Voyager camera pointing information Options

[Brian Burns]

Sorry if this has been discussed anywhere but I can't seem to find much information about it - why is it that Voyager's pointing is so haphazard, as in this video of all the RAW Jupiter images - https://www.youtube.com/watch?v=bf5QJ8iFxUs?

I came across this link which says that pointing information for the images exists - http://pds-rings.seti.org/voyager/ck.html, but have also read on this forum that it's not very accurate. Would the information be useful in automatically aligning composite images and mosaics, or is it too coarse? Would it at least be useful in getting general alignments that could be refined by hand?

And does anyone know why the cameras could not be pointed more accurately, or why accurate information could not be returned with the images? I assume it was some technical limitation, but just curious what it might be.

[Brian Burns]

The links to the downloads on the C kernels page weren't working so I wrote to Mark Showalter - he is working on C-smithing the Cassini kernels right now, and plans to C-smith the Voyager kernels once the Cassini data is done, which might be another year or so.

So regarding the accuracy of the C kernels - for the kernels obtained from the SEDR data:

Long experience with the SEDR file has revealed its pointing information to be
accurate to typically ~ 100 narrow-angle pixels, which is equivalent to ~ 0.05
degrees or ~ 1 milliradian.

This C kernel was generated by the PDS Rings Node. We hope to generate improved
C kernels (continuous and C-smithed) at a later date.

http://pds-rings.seti.org/voyager/ck/vg1_j...e1_iss_sedr.txt

and for the C-smithed kernels (just Voyager 1 at Saturn at the moment), obtained from the SEDR data with some corrections:

The pointing information was "C-smithed" using two additional sources of data:

(1) Mark Showalter's personal collection of pointing corrections for 834
Voyager 1 images of Saturn and the rings.

(2) A collection of SEDR updates obtained from JPL/MIPL for 259 images
of Saturn's satellites. These udpates date back to the early 1990s.

In general, pointing information should be accurate to the level of a few tens
of narrow-angle pixels, i.e., ~ 0.01 degrees or ~0.2 milliradians. However, some
errors may be larger, particularly around the closest approach period when the
scan platform was moving rapidly.

http://pds-rings.seti.org/voyager/ck/V1SAT...SS_CSMITHED.txt

So at the moment they wouldn't be accurate enough to reconstruct the movies, but maybe having centered and corrected images would be helpful in constructing more accurate C kernels.

I'm still working on setting up a usable system - at the moment it's a bit laborious to correct the mis-centered images - ideally it would be tied into an image editor where you could outline the target with a circle and have it write a record to the centering corrections file. And then for aligning channels for the closeups it could start with the existing C kernels and run some image alignment code, then let the user do any fine tuning in an editor - similarly for the mosaics. There are thousands of images, so it would need to be pretty simple and easy to do.