Caveat: Ephemeris Accuracy
Return to: Data Caveats IndexOur goal is to distribute data products within a week of the observation. Since the definitive orbit ephemeris data (orbit*eph1.fits) are usually not available until a week after the observation period, a predictive orbit ephemeris (orbit*eph0.fits) is shipped with all data.
Use of predictive ephemerides is perfectly fine for most purposes, since the accuracy for the first week is certainly better than 300 km, or 1 ms. The exception is applying barycenter corrections to fast pulsars.
Users may pick up definitive ephemeris files, either through the Chandra Data Archive Search and Retrieval (ChaSeR) interface by retrieving them for a public observation in the same week, or from a temporary depository at our FTP site.
