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COS Data Handbook 2.00
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COS Data Handbook > Chapter 2: COS Data Files > 2.2 COS File Names

The naming convention for COS files is rootname_*.fits, where rootname follows the ippsoot naming convention (see Chapter 5 of the Introduction to HST Data Handbooks), and * is a three to nine character file suffix. The suffix identifies the type of data within the file. All FUV data files with the exception of the lampflash, x1d and x1dsum files will have an additional suffix of _a or _b (e.g. rootname_*_[a,b].fits) to denote the detector segment. However, if segment=A is specified in the Phase II proposal there will be no corresponding _b files and vice versa. The FUV lampflash, x1d and x1dsum files will always be segment combined and therefore will not have the additional suffix.
Table 2.1 lists the file suffixes for the COS data files and indicates which files are produced by the different types of observations. Depending on the type of observation, and the path it has taken through the calibration pipeline (see calibration flow charts; Figure 3.1-Figure 3.5), there will be an appropriate subset of these files in a given dataset. Note, the format of some of the COS files can be different depending on the observing mode; see Section 2.3 for more details.
COS data utilize a modified naming convention from other HST instruments. In, particular COS FUV files can have TWO suffixes. The first suffix identifies the filetype and the second suffix if present identifies the FUV detector segment. For the remainder of this document the use of “suffix” will refer to the first suffix which identifies the filetype and will always include filetypes with the additional FUV segment suffix if they exist.
Table 2.1: Data Types and File Naming Conventions
Raw NUV TIME-TAG events list
Raw FUV TIME-TAG events list
Raw NUV ACCUM image
Raw FUV ACCUM image
The raw trailer file is updated with a historical record and errors log of calibration pipeline processing1
NUV TIME-TAG events list with calibrated values
FUV TIME-TAG events list with calibrated values
1-D extracted TAGFLASH (FLASH=yes) spectra
Summed flat-fielded image (imaging only). Final calibrated association product for all COS imaging datasets
Final combined 1-D extracted spectra for multiple exposures with the same grating, central wavelength and aperture combining all FPPOS. Final calibrated association product for all COS spectroscopic datasets.

Only updated during processing and ingestion by the HDA. When reprocessing data in a user’s home environment the trl file will not be updated. Instead reprocessing will generate an ASCII tra file.

For ACCUM data the time stamps in the first extension are set to the median value in the corrtag files; each count in the rawaccum file becomes an event. See Section 2.4.2.

Only for TIME-TAG with FLASH=yes (TAGFLASH mode)

<n> can be 1,2,3,4 and denotes the FPPOS number.

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