Reprocessing Historical Images, Looking for REALLY big challenges? |
Reprocessing Historical Images, Looking for REALLY big challenges? |
Apr 21 2005, 11:26 PM
Post
#1
|
|
Member Group: Members Posts: 123 Joined: 21-February 05 Member No.: 175 |
.
|
|
|
May 23 2005, 04:58 AM
Post
#2
|
|
Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
A number of postings back, somebody was "dissing" the Pioneer Spin-Scan Multi-Polariimiter/Camera as a primitive camera. I'd like to come, a bit, to it's defense.
The camera was actually 3 instruments in one. It was a zodiacal light photometer/polarimiter. On it's way out to Jupiter and beyond, it repeatedly imaged the entire sky except near the sun in red and blue light with full polarization analysis abilities. The resolution was terrible, about 1 or 1 1/2 degrees, but they were mapping the skyglow of the solarsystem, not taking pictures. They proved that the backscattered glow from the zodiacal light disappeared as you went through the asteroid belt to undetectably low levels, and proved that the gegenshein <counterglow--a bright patch in the zodiacal light centered on zero degree phase angle> was a photometric effect, and not due to a dust-cloud orbiting the sun at say the earth's L2 point. Processing the zodiacal photometry stuff involved mapping the pixels onto the celestial sphere, identifying detectible stars in each field of view, and subtracting the calculated starlight to get sky maps free from bright star contamination. The team doing this work never produces sky-map images from the data, and I've always wanted to see color/polarization maps of the sky from the Pioneers. The cameras also took intermediate resolution spin-scan polarimetry maps of Jupiter and Saturn with the disks well resolved at a full range of phase angles, not available from earth. Again, the images were 2 color, with full polarization analysys. This provided large amounts of QUANTITATIVE information on light scattering by cloud particles in the upper troposphere and stratosphere, data that was not duplicated or improved on in any way by the Voyagers. This data was and continues to be of use in modeling the structure of the visible parts of these planet's atmospheres. Finally, the best images from Pioneer 10 had resolution approaching Voyager's best. Pioneer took a picture with 60 km/pixel <if I recall> resolution at closest approach. It''s reproduced in the Journal of Geophysical Research's Pioneer 10 special issue. Radiation hits caused the gain of the camera <basically exposure> to shift a few times during the sequence, and the data has a strong periodic noise component possibly associated with radiation hitting the spinning spacecraft, but it couild and should have been restored and composited into a color image. Voyager's best resolutions on Jupiter were only some 15 to 20 km. |
|
|
Lo-Fi Version | Time is now: 14th June 2024 - 02:17 PM |
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. |