Re: SPICE rotation models
Posted: 05.02.2009, 23:40
For the IAU Rotations, I am using ftp://naif.jpl.nasa.gov/pub/naif/CASSIN ... merged.tpc , which is the latest such file for Saturn's small satellites.
This file seems to work just fine for most of the rocks, except Janus, Epimetheus, and Anthe. For the first two, I get a result similar to when I was first trying out rotation kernels for Cassini. the only thing that is different about Janus and Epimetheus is that they have nutation in there. For some reason, Anthe doesn't rotate... all the others work fine. The rotation period seems to be fine for all the others, even Atlas, which I think you are right, the offsets were due to some kind of orbital precession not accounted for in the .tpc file rather than non-synchronous rotation resulting from slight differences between the rotation rate in the .tpc file and the orbital period.
This file seems to work just fine for most of the rocks, except Janus, Epimetheus, and Anthe. For the first two, I get a result similar to when I was first trying out rotation kernels for Cassini. the only thing that is different about Janus and Epimetheus is that they have nutation in there. For some reason, Anthe doesn't rotate... all the others work fine. The rotation period seems to be fine for all the others, even Atlas, which I think you are right, the offsets were due to some kind of orbital precession not accounted for in the .tpc file rather than non-synchronous rotation resulting from slight differences between the rotation rate in the .tpc file and the orbital period.