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20.3 Types of STIS Files

The naming convention for STIS files is rootname_xxx.fits, where xxx is a three-character file suffix. The suffix identifies the type of data within the file. Table 20.3 lists the file suffixes for both uncalibrated and calibrated data files. Depending on the type of observation you have obtained, and therefore on the path it has taken through the calibration pipeline, you will find an appropriate subset of these files in your particular data set. Table 20.4 gives examples of typical STIS datasets for different types of observations.


Data File Naming Conventions

Suffix

Type

Contents

Unalibrated

_raw

image

Raw science1

_tag

table

Timetag event list

_spt

image

Support file (planning & telemetry information)

_wav

image

Associate wavecal exposure

_wsp

image

Wavecal support file (planning & telemetry information)

_asn

table

Association file

_trl

table

Trailer file (input)

_lrc

image

Local rate check image

_lsp

text

Local rate check support file

_jit

table

See Appendix C

_jif

image

See Appendix C

_pdq

table

See Appendix B

Calibrated

_flt

image

Flatfielded science

_crj

image

Cosmic ray-rejected, flatfielded science

_sfl

image

Summed Flatfield ed science

_x1d

table

1-D extracted spectra:

* aperture extracted, background subtracted, flux and wavelength calibrated spectra

_x2d

image

2-D extracted data:

* rectified, wavelength and flux calibrated spectra or

* geometrically corrected imaging data.

_sx1

table

Summed 1-D extracted spectra

_sx2

image

Summed 2-D extracted spectra

_trl

table

Trailer file (output); historical record of processing

1 Raw data from isolated wavecals, biases, darks, and flats, as well as from ACQs and ACQ/PEAKs, have the _raw suffix.



Typical STIS Output Products by Observation Type

Observation Type

Uncalibrated Files

Calibrated
Files

ACQ, ACQ/PEAK

_raw

none

IMAGING, ACCUM MODE,

ASSOCIATED SET

(crsplit or repeatobs)

_raw, _spt, _asn, _trl

_flt, _crj,
_sf1,
(MAMA only),
_crj (CCD only)

IMAGING, ACCUM MODE,

Single Exposure

_raw, _spt, _asn, _trl

_flt

FIRST ORDER SPECTROSCOPY, ACCUM MODE

ASSOCIATED SET (crsplit or repeatobs)

_raw, _wav, _asn, _spt, _wsp, _trl

_flt, _sx2, _sx1
_crj
( CCD only)

FIRST ORDER SPECTROSCOPY, ACCUM MODE

Single Exposure

_raw, _wav, _asn, _spt, _wsp, _trl

_flt, _x2d, _x1d

ECHELLE SPECTROSCOPY, ACCUM MODE

single exposure or ASSOCIATED SET

_raw, _wav, _asn, _spt, _wsp, _trl

_flt, _x2d, _x1d

TIMETAG IMAGING and SPECTROSCOPIC

_tag + ACCUM extensions

ACCUM extensions

Shading indicates files most likely to be of use during data analysis.

20.3.1 Understanding Associations

A single FITS file will contain multiple science exposures whenever an associated set of science exposures is taken. Associations are created for target acquisitions, auto-wavecals, crsplits, and repeatobs (nexp=many in the RPS2 file). You can recognize a data file as an associated set for STIS because there will be a zero in the last position of the rootname (e.g., o3tt01010_raw.fits). The rootnames of the individual exposures in an associated data set are contained in the association file, which has suffix _asn (e.g., o3tt01010_asn.fits). An association file holds a single binary table extension, which can be displayed with the IRAF tasks tprint or tread. The information within an association table shows how the associated exposures are related. Figure 20.2 illustrates the contents of the association table for a CRSPLIT=2 observation, with an associated autowavecal.

Figure 20.2: Contents of Association Table

The association table above tells the user that the product, or data set, will have the rootname o3tt01010, that there will be two science exposures contained in the o3tt01010_raw.fits file which are CRSPLITS, and that a o3tt01010_wav.fits file should exist containing the contemporaneously obtained automatic wavecal. The o3tt01010_raw.fits file will contain six image extensions, one triplet of {SCI, ERR, DQ} for each exposure (see Figure 20.1). The pipeline will calibrate this data as a unit, producing a single cosmic ray rejected image (rootname_crj.fits) along with its data quality and error images as well as rectified spectra. Similarly, for repeatobs observations, in which many identical exposures are taken to obtain a time series, all the science data will be stored in sequential triplet extensions of a single FITS file. These will be processed through the calstis pipeline as a unit, with each image extension individually calibrated and the set of images also being combined to produce a total time-integrated, calibrated image. See Chapter 21 for more information about the pipeline processing.



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