AOCS is the Attitude and Orbit Control System file. It contains basic, detailed information about the satellite pointing which is used by the Offline Processing pipeline to produce files specific to a single observation (IIPH and IRPH). The IIPH and IRPH files are more usable to the astronomer.
FITS header keywords include the file origin, telescope (ISO), the internal filename and version in the ISO archive, the file creation date, the Offline Processing system version identification, the equinox, and the telemetry rate in kilobits/second, as well as a few comments.
The fields contain the Uniform Time Key (UTK is not to be confused with UTC), the frame quality and raw attitude and control system frames. It is not anticipated that the Observer will want to use this file directly in data analysis.
PPH is the Aperture Pointing History. It has 5 keywords in the FITS header which specify the interval of time covered by information in the file, the time the file was generated, the satellite revolution (orbit) number, and the Attitude Pointing History version number.
The APPH file is used by the Offline Processing Pipeline to produce the Instrument Instantaneous Pointing History (IIPH) and Instrument Reference Pointing History (IRPH) files at the Standard Processed Data (SPD) level.
It is not yet known that the APPH file will be distributed to observers with the science data.
EOHA is the Executed Observation History per Astronomical Observing Template (AOT). It is used to transfer information between the uplink and downlink to the satellite which is not used in observing but which is used in processing the data (Transparent Data, TDATA). The EOHA file is related to the EOHI file because each AOT is made up a series of Instantiated Command Sequences.
It includes information such as the proposal identification, the proposer's identification, target name, etc. as well as fields which are specific to each instrument. It also includes the timestamp of the AOT-to-OCT logic which is used to translate the details of the proposal (as entered by the observer into the Proposal Generation Aid) into spacecraft-related commands.
It is unlikely that the observer will wish to use the information contained in this file in analyzing data, however, the observer may wish to establish (for example) that the AOT-to-OCT logic for a particular AOT may have changed during the course of the ISO mission.
EOHI is the Executed Observation History per Instantiated Command Sequence (ICS). It is used to transfer information between the uplink and downlink to the satellite which is not used in observing but which is used in processing the data (Transparent Data, TDATA).
It includes information such as the time (UTC) of sending the associated Instrument Command Sequence. Each instrument uses a field (EOHIMSG1) which gives AOT-specific information on an ICS-level of detail.
The GEHK file is the General Housekeeping file. It contains information associated with general housekeeping and science housekeeping.
FITS header keywords include the file origin, telescope (ISO), the internal filename and version in the ISO archive, the file creation date, the Offline Processing system version identification, the equinox, and the telemetry rate in kilobits/second, as well as a few comments.
The fields contain the Uniform Time Key (UTK is not to be confused with UTC), the frame quality and housekeeping frames.
It is not anticipated that the Observer will want to use this file directly in data analysis.
The IIPH file is the Instrument Instantaneous Pointing History file. It gives the pointing direction of the instrument as a function of time. It refers to a single observation. The IIPH is derived from the Aperture Pointing History file (APPH) which may (or may not) be distributed to observers with their science data.
The IIPH file covers the same time period as the Standard Processed Data (SPD) product. It contains the same standard SPD FITS keywords. The IIPH was designed to have entries for updated positions (right ascension and declination, roll angle (all in degree units) every two seconds. During performance verification phase, the entries contain constant positions per raster point. At some later date, CAM parallel pointings may be used to reconstruct any drift during the observations.
The observer will probably wish to examine the IRPH file instead of the IIPH file as it contains only one point per raster position.
The IRPH file is the Instrument Reference Pointing History. It contains the reference pointing position for each raster point. Pointing drift with time during the observation is not included.
The IRPH refers to a single observation. Its contents are derived from the Aperture Pointing History file (APPH) which may (or may not) be distributed to observers with their science data.
The IRPH file covers the same time period as the Standard Processed Data (SPD) product for a given observation. It contains the same standard SPD FITS keywords. In addition to the standard SPD keywords, the FITS header contains keywords for quaternions for the startracker, STR/QSS misalignment, and QSS/instrument alignment.
Various fields give the expected Coordinated Universal Time in seconds since 1989.0, the raster-pointer id, the raster-point quaternion, the right ascension, declination, and roll angle (the last three are in units of degrees).
We recommend that the observer compare the requested target position (J2000) to the actual observed right ascension and declination (in degrees, J2000) given in this file. There will be several entries if the observation was made using a raster; for single pointing observations there will be only one entry.
make