Now I'd like to review ISEE-3's orbit and compare it to calculations since receiving this welcomed answer.
When I go to Horizons, I can only get circa 2014-2016, the 'ISEE3 Reboot'. I don't see ICE or ISEE-3 in the NAIF folders.
Is there some way I can get the 1978-82 timeframe Horizons orbit data (state vectors), either through Horizons, or at least the kernels, as I did in this case?
Or, is there some standard way to request the data be reposted?