Obtaining Voyager positions relative to targets Options

[Brian Burns]

I'd like to obtain or create a table for the Voyager images with distance information, e.g.

Volume, Image, Target, Distance (km)
5101, C1327538, Io, 134474

(The indexes with the PDS volumes have the times for each image)

Does anyone know a source for this or good or simple way to calculate it? I've just started looking at the documentation for SPICE at http://naif.jpl.nasa.gov/naif/, which looks like it would be the way to do it, but I'm not sure how involved it would be.

This would give you the size of the target relative to the camera field of view, which would allow you to interleave the narrow and wide angle camera views, and also turn off the center-detection algorithm when generating movies.

Thank you for any pointers!

[Mike Martin]

Thanks for the comments/suggestions. It looks like the NAIF kernels and software are right and the reference to "It came within 570,000 km of the planet's cloud tops", which may come from a JPL Voyager web page is wrong. The Wikipedia article for Voyager 2 detailed "Timeline of Travel" says "1979-07-09 - 22:29 Jupiter closest approach at 721,670 km from the center of mass", which matches the NAIF/SPICE values. By the way, when I tried running the script with target JUPITER instead of JUPITER_BARYCENTER I got an error "Insufficient ephemeris data has been loaded to compute the position of 599 (JUPITER) relative to -32 (VOYAGER 2) at the ephemeris epoch 1979 JUL 08 00:00:50.183."

[mcaplinger]

By the way, when I tried running the script with target JUPITER instead of JUPITER_BARYCENTER I got an error "Insufficient ephemeris data has been loaded...

Yes, that's typical. If the kernel doesn't contain records for the geometric object you have to use the barycenter. The offset is insignificant for most purposes.

In my experience numerical values in press releases and other prose descriptions are sometimes not very trustworthy.