginal individual striped images are avaible to public. Sure they are. They're called Full Resolution Basic Image Data Records or F-BIDRs. See http://pds-geosciences.wustl.edu/missions/magellan/ Getting rid of shading at the boundaries of the swaths was extremely difficult because of radar artifacts. Maybe in the 20+ years since I've looked at Magellan data someone has improved the processing. |
| Forum: Image Processing Techniques · Post Preview: #229370 · Replies: 10 · Views: 10808 |
| Posted on: Jan 17 2016, 09:30 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I'm kind of surprised that this part of the sensor calibration isn't already done for the data available in the PDS. I haven't really looked at the RDR data yet... EDRs are never corrected/flat-fielded because they represent the least-processed form of the data. In the list you linked to, "rad-corrected" RDRs would typically be flat-fielded, though I haven't looked at the engineering camera products. Some of the MMM RDR products are radiometrically corrected and some aren't, the RDR subtypes are not captured in the list you linked to. |
| Forum: MSL · Post Preview: #229092 · Replies: 529 · Views: 461044 |
| Posted on: Jan 15 2016, 03:51 AM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I've implemented a quick&dirty de-blocking algorithm, which just estimates a constant grey value offset for each 16x16-pixels block in the EDR image. Is what you're calling the "raw" image stretched or something? The raw data don't/shouldn't have anything like the level of visible blockiness that this image has. Either there is something wrong with whatever you're using to convert formats or something messed up in the EDR files themselves. [Indeed, on further checking my original decompressed version of EFB13 doesn't show these block artifacts. Something is screwed up in our processing chain that produced the EDRs. Thanks for noticing this!] |
| Forum: Juno · Post Preview: #229051 · Replies: 183 · Views: 181452 |
| Posted on: Jan 14 2016, 04:03 AM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I didn't find information, how the raw data numbers can be restored. So some questions about alternative approaches arose: - Do there exist additional tables of grey value offsets for each macroblock? - Does there exist a convention how to calculate the relative offset between two neighboring macroblocks? - Is a subsequent application of a H.264-compliant or some similar deblocking post-process assumed? I'm not sure exactly what you mean by this. The 16x16 block artifacts are from the onboard data compression (same as was used for the MOC way back when -- JPEG-like but with 16x16 transform blocks.) There is no way in general to restore anything as the raw image was never transmitted. The only difference between the EDR and the RDR is that the RDR has been linearized and a radiometric scale factor applied. If this had been a real PDS release you would also have access to the documentation. That release is coming but I don't know when; unlike previous missions we don't deliver directly to the PDS. For now I'll see if I can post the documentation on the web site. |
| Forum: Juno · Post Preview: #229026 · Replies: 183 · Views: 181452 |
| Posted on: Jan 13 2016, 02:55 PM | ||
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Juno does plan to take some images during approach. Certainly, but at a range of 5.2e6 km on JOI-5d, Jupiter is about 40 pixels across, so they won't be great images. [Junocam, maybe JIRAM does better.] Handy formula: Junocam Jupiter size in pixels ~ 210/d, d in millions of km |
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| Forum: Juno · Post Preview: #229007 · Replies: 71 · Views: 92523 |
| Posted on: Jan 7 2016, 12:19 AM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Today is Jupiter Orbit Insertion (JOI) minus 180 days. 53.5 days after JOI, Juno will make its next close pass to Jupiter, and that's when we expect to get the first good images from Junocam, although there may be some imaging during approach and earlier on the first orbit. |
| Forum: Juno · Post Preview: #228906 · Replies: 71 · Views: 92523 |
| Posted on: Jan 6 2016, 11:11 PM | ||
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Here's a dimensioned drawing of the Junocam color filter array (dimensions in mm). In looking at EFB12, I would venture to guess that a lot of the stray light features are actually interline smear from the clear areas in the CFA adjacent to the CH4 region, not all of which are occluded by the light shield. These are exacerbated by the short exposure times we had to use in EFB. Reflections off the light shield are not very plausible, as the shield and all of the internals of the optics are bead-blasted and black anodized. The AR coatings on the glass surfaces are as good as we could obtain but certainly there are paths from the filter edges, from the CCD die, bond pads, metallization, etc. Since the instrument is not intended to be radiometrically precise and the stray light is only especially visible off the limb, I'm not thinking this is going to be much of an issue for most applications. I'm still more concerned about band-to-band registration, for which no perfect model yet exists. Mods: again, I suggest this material be moved to a subforum as it's unlikely to be very interesting to most. [moderator note: A Juno subforum will probably be created soon and the Juno thread split and/or reorganized when this happens] |
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| Forum: Juno · Post Preview: #228904 · Replies: 20 · Views: 23859 |
| Posted on: Jan 5 2016, 04:27 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
a detailed plan of the geometry of all surfaces possibly in contact with non-negligible light eventually reaching the sensors together with BDRF data (including anti-reflective coatings), and the refractive indices of the translucent materials would be helpful. I'll see what we can release. Some of that doesn't even exist -- for example, no BRDF measurements were made for this non-radiometric instrument. The ray trace of the optics in the Junocam paper is accurate if non-quantitative. BTW, the most rigorous attempt I'm aware of to characterize the radiometric properties of a pushframe system (including stray light) can be found in "Inflight Calibration of the Lunar Reconnaissance Orbiter Camera Wide Angle Camera" http://asu.pure.elsevier.com/en/publicatio...rbiter-camera-w (not open access, unfortunately.) |
| Forum: Juno · Post Preview: #228880 · Replies: 20 · Views: 23859 |
| Posted on: Jan 4 2016, 07:20 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
As described in the article, I've applied methods related to the Newton method to fit peaks into the EFB03 data. Keep in mind that EFB03 was taken in a mode that is unlikely to be duplicated for Jupiter observations (lots of TDI in a visible channel). We will probably only use a lot of TDI for the CH4 channel. In the diagram you show above of the CFA, be aware that there is a light shield between the top of the CCD and the back of the optics with an aperture nominally 0.231x0.473 inches centered on the center of the sensor. This is intended to block stray light paths from the sensor bond wires and metallization on the sensor package, though there could be some misalignment and some small paths could still exist. Mods: it might make sense to create a subforum for this material, much as was done with the MSL discussion of technical details about the cameras. |
| Forum: Juno · Post Preview: #228874 · Replies: 20 · Views: 23859 |
| Posted on: Jan 4 2016, 05:17 AM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
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| Forum: Past and Future · Post Preview: #228870 · Replies: 130 · Views: 266058 |
| Posted on: Jan 3 2016, 07:42 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
This is vaguely reminiscent of the problems that Dawn had during its development cycle... Thanks for pointing that out, John, I had forgotten that tale of woe. What's missing from Dawn is the international aspect; although much of Dawn's payload was provided by foreign partners, as far as I know most of the developmental problems were with the spacecraft. I wish there was better information about what actually happened with Dawn and how it was resolved; the best I've been able to find is http://www.spaceref.com/news/viewnews.html?id=1112 but that falls well short of an official report/policy statement. |
| Forum: Past and Future · Post Preview: #228863 · Replies: 147 · Views: 284649 |
| Posted on: Jan 1 2016, 05:48 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
One primary reason that's not possible is that new instruments require not only testing of said instruments but also integration and testing with (and of) the entire spacecraft. More fundamentally, there are typically not spare data and power connectors on spacecraft like this. Even adding mounting holes to bolt on new stuff is non-trivial; assuming there was enough unused area at all, the spacecraft would have to be at least partially disassembled to do so. The combination of Insight being a cost-capped PI mission and the problem instrument not being funded by NASA makes this a complex and AFAIK unprecedented situation. We'll just have to wait and see how it develops. |
| Forum: Past and Future · Post Preview: #228850 · Replies: 147 · Views: 284649 |
| Posted on: Dec 30 2015, 08:02 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
So what happens to the readied Atlas V that they were going to launch with in this sort of case? ULA takes it back and uses it for something else. There's almost certainly a cancellation cost in the launch contract. Usually the mission-specific fairing sticker isn't put on until encapsulation, but if it's on already they can peel it off pretty easily |
| Forum: Past and Future · Post Preview: #228845 · Replies: 147 · Views: 284649 |
| Posted on: Dec 30 2015, 07:24 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
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| Forum: Past and Future · Post Preview: #228844 · Replies: 147 · Views: 284649 |
| Posted on: Dec 29 2015, 09:53 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
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| Forum: MSL · Post Preview: #228833 · Replies: 349 · Views: 342884 |
| Posted on: Dec 28 2015, 05:12 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I would submit that this is the reason navcams look underexposed, they don't appear to use the square root encoding the color cameras do. They could use a similar scaling, but this capability seems to be rarely used. For MER, from http://onlinelibrary.wiley.com/doi/10.1029/2007JE003003/full QUOTE Employing a roughly square-root LUT can thus allow the image size (in bits) to be reduced without losing statistically significant information. While most Pancam images utilize this ability [Bell et al., 2006], only 12.6% of Navcam images acquired through the first 1000 sols have been scaled to 8 bits per pixel. This is probably to simplify the onboard stereo processing, but I'm not certain. |
| Forum: MSL · Post Preview: #228817 · Replies: 529 · Views: 461044 |
| Posted on: Dec 22 2015, 04:25 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
The REMS booms are on the remote sensing mast, not the arm. |
| Forum: MSL · Post Preview: #228739 · Replies: 349 · Views: 342884 |
| Posted on: Dec 18 2015, 03:53 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Earthrise from LRO: http://lroc.sese.asu.edu/posts/895 |
| Forum: LRO & LCROSS · Post Preview: #228679 · Replies: 509 · Views: 554973 |
| Posted on: Dec 16 2015, 06:30 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
I take what I see and try to make better sense of it... Moving dust is utterly unlike moving sand. Google for "martian saltation kok" for example. J.F. Kok "Difference in the wind speeds required for initiation versus continuation of sand transport on Mars: Implications for dunes and dust storms" QUOTE We show here that saltation can be maintained on Mars by wind speeds an order of magnitude less than required to initiate it. We further show that the resulting hysteresis effect causes saltation to occur for much lower wind speeds than previously thought. |
| Forum: MSL · Post Preview: #228635 · Replies: 8 · Views: 10627 |
| Posted on: Dec 16 2015, 03:51 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
The distance these dunes (and others) move per MOC and HiRise images contradicts known wind speeds vs *observed* Atm pressures...so something is off... Uh, no. See http://www.mars.asu.edu/christensen/docs/e...unes_JGR_91.pdf |
| Forum: MSL · Post Preview: #228625 · Replies: 8 · Views: 10627 |
| Posted on: Dec 15 2015, 08:09 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Tough crowd. And I must have missed the memo that said peer review could be done over Twitter. The system will sort this out. I don't think you want to introduce a chilling effect where interesting results, even if premature, can't be put out on arxiv. The authors are taking chances of being criticized, but those are their chances to take. |
| Forum: Telescopic Observations · Post Preview: #228605 · Replies: 40 · Views: 35636 |
| Posted on: Dec 11 2015, 08:46 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
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| Forum: Telescopic Observations · Post Preview: #228532 · Replies: 40 · Views: 35636 |
| Posted on: Dec 10 2015, 08:46 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Maybe I'm missing something... Did you read section 4.1? They certainly try to address why the object is not associated with alpha Cen. As I read it, the basic argument is that it's too bright to be at that distance and not have been seen previously. Statistically I agree, the chance that the object just happened to be in line with alpha Cen but not associated with it seem very low. Assuming this object is real, the most likely explanation can't be discussed here due to rule 1.3. |
| Forum: Telescopic Observations · Post Preview: #228495 · Replies: 40 · Views: 35636 |
| Posted on: Nov 5 2015, 05:52 AM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Unfortunately, here in reality the relationship between cost and probability of mission success is not quantifiable with any precision. I'm not even sure that spending more money increases probability of success in all cases. |
| Forum: Venus · Post Preview: #227877 · Replies: 139 · Views: 389419 |
| Posted on: Nov 4 2015, 10:12 PM | |
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Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2559 Joined: 13-September 05 Member No.: 497 |
Going through the rover images, I found a section of the rover was imaged by Mastcam Z [sic] (accidentally? on purpose?) on sol 25 as part of a 360 1-tier panorama. Accidentally. We can command in many reference frames, both rover-relative and surface-relative, and if the rover orientation post-drive is not what we expected during planning, these sorts of things can happen. (Note that these images are focused on the stuff behind the rover, not on the rover itself.) There are some cases where the arm was imaged because it was in an unexpected pose, too. I've tried to imagine a way in which the entire rover could be imaged by "accident" but I haven't come up with a plausible story. Yet. |
| Forum: MSL · Post Preview: #227866 · Replies: 999 · Views: 868401 |
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