8.2 Description of content and use

This section gives for every product file a short description of the contents and of the use of this file.

8.2.1 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 n can be calculated using:

where:

• is the ITK for this science record (number n)
• 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 House Keeping frame 17).
• is the Spacecraft clock frequency (= )

8.2.2 General FITS header keywords for LWS Data

Table 8.1 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.

Table 8.1: The general keywords that are used in the headers of all product files.

8.2.3 Edited Raw Data

8.2.3.1 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 end time of that time period and on the status of the instrument. The record structure can be found in table 8.2.

 

Table 8.2: 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 subsystem and a low byte that subdivides different types within the subsystem. The subsystem values are:

   '0100'X  Illuminator subsystem
   '0200'X  Grating subsystem
   '0300'X  FPS subsystem
   '0400'X  FPL subsystem
   '0000'X  Other

Using this and the LSTASTAT field the status of the instrument at any given time can be determined:

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 subsystems have to be read-out. The following list gives the possible sample lists for LWS.

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

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

8.2.3.2 LIER: LWS Illuminator ERD file

Type of File:

FITS binary table

Contents:

For every read-out this contains the timing data for that read-out, 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 8.3.

 

Table 8.3: 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

 

8.2.3.3 LGER: LWS Grating ERD file

Type of File:

FITS binary table

Contents:

For every read-out this contains the timing data for that read-out, 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 8.4.

 

Table 8.4: 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

 

8.2.3.4 LSER: LWS Short wavelength Fabry-Perot ERD file

Type of File:

FITS binary table

Contents:

For every read-out this contains the timing data for that read-out, 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 8.5 .

 

Table 8.5: 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

 

8.2.3.5 LLER: LWS Long wavelength Fabry-Perot ERD file

Type of File:

FITS binary table

Contents:

For every read-out this contains the timing data for that read-out, 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 8.6.

 

Table 8.6: 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

 

8.2.3.6 LWHK: LWS Housekeeping ERD file

Type of File:

FITS binary table

Contents:

For every read-out this contains the timing data for that read-out, the farme quality flag (quality of the house keeping data) and the housekeeping data that is necessary for the data processing.

The record structure can be found in table 8.7.

 

Table 8.7: LWS House Keeping 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	House keeping Frame 1
LWHKFR17	264	128	I*2	House keeping 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 House keeping frames 1 and 17 contain the essential house keeping of the instrument and are used in the processing. The most important parameters that can be found in these house keeping frames are given in Tables 8.8, 8.9,8.10 and 8.2.3.6.

 

 

Table 8.8: Position in the House Keeping frames of the detector bias values.

 

 

Table 8.9: Location of the most important amplifier parameters in the House Keeping frames.

 

 

Table 8.10: Location of the most important grating parameters in the LWS House Keeping frames.

 

 
Table 8.11: Location of Fabry Perot parameters in the Housekeeping frames.

8.2.4 Standard Processed Data

8.2.4.1 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-Perot positions. The information contained in the SPD includes:

• timing information
• the mechanism position
• detector photo-current s for all ten detectors (ŭncalibrated against the internal illuminator s) including their uncertainties
• detector photo-current s 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 photo-current s for one detector at all mechanism position s in one scan will constitute one LWS ``mini-spectrum''.

The units for the LWS derive-SPD data are:

• The photo-current s contained in an SPD record are in units of amps.
• The mechanism position s contained in an SPD record are raw values.
• The timing information is expressed as LWS ITK.

Table 8.12 gives the record structure for the LWS SPD product file.

 

Table 8.12: 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 photo-currents
LSPDPHCU	84	10	R*4	A	Detector photo-current uncertainties
LSPDDPUD	124	10	R*4	A	Detector photo-current without deglitching
LSPDDUUD	164	10	R*4	A	Uncertainty in photo-current without
					deglitching
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 ganeral FITS keywords described in section 8.2.2. It also contains the additional keywords listed in table 8.13.

 

Table 8.13: LWS SPD file header keywords

Keyword	Type	Unit	Description
LSWAVE	R	m	Start wavelength of requested range
LEWAVE	R	m	End wavelength of requested range
LSVERSn	C	none	LWS version information for each calibration
			file (n=1,2,3,...).
LBIASdd	I	none	Bias level for each detector.
LCD1*	*	*	Various keywords which detail how first level
			deglitching functioned. These are copied from
			the LCD1 calibration file used
			(see table 8.23)
LCD2*	*	*	Keywords for second level deglitching, see
			table 8.25. Now not used.
LCD3*	*	*	Keywords for third level deglitching, see
			table 8.27. Now not used.
LCFORD	I		Order of slope fit for detector ramps
			(1=first order, 2=second order, 0=auto selection)
			For pipeline processing this value is fixed.
LCF*	L	none	Set of flags indicating the processing options
			that were selected. For pipeline processing these
			are fixed at standard settings.
LPHOTOM	L	none	Flag indicating if observation is done
			in photometric mode (fixed grating).

 

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 8.14. 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 6.3.

 

Table 8.14: 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.
LSRDG2*	I	none	Statistics related to second level deglitching.
			No longer used, so should always be zero.
LSRDG3*	I	none	Statistics related to third level deglitching.
			No longer used, so should always be zero.
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 points rejected because they were saturated.
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 debiasing parameter. Only
			calculated for second order slope fits. Set to
			zero if not calculated.
LSRMINDn	R	1/V	Minimum calculated debiasing 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.

 

8.2.4.2 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 photo-currents 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 principle 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 8.2.5).

8.2.4.3 LWGH: LWS Glitch History File

Type of File:

FITS binary table

Contents:

There is a separate LWGH file produced for every AOT processed. The DERIVE SPD program processes one TDT (Target Dedicated Time). A TDT will normally contain only one AOT, but it can contain more than one AOT. Therefore each run of DERIVE SPD will result in the creation of one or more LWGH files.

Each time a glitch event is detected by first level deglitching within DERIVE SPD a record of data is written to the LWGH file.

There is a maximum number of glitch events which can be written to the file per AOT. This is to prevent the file size from growing uncontrollably in case of software or hardware problems. The maximum size shall be set so that all glitches are recorded while the glitch rate is valid. If the maximum number of glitches is exceeded then no more records are written to the file, but a count of the number of glitches is maintained and written into the file header.

Each record of the LWGH file shall contain the fields given in table 8.15.

 

Table 8.15: LWGH file record structure

Name	offset	num	type	Description
LWGHDTGH	0	1	I*2	Detector ID (4 bits)
				Glitch Height (12 bits)
LWGHTIME	2	1	I*2	Glitch time (offset in 2 second units
				from TREFUTC1)

 

The detector ID identifies which detector the glitch occurred on. This is encoded as a number between 0 and 9, where 0 represents detector SW1 and 9 represents detector LW5.

The glitch height is encoded as a twelve bit number. If this is written as an unsigned number then this allows glitch heights to be resolved into 4096 different levels. The FITS keywords LWGHSCAL and LWGHZERO shall be used in order to convert this number into a voltage as follows:

             Voltage = LWGHZERO + (LWGHSCAL * glitch height number)

The time that the glitch occurred is specified as the number of 2 second units relative to the keyword TREFUTC1. This keyword is present in the header of each ERD file and specifies the UTC of an arbitrary format during the observation. It was decided that the time should be specified to the nearest 2 seconds, rather than to the nearest second because otherwise an integer overflow will occur if a TDT exceed 32,767 seconds (9.1 hours) duration.

The FITS header for the file must contain, in addition to the mandatory keywords, at least the additional keywordsgiven in table 8.16.

 

Table 8.16: LWS Glitch History file keywords

Name	Type	Description
TREFUTC1	I	The Universal time, in seconds, of an arbitrary format
		during the observation. The field LWGHTIME specifies
		the time of the glitch relative to this point
TREFUTC2	I	Remaining fractions of a second of time specified by
		TREFUTC1
TREFITK	I	ITK time corresponding to TREFUTC1
TREFUTK	I	UTK time corresponding to TREFUTC1
LWGHZERO	F	Zero value for conversion of glitch height voltage
LWGHSCAL	F	Scaling factor for conversion of glitch height voltage
LWGHOVFL	I	Number of glitches that overflowed the maximum glitch
		height value that could be represented by the twelve
		bit value in LWGHDTGH. This should normally be
		zero
LWGHMORE	I	Number of additional glitches found after maximum
		number of glitch records allowed in file had been
		exceeded
LSVERSn	C	LWS version information for each calibration file
		used (n=1,2,3,...)
LCD1*	*	Various keywords which detail how first level
		deglitching functioned. These are copied from
		the LCD1 calibration file used
		(see table 8.23)

 

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

8.2.5 LSPD and LIPD Status words

8.2.5.1 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 10 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 8.17.

These fields are described in more detail below.

• Glitch flag. This flag is set if one or more glitches occurred.
• Saturation flag. This flag is set if the ramp contains one or more saturated points.
• Number of ramps or mini-ramps averaged for this detector at this mechanism position. A `mini-ramp' refers to a sub-section of a ramp after part of the ramp has been discarded, usually because of a glitch. As the averaging of ramps at each mechanism position is no longer performed, this value should be either one or zero. It will be zero if the ramp has been deleted because of a glitch, saturated points etc.

  If the averaging is ever switched on again then this number can go up

  The value is stored as a three bit number. If averaging of ramps at each mechanism position is switched on again the this number can go up to a value of 7. The value 7 means `7 or more'.

• The percentage of available data used refers to the number of detector readouts for 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

8.2.5.2 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 8.18

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 (see user manual for SPL). This value is also written into the header of the LSPD file as the keyword LCFGRWAR.

8.2.6 SPD calibration files

Each SPD calibration file contains a version number and date for identification purposes. The version numbers are contained in the keywords named XXXXVER, where XXXX is the four letter name of the calibration file. The date is contained in the keyword LDATE. The date and version numbers of the calibration files used by Derive-SPD are written into the header of the SPD file as a series of keywords named LVERSn (n=1,2,...).

8.2.6.1 LCDT: Discard times file

Type of File:

FITS Header

Contents:

• For each detector there are two different discard times which specify the amount of data to be discarded following a detector reset. The first discard time is used when the number of samples in the ramp is less than or equal to the value of keyword LCDTNSAM. The second discard time is used for ramps which have more samples than this value. The discard times are specified in milliseconds. See table 8.19. This feature is intended to allow longer discard times for lower signal levels (longer ramps).
• Two keywords specifying the time period that must be discarded after a movement of the grating or Fabry-Perot. The time is specified in milliseconds. See table 8.19. Note that these times are concurrent with the time discarded due to detector resets. Currently they are less than the time discarded due to detector resets and so they have no effect.

 

Table 8.19: LCDT calibration file keywords

name	type	unit	description
LCDTNSAM	I	none	Threshold for switching from standard set of
			detector reset discard times to alternate set.
LCDTTRTn	R	ms	Standard discard time for detector n (n=0...9)
			following detector reset. Only used if number of
			samples in ramp is less than or equal to LCDTNSAM.
LCDTTRAn	R	ms	Alternate discard time for detector n (n=0...9)
			following detector reset. Only used if number of
			samples in ramp is greater than to LCDTNSAM.
LCDTTGR	R	ms	discard time after Grating movement
LCDTTFP	R	ms	discard time after Fabry-Perot movement

 

Use:

To determine how much of every integration ramp has to be discarded. Used in Derive-SPD processing step "Construct ramps and discard unusable readouts, see section 6.3.2.

8.2.6.2 LCAL: Readout limits for the analogue electronics

Type of File:

FITS header

Contents:

• Ten values specifying for each detector the minimum readout value below which the analog amplification chain does not respond. All readouts which are below this value are discarded. See table 8.20 for the keywords.
• The following ten keywords specify for each detector the maximum readout value above which the analog amplification chain saturates. All readouts above this value are discarded. See table 8.20 for the keywords.

 

Table 8.20: LCAL calibration file keywords

name	type	unit	description
LCALDMI0	I	-	Detector SW1 minimum readout
LCALDMI1	I	-	Detector SW2 minimum readout
LCALDMI2	I	-	Detector SW3 minimum readout
LCALDMI3	I	-	Detector SW4 minimum readout
LCALDMI4	I	-	Detector SW5 minimum readout
LCALDMI5	I	-	Detector LW1 minimum readout
LCALDMI6	I	-	Detector LW2 minimum readout
LCALDMI7	I	-	Detector LW3 minimum readout
LCALDMI8	I	-	Detector LW4 minimum readout
LCALDMI9	I	-	Detector LW5 minimum readout
LCALDMX0	I	-	Detector SW1 maximum readout
LCALDMX1	I	-	Detector SW2 maximum readout
LCALDMX2	I	-	Detector SW3 maximum readout
LCALDMX3	I	-	Detector SW4 maximum readout
LCALDMX4	I	-	Detector SW5 maximum readout
LCALDMX5	I	-	Detector LW1 maximum readout
LCALDMX6	I	-	Detector LW2 maximum readout
LCALDMX7	I	-	Detector LW3 maximum readout
LCALDMX8	I	-	Detector LW4 maximum readout
LCALDMX9	I	-	Detector LW5 maximum readout

 

Use:

To determine which readouts are outside the limits of the electronics

8.2.6.3 LCVC: Detector voltage conversion file

Type of File:

FITS header

Contents:

Two keywords are used in the conversion of raw detector readouts into voltages. The conversion is done using the formula:

         V = (raw detector value - LCVCVOFF) * LCVCVFAC

where the keywords are:

      LCVCVFAC= Conversion factor, Volts per raw value
      LCVCVOFF= Offset to be subtracted from raw value

  The conversion factor and the offset value are REAL values.

Use:

To convert the read-outs into voltages.

8.2.6.4 LCGA: Analogue amplification gains

Type of File:

FITS header

Contents:

Eighty keywords (all REAL values) specify the analogue amplification gain for each gain setting of each detector. Each keyword has the format: LCGADG<detector><gain>, where <detector> specifies the detector as a number between 0 and 9, and <gain> specifies the gain setting as a number between 0 and 7.
 

Use:

In Derive SPD for the conversion of readouts to voltages

8.2.6.5 LCJF: JF4 amplifier parameters

Type of File:

FITS Header

Contents:

Ten keywords specifying the fixed gain of the JF4 amplifier for each detector. And ten keywords specifying the capacitances associated with each of the JF4 amplifiers. See table 8.21 for the keyword names.

 

Table 8.21: LCJF calibration file keywords

name	type	unit	description
LCJFJG0	R	-	Detector SW1 JF4 gain
LCJFJG1	R	-	Detector SW2 JF4 gain
LCJFJG2	R	-	Detector SW3 JF4 gain
LCJFJG3	R	-	Detector SW4 JF4 gain
LCJFJG4	R	-	Detector SW5 JF4 gain
LCJFJG5	R	-	Detector LW1 JF4 gain
LCJFJG6	R	-	Detector LW2 JF4 gain
LCJFJG7	R	-	Detector LW3 JF4 gain
LCJFJG8	R	-	Detector LW4 JF4 gain
LCJFJG9	R	-	Detector LW5 JF4 gain
LCJFJC0	R	farad	Detector SW1 JF4 capacitance
LCJFJC1	R	farad	Detector SW2 JF4 capacitance
LCJFJC2	R	farad	Detector SW3 JF4 capacitance
LCJFJC3	R	farad	Detector SW4 JF4 capacitance
LCJFJC4	R	farad	Detector SW5 JF4 capacitance
LCJFJC5	R	farad	Detector LW1 JF4 capacitance
LCJFJC6	R	farad	Detector LW2 JF4 capacitance
LCJFJC7	R	farad	Detector LW3 JF4 capacitance
LCJFJC8	R	farad	Detector LW4 JF4 capacitance
LCJFJC9	R	farad	Detector LW5 JF4 capacitance

 

Use:

In derive SPD for the conversion of read-outs to voltages.

8.2.6.6 LCDB: Debiasing parameters, maximum voltages and thresholds for slope fitting

Type of File:

FITS Header

Contents:

The first section contains a table of of de-biasing parameters. There is one de-biasing parameter for each detector at each of the six standard bias settings. The keywords have the format LCDB<bias>DB<det>, where <bias> is the bias level (0 to 5) and <det> is the detector number (0 to 9). Bias levels 6 and 7 are not used during observations and are therefore not included in this table. The second section contains for each detector the maximum allowable voltage readout. Readouts which are above this voltage are rejected. Table 8.22 gives a list of these keywords. Finally the file contains the voltage thresholds for switching between first and second order slope fitting. These are specified for each detector as a fraction of 1/debiasing parameter.

 

Table 8.22: LCDB calibration file keywords

name	type	unit	description
LCDB<bias>DB<det>	R	1/volts	Debiasing parameters (60 total)
LCDBVM0	R	Volts	Detector SW1 maximum readout
LCDBVM1	R	Volts	Detector SW2 maximum readout
LCDBVM2	R	Volts	Detector SW3 maximum readout
LCDBVM3	R	Volts	Detector SW4 maximum readout
LCDBVM4	R	Volts	Detector SW5 maximum readout
LCDBVM5	R	Volts	Detector LW1 maximum readout
LCDBVM6	R	Volts	Detector LW2 maximum readout
LCDBVM7	R	Volts	Detector LW3 maximum readout
LCDBVM8	R	Volts	Detector LW4 maximum readout
LCDBVM9	R	Volts	Detector LW5 maximum readout
LCDBORDn	R	Volts	Voltage threshold for switch to second order
			slope fitting for detector n (n=1...9).

 

Use:

In Derive SPD for the calculation of ramp slopes.

8.2.6.7 LCD1: First level deglitching parameters

Type of File:

FITS Header

Contents:

See table 8.23 for the contents of this file.

 

Table 8.23: LCD1 calibration file keywords.

name	type	unit	description
LCD1GFRA	R	none	Glitches whose height is below this fraction of
			the ramp height will be rejected
LCD1SPRA	R	none	'Spikes' whose height is below this fraction of
			the ramp height will be rejected
LCD1SDRJ	R	none	Number of standard deviations from mean for point
			to be marked as an outlier.
LCD1PGRJ	I	none	Number of ramps to discard after a positive glitch.
LCD1NGRJ	I	none	Number of ramps to discard after a negative glitch.
LCD1GRRJ	L	none	Indicates if the whole of the glitched ramp should
			be discarded.
LCD1PGRI	I	none	For illuminator flashes, the number of ramps to
			discard after a positive glitch.
LCD1NGRI	I	none	For illuminator flashes, the number of ramps to
			discard after a negative glitch.
LCD1GRRJ	L	none	For illuminator flashes, indicates if the whole of
			the glitched ramp should be discarded.

 

Use:

Contains various parameters which control the detection and removal of glitched points by first level deglitching.

8.2.6.8 LCGH: Glitch history file parameters

Type of File:

FITS Header

Contents:

The first keyword (LCGHGHMR) gives the maximum number of records that can be written to the LWS Glitch History file. The following two keywords (LCGHGHV0 and LCGHGHVS) are used for the conversion of the glitch height in volts to a 12 bit integer number representing the glitch height, which is written to the glitch history file. Table 8.24 lists the keywords.

 

Table 8.24: LCGH calibration file keywords

name	type	unit	description
LCGHGHMR	I	-	Maximum number of records
LCGHGHV0	R	Volts	Offset to be subtracted
LCGHGHVS	R		Scaling factor

 

Use:

For writing data to the LWS glitch history file.

8.2.6.9 LCD2: Second level deglitching parameters

Type of File:

FITS Header

Contents:

Ten values that specify the goodness of fit rejection level for each detector, used during second level deglitching. These values specify the maximum RMS deviation of the goodness of fit of any slope from the goodness of fit of the set of slopes at the same mechanism position. Any slope which deviates by more than this amount is rejected. The keywords can be found in table 8.25. Currently not used in the pipeline processing.

 

Table 8.25: LCD2 calibration file keywords.

name	type	unit	description
LCD2D2R0	R	-	SW1 rejection level
LCD2D2R1	R	-	SW2 rejection level
LCD2D2R2	R	-	SW3 rejection level
LCD2D2R3	R	-	SW4 rejection level
LCD2D2R4	R	-	SW5 rejection level
LCD2D2R5	R	-	LW1 rejection level
LCD2D2R6	R	-	LW2 rejection level
LCD2D2R7	R	-	LW3 rejection level
LCD2D2R8	R	-	LW4 rejection level
LCD2D2R9	R	-	LW5 rejection level

 

Use:

Currently the Off-line processing does not perform second level deglitching. This file therefore is not used by OLP. However, the Derive-SPD process still reads it.

8.2.6.10 LCFP: Parameters for electronic filters

Type of File:

FITS Header

Contents:

Ten keywords containing the time constants for the high pass filter for each detector. The times are specified in seconds. The keywords can be found in table 8.26

 

Table 8.26: LCFP calibration file keywords

name	type	unit	description
LCFPHFT0	R	seconds	Detector SW1 time constant
LCFPHFT1	R	seconds	Detector SW2 time constant
LCFPHFT2	R	seconds	Detector SW3 time constant
LCFPHFT3	R	seconds	Detector SW4 time constant
LCFPHFT4	R	seconds	Detector SW5 time constant
LCFPHFT5	R	seconds	Detector LW1 time constant
LCFPHFT6	R	seconds	Detector LW2 time constant
LCFPHFT7	R	seconds	Detector LW3 time constant
LCFPHFT8	R	seconds	Detector LW4 time constant
LCFPHFT9	R	seconds	Detector LW5 time constant

 

Use:

In Derive-SPD for the calculation of photo currents.

8.2.6.11 LCD3: Third level deglitching parameters

Type of File:

FITS Header

Contents:

Ten values that specify the rejection levels for each detector used during third level deglitching. These values specify the maximum RMS deviation of any photocurrent from the set of photocurrents at each mechanism position. Any slope with a photocurrent which deviates by more than this amount is rejected. The keywords can be found in table 8.27. Currently not used in the pipeline processing.

 

Table 8.27: LCD3 calibration file keywords.

name	type	unit	description
LCD3D3R0	R	-	SW1 rejection level
LCD3D3R1	R	-	SW2 rejection level
LCD3D3R2	R	-	SW3 rejection level
LCD3D3R3	R	-	SW4 rejection level
LCD3D3R4	R	-	SW5 rejection level
LCD3D3R5	R	-	LW1 rejection level
LCD3D3R6	R	-	LW2 rejection level
LCD3D3R7	R	-	LW3 rejection level
LCD3D3R8	R	-	LW4 rejection level
LCD3D3R9	R	-	LW5 rejection level

 

Use:

Currently the Off-line processing does not perform third level deglitching. This file therefore is not used by OLP. However, the Derive-SPD process still reads it.

8.2.7 Auto Analysis results

8.2.7.1 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 10.

The units for the data in this product are:

• The fluxes and their uncertainties are in W/cm m for grating scans. For FP scans the units are in W/cm as the spectral bandwidth correction is not performed for FP scans.
• 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
• corresponding flux and its uncertainty

The record structure is given in table 8.28. 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 8.29 gives the keywords that contain this information.

 

Table 8.28: LWS AA product file record structure. Note that for FP spectra the units for the Flux and the uncertainty in the flux are W/cm .

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	m	Wavelength
LSANWAVU	28	1	R*4	m	Uncertainty in wavelength
LSANFLX	32	1	R*4	W/cm m	Flux on detector
LSANFLXU	36	1	R*4	W/cm m	Uncertainty in flux
LSANSTAT	40	1	I*4	-	Status word
LSANITK	44	1	I*4	-	ITK time

 

 

Table 8.29: LWS Auto Analysis file keywords

Name	Type	Description
LSVERSn	C	LWS version number for each SPL calibration file
		(n=1,2,3.....)
LPHOTOM	L	Flag indicating if observation is done
		in photometric mode (fixed grating).
LVERSn	C	LWS version number for each AAL calibration file
		(n=1,2,3.....)
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
LOWRTALL	L	Flag indicating whether LSAN file contains all data
LOSKPDRK	L	Indicates if dark current subtraction was omitted
LOSKPFPR	L	Indicates if FP spectral responsivity stage was omitted
LOSKPVEL	L	Indicates if FP velocity correction stage was omitted
LOABSOPT	I	Abs. responsivity option, 0=off, 1=on, 2=select
LORELOPT	I	Rel. responsivity option, 0=off, 1=on, 2=select
LVCOEFn	R	Coefficient 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

 

8.2.7.2 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 8.2.8).

8.2.7.3 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 currently 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.

8.2.7.4 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
• Other information which is constant over the scan

8.2.7.5 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 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

8.2.8 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. 8 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 8.30.

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.

Note that the `level' number relates to the order of the valid illuminator operations specified in the LCSI calibration file. It does not necessarily relate to the order that the operations were taken within the illuminator flash. You must check the LCSI calibration file in order to determine which illuminator operation corresponds to which level.

The invalid photocurrent flag indicates that the value of the detector photocurrent from the SPD data was outside the acceptable range for this observation. Invalid photocurrent values may be caused by glitches which have not been detected.

8.2.9 Auto-analysis calibration files

8.2.9.1 General information

All Auto Analysis calibration files contain a set of standard keywords in their header to identify the version and validity of the file. These keywords can be used to check that the calibration files are valid for the data that is being processed. The keywords are checked during the automatic processing of the data in the SOC-OLP pipeline.

The keywords can be found in table 8.31

 

Table 8.31: AA calibration files general keywords

name	type	unit	description
LDATE	C	-	date of creation or update
LVER	I	-	version number
LMODEL	C	-	identifies instrument model (always FM)
LVLSTART	I	-	UTK of start of validity
LVLEND	I	-	UTK of end of validity
LVLBIAn	I	-	indicates the bias level for which
			the file is valid for each detector
			(0-9). If LVLBIA0 is set to -1
			file is independent of bias, other
			bias levels are then not present

The version number and date of all the calibration files used by Auto Analysis are written into the header of the LSAN file as a series of keywords named LVERSn (n=1,2,...).

8.2.9.2 LCIR: Illuminator reference file

Type of File:

FITS binary table

Contents:

The LCIR file is a calibration file which contains a reference photo-current value for each ramp in an illuminator flash for each detector. The LCIR is a FITS binary table extension file of shape 1, ie. there is only one LCIR file which covers the whole mission.

The file contains an illuminator `type' number as part of each record, allowing it to contain reference data for more than one `type' of illuminator flash. The comments in the LCIR file header should describe each flash type stored in the file.

For each flash type the LCIR file contains only the data starting from when the first illuminator was switch on and ending when the last illuminator was switched off. The background measurements at the beginning and end of the flash are not contained in the LCIR file. The the reference photo-current values in the LCIR file have had the background photo-current already subtracted.

Each LCIR record contains a status flag which allows selected points to be ignored when ratioing against the flash data. This can be used to mask out data from illuminator levels which do not provide useful data. Any photocurrent value in the LCIR file which is set to zero will also be ignored in the same way. Values may be zero because of glitches in the reference data.

The header of the LCIR file contains keywords which specify NSD, the number of standard deviations for median clipping the data. These keywords are: LCIRNSDB (Number of Standard deviations to use for median clipping of background) and LCIRNSDF (Number of Standard deviations to user for median clipping of flash data).

The record structures is given in table 8.32

 

Table 8.32: LCIR calibration file record structure

name	offset	Number	type	unit	description
LCIRTYPE	0	1	I*4	-	Number identifying type of
					illuminator flash
LCIRPHC	4	10	R*4	A	Reference photo-current,
					with background subtracted
LCIRPHCU	44	10	R*4	A	Uncertainty in reference
					photo-current
LCIRSTAT	84	1	I*4	-	Status word. 1=use this value,
					0=ignore this value
LCIRICS	88	1	I*4	-	Illuminator commanded status

 

Use:

For the flux calibration of the data.

8.2.9.3 LCGW: Grating position to wavelength conversion table

Type of File:

FITS primary array.

Contents:

This file contains a table for the conversion between grating position and wavelength. The grating position is specified in LVDT read-out units. There is an entry in the table for each possible value of the LVDT. The records in the file are stored in order of decreasing wavelength. The file is written as a FITS primary array with three axis (NAXIS=3). The axis are defined as given in table 8.33.

 

Table 8.33: LCGW calibration file structure.

name	Number of	type	unit	description
	elements
NAXIS1	2	R*4	micron	Wavelength and uncertainty
NAXIS2	10	R*4	-	Detector number
NAXIS3	4096	R*4	-	Grating LVDT value

 

In the header of this file there are two special keywords: LSTARPOS and LENDPOS both of which are integers. These keywords give respectively the first and the last valid grating position.

Use:

Wavelength calibration of the grating.

8.2.9.4 LCGR: Grating relative response file

Type of File:

FITS primary array

Contents:

This FITS file contains the grating relative wavelength responsivities for each detector at selected wavelengths. The file applies for a particular bias level. The data are normalized to the wavelength at which the absolute responsivity is measured. The relative responsivity includes a correction for the aperture size of the instrument, assuming the source is a point source in the center of the beam. The unit of the relative responsivity therefore is cm . The file is written as a FITS primary array with three axis (NAXIS=3). The axis are defined as given in table 8.34.

 

Table 8.34: LCGR calibration file structure.

name	Number of	type	unit	description
	elements
NAXIS1	4	R*4	m	Wavelength
		R*4	m	uncertainty in wavelength
		R*4	cm	Relative Responsivity
		R*4	cm	Uncertainty in responsivity
NAXIS2	10	R*4	-	Detector number
NAXIS3	4096	R*4	-	Grating LVDT value

 

In the header of this file there are two special keywords: LSTARPOS and LENDPOS both of which are integers. These keywords give respectively the first and the last valid grating position.

Use:

Relative responsivity correction for grating mode.

8.2.9.5 LCFW: FP wavelength calibration parameters

Type of File:

FITS Header

Contents:

This FITS file contains the parameters required for converting FP position into wavelength. The parameters are the coefficients for the third order polynomial that is used to describe the dependence of the wavelength on the position of the FP etalons. Because of the precision of the FP wavelength calibration, these values should be read into real*8 variables. Table 8.35 gives the keywords for this file.

 

Table 8.35: LCFW calibration file keywords

name	type	unit	description
LCFWFLC0	D	-	FPL zeroth order coefficient
LCFWFLC1	D	-	FPL first order coefficient
LCFWFLC2	D	-	FPL second order coefficient
LCFWFLC3	D	-	FPL third order coefficient
LCFWFSC0	D	-	FPS zeroth order coefficient
LCFWFSC1	D	-	FPS first order coefficient
LCFWFSC2	D	-	FPS second order coefficient
LCFWFSC3	D	-	FPS third order coefficient

 

Use:

Wavelength calibration of Fabry-Perot data.

8.2.9.6 LCLR_;<det>: FPL relative wavelength responsivity file for detector ;<det>.

Type of File:

FITS binary table

Contents:

This file has been split into ten separate files. Each file contains the FPL Spectral response curve for one detector. The file is divided into a number of mini spectra of the response curve. Each record contains the start and end grating position, and the responsivity as a function of the relative FP position. This position is given relative to the rest positions as given in the LCLRZ file. The description of the record structure is given in table 8.36.

 

Table 8.36: LCLR_;<det> calibration file record structure.

name	offset	number	type	unit	description
STARTGP	0	1	I*2	-	Start grating position
ENDGP	2	1	I*2	-	End grating position
NRES	4	1	I*4	-	Number of valid responsivity values
RELFP	8	500	I*2	-	Relative FP position
RES	1008	500	R*4	-	Rel.Responsivity for this detector
RESU	3008	500	R*4	-	Uncertainty in responsivity

 

Use:

For the Spectral response correction for FPL observations.

8.2.9.7 LCLRZ: Auxiliary file for LCLR files

Type of File:

FITS binary table

Contents:

This file contains the zero positions of the FP, relative to which the FP positions in the LCLR files are given. For each standard grating position, this file contains 10 FP positions (one for each detector). The record structure can be found in table 8.37.

 

Table 8.37: LCLRZ calibration file record structure.

name	offset	number	type	unit	description
GPOS	0	1	I*2	-	Grating LVDT position
FPZERO	2	10	I*2	-	FP zero position
FILL	22	1	I*2	-	filler

 

Use:

For the Spectral response correction for FPL observations.

8.2.9.8 LCSR_;<det>: FPS relative wavelength responsivity file for detector ;<det>.

Type of File:

FITS binary table

Contents:

This file has been split into ten separate files. Each file contains the FPS Spectral response curve for one detector. The file is divided into a number of mini spectra of the response curve. Each record contains the start and end grating position, and the responsivity as a function of the relative FP position. This position is given relative to the rest positions as given in the LCSRZ file. The description of the record structure is given in table 8.38.

 

Table 8.38: LCSR_;<det> calibration file record structure.

name	offset	number	type	unit	description
STARTGP	0	1	I*2	-	Start grating position
ENDGP	2	1	I*2	-	End grating position
NRES	4	1	I*4	-	Number of valid responsivity values
RELFP	8	500	I*2	-	Relative FP position
RES	1008	500	R*4	-	Rel. Responsivity for this detector
RESU	3008	500	R*4	-	Uncertainty in responsivity

 

Use:

For the Spectral response correction for FPL observations.

8.2.9.9 LCSRZ: Auxiliary file for LCSR files

Type of File:

FITS binary table

Contents:

This file contains the zero positions of the FP, relative to which the FP positions in the LCSR files are given. For each standard grating position, this file contains 10 FP positions (one for each detector). The record structure can be found in table 8.39.

 

Table 8.39: LCSRZ calibration file record structure.

name	offset	number	type	unit	description
GPOS	0	1	I*2	-	Grating LVDT position
FPZERO	2	10	I*2	-	FP zero position
FILL	22	1	I*2	-	filler

 

Use:

For the Spectral response correction for FPS observations.

8.2.9.10 LCGB: Grating spectral bandwidth correction factors

Type of file:

FITS binary table

Contents:

The correction factor for the grating spectral bandwidth for each of the ten LWS detectors. For each detector the factor and its uncertainty is given. The record structure can be found in Table 8.40.

 

 

Table 8.40: LCGB calibration file record structure

Use:

In Auto Analysis to correct fluxes for the spectral bandwidth for grating spectra.