TGO CaSSIS Calibrated Data

Instrument: CASSIS

PDS4 Collection: urn:esa:psa:em16_tgo_cas:data_calibrated

PDS4 Bundle: urn:esa:psa:em16_tgo_cas

CaSSIS Calibrated data are produced by an IDL pipeline created and maintained by UBE (the University of Bern). The steps to convert raw data into calibrated data are performed in the following order:

  • Bias calibration.

  • Flat calibration.

  • Bad pixel calibration.

  • Expand binned data.

  • Perform absolute calibration.

  • Straylight calibration.

  • Framelet to framelet offset correction.

A detailed description of the calibration steps can be found in the CaSSIS Calibration Report which is planned to be archived during 2020. An overview of the on-ground calibration can also be found in the CaSSIS Calibration Programme (EXM-CA-PLN-UBE-10000) archive document. A summary of each part of the calibration procedure is given in the Section 4.3.4 of CASSIS EXPERIMENT TO ARCHIVE INTERFACE CONTROL DOCUMENT.

Calibrated data are stored as data files for each framelet with a corresponding xml header file. The data files are 4-byte floating points in a 2D array, where the data file is an unformatted binary. The xml header files for calibrated data produced by UBE are not PDS4 compatible. Similarly to the raw data, calibrated data are delivered to ESAC (European Space Astronomy Centre), where the xml files are put through a parser to make them PDS4 compatible.

The calibrated framelet data files produced by UBE and corresponding PDS4 compatible xml header files are ingested into the PSA (Planetary Science Archive).

CaSSIS Calibrated science data stored on the PSA follow the LID naming convention:

cas_cal_sc_YYYYMMDDThhmmss-YYYYMMDDThhmmss-CCC-NN-FFF-UID-SEQ-WIN.<ext>

where:

YYYY = year, MM = month, DD = day, hh = hour, mm = minute, ss = second. The two times are the beginning and end time in UTC of the full image sequence respectively (see below for details).

CCC = orbit number

NN = observation number (from science file name)

FFF = filter used (BLU, RED, NIR, PAN)

UID = image id

SEQ = sequence number (sub-exposure in sequence)

WIN = Window number (filter used 1-6). Note window 1 and 6 are the control windows described in Section 3.4. of

CASSIS EXPERIMENT TO ARCHIVE INTERFACE CONTROL DOCUMENT

<ext> = dat, xml, tab for the data, xml, and table file respectively.

The beginning and end time in the filename is given to second resolution. However, the time between CaSSIS exposures is roughly 0.3 seconds. The sub-second beginning time of a framelet observation is not used in the filename. The end time in the filename is always taken to be 4 seconds after the beginning time. This difference is included for consistency across all datasets only, it is not representative of the actual end time of a given framelet exposure.

The times used in the filename should therefore not be used for fine time calculations of when a framelet exposure began and finished. The xml file for a given data product contains the actual framelet observation start time to the milli-second level.