[Spice_discussion] Delta_t from Earth PCK?

Ernie Wright ernest.t.wright at nasa.gov
Thu Jun 18 14:22:04 PDT 2015

It seems like I should be able to infer a delta_t from any of the binary 
Earth PCKs, but I can't seem to wrap my head around how to do it.

If I PXFORM from Earth-fixed (supplied by the PCK) to true equinox and 
epoch of date equatorial coordinates, I should be getting something like 
UT1, I think.  (The TOD frame should cancel out the precession and 
nutation built into the Earth orientation, leaving the diurnal rotation.)

I have the vague notion that the next step would be to subtract the "TAI 
rotation", but I really don't know what that means.

- Ernie

Ernest T. Wright                                ernest.t.wright at nasa.gov
Scientific Visualization Studio                 http://svs.gsfc.nasa.gov
NASA/Goddard Space Flight Center, Code 606.4      voice: +1 301 286-1569
Greenbelt, MD 20771                                 fax: +1 301 286-1634

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