The Top of Vera Rubin Ridge Part 2, Site 67-73, sol 1944-2297, 24 Jan 2018-22 Jan 2019 |
The Top of Vera Rubin Ridge Part 2, Site 67-73, sol 1944-2297, 24 Jan 2018-22 Jan 2019 |
Jun 21 2018, 09:28 PM
Post
#316
|
|
Senior Member Group: Members Posts: 2802 Joined: 22-April 05 From: Ridderkerk, Netherlands Member No.: 353 |
|
|
|
Jun 21 2018, 10:27 PM
Post
#317
|
|
Member Group: Members Posts: 306 Joined: 4-October 14 Member No.: 7273 |
|
|
|
Jun 22 2018, 12:51 AM
Post
#318
|
|
Senior Member Group: Members Posts: 4245 Joined: 17-January 05 Member No.: 152 |
I'm not sure which sol we hit tau > 8 in Gale, but on 2086 the sun was still visible in MR:
http://mars.jpl.nasa.gov/msl-raw-images/ms...040C00_DXXX.jpg I'm guessing that frame was without solar ND filter, since several frames around that sol show almost nothing and presumably did use the ND filter. So the sun wasn't very bright, as you'd expect for a roughly e^{-8} ~ 1/3000 attenuation. |
|
|
Jun 22 2018, 02:48 AM
Post
#319
|
|
Member Group: Members Posts: 507 Joined: 10-September 08 Member No.: 4338 |
|
|
|
Jun 22 2018, 04:21 AM
Post
#320
|
|
Member Group: Members Posts: 306 Joined: 4-October 14 Member No.: 7273 |
I'm not sure which sol we hit tau > 8 in Gale, but on 2086 the sun was still visible in MR: http://mars.jpl.nasa.gov/msl-raw-images/ms...040C00_DXXX.jpg I'm guessing that frame was without solar ND filter, since several frames around that sol show almost nothing and presumably did use the ND filter. So the sun wasn't very bright, as you'd expect for a roughly e^{-8} ~ 1/3000 attenuation. The most recent frame for tau measurement that had been downlinked when that press release came out was on Sol 2079, so either it was estimated from a thumbnail image or the landscape images from sols 2084/2085. You can barely see the sun in the Sol 2085 right MastCam image (I was only able to see the right half of the disk), so I wouldn't be surprised if the tau measurement of 8 was from an earlier sol. It looks closer to Opportunity's last image from Meridiani Planum, but I don't know how the two rovers' ND filters compare to one another. |
|
|
Jun 22 2018, 02:03 PM
Post
#321
|
|
Senior Member Group: Members Posts: 2802 Joined: 22-April 05 From: Ridderkerk, Netherlands Member No.: 353 |
|
|
|
Jun 22 2018, 02:53 PM
Post
#322
|
|
Senior Member Group: Members Posts: 2802 Joined: 22-April 05 From: Ridderkerk, Netherlands Member No.: 353 |
|
|
|
Jun 23 2018, 01:45 PM
Post
#323
|
|
Senior Member Group: Members Posts: 2802 Joined: 22-April 05 From: Ridderkerk, Netherlands Member No.: 353 |
|
|
|
Jun 23 2018, 03:16 PM
Post
#324
|
|
Senior Member Group: Members Posts: 2502 Joined: 13-September 05 Member No.: 497 |
I don't know how the two rovers' ND filters compare to one another. The filters are basically the same (440 nm and 880 nm centers, ND5 neutral density) but obviously the cameras are quite different in their pixel size, f/number, and quantum efficiency. But without knowing the exposure times of the images (alas, not available until PDS archiving AFAIK) it's tough to figure out the radiometry. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
|
|
|
Jun 24 2018, 08:01 AM
Post
#325
|
|
Senior Member Group: Members Posts: 1043 Joined: 17-February 09 Member No.: 4605 |
|
|
|
Jun 24 2018, 10:04 AM
Post
#326
|
|
Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
The dusty atmosphere may be layered in a different way. The tau measurements on the the basis of images of the sun refer to the whole atmospheric column. Global dust transport may prefer higher atmospheric layers. When talking about clarity, we should consider the distance of the objects we are looking at, as well as the wavelength of the light.
Note also, that directional transmittance and illuminance are only very loosely correlated. |
|
|
Jun 24 2018, 11:21 AM
Post
#327
|
||
Senior Member Group: Members Posts: 2424 Joined: 30-January 13 From: Penang, Malaysia. Member No.: 6853 |
I think this may be the left mast camera frame that would normally capture a section of the north wall of the crater rim, that they regularly use to measure the LOS extinction (Line-of-Sight) which combined with other measurements gives the tau value. The large Butte / Mesa in the lower part of the frame may eventually be obscured by worsening levels of dust. Do we know the approximate distance to it from the current location after the drive on sol 2089? I ask as we don't know the exposure times of the images, so images with darker terrain don't necessarily mean more suspended dust etc. May just be a good indication for us to use, as it doesnt look like the MSL team will release tau values as the Oppy team do.
|
|
|
||
Jun 24 2018, 02:01 PM
Post
#328
|
|
Senior Member Group: Members Posts: 2502 Joined: 13-September 05 Member No.: 497 |
I am having the greatest of difficulty correlating the clarity of the images from Curiosity... Since I expect these are all autoexposed, you can't really compare them to anything sensibly. The best way to show this would be to show a series of images all taken with the same exposure time, or at least normalized to a single exposure time. Also, the color processing between the two cameras is significantly different. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
|
|
|
Jun 24 2018, 04:20 PM
Post
#329
|
|
Senior Member Group: Members Posts: 4245 Joined: 17-January 05 Member No.: 152 |
Picking up some dust on FLB, visible on 2089:
http://mars.jpl.nasa.gov/msl-raw-images/pr...FHAZ00339M_.JPG compared with 2082: http://mars.jpl.nasa.gov/msl-raw-images/pr...FHAZ00337M_.JPG |
|
|
Jun 24 2018, 05:09 PM
Post
#330
|
|
Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
|
|
|
Lo-Fi Version | Time is now: 19th March 2024 - 08:43 AM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |