CLIPhIT, Berlin, Germany1. COROT DPU ONBOARD SOFTWAREA main part of the COROT on-board software runson the COROT DPU. It is divided in to the PrimaryBoot Software (PBS) located in a radiation hardPROM and the Application Software (APS) locatedin the EEPROM. The COROT instrument becomesvisible over the software and within the telemetrydata sent to the ground.1.1. Data processing and Control FunctionsThe APS functions represent the operational statewhere different science and control modes are pos-sible to be executed. It controls the BEX and pro-cesses the science data of the Astero and Exo chan-nels independently. The user has high flexibilityfor configuring several data processing modes andtelemetry data rates based on over 200 parametersto be commanded from ground. For reducing thedata volume the science data processing is windoworiented. That means either in BEX or within theDPU the content of windows are processed and theresults are sent by telemetry. Of course, for calibra-tion or test purposes sending of raw image data issupported too. The APS provides angle error datawith high accuracy used on-board by the AOCS forspacecraft pointing.1.2. High reliability and qualityThe quality aspects are essential for the mission suc-cess. The PBS manages the COROT DPU power-onprocedure in Secure State. Additionally the mem-ory management services are performed to be ableto upload the APS over the Proteus platform fromground. PBS and APS are designed as high reliablesoftware applications, running over long time evenin case of Single Event Effects during SAA cross-ing. Advanced diagnosis and failure handling func-tions are implemented supporting the proper oper-ation in all COROT development, integration andoperational phases.1.3. Software DesignThe PBS is completely written in Assembler dueto code size constraints of the PROM. The APS ismainlywritteninCwithlowlevelfunctionsinAs-sembler for speed and code optimization. The Win-drivers Real Time Operating System (RTOS) VIR-TUOSOisusedasreliablesoftwarekerneloftheAPS. Up to 17 processes run simultaneously. Thedesign contains more than 130 functions with over100K instruction and parameter size.2. PHOTOMETRIC MONITORING OFCOROT FIELDSThe COROT mission will monitor a large number ofstars in several selected target fields to detect plan-etary transit events in the exo-channel. The inten-sity of each star is measured on board by aperturephotometry in optimized windows applied to eachobserved star. To define an optimal target list it isimportant to obtain as much information about thefield stars as possible. For transit search, it is es-pecially helpful to know in advance whether a staris variable since transit detections in such cases willbe more difficult (e.g. eclipsing binaries mimickingtransit events). The signal of grazing binaries ora binary signal diluted by entering the same aper-ture window as the target star requires careful radialvelocity follow-up to identify such events as “false