[Spice_discussion] Magnetic coordinates
William Thompson
William.T.Thompson.1 at gsfc.nasa.gov
Thu Mar 18 12:10:44 PST 2004
Hello:
I've recently downloaded and installed the Icy/C-SPICE package, and have been
able to use it to read a draft trajectory file for the upcoming STEREO mission.
I've been able to figure out most of what I need to know, but I have a few
questions which may have already been addressed by other people or projects.
Some of these may require additional data files which I don't yet have. Please
excuse me if these questions are off-topic for this list.
My main question has to do with magnetic coordinates. How do I derive positions
in coordinate systems which have Earth's magnetic dipole as one of the axes,
such as GSM, SM, or MAG? My suspicion is that I would have to have an
additional data file, such as a PCK or FRM file, giving the orientation of
Earth's magnetic axis as a function of time, including secular drifts. Does
such a thing exist?
My other question should be much simpler. I'm able to derive ecliptic
coordinates in the J2000 reference frame using SPKEZR. I need to convert these
to the mean ecliptic of date. I've found some equations which should allow me
to do this, but I wondered if there was already a simple way to do this already
built-in to SPICE?
Thank you,
--
William Thompson
NASA Goddard Space Flight Center
Code 682.3
Greenbelt, MD 20771
USA
301-286-2040
William.T.Thompson.1 at gsfc.nasa.gov
(Please note changed email address.)
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