Subsections

• A.4.1 Auto-Analysis Results (AAR)
  • A.4.1.1 Headers
  • A.4.1.2 Records
  • A.4.1.3 SWAALINE and SWAASCNT

A.4 Second Stage of the Pipeline

There is one file in this section, the SWS Auto-Analysis Results file.

A.4.1 Auto-Analysis Results (AAR)

A.4.1.1 Headers

The AAR files, normally named swaa*.fits by the IDA, contain primary headers, very much the same as those of the SPD-files with some obvious exceptions and some more calibration files listed. See Section A.3.1. No example of an AAR-header is presented here.

A.4.1.2 Records

The AAR file contains records with the fields described in Table A.10. In the FITS file they are defined in the binary header.

Table A.10: Records in the AAR file

Field name	Number	Format	Unit	Comment
SWAAWAVE	1	R*4	m	Wavelength of data point
SWAAFLUX	1	R*4	Jy	Flux
SWAASTDV	1	R*4		Standard deviation of the slope
SWAATINT	1	I*4	samples	Number of samples used
SWAADETN	1	I*4		detector number
SWAAITK	1	I*4		SWS instrument time key
SWAAUTK	1	I*4		ISO uniform time key
SWAARPID	2	I*1		raster point id
SWAASPAR	2	I*1		Contains error information
SWAALINE	1	I*4		line number
SWAASDIR	1	I*4		scan direction
SWAASCNT	1	I*4		scan number
SWAASTAT	1	I*4		status word
SWAAFLAG	1	I*4		flag word

1. SWAATINT is the total number of 1/24 second samples used in the calculation of the flux of this data point.
2. SWAARPID, the raster point id, is copied over from the GPSCRPID in the SPD. As SWS has no raster AOTs it is always (1,1) (unless a Solar System Object is being tracked), but is included so that the format of SWS AAR is compatible with LWS AAR.
3. These two bytes contain the error information described in Section 7.4.
4. Section A.4.1.3 discusses SWAALINE and SWAASCNT.
5. SWAASDIR is used to identify if the data point is from an up-scan (1) or a down scan (1). 0 is undefined (and do not use the data). See Section 3.2.1 for a definition of up-down scans.
6. SWAASTAT is copied over from SWSPSTAT. For a description of this see Table A.6.
7. SWAAFLAG is copied over from SWSPFLAG. For a description of this see Table A.7.

A.4.1.3 SWAALINE and SWAASCNT

SWAALINE and SWAASCNT are both counts of the valid data present in an AAR. All valid data means data that are flagged as `Data', with the `SW', `LW' or `FP' runflags set but without being flagged simultaneously as `darkcurrent', `photometric check'. Additionally the data should have a valid order assigned.

SWAALINE is a count of the valid ranges in a dataset. For SWS01, it is filled with the band number (see Table 2.1). For an SWS02 observing X lines it will count from 1 to X, with 0 reserved for any datapoints not associated with a line. Note that the datapoints associated with SWAALINE set to, e.g. 1, may not correspond to the first entered line number in your AOT as the logic may re-arrange them to increase efficiency. For SWS06 it effectively counts the number of scans, including reference checks etc. For an example see Table A.11.

SWAASCNT has nothing to do with the number of scans required for an AOT. It is a count of the number of lines/bands containing requested (i.e. what was requested in the AOT) data, starting with 1. Any data outside the requested ranges will have SWAASCNT set to 0. Note that even if SWAASCNT is greater than 0, the flag and status word should be checked to ensure the data is okay. For SWS01 SWAASCNT is filled with 1.

The decision whether to increment SWAALINE or SWAASCNT depends on whether a scan starts and ends at the same grating position as the preceding scan. Initially both are set to one. If a scan starts and ends at the same grating position as the preceding scan the line counter is not incremented but the scan counter is. If the wavelength range is different the line counter is incremented and the scan counter is (re-)set to one. Users should note that this effectively results in a difference in the behaviour of SWAALINE for SWS02's and 6's. For SWS02 there is one value per each up-down pair, whereas for an SWS06 there is one value per individual up- or down-scan.