• 8.1 Inventory and naming convention
• 8.2 Description of content and use
  • 8.2.1 Timing information in the products; the ITK
  • 8.2.2 General FITS header keywords for LWS Data
  • 8.2.3 Edited Raw Data
    • 8.2.3.1 LSTA: The LWS Compact Status History.
    • 8.2.3.2 LIER: LWS Illuminator ERD file
    • 8.2.3.3 LGER: LWS Grating ERD file
    • 8.2.3.4 LSER: LWS Short wavelength Fabry-Perot ERD file
    • 8.2.3.5 LLER: LWS Long wavelength Fabry-Perot ERD file
    • 8.2.3.6 LWHK: LWS Housekeeping ERD file
  • 8.2.4 Standard Processed Data
    • 8.2.4.1 LSPD: LWS Standard Processed Data
    • 8.2.4.2 LIPD: LWS Illuminator processed data file
    • 8.2.4.3 LWGH: LWS Glitch History File
  • 8.2.5 LSPD and LIPD Status words
    • 8.2.5.1 Detector status word
    • 8.2.5.2 Mechanism status word
  • 8.2.6 SPD calibration files
    • 8.2.6.1 LCDT: Discard times file
    • 8.2.6.2 LCAL: Readout limits for the analogue electronics
    • 8.2.6.3 LCVC: Detector voltage conversion file
    • 8.2.6.4 LCGA: Analogue amplification gains
    • 8.2.6.5 LCJF: JF4 amplifier parameters
    • 8.2.6.6 LCDB: Saturation voltage thresholds for slope fitting
    • 8.2.6.7 LCD1: First level deglitching parameters
    • 8.2.6.8 LCGH: Glitch history file parameters
    • 8.2.6.9 LCD2: Second level deglitching parameters
    • 8.2.6.10 LCFP: Parameters for electronic filters
    • 8.2.6.11 LCD3: Third level deglitching parameters
  • 8.2.7 Auto Analysis results
    • 8.2.7.1 LSAN: LWS Auto Analysis Results
    • 8.2.7.2 LSNR: LWS Auto Analysis Results without responsivity correction
    • 8.2.7.3 LIAC: LWS Illuminator summary file
    • 8.2.7.4 LSCA: LWS Scan summary file
    • 8.2.7.5 LGIF: LWS Group information file
  • 8.2.8 LSAN Status words
  • 8.2.9 Auto-analysis calibration files
    • 8.2.9.1 General information
    • 8.2.9.2 LCIR: Illuminator reference file
    • 8.2.9.3 LCGW: Grating position to wavelength conversion parameters
    • 8.2.9.4 LCGR: Grating relative response file
    • 8.2.9.5 LCFW: FP wavelength calibration parameters
    • 8.2.9.6 LCLR_<det>: FPL relative wavelength responsivity file for detector <det>.
    • 8.2.9.7 LCLRZn: Auxiliary file for LCLR files
    • 8.2.9.8 LCSR_<det>: FPS relative wavelength responsivity file for detector <det>.
    • 8.2.9.9 LCSRZn: Auxiliary file for LCSR files
    • 8.2.9.10 LCGB: Grating spectral bandwidth correction factors

   
8. Guide to instrument related data products.

   
8.1 Inventory and naming convention

The LWS specific files that are included on the CD-ROM have been named with the following naming convention:

• All file names start with an L (indicating LWS)
• The following 3 characters give a three letter code indicating the product type (see below)

The convention for the product code is

LSTA   -  LWS Compact status history file
LIER   -  LWS Illuminator ERD file
LGER   -  LWS Grating ERD file
LSER   -  LWS Short wavelength FP ERD file
LLER   -  LWS Long wavelength FP ERD file
LWHK   -  LWS Housekeeping ERD file
LSPD   -  LWS SPD file
LIPD   -  LWS illuminator processed data
LWGH   -  LWS Glitch history file
LSAN   -  LWS Auto analysis product file
LSNR   -  LWS Auto analysis product file without responsivity corrections
LIAC   -  LWS Auto analysis illuminator summary file
LSCA   -  LWS Auto analysis scan summary file
LGIF   -  LWS Auto analysis group information file
LC**   -  LWS calibration file (see chapter 5)

Depending on the AOTs that are used, an observer will find different sets of files on the CD-ROM.

• For Grating AOTs (AOT L01 and L02) files:

    Raw data:
        LGER
        LIER
        LSTA
        LWHK
    Standard processed data:
        LIPD
        LSPD
        LWGH
    Auto Analysis results:
        LSAN
        LSNR
        LIAC
        LSCA
        LGIF
  

  Plus the necessary calibration files (see chapter 5 for a list).
• For Fabry-Perot AOT (AOTs L03 and L04):

    Raw data:
        LIER
        LLER
        LSER
        LSTA
        LWHK
    Standard processed data:
        LIPD
        LSPD
        LWGH
    Auto Analysis results:
        LSAN
        LSNR
        LIAC
        LSCA
        LGIF
  

  Plus the necessary calibration files (see chapter 5 for a list).

   
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 2^-14 of a second. The ITK for science record n can be calculated using:

(8.1)

• ITK_n is the ITK for this science record (number n)
• ITK_ref is the ITK for the start of the revolution, which can be found in the header of each product
• UTK_f is the UTK for this format
• UTK_ref is the UTK corresponding to ITK_ref
• T_d is the time delay after the start of a format (=248 ITK units)
• D(L_s) is the number of ticks of the spacecraft clock (taken from House Keeping frame 17).
• is the Spacecraft clock frequency (=2¹⁸)

   
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.

   
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 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

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:

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 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.

Detector biases   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

 

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

Amplifier gains   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                         Other amplifier parameters: 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 8.10: Location of the most important grating parameters in the LWS House Keeping frames.

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

Fabry Perot parameters 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

   
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-currents for all ten detectors (uncalibrated against the internal illuminators) including their uncertainties
• detector photo-currents 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-currents 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 photo-currents 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 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 RMS of detector ramp fit LSPDDPUD 124 10 R*4 A Detector photo-current 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 ganeral FITS keywords described in section 8.2.2. It also contains the additional, LWS specific, keywords listed in table 8.13 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 3.2.2 for more details about TDATA).

 

Table 8.13: 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 m 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 m Start wavelength of requested range.       (L01 and L03 only) LEOHEWAV R m 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 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. 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 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. LSRGRATn R sec-1 Estimated glitch rate per detector. LSRGRTOT R sec-1 Estimated total glitch rate.

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:

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 8.15. Note that the layout has changed compared to the OLP V6 version. The V6 version contained fewer fields and required the time key and glitch height to be extracted from bit fields.

 

Table 8.15: LWGH file record structure

Name offset num type Description LWGHITK 0 1 I*4 ITK time of start of glitch LWGHRITK 4 1 I*4 ITK time of start of glitched ramp LWGHDET 8 1 I*2 Detector number (0-9) LWGHRAT 10 1 I*2 Estimated glitch height to ramp height ratio         expressed in multiples of 0.01 LWGHHI 12 1 R*4 Estimated height of glitch, in volts

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 LWGHMORE I Number of additional glitches found after maximum     number of glitch records allowed in file had been     exceeded. Should always be zero. 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.

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.

   
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 warning flag. This flag is set if the ramp contains one or more saturated points. Saturated points are still processed. See section 6.3.4 for details.
• Number of (mini) ramps. This field is obsolete and does not contain useful information.
• 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

The contents and usage of the SPD calibration files have changed as the pipeline has developed. Some of the calibration files which are still read by SPL are no longer used during the processing. Other files contain information which is no longer used. In the following sections only the information which is actually used is identified.

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 and AAR files as a series of keywords named LSVERSn (n=1,2,...).

8.2.6.1 LCDT: Discard times file

Type of File:

FITS Header

Contents:

• The amount of time to be discarded following each detector reset, in milliseconds. The LCDT file for V7 effectively contains only a single discard time which applies to all ramps of all detectors. However, due to requirements for previous versions of the pipeline, this is implemented as two separate discard times for each of the ten detectors. One discard time is for `short' (high signal) ramps, the other discard time for `long' (low signal) ramps. Since the introduction of the method of slope fitting in V7, all discard times are set to the same value.

• Two keywords specifying the time period that must be discarded after a movement of the grating or Fabry-Perot. These times are not in use as the amount of time discarded after each detector reset has been found to be sufficient to cover mechanism settling times as well.

 

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.

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. Note that this is not the same as the `saturation' limits. These limits are specified in the LCDB file

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: Saturation voltage thresholds for slope fitting

Type of File:

FITS Header

Contents:

This file contains the maximum allowable voltage before a point is regarded as being saturated. See section 6.3.4 for a description of how saturated points are handled.

This file also contains values for the `de-biasing' parameters and the thresholds for switching between first and second order slope fitting. These values have not been used since the introduction of the method of slope fitting in pipeline 7.

 

Table 8.22: LCDB calibration file keywords

name type unit description 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

Use:

In Derive SPD for identifying saturated points

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. This was introduced because of early fears that this file might grow uncontrollably. In fact this has not proved to be the case and this value is set to a high enough value to cope with all observations.

 

Table 8.24: LCGH calibration file keywords

name type unit description LCGHGHMR I - Maximum number of records

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:

This file relates to a deglitching stage used during early versions of the pipeline. This file is still currently read by SPL, but its contents are not used.

Use:

Not used

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.

These values have not been used since the introduction of the method of slope fitting in pipeline 7.

Use:

Not used

8.2.6.11 LCD3: Third level deglitching parameters

Type of File:

FITS Header

Contents:

This file relates to a deglitching stage used during early versions of the pipeline. This file is still currently read by SPL, but its contents are not used.

Use:

Not used

   
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 are in W/cmm for grating scans. For FP scans the units are in W/cm² as the spectral bandwidth correction is not performed for FP 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 8.25. 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 8.26 gives the keywords that contain this information.

 

Table 8.25: LWS AA product file record structure. Note that for FP spectra the units for the Flux and the uncertainty in the flux are W/cm².

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/cmm Flux on detector LSANFLXU 36 1 R*4 none Fractional systematic flux error           due to calibration. LSANSTAT 40 1 I*4 - Status word LSANITK 44 1 I*4 - ITK time

 

Table 8.26: 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 um 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' LOSKPDRK L Indicates if dark current subtraction was omitted     Should always be `F' LOSKPFPR L Indicates if FP spectral responsivity stage was omitted     Should always be `F' 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 8.13) LEI* * Copy of EOHI information from LSPD header (see table 8.13)

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
• The dark current/straylight value subtracted from the scan in AAL.
• 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 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

   
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 8.27.

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 6.4.3 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.

   
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 8.28

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 8.29

 

Table 8.29: 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 parameters

Type of File:

FITS binary table.

Contents:

This file contains the parameters required for converting the grating LVDT readout values into wavelength. Since the wavelength calibration changes over time this file contains different sets of coefficients for different time periods. Each record of the LCGW file contains one set of coefficients, which are valid for a particular time period. Rather than use a time key directly, the LCGW file uses the revolution number to identify which record is valid for which time period. Each record contains the start and end revolution numbers for which it is valid.

The record structure of the LCGW file is shown in table 8.30.

The header of the LCGW file also contains keywords which contain fixed values for use in the conversion. These keywords are shown in table 8.31.

   

Table 8.30: LCGW calibration file record structure.

name Offset number type unit description LCGWSREV 0 1 I*4 - Revolution number of start           of validity for this record LCGWEREV 4 1 I*4 - Revolution number of end of           validity for this record LCGWCOEF 8 5 R*4 - Conversion coefficients LCGWADET 28 10 R*4 deg Angle for each detector

 

Table 8.31: LCGW keywords.

name type unit description LCGWLINE R - Number of lines per m on grating LCGWOdet I - Order number for each detector       (det=`SW1'...`LW5')

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 cm². The file is written as a FITS primary array with three axis (NAXIS=3). The axis are defined as given in table 8.32.

 

Table 8.32: 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 cm2 Relative Responsivity     R*4 cm2 Uncertainty in responsivity NAXIS2 10 R*4 - Detector number NAXIS3 4096 R*4 - Grating LVDT value

The header of the file contains keywords which specify the range of grating positions which are used within the file and the `nominal' wavelength range for each detector. The `nominal' range is where the calibration is of acceptable quality. Everything outside the nominal range has poor calibration and is flagged with a warning flag in the LSAN status word. These keywords are shown in table 8.33.

 

Table 8.33: LCGR keywords.

name type unit description LSTARPOS I - First valid grating position in file LENDPOS I - Last valid grating position in file LSTRNOMn R m Start of nominal wavelength range       for detector n (n=0...9) LENDNOMn R m End of nominal wavelength range       for detector n (n=0...9)

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 8.34 gives the keywords for this file.

 

Table 8.34: 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 8.35.

 

Table 8.35: 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 LCLRZn: 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). Since the file depends on the grating calibration there are at present two versions of this file, one for data taken before revolution 346 (LVLRZ1) and one for data taken after that (LCLRZ2). The record structure can be found in table 8.36.

 

Table 8.36: 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 8.37.

 

Table 8.37: 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 LCSRZn: 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). Since the file depends on the grating calibration there are at present two versions of this file, one for data taken before revolution 346 (LVSRZ1) and one for data taken after that (LCSRZ2). The record structure can be found in table 8.38.

 

Table 8.38: 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 8.39.

 

Table 8.39: LCGB calibration file record structure

name offset number type unit description LCGBDET 0 1 C*3 - Detector LCGBSPAR 3 1 I*1 - Filler LCGBSB 4 1 R*4 m Bandwidth LCGBSBU 8 1 R*4 m Uncertainty in bandwidth

Use:

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