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| Name | Last modified | Size | Description |
|---|---|---|---|---|
| Parent Directory | - | ||
| data/ | 2013-08-07 17:25 | - | |
This directory contains ephemeris files obtained from JPL Horizons service.
These files provide ephemerides for the 200 Solar System Object (SSO) targets that were observed during the mission, as listed in the file NAIF_POS. These were used in the Scientific Mission Planning System (SMPS) for generating commands to track moving targets. They are also used in the data processing.
The files included here are a clean set retrieved from Horizons on 2013-08-06 after the end of the operational mission. They give the best a posteriori estimate of the target coordinates for data processing. These supersede the files used for mission planning which were the best predictions at the time. In most cases there is negligible difference.
The ephemerides use the Solar System Barycentre (SSB) as centre, rather than the spacecraft and do not include light-time or aberration corrections. There were two reasons for this:
It allowed the most up-to-date orbit file to be used to compute the spacecraft-centric states, before the orbit data became available in Horizons.
It avoided the need to retrieve the files from Horizons each time the orbit file changed.