|
These data sets are used as input to the standard calibration program, CALFOC, which produces three types of calibrated science files:
For spectrographic images, geometric correction is done first, so it is the C0 image that is fully corrected.
Flat fields (C2), are not images in the usual sense, although they are in the same format. The C2 file is a list of the locations of reseau marks found in the raw flat field. Positions are in photocathode coordinates. No other processing is done on flat fields.
The Standard Header Packet, Unique Data log, and Data Quality files are not used in the calibration.
All files for a particular observation have the same
root file name;
the type of data in each file is identified by its extension.
The format of all retrieved files from the ST-ECF archive is FITS.
| File Type | Short Name | File Extension | Short Description |
|---|---|---|---|
| Standard Header Packet | SH | shf.fits | Telemetry values and spacecraft operation data (such as target position and spacecraft orbit). |
| Unique Data Log | UL | ulf.fits | Command values for the instrument (such as exposure parameters) as well as observation-specific information (such as temperature) |
| Science Data file | D0 | d0f.fits | The Science Data file is a two-dimensional image stored as single-precision floating-point values. Values in the header specify the instrument configuration, such as the filters and the relay. Other header keywords give the names of calibration reference files and flags to indicate what processing is to be done by CALFOC. |
| Data Quality file | PD | pdq.fits | The Data Quality file is an image having the same dimension and size as the Science Data file. Each pixel in the data quality file is a flag used to identify invalid data points. For each pixel, a value of zero in the data quality file indicates that there is no known problem with the corresponding pixel in the science file. If because of data-dropouts the datum has been filled, the data quality value is 16. If the datum failed the Reed-Solomon error check, the data quality value is 1. |
| Photometrically corrected image | C0 | c0.fits | For spectrographic images, geometric correction is done first, so it is the C0 image that is fully corrected. |
| Geometrically corrected image | C1 | c1.fits | For the normal-image mode, photometric correction is done first, followed by geometric correction; this means that the C1 image is fully corrected. |
| Locations of reseau marks | C2 | c2.fits | The C2 file is a list of the locations of reseau marks found in the raw flat field. Positions are in photocathode coordinates. |
If both
geometric correction and flat-field correction (UNI or SDE) are
done, then the extensions will be ".c0" and ".c1" as usual.
Otherwise, the files will have the following extensions:
| CB | cb.fits | Output from first set of processing steps (background, ITF, pixel splitting, and absolute DE) when no subsequent processing is done. |
|---|---|---|
| CG | cg.fits | Geometrically corrected image if no flat-field correction is done. |
| CU | cu.fits | Flat-fielded image if no geometric correction is done. |