Subsections

• 7.2.1 Timing information in the products: the ITK
• 7.2.2 General FITS header keywords for LWS data
• 7.2.3 Transparent data
• 7.2.4 Edited Raw Data (ERD files)
  • 7.2.4.1 LSTA: The LWS Compact Status History
  • 7.2.4.2 LIER: LWS illuminator ERD file
  • 7.2.4.3 LGER: LWS grating ERD file
  • 7.2.4.4 LSER: LWS short-wavelength Fabry-Pérot ERD file
  • 7.2.4.5 LLER: LWS long-wavelength Fabry-Pérot ERD file
  • 7.2.4.6 LWHK: LWS housekeeping ERD file
• 7.2.5 Standard Processed Data (SPD product files)
  • 7.2.5.1 LSPD: LWS standard processed data
  • 7.2.5.2 LIPD: LWS illuminator processed data file
  • 7.2.5.3 LWGH: LWS Glitch History file
  • 7.2.5.4 LPSP: LWS parallel Standard Process Data
  • 7.2.5.5 LSSP: LWS serendipity Standard Process Data
• 7.2.6 LSPD and LIPD status words
  • 7.2.6.1 Detector status word
  • 7.2.6.2 Mechanism status word
• 7.2.7 Auto-Analysis results (AAR product files)
  • 7.2.7.1 LSAN: LWS Auto-Analysis results
  • 7.2.7.2 LSNR: LWS Auto-Analysis results without responsivity correction
  • 7.2.7.3 LIAC: LWS illuminator summary file
  • 7.2.7.4 LSCA: LWS scan summary file
  • 7.2.7.5 LGIF: LWS Group Information File
  • 7.2.7.6 LPAA: LWS parallel Auto-Analysed data
  • 7.2.7.7 LSAA: LWS serendipity Auto-Analysed data
  • 7.2.7.8 LPAD: LWS parallel averaged data
• 7.2.8 LSAN status words

7.2 Product Files - Description of Content and Use

This section gives for every product file a short description of the content and the use of the file. The most common starting point for data reduction is LSAN file (Section 7.2.7.1) which is the final output file from the automated processing of standard observations (L01, L02 and L04). If an observer wishes to re-process their data with interactive analysis then they will require the SPD level files LSPD (Section 7.2.5.1) and LIPD (Section 7.2.5.2), the Glitch History file LWGH (Section 7.2.5.3) is not needed as it is not used in Auto-Analysis stage.
Note: at present the L03 data is only scientifically validated to SPD level due to the problem relating to the placement of the grating resolution element (Section 6.13) therefore L03 observers must start their reduction with this data and it is recommended that they use LWS interactive analysis. It is unlikely that any observer will wish to use ERD level products (Section 7.2.4) however these are included in this chapter in order to give a complete set of information.

7.2.1 Timing information in the products: the ITK

The LWS Instrument Time Key (ITK) is the main source of timing information in the products for one AOT, and is therefore extremely important for the processing. The LWS ITK is unique over an orbit. It is given in units of of a second. The ITK for science record can be calculated using:

(7.1)

where:

• is the ITK for this science record (number )
• is the ITK for the start of the revolution, which can be found in the header of each product
• is the UTK for this format
• is the UTK corresponding to
• is the time delay after the start of a format (=248 ITK units)
• is the number of ticks of the spacecraft clock (taken from housekeeping frame 17).
• is the spacecraft clock frequency (=)

7.2.2 General FITS header keywords for LWS data

Table 7.1 gives the general keywords that are used in the header of every data product. Some of these are general FITS keywords, others are specific for ISO data.

7.2.3 Transparent data

Transparent data are AOT specific data that are not processed by the satellite, but are passed directly from the uplink side of the ground station to the down link side (`transparent' in this case thus means bypassing the satellite). The Transparent Data (TDATA) contains information generated during the processing of the observer's input which may be required when processing the data for an observation, but is not required by the instrument to execute the observation on the satellite. The TDATA messages either relate to a complete observation (or AOT) or to the execution of a particular Instrument Command Sequence (ICS) and are written to the EOHA and EOHI files respectively. The main TDATA information appears as the fields EOHAAOTV and EOHIMSG1 in the EOHA and EOHI files. Their contents are shown in Tables 7.2 and 7.3.

As the TDATA is not sent to the satellite it is not synchronised accurately with the execution of ICSs by the instrument, or to the telemetry stream from the instrument. A counter has therefore been implemented in the LWS housekeeping which increments when each relevant ICS is executed allowing the data produced to be associated with the correct TDATA information by the ISO data processing software.

7.2.4 Edited Raw Data (ERD files)

7.2.4.1 LSTA: The LWS Compact Status History

Type of File:

FITS binary table

Contents:

For every period where the instrument is in the same status this file holds a record giving information on the begin and end time of that period and on the status of the instrument. The record structure can be found in Table 7.4.

Table 7.4: LWS Compact Status record structure.

Field	Number	Type	Description
CSGPUKST	1	I*4	UTK start time
CSGPUKEN	1	I*4	UTK end time
CSGPIKST	1	I*4	ITK start time
CSGPIKEN	1	I*4	ITK end time
CSGPUTST	2	I*4	UTC start time
CSGPUTEN	2	I*4	UTC end time
CSGPOSN	1	I*1	Observation Sequence Number
CSGPFILL	15	I*1	Spare
LSTASMP1	1	I*2	Sample list word 1
LSTASMP2	1	I*2	Sample list word 2
LSTASMP3	1	I*2	Sample list word 3
LSTASMP4	1	I*2	Sample list word 4
LSTASMP5	1	I*2	Sample list word 5
LSTASMP6	1	I*2	Sample list word 6
LSTASMP7	1	I*2	Sample list word 7
LSTALTYP	1	I*2	Sample list type
LSTASPA1	1	I*2	Spare
LSTAGRSN	1	I*2	Grating scan number
LSTAGRSD	1	I*2	Grating scan direction (0:forward; 1:reverse)
LSTASTAT	1	I*2	Instrument status
LSTAFPSN	1	I*2	FP scan number
LSTAFPSD	1	I*2	FP scan direction (0:forward; 1:reverse)
LSTAXTRA	1	I*4	Spare

LSTATYPE is Integer*2 variable consisting of a high byte which identifies the sub-system and a low byte that subdivides different types within the sub-system. The sub-system values are:

     `0100'X  Illuminator sub-system
     `0200'X  Grating sub-system
     `0300'X  FPS sub-system
     `0400'X  FPL sub-system
     `0000'X  Other

Using this and the LSTASTAT field the status of the instrument at any given time can be determined (Table 7.5).

Table 7.5: Meaning of the LSTASTAT field

LSTATYPE	LSTASTAT	Meaning
Grating	0	Grating sample list, grating not scanning
Grating	1	Grating sample list, grating scanning
FPS	0	FPS sample list, FP not scanning
FPS	1	FPS sample list, FP scanning
FPL	0	FPL sample list, FP not scanning
FPL	1	FPL sample list, FP scanning
Illuminator	0	Illuminator sample list, illuminators off
Illuminator	1	Illuminator sample list, illuminators on
Other	n/a	Other sample list

The sample list is used to tell the instrument which sub-systems have to be readout. Table 7.6 gives the possible sample lists for LWS.

In principle the only things that are of interest to the general user of LWS are the detector readouts, the positions of grating and FP, and the illuminator status. The temperatures are put here as well for use by the LWS instrument team.

Table 7.6: LWS sample list.

Sample list	Sampled data
Grating	10 detectors, grating position (LVDT), grating coil current,
	grating structure temperature, grating electronics temperature,
	grating commanded position
FPS	10 detectors, grating LVDT position, 3 FPL error signals
	FPS commanded position, grating
FPL	10 detectors, grating LVDT position, 3 FPL error signals
	FPL commanded position,
Illuminator	10 detectors, illuminator current, grating structure
	temperature, detector temperature A or temperature B,
	FPL temperature, illuminator status

7.2.4.2 LIER: LWS illuminator ERD file

Type of File:

FITS binary table

Contents:

For every readout this contains the timing data for that readout, the raster point information plus the raw science data for the 15 sampled science channels of LWS.

The record structure can be found in Table 7.7.

Table 7.7: LWS illuminator ERD file record structure.

Field	Offset	Number	Type	Description
GPSCTKEY	0	1	I*4	Instrument Time Key
GPSCRPID	4	2	I*1	Raster point ID (also for single pointing)
GPSCFILL	6	1	I*2	Spare
LIERDSW1	8	1	I*2	SW1 detector readout
LIERDSW2	10	1	I*2	SW2 detector readout
LIERDSW3	12	1	I*2	SW3 detector readout
LIERDSW4	14	1	I*2	SW4 detector readout
LIERDSW5	16	1	I*2	SW5 detector readout
LIERDLW1	18	1	I*2	LW1 detector readout
LIERDLW2	20	1	I*2	LW2 detector readout
LIERDLW3	22	1	I*2	LW3 detector readout
LIERDLW4	24	1	I*2	LW4 detector readout
LIERDLW5	26	1	I*2	LW5 detector readout
LIERGST	28	1	I*2	Grating structure temperature
LIERDTA	30	1	I*2	Detector temperature A
LIERLTMP	32	1	I*2	FPL temperature
LIERICUR	34	1	I*2	Illuminator current
LIERICS	36	1	I*2	Illuminator commanded status
LIERFIL2	38	1	I*2	Spare

7.2.4.3 LGER: LWS grating ERD file

Type of File:

FITS binary table

Contents:

For every readout this contains the timing data for that readout, the raster point information plus the raw science data for the 15 sampled science channels of LWS.

The record structure can be found in Table 7.8.

Table 7.8: LWS grating scan ERD file record structure.

Field	Offset	Number	Type	Description
GPSCTKEY	0	1	I*4	Instrument Time Key
GPSCRPID	4	2	I*1	Raster point ID (also for single pointing)
GPSCFILL	6	1	I*2	Spare
LGERDSW1	8	1	I*2	SW1 detector readout
LGERDSW2	10	1	I*2	SW2 detector readout
LGERDSW3	12	1	I*2	SW3 detector readout
LGERDSW4	14	1	I*2	SW4 detector readout
LGERDSW5	16	1	I*2	SW5 detector readout
LGERDLW1	18	1	I*2	LW1 detector readout
LGERDLW2	20	1	I*2	LW2 detector readout
LGERDLW3	22	1	I*2	LW3 detector readout
LGERDLW4	24	1	I*2	LW4 detector readout
LGERDLW5	26	1	I*2	LW5 detector readout
LGERGLVP	28	1	I*2	Grating LVDT position
LGERGCUR	30	1	I*2	Grating current
LGERGST	32	1	I*2	Grating structure temperature
LGERGET	34	1	I*2	Grating electronics temperature
LGERGCP	36	1	I*2	Grating commanded position
LGERFIL2	38	1	I*2	Spare

7.2.4.4 LSER: LWS short-wavelength Fabry-Pérot ERD file

Type of File:

FITS binary table

Contents:

For every readout this contains the timing data for that readout, the raster point information plus the raw science data for the 15 sampled science channels of LWS. The record structure can be found in Table 7.9.

Table 7.9: LWS FPS scan ERD file record structure.

Field	Offset	Number	Type	Description
GPSCTKEY	0	1	I*4	Instrument Time Key
GPSCRPID	4	2	I*1	Raster point ID (also for single pointing)
GPSCFILL	6	1	I*2	Spare
LSERDSW1	8	1	I*2	SW1 detector readout
LSERDSW2	10	1	I*2	SW2 detector readout
LSERDSW3	12	1	I*2	SW3 detector readout
LSERDSW4	14	1	I*2	SW4 detector readout
LSERDSW5	16	1	I*2	SW5 detector readout
LSERDLW1	18	1	I*2	LW1 detector readout
LSERDLW2	20	1	I*2	LW2 detector readout
LSERDLW3	22	1	I*2	LW3 detector readout
LSERDLW4	24	1	I*2	LW4 detector readout
LSERDLW5	26	1	I*2	LW5 detector readout
LSERGLVP	28	1	I*2	Grating LVDT position
LSERSCP	30	1	I*2	FPS commanded position
LSERSEC1	32	1	I*2	FPS error signal 1
LSERSEC2	34	1	I*2	FPS error signal 2
LSERSEC3	36	1	I*2	FPS error signal 3
LSERFIL2	38	1	I*2	Spare

7.2.4.5 LLER: LWS long-wavelength Fabry-Pérot ERD file

Type of File:

FITS binary table

Contents:

For every readout this contains the timing data for that readout, the raster point information plus the raw science data for the 15 sampled science channels of LWS. The record structure can be found in Table .

Table 7.10: LWS FPL ERD file record structure.

Field	Offset	Number	Type	Description
GPSCTKEY	0	1	I*4	Instrument Time Key
GPSCRPID	4	2	I*1	Raster point ID (also for single pointing)
GPSCFILL	6	1	I*2	Spare
LLERDSW1	8	1	I*2	SW1 detector readout
LLERDSW2	10	1	I*2	SW2 detector readout
LLERDSW3	12	1	I*2	SW3 detector readout
LLERDSW4	14	1	I*2	SW4 detector readout
LLERDSW5	16	1	I*2	SW5 detector readout
LLERDLW1	18	1	I*2	LW1 detector readout
LLERDLW2	20	1	I*2	LW2 detector readout
LLERDLW3	22	1	I*2	LW3 detector readout
LLERDLW4	24	1	I*2	LW4 detector readout
LLERDLW5	26	1	I*2	LW5 detector readout
LLERGLVP	28	1	I*2	Grating LVDT position
LLERLCP	30	1	I*2	FPL commanded position
LLERLEC1	32	1	I*2	FPL error signal 1
LLERLEC2	34	1	I*2	FPL error signal 2
LLERLEC3	36	1	I*2	FPL error signal 3
LLERFIL2	38	1	I*2	Spare

7.2.4.6 LWHK: LWS housekeeping ERD file

Type of File:

FITS binary table

Contents:

The LWHK file contains the contents of the housekeeping frames 1 and 17 from each telemetry format. These frames contain important information about the instrument status, which are used during the data processing. Each record in the LWHK file contains the data from a single telemetry format. The LWHK data are therefore only available once per format (every two seconds at the nominal telemetry rate). This compares with the contents of the LGER, LLER, LSER and LIER files, which are sampled at a much higher rate.

The record structure can be found in Table 7.11.

Table 7.11: LWS housekeeping ERD file record structure.

Field	Offset	Number	Type	Description
GEPRTKEY	0	1	I*4	Instrument Time Key
GEPRQUAL	4	2	I*1	Frame quality flag (see note)
LWHKFR01	8	128	I*2	Housekeeping Frame 1
LWHKFR17	264	128	I*2	Housekeeping Frame 17

The frame quality flag is set to 0 for perfect data, and is non-zero for imperfect quality data (i.e. frame 1 or 17 are bad). The housekeeping frames 1 and 17 contain the essential housekeeping of the instrument and are used in the processing. The most important parameters that can be found in these housekeeping frames are given in Tables 7.12, 7.13, 7.14 and 7.15.

Table 7.12: Position in the housekeeping frames of the detector bias values.

MSB

LSB

det

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Frame 1 bytes 122-123, Frame 17 bytes 10-11

SW1

x

x

x

SW2

x

x

x

SW3

x

x

x

SW4

x

x

x

SW5

x

x

x

Frame 1 bytes 124-125, Frame 17 bytes 12-13

LW1

x

x

x

LW2

x

x

x

LW3

x

x

x

LW4

x

x

x

LW5

x

x

x

MSB

LSB

det

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Frame 17 bytes 14-15

SW1

x

x

x

SW2

x

x

x

SW3

x

x

x

SW4

x

x

x

SW5

x

x

x

Frame 17 bytes 16-17

LW1

x

x

x

LW2

x

x

x

LW3

x

x

x

LW4

x

x

x

LW5

x

x

x

Table 7.13: Location of the most important amplifier parameters in the housekeeping frames.

Parameter	Frame	bytes
Current sample number	17	172-173
Current number of resets from step	17	174-175
Number of resets after saturation	17	176-177
Commanded number of resets per step	17	170-171
Commanded number of samples per reset	17	168-169

Table 7.14: Location of the most important grating parameters in the LWS housekeeping frames.

Parameter	Frame	bytes
Grating commanded position	17	44-45
Grating LVDT position	17	62-63
Grating requested scan mode	17	64-65
Grating current scan number	17	56-57
Grating requested start position	17	46-47
Grating requested step size	17	50-51
Grating requested number of steps	17	48-49
Grating current step number	17	52-53

Table 7.15: Fabry-Pérot parameters:
Location of Fabry-Pérot parameters in the housekeeping frames.

Parameter	Frame	bytes
FP requested scan mode	17	88-89
FP S or L commanded selection	17	72-73
FP requested start position	17	76-77
FP requested step size	17	80-81
FP requested number of steps	17	78-79
FP current scan number	17	86-87
FP current step	17	82-83
FP current commanded position	17	74-75
FPS power ON/OFF	17	90-91
FPS offset 2	17	92-93
FPS offset 3	17	94-95
FPS coil current 1	17	102-103
FPS coil current 2	17	104-105
FPS coil current 3	17	106-107
FPS error coil 1	17	96-97
FPS error coil 2	17	98-99
FPS error coil 3	17	100-101
FPL power ON/OFF	17	108-109
FPL offset 2	17	110-111
FPL offset 3	17	112-113
FPL coil current 1	17	120-121
FPL coil current 2	17	122-123
FPL coil current 3	17	124-125
FPL error coil 1	17	114-115
FPL error coil 2	17	116-117
FPL error coil 3	17	118-119

7.2.5 Standard Processed Data (SPD product files)

7.2.5.1 LSPD: LWS standard processed data

Type of File:

FITS binary table

Contents:

The LWS SPD contains the detector photocurrents for all ramps taken at all grating or Fabry-Pérot positions. The information contained in the SPD includes:

• timing information
• the mechanism position
• detector photocurrents for all ten detectors (uncalibrated against the internal illuminators, including their uncertainties
• detector photocurrents for all ten detectors without deglitching, and their uncertainties

For FP spectra only a subset of those (for certain detectors) will contain scientifically usable data. The SPD contains sufficient information which identifies the data specifically requested by the observer.

The photocurrents for one detector at all mechanism positions in one scan will constitute one LWS `mini-spectrum'.

The units for the LWS Derive-SPD data are:

• The photocurrents contained in an SPD record are in units of amps
• The mechanism positions contained in an SPD record are raw values
• The timing information is expressed as LWS ITK

Table 7.16 gives the record structure for the LWS SPD product file.

Table 7.16: LWS SPD file record structure.

Field	Offset	Number	Type	Unit	Description
GPSCTKEY	0	1	I*4	-	General prefix: ITK
GPSCRPID	4	2	I*1	-	General prefix: Raster Point ID
GPSCFILL	6	1	I*2	-	General prefix: Spare
LSPDTYPE	8	1	I*4	-	Record type
LSPDADET	12	1	I*4	-	Active detector flags. Bit 0 = SW1,
					bit 1 = SW2... (bit 0=LSB)
LSPDLINE	16	1	I*4	-	Line number
LSPDSCNT	20	1	I*4	-	Scan count
LSPDSDIR	24	1	I*4	-	Scan direction (0=forward; 1=reverse;
					999=error)
LSPDGCP	28	1	I*4	-	Grating commanded position
LSPDGLVP	32	1	R*4	-	Grating LVDT position (average over
				-	mechanism position)
LSPDGLVU	36	1	R*4	-	Uncertainty in grating LVDT position
LSPDFPOS	40	1	I*4	-	FP position
LSPDPHC	44	10	R*4	A	Detector photocurrents
LSPDPHCU	84	10	R*4	A	rms of detector ramp fit
LSPDDPUD	124	10	R*4	A	Detector photocurrent without deglitching
LSPDDUUD	164	10	R*4	A	rms of undeglitched detector ramp fit
LSPDSTAT	204	10	I*1	-	Detector status bytes
LSPDMAUX	214	1	I*2	-	Auxiliary data for this mechanism position

The header of the LWS SPD file contains the general FITS keywords described in Section 7.2.2. It also contains the additional, LWS specific, keywords listed in Table 7.17. Keywords with the prefix `LEI' are copied from the EOHI TDATA information. Keywords with the prefix `LEOH' are copied from the EOHA TDATA information (see Section 7.2.3 for more details about TDATA).

Table 7.17: LWS SPD file header keywords.

Keyword	Type	Unit	Description
LBIASxx	I	none	Bias level for each detector
LCD1*	*	none	Various values from LCD1 calibration file
LCF*	*	none	Processing options selected. For pipeline
			these are fixed at standard values
LEIWAVnn	R		For line AOTs give the expected wavelength
			for line nn. For wavelength range AOTs gives
			the wavelength of the reference line which
			determined the integration time for part nn
			of spectrum
LEOHFPS	L	none	Indicates if FPS was used.
			(FP observations only)
LEOHFPL	L	none	Indicates if FPL was used.
			(FP observations only)
LEOHSPCT	I	none	Number of spectra obtained
LEOHSDET	I	none	Detector used for start wavelength (L01 only)
LEOHEDET	I	none	Detector used for end wavelength (L01 only)
LEOHSZNE	I	none	Start zone (L03 only)
LEOHEZNE	I	none	End zone (L03 only)
LEOHBZNE	I	none	Break zone (L03 and L04 only)
LEOHSWAV	R		Start wavelength of requested range.
			(L01 and L03 only)
LEOHEWAV	R		End wavelength of requested range.
			(L01 and L03 only)
LPHOTOM	L	none	Flag indicating if observation was done
			in photometric mode (fixed grating)
LSVERSnn	C	none	LWS version information for each calibration
			file used by SPL

In addition to these keywords, the SPD header also contains various statistics on the data. These are intended more for diagnostics, so they should be treated with caution by observers. They are listed in Table 7.18. The letter `n' at the end of the keyword is used to indicate that there is a set of keywords with one keyword per detector. The value of n ranges from 0 to 9, with 0 representing detector SW1, etc. See also the description of the processing performed by Derive-SPD in Section 4.3.

Table 7.18: LSPD statistics keywords.

Keyword	Type	Unit	Description
LSRNDAT	I	none	Total number of raw data points read from ERD per
			detector
LSRNRMP	I	none	Total number of ramps read from ERD per detector
LSRNITKJ	I	none	Number of jumps in ITK (indicated missing data
			caused by telemetry dropouts etc.).
LSRNSPKn	I	none	Number of anomalous points found. See description
			of first level deglitching.
LSRUNRn	I	none	Number of points rejected due to detector resets
			and mechanism movements.
LSRDNRn	I	none	Number of points rejected as having invalid raw
			values.
LSRDG1Rn	I	none	Number of points rejected due to glitches
			detected by first level deglitching.
LSRDG1Nn	I	none	Number of glitches found by first level
			deglitching.
LSRDG1An	I	none	Number of ramps affected by glitches found by
			first level deglitching. (Ramp could contain
			more than one glitch.)
LSRFIT1n	I	none	Number of ramps fitted with first order slope fit.
LSRFIT2n	I	none	Number of ramps fitted with second order slope fit.
LSRFEWRn	I	none	Number of points rejected because too few points
			remained in ramp for slope to be fitted.
LSRVLTRn	I	none	Number of saturated points.
LSRSATRn	I	none	Ramps containing 1 or more saturated points.
LSRNPNTn	I	none	Number of data points actually processed into SPD.
LSRMAXPn	R	A	Maximum photocurrent
LSRMINPn	R	A	Minimum photocurrent
LSRMAXGn	R	A	Maximum goodness of fit of slopes
LSRMINGn	R	A	Minimum goodness of fit of slopes
LSRMAXDn	R	1/V	Maximum calculated de-biasing parameter. Only
			calculated for second order slope fits. Set to
			zero if not calculated.
LSRMINDn	R	1/V	Minimum calculated de-biasing parameter. Only
			calculated for second order slope fits. Set to
			if not calculated.
LSRPERn	R	none	Percentage of raw data points actually used to
			calculate SPD results.
LSRGRATn	R	s	Estimated glitch rate per detector.
LSRGRTOT	R	s	Estimated total glitch rate.

7.2.5.2 LIPD: LWS illuminator processed data file

Type of File:

FITS binary table

Contents:

The LIPD is similar to the LSPD file, but contains the results of processing the ramps of an illuminator flash rather than a grating or FP scan. This file contains the following information:

• Timing information
• The value of the illuminator commanded status word
• Detector photocurrents for all ten detectors, plus their uncertainties
• Other auxiliary information

The units are as follows:

• The timing information is expressed as LWS ITK
• The photocurrents are in units of amps

The LIPD has two principal purposes. Firstly it is used by Auto-Analysis to perform the absolute responsivity correction. This is done by comparing the photocurrents in the LIPD file against reference photocurrents in the LCIR calibration file. Secondly the ramps at the start of `closed' illuminator flashes provide a measure of the background and straylight at that time.

The header of the LIPD file contains the same keywords as the header of the LSPD file. The LIPD file contains the same detector status word as the LSPD file (see Section 7.2.6).

7.2.5.3 LWGH: LWS Glitch History file

Type of File:

FITS binary table

Contents:

The LWGH file contains a record of all glitches detected by SPL during an observation (including the illuminator flashes). Each record of the LWGH file contains the information for a single glitch. The information stored includes the time of the glitch, the detector number and the height of the glitch. The full layout of the LWGH file is given in Table 7.19.

The FITS header for the file must contain, in addition to the mandatory keywords, at least the additional keywords given in Table 7.20.

The keywords TREFUTC1, TREFUTC2, TREITK, and TREFUTK are copied from the header of the ERD file being processed.

The keyword LWGHMORE gives the number of glitches which occured after the maximum size of the LWGH file was reached. In practice this should always be zero as the maximum size has been set to a sufficiently large value to cope with all observations.

7.2.5.4 LPSP: LWS parallel Standard Process Data

Type of File: FITS binary table

Contents: The LPSP file contains the Standard Process Data for parallel mode observations.

7.2.5.5 LSSP: LWS serendipity Standard Process Data

Type of File: FITS binary table

Contents: The LSSP file contains the Standard Process data for serendipity mode observations.

7.2.6 LSPD and LIPD status words

7.2.6.1 Detector status word

Each LSPD and LIPD record contains a status word for each of the ten detectors for the current ramp. This has been implemented as the field LSPDSTAT or LIPDSTAT, which are arrays of ten words, with one word for each detector.

The detector status word contains the fields (Bit position 0 is the least significant bit) given in Table 7.23.

These fields are described in more detail below.

• Glitch flag: this flag is set if one or more glitches occurred.
• Saturation warning flag: this flag is set if the ramp contains one or more saturated points. Saturated points are still processed. See Section 4.3.4 for details.
• Invalid data flag: indicates that the point is invalid and should not be used.
• Discarded following glitch flag: indicates that the point has been declared invalid because it is deemed to be affected by a glitch occuring in a previous ramp. Whenever this flag is set the `invalid data' flag will also be set.
• The percentage of available data used refers to the number of detector readouts from this detector for this ramp which were used to calculate the photocurrent value. This is expressed as a percentage of the available data points.

  The number of `available' data points is defined as the number of sampled detector readouts for this ramp, minus the number of points discarded because of detector resets and mechanism movements.

  The following table gives the meaning of each of the possible values of this bit field:

  Bit value	Meaning
  0
  1
  2
  3
  4
  5
  6
  7

7.2.6.2 Mechanism status word

Each record of the LSPD file contains a single integer*2 field called LSPDMAUX. This word contains various status information associated with the current mechanism position.

The meaning of each of the bits in this word are given in Table 7.24

These fields are described in more detail below.

• NRESETS is the commanded number of ramps per mechanism position. It is copied from the LWS housekeeping data file (LWHK).
• NSAMPLES is the commanded number of samples per ramp. It is copied from the LWS housekeeping data file (LWHK).
• Grating LVDT error is defined as the grating LVDT position differing by more than a given amount from the grating commanded position for the current ramp. The value of this threshold is specified in the configuration file. This value is also written into the header of the LSPD file as the keyword LCFGRWAR.

7.2.7 Auto-Analysis results (AAR product files)

7.2.7.1 LSAN: LWS Auto-Analysis results

Type of File:

FITS binary table

Contents:

This product contains the set of individual spectra for each detector including the range required by the observer. Each spectrum consists of calibrated flux and wavelength, together with their uncertainties, and has been derived from data gathered from a single detector during a single scan whilst observing a single point on the sky (could be one point of a raster) in a single AOT.

The user is reminded that within the LWS off-line Processing chain there will be:

• no averaging of data points at the same grating or FP position
• no joining together of spectra from adjacent detectors
• no generation of maps for raster scans
• no subtraction of the local astronomical background

For some information on these additional processing steps that could be made we refer to Chapter 8.

The units for the data in this product are:

• The fluxes are in Wcm m for grating and Fabry-Pérot scans. The uncertainties in these values cannot be calculated by the pipeline. However, the LSAN file does contain the fractional systematic error due to the calibration, which forms part of the overall uncertainty.
• The wavelengths and their uncertainties are in microns
• Timing information is given as both UTK and ITK.

Each record of the LSAN contains:

• General Auto-Analysis record prefix (including UTK)
• Detector ID
• Wavelength and uncertainty
• The flux falling on the detector.

The record structure is given in Table 7.25. The header of the LSAN file contains information about the calibration that was used to derive the product, in particular the flux calibration and the velocity correction. Table 7.26 gives the keywords that contain this information.

Table 7.25: LWS Auto-Analysis product file record structure.

Field	Offset	Number	Type	Unit	Description
LSANUTK	0	1	I*4	-	UTK time
LSANRPID	4	2	I*1	-	Raster Point ID
LSANFILL	6	1	I*2	-	Filler
LSANLINE	8	1	I*4	-	Line number
LSANDET	12	1	I*4	-	Detector ID
LSANSDIR	16	1	I*4	-	Scan direction
LSANSCNT	20	1	I*4	-	Scan count
LSANWAV	24	1	R*4		Wavelength
LSANWAVU	28	1	R*4		Uncertainty in wavelength
LSANFLX	32	1	R*4		Flux on detector
LSANFLXU	36	1	R*4	none	Flux uncertainty
LSANSTAT	40	1	I*4	-	Status word
LSANITK	44	1	I*4	-	ITK time

Table 7.26: LWS Auto-Analysis file keywords.

Name	Type	Description
LSVERSn	C	LWS version number for each SPL calibration file
		(n=1,2,3.....)
LVERSn	C	LWS version number for each AAL calibration file
		(n=1,2,3.....)
LPHOTOM	L	Flag indicating if observation is done
		in photometric mode (fixed grating).
LCGBdet	R	Grating spectral bandwidth correction factor for
		detector det (det=SW1....LW5) from LCGB file
LCGBUdet	R	Uncertainty in grating spectral bandwidth correction
		factor for detector det (det=SW1...LW5) from LCGB file
LCFWFLCn	R	4 double precision numbers (n=0,1,2,3) giving FPL
		wavelength conversion coefficients (FP observations only)
LCFWFSCn	R	4 double precision numbers (n=0,1,2,3) giving FPS
	R	wavelength conversion coefficients (FP observations only)
LCGWCOn	R	(n=0,1,2,3,4) Coefficients used during conversion of
		grating LVDT to wavelength
LCGWLINE	R	Number of lines per m on grating. Used during
		conversion of grating LVDT to wavelength
LCGWAdet	R	(Det=`SW1'...`LW5') Angle for each detector used during
		conversion of grating LVDT to wavelength
LSTRNOMn	R	(n=0-9) Start of wavelength range for which GR RSRF is
		valid for each detector
LENDNOMn	R	(n=0-9) End of wavelength range for which GR RSRF is
		valid for each detector
LOWRTALL	L	Flag indicating whether LSAN file contains all data
		Should always be `T'
LODRKOPT	L	Dark current option: 0=off; 1=use measured value;
		2=use standard (fixed) value; 3=autoselect
LOSKPTHP	L	True if FP throughput correction was omitted
LOSKPVEL	L	Indicates if FP velocity correction stage was omitted
		Should always be `F'
LOABSOPT	I	Abs. responsivity option, 0=off; 1=on; 2=select
		Should always be 2
LORELOPT	I	Rel. responsivity option, 0=off; 1=on; 2=select
		Should always be 2
LVCOEFn	R	Coefficients of 2nd order fit for the velocity
		correction (n=0,1,2).
LOABSDN	L	Indicates if absolute responsivity correction was done
LORELDN	L	Indicates if relative responsivity correction was done
LEOH*	*	Copy of EOHA information from LSPD header (see Table 7.17)
LEI*	*	Copy of EOHI information from LSPD header (see Table 7.17)

7.2.7.2 LSNR: LWS Auto-Analysis results without responsivity correction

Type of File:

FITS binary table

Contents:

The LSNR file contains the same results as the LSAN file, but without the absolute responsivity and responsivity drift corrections applied. The layout is identical to the LSAN file, except that the field names have the prefix `LSNR' rather than `LSAN'. The keywords in the header of the LSNR file are identical to those in the LSAN file. See description of LSAN file for more details. The LSNR file contains the same status words as the LSAN file (see Section 7.2.8).

Note: This file is no longer produced from OLP Version 8 onwards

7.2.7.3 LIAC: LWS illuminator summary file

Type of File:

FITS binary table

Contents:

This file contains the final results of processing the illuminator flashes. One record is written to this file for each illuminator flash in the observation. Note that only the information from `closed' illuminator flashes are actually used in the processing. However, the LIAC file will contain the results for all illuminator flashes, regardless of whether they are open or closed. Each record of the LIAC file contains the following fields:

• Timing information in both ITK and UTK units
• The wheel position during the flash. Wheel positions are: 0=FPS; 1=Grating; 2=FPL; 3=blank (not used). A value of 0, 2 or 3 indicates that the flash is `closed'
• The photocurrent backgrounds measured at the start of the flash for each detector, in amps
• The ratio between the flash data and the calibration reference data in the LCIR file for each detector
• Other auxiliary information

7.2.7.4 LSCA: LWS scan summary file

Type of File:

FITS binary table

Contents:

This file contains summary information for each scan processed by Auto-Analysis. The main purpose of this file is to enable the correction for the drift in responsivity to be performed. Each record of the LSCA file contains:

• The average photocurrent for each detector for a single scan
• The ITK times of the beginning, middle and end of the scan
• The dark current/straylight value subtracted from the scan in AAL.
• Other information which is constant over the scan

Table 7.28: LSCA product file record structure.

Field	Number	Format	Description
LSCARPID	2	I1	Raster point ID
LSCAADET	3	I1	Active detector as string
LSCAFILL	3	I1	Filler (Record must be multiple of 4 bytes)
LSCAITKS	1	I4	ITK of start of scan
LSCAITKE	1	I4	ITK time of end of scan
LSCAITKR	1	I4	ITK time of reference point in scan
LSCAFLX	10	R4	Average detector flux for scan for each detector
LSCANRMT	1	I4	Total number of ramps in scan
LSCANRMF	10	I4	Number of ramps used in calculation of average
LSCALINE	1	I4	Line number (L02 and L04 only)
LSCAGPOS	1	I4	Grating measured position at start of scan (L03)
LSCASCNT	1	I4	Scan count (0,1...)
LSCASDIR	1	I4	Scan direction (0=forward; 1=reverse; 999=error)
LSCAORD	10	R4	Order numbers (L03, L04)
LSCABK	10	R4	Background/straylight subtracted from scan
LSCABKU	10	R4	Uncertainties in background/straylight

7.2.7.5 LGIF: LWS Group Information File

Type of File:

FITS binary table

Contents:

The LGIF file provides information about the absolute responsivity correction and responsivity drift correction applied to the final LSAN data. It contains one record for each `group' of data in the LSAN file. A group is a time interval during which a single absolute responsivity correction factor and drift correction factor is applied for each detector. Each record of the LGIF file contains:

• The start and end times of this group, in ITK units
• The reference time of the group in ITK units. This is the point at which the absolute responsivity correction factors are calculated and at which the responsivity drift is normalised
• The absolute responsivity correction factor and its associated uncertainty for each detector
• A set of flags indicating if responsivity drift information has been calculated for each detector
• The coefficients of the drift slope applied to correct for the responsivity drift for each detector. The coefficients give the LSPD value at the ITK reference time for the group and the gradient of the slope in LSPD units per ITK unit
• Other information which is constant for the group

7.2.7.6 LPAA: LWS parallel Auto-Analysed data

Type of File: FITS binary table

Contents: The LPAA file contains the Auto-Analysis data for parallel mode observations.

Table 7.30: LPAA product file record structure.

Field	Dimension	Format	Description
GPSCTKEY	1	I*4	Instrument Time Key
GPSCRPID	2	I*1	Raster point ID
GPSCFILL	1	I*2	Spare
UTK	1	I*4	UTK time
LWINTKEY	1	I*4	LWS window time key (seconds since beginning of LWS parallel
			observation window in current revolution) TUNIT=second
FLUX	10	R*4	Detector Data TUNIT= Wcmm
PROCFLGS	10	I*2	Processing flags
OTF	1	I*2	On Target Flag (Star Tracker flag)
STABLE	1	I*2	Stability flag (computed)
RA	1	R*8	RA coordinates TUNIT=degree
DEC	1	R*8	DEC coordinate TUNIT=degree
ROLL	1	R*8	Roll angle TUNIT=degree

7.2.7.7 LSAA: LWS serendipity Auto-Analysed data

Type of File: FITS binary table

Contents: The LSAA file contains the Auto-Analysis data for serendipity mode observations.

7.2.7.8 LPAD: LWS parallel averaged data

Type of File: FITS binary table

Contents:

Table 7.32: LPAD product file record structure.

Field	Dimension	Format	Description
GPSCTKEY	1	I*4	Instrument Time Key
GPSCRPID	2	I*1	Raster point ID
GPSCFILL	1	I*2	Spare
UTK	1	I*4	UTK time
LWINTKEY	1	I*4	LWS window time key (seconds since beginning of LWS parallel
			observation window in current revolution) TUNIT=second
FLUX	10	R*4	Averaged data ( )
STDEV	10	R*4	Standard deviation on Flux
WEIGHT	10	I*4	Number of samples effectively used
PROCFLGS	10	I*2	Processing flags
OTF	1	I*2	On Target Flag (Star Tracker flag)
STABLE	1	I*2	Stability flag (computed)
RA	1	R*8	Average RA coordinate TUNIT=degree
RAERR	1	R*8	Error on RA coordinate
DEC	1	R*8	Average DEC coordinate TUNIT=degree
DECERR	1	R*8	Error on DEC coordinate TUNIT=degree
ROLL	1	R*8	Average Roll angle TUNIT=degree
ROLLERR	1	R*8	Error on Roll angle TUNIT=degree

7.2.8 LSAN status words

The LSAN file contains one record per detector for each ramp. The status words in the LSNR files are identical in layout and content to the status words in the LSAN file.

Each record of the LSAN file contains one 32 bit status word per record. Eight bits of this status word are simply a copy of the status word for the appropriate detector from the LSPD file.

The layout of the LSAN status word for each detector is as given in Table 7.33.

The invalid data flag indicates that the flux value is not valid. This flag will be set if the SPD contained no data for this point, or an error occurred during the spectral responsivity correction stage (see below), or if the invalid photocurrent flag is set (see below). If the `percentage data' field in the SPD status word is set to 0 then there was no SPD data for this point. This is usually due to data being discarded due to glitches.

The spectral responsivity error flag indicates that either no responsivity value could be found in the calibration files for this point, or that the responsivity value found was set to zero.

The active detector flag indicates for L02 and L04 AOTs if this detector is the `active' detector. For these AOTs only one detector can be active at any one time. For L01, L03 and photometric L02 AOTs this flag is not applicable and will not be set for any detector.

The grating spectral responsivity warning flag indicates data points which are poorly calibrated. Any points with this flag set should only be used for wavelength identification of features. See Section 4.4.4 for more details.

The invalid photocurrent flag indicates that the value of the detector photocurrent from the SPD data was outside the acceptable range for this observation. This flag is set when the photocurrent value is a negative value which is less than 1 times the absolute value of the dark current/straylight. Invalid photocurrent values may be caused by glitches which have not been detected.