ALOS Data Users Handbook

Section 7 Overview of Processing Algorithmsb) Telemetry packet processingThe low rate mission telemetry data is extracted from the CCSDS packet to generate a set of telemetry data.c) Transformation of the engineering value of telemetryThe telemetry data is transformed to the engineering value.d) GPSR data processingThis processing is carried out only when the GPSR data is used. Position and speed data are obtained fromthe GPSR telemetry to conduct the primary check. The time data at the time when absolute navigation wascarried out is generated.e) Attitude data processingThe primary check of the attitude data is carried out. In case of the standard attitude determination system, aquaternion is generated. The time data at the time when the attitude determination was carried out isgenerated. If the data deficit occurs due to the VCDU frame loss, the attitude data is generated byinterpolation.f) Automatic checkThe sensor telemetry, the orbit and the attitude data, and image quality are checked automatically.g) Orbit data settingThe orbit data to be used is selected from an ALOS precision orbit data or an ALOS conventional orbit data(definitive / predictive).h) Attitude data settingThe attitude data to be used is selected from an onboard attitude data or a precision attitude data.i) Detection of the pointing angle switchinDeciding whether the pointing angle was switched or not during the one scene from the starting pixel valueof the extraction in case of PRISM, and from the encoder data of the pointing angle in case of AVNIR-2. If ithas been switched, the processing is ended.j) Detection of the attitude determination system switchingDetecting whether the attitude determination system was switched or not by the attitude determination7-8