The O.D.A.S. data reduction and analysis process

The analysis of the acquired frames is done in several steps, partly during the night of observation at the telescope, partly during the day following the observations. Each triplet (scan or stare image) is processed with SExtractor (a public domain image processing software package developed by Emmanuel Bertin and S. Arnouts, IAP, Paris), to obtain three catalogs of positions (x,y pixel coordinates) and magnitudes (in instrumental system) of all objects detectable by the software. No pre-processing (flat-fielding, etc.) is done.

A second software package (called Rackis, developed by Magnus Lundström) is used to find moving objects and determine their astrometric positions in MPC format. This is done fully automatic and run (together with the SExtractor step) in batch mode; usually after the acquisition of the third frame of a field. (Currently, this step is performed on a PC, equipped with 166 MHz Pentium processor and takes somewhat less than one hour).

Rackis produces a "blink-file" for each moving object found. In order to verify the validity of a detected asteroid or comet, these blinks have to be examined visually by the operator. For this purpose a special piece of software, called Blink, was developed by Stefano Mottola. Blink allows interactively to distinguish real moving objects from fake ones.

Finally, the preliminary positions and the corresponding logs from the blinking for a whole night (or several nights for that matter) are processed with a routine called MPC_prep (written by Gerhard Hahn) which produces a file with the positions to be submitted to the Minor Planet Center (M.P.C.) in Cambridge, Mass.

Normally, the blinking step is done twice, by two different observers, to safeguard for possible misidentifications. A first check is often done at the telescope, while the preparation step for the M.P.C. is made at the IPE in Berlin. The blink-files, together with the position-file and blink.logs are transferred to the IPE at the end of an observing night, so that a support observer at the IPE can take over and finish the processing of the observations by sending the final product via email to the M.P.C.

In addition to archiving the obtained astrometric positions, some analysis for statistical purposes is made. For interesting discoveries (i.e. FMOs, or objects with peculiar motion identified during the blinking procedure) orbit determination software is used to check the validity of the positions prior to their submission to the M.P.C. Software for plotting motion vectors and ephemeris generation are available as identification aids and for planning follow up observations.