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Chapter 6
FITS File Headers

6.1 Science Data File Headers

The main header, or HDU1, typically contains most of the information about the file, while the headers for the extensions usually give additional information about the data in each extension. The main headers are parsed into sections, and all science data files (RAW, CAL, IDF, ALL, ANO, and NVO) contain the same sections. However, for the RAW images, not all of the fields are populated. Several of the ancillary files contain similar information. The following sections describe these standard header sections.

This chapter contains general information useful to the "Advanced" and "Intermediate" user. Its contents are not, however, of immediate relevance to the "Casual" user.

DATA DESCRIPTION KEYWORDS: This set of keywords is fairly self-explanatory. For exposure level files, OBS_STAT is replaced with EXP_STAT.

              DATA DESCRIPTION KEYWORDS                                         
TELESCOP= 'FUSE              ' / Telescope used to acquire data                 
INSTRUME= 'FUV               ' / Instrument in use (one of FUV, FESA, or FESB)  
ROOTNAME= 'A1330147002       ' / Rootname of the observation set (ppppttooeee)  
FILENAME= '' / Name of file                        
FILETYPE= 'CALIBRATED EXTRACTED SPECTRUM' / Type of data found in data file     
EXP_STAT=                    0 / Science data processing status (0=good)

PROPOSAL INFORMATION: This section is populated from the Mission Planning Database (MPDB).

              PROPOSAL INFORMATION                                              
PRGRM_ID= 'A133              ' / Program ID from data header                    
TARG_ID = '01                ' / Target ID from data header                     
SCOBS_ID= '47                ' / Observation ID from data header                
EXP_ID  = '002               ' / Exposure ID from data header                   
OBS_ID  = '47                ' / Observation ID from proposal database          
PR_INV_L= 'Fullerton         ' / Last name of principal investigator            
PR_INV_F= 'Alex              ' / First name of principal investigator

TARGET INFORMATION: These keywords are also populated from the MPDB and are not measured quantities. The expected fluxes and count rates come from the Phase 2 Proposal form submitted by the observer. A key to the numerical Object Classes are given in Section 8.4.5.

              TARGET INFORMATION                                                
TARGNAME= 'SK-67D166         ' / Target name on proposal                        
RA_TARG =            82.934625 / [deg] Right ascension of the target (J2000)    
DEC_TARG=             -67.6335 / [deg] Declination of the target (J2000)        
APER_PA =            23.518158 / [deg] Position angle of Y axis (E of N)        
EQUINOX =               2000.0 / Equinox of celestial coordinate system         
ELAT    =  -8.705045834317E+01 / [deg] Ecliptic latitude                        
ELONG   =   3.354528613035E+02 / [deg] Ecliptic longitude                       
GLAT    =  -3.248583704098E+01 / [deg] Galactic latitude                        
GLONG   =   2.778388799536E+02 / [deg] Galactic longitude                       
OBJCLASS=                   13 / Object class (modified IUE classification)     
SP_TYPE = 'O4If+             ' / MK spectral type and luminosity class (or other
SRC_TYPE= 'PC                ' / [P]oint or [E]xtended, [C]ontinuum, [E]mission 
VMAG    =                12.27 / Target V magnitude                             
EBV     =                  0.1 / Color excess E(B-V)                            
Z       =                  0.0 / Redshift                                       
EFLX_950=              1.9E-12 / Expected flux at 950 A                         
EFLX1050=              2.7E-12 / Expected flux at 1050 A                        
EFLX1150=              2.6E-12 / Expected flux at 1150 A                        
HIGH_PM = 'F                 ' / High proper motion target (T or F)             
MOV_TARG= 'F                 ' / [F]ixed or [M]oving target                     
PCNTRATE=               1592.9 / Expected count rate (sum of all channels)

SUMMARY EXPOSURE INFORMATION: This section contains the date and time of the observation, including the exposure start and end time, and the computed exposure time. Exposure start and end times are expressed in Modified Julian Date (MJD = JD-2400000.5). The EXPENDC keyword indicates the reason for the termination of the exposure - entry into South Atlantic Anomaly (SAA), occultation (OCC), end of night (NGHT), or the natural end of exposure (ENDE) or end of observation (ENDO). The Sun and Moon angles, and the minimum pointing angle above the Earth limb are computed by the calibration software, and are therefore 0 in the raw data files. For TTAG data, the calibration software also screens photon address data, and ignores bad data taken in, for instance, the SAA. There are a number of keywords reporting the actions taken by this screening step, and are shown below. The meanings of these codes are summarized in Table 4.104.11, and 4.12 of Section If data are screened out, then EXPTIME will be smaller than RAWTIME in the IDF and the calibrated files.

              SUMMARY EXPOSURE INFORMATION                                      
DATEOBS = '2000-10-12'         / UT date of start of exposure (yyyy-mm-dd)      
TIMEOBS = '14:38:30'           / UT start time of exposure (hh:mm:ss)           
EXPSTART=   5.182961006944E+04 / Exposure start time (Modified Julian Date)     
EXPEND  =   5.182962262750E+04 / Exposure end time (Modified Julian Date)       
EXPTIME =                1085. / [s] Total time after screening                 
EXPENDC = 'ENDO              ' / End condition (ENDO; SAA; OCC; NGHT; ENDE)     
NEVENTS =               421399 / Number of events in raw data file              
RAWTIME =   1.085015625000E+03 / [s] Exposure duration of raw data file         
PLANTIME=                 1020 / [s] Planned exposure time                      
SUNANGLE=     92.1169468703347 / [deg] Angle between sun and Z axis             
MOONANGL=     83.0809764100487 / [deg] Angle between moon and Z axis            
POLEANGL=     160.545069830942 / [deg] Angle between orbit pole and Z axis      
GEO_LONG=     164.355774107397 / [deg] Geocentric longitude                     
GEO_LAT =     24.3003425210518 / [deg] Geocentric latitude                      
MAG_LAT =     30.5899872994262 / [deg] Geomagnetic latitude                     
MIN_LIMB=     11.9518247749345 / [deg] Minimum angle above Earth limb           
NBADEVNT=                10910 / Number of events deleted in screening          
NBADPHA =                  919 / Number of events deleted in PHA screening      
EXP_BAD =                    0 / [s] Time lost to screening                     
EXP_BRST=                    0 / [s] Time lost to event bursts                  
EXP_HV  =                    0 / [s] Time lost to low voltage/FIFO overflow     
EXP_JITR=                    0 / [s] Time lost to jitter                        
EXP_LIM =                    0 / [s] Time with low limb angle                   
EXP_SAA =                    0 / [s] Time while in SAA                          
EXPNIGHT=                 1085 / [s] Night time after screening                 
V_GEOCEN=     2.38573645263126 / [km/s] Observed to geocentric velocity         
V_HELIO =    -1.08708418297615 / [km/s] Geocentric to heliocentric velocity     
V_LSRDYN=    -12.7521820068359 / [km/s] Heliocentric to dynamical LSR           
V_LSRSTD=     -15.775110244751 / [km/s] Heliocentric to standard solar LSR      
              Geocentric and helocentric conversions are applied by the         
              CALFUSE calibration pipeline.  LSR conversion is not.

SCIENCE INSTRUMENT CONFIGURATION: These keywords contain planned as well as telemetered values for the instrument configuration. Most of the keywords shown below are self-explanatory. For the detector mask, DET_MASK, AIC1 is an open mask, i.e., none of the photon events are masked out. The focal plane assembly (FPA) X and Z positions from the telemetry are recorded in the header keywords. Note that the FES_FILT keyword is always set to CLR. The mirror focus MIR*FOC keywords are populated only for bright object defocus test exposures.

              SCIENCE INSTRUMENT CONFIGURATION                                  
INSTMODE= 'TTAG              ' / Instrument mode (TTAG or HIST)                 
DETECTOR= '1B                ' / Detector for data in this file (1A, 1B, 2A, 2B)
APERTURE= 'LWRS              ' / Planned target aperture: HIRS, MDRS, LWRS, RFPT
BRIT_OBJ= 'NO                ' / Special configuration for bright-object obs    
APER_ACT= 'LWRS_SIC'           / Extracted aperture in this file                
DET_MASK= 'AIC1              ' / Detector mask used                             
NUM_APS =                    1 / Number of apertures in use in the observation  
INITBINX=                    1 / Initial binning in X coordinate                
INITBINY=                    1 / Initial binning in Y coordinate                
SPECBINX=                    1 / Current binning in X coordinate                
SPECBINY=                    1 / Current binning in Y coordinate                
SIA_TBL = '                  ' / SIA Table name                                 
NUM_HIST=                    0 / Number of histograms in the observation        
INT_CAL = '                  ' / Internal Calibration (STIM, NONE)              
FPSPLIT =                    0 / Number of FP Split positions                   
FPASXPOS=              140.145 / [microns] FPA SiC X position                   
FPALXPOS=              116.107 / [microns] FPA LiF X position                   
FPASZPOS=             -98.9776 / [microns] FPA SiC Z position                   
FPALZPOS=             -34.4119 / [microns] FPA LiF Z position                   
MIRL1FOC=             0.000000 / [microns] LiF 1 mirror position                
MIRL2FOC=             0.000000 / [microns] LiF 2 mirror position                
MIRS1FOC=             0.000000 / [microns] SiC 1 mirror position                
MIRS2FOC=             0.000000 / [microns] SiC 2 mirror position                
TTPERIOD=                  1.0 / [s] Time marker insertion period               
ENGSNAPT=                  300 / [s] Engineering snapshot period                
TACQSEQ = 'ACQ-T-NOPKUP      ' / Target acquisition sequence                    
ROLLOFF =                  0.0 / [Deg] Roll offset                              
FES_BIN =                    1 / FES binning factor (1;2;4;8)                   
FES_FILT= 'CLR               ' / FES filter wheel position: CLR=Clear, COL=Color
FES_TPOS= 'OUT               ' / FES target position: IN or OUT

DETECTOR HV BIAS RANGES: These keywords list the minimum and maximum high voltage level for all segments during the exposure. The minimum and maximum for a given segment should normally be the same. The nominal high voltage levels were adjusted periodically during the mission; see Table 7.4.

              DETECTOR HV BIAS RANGES                                           
DET1HVAL=                  128 / Det1 MCP A HV bias minimum setting             
DET1HVAH=                  128 / Det1 MCP A HV bias maximum setting             
DET1HVBL=                  128 / Det1 MCP B HV bias minimum setting             
DET1HVBH=                  128 / Det1 MCP B HV bias maximum setting             
DET2HVAL=                  128 / Det2 MCP A HV bias minimum setting             
DET2HVAH=                  128 / Det2 MCP A HV bias maximum setting             
DET2HVBL=                  101 / Det2 MCP B HV bias minimum setting             
DET2HVBH=                  101 / Det2 MCP B HV bias maximum setting             
HV_FLAG =                    4 / Detector voltage full throughout exposure

ORBITAL EPHEMERIS: These keywords contain the Keplerian elements for the FUSE orbital ephemeris. Together with the time of observation, these values can be used to calculate where the satellite was in its orbit (although much of this information is already in the timeline table in the IDF files). The calibration software, for instance, uses these values to compute the Doppler correction to apply as it produces the calibrated data.

              ORBITAL EPHEMERIS                                                 
EPCHTIMD=               51829. / Epoch time of parameters whole day (MJD)       
EPCHTIMF=    0.943173899999238 / Epoch time of parameters fraction of day (MJD) 
INCLINAT=              24.9842 / [deg] Inclination                              
ECCENTRY=            0.0011377 / Eccentricity                                   
MEANANOM=             238.2636 / [deg] Mean anomaly                             
ARGPERIG=             121.8967 / [deg] Argument of perigee                      
RASCASCN=              301.572 / [deg] RA of ascending node                     
SEMIMAJR=     7137.84084370588 / [km] Semi-major axis                           
MEANMOTN=          14.39635355 / [revs/day] Mean motion                         
FDM2COEF=             9.37E-06 / First time derivative of mean motion / 2       
SDM6COEF=                   0. / Second time derivative of mean motion / 6      
DRAGCOEF=           0.00023849 / B star drag coefficient                        
PROPMODL= 'SGP4    '           / Propagation model

SCIENCE DATA PROCESSING STEPS: These keywords indicate which steps of the calibration pipeline have been applied to the data. All processing steps are set to a value of INITIAL in the raw data files. The first pipeline module sets them to either PERFORM or OMIT, depending on whether the corresponding calibration step is to be performed or not. Once a step is completed, its keyword is changed to a value of COMPLETE. If a pipeline module decides not to perform a step labeled PERFORM, it changes the keyword to SKIPPED. Thus, COMPLETE, OMIT, and SKIPPED are all valid keywords in extracted spectral files (see Dixon et al. (2007)).

              SCIENCE DATA PROCESSING STEPS                                     
INIT_COR= 'COMPLETE'           / Initialize processing                          
DIGI_COR= 'COMPLETE'           / Check digitizer values                         
ELEC_COR= 'COMPLETE'           / Detector dead-time correction                  
IDS__COR= 'COMPLETE'           / IDS dead-time correction                       
FIFO_COR= 'COMPLETE'           / FIFO overflow correction                       
DEAD_COR= 'COMPLETE'           / Apply all dead-time corrections                
THRM_COR= 'COMPLETE'           / Thermal distortion correction                  
RATE_COR= 'COMPLETE'           / Count-rate Y distortion                        
TMXY_COR= 'COMPLETE'           / Temporal X and Y corrections                   
GEOM_COR= 'COMPLETE'           / Geometric distortion                           
PHAH_COR= 'OMIT    '           / Assign pulse heights to HIST data              
PHAX_COR= 'COMPLETE'           / Low pulse-height X distortion (walk)           
ACTV_COR= 'COMPLETE'           / Define detector active region                  
LIMB_COR= 'COMPLETE'           / Limb-angle screening                           
SAA__COR= 'COMPLETE'           / SAA screening                                  
VOLT_COR= 'COMPLETE'           / Confirm detector voltage                       
BRST_COR= 'COMPLETE'           / Screen for bursts                              
APER_COR= 'COMPLETE'           / Screen for target out of aperture              
UGTI_COR= 'COMPLETE'           / Set user good-time intervals                   
FLAG_COR= 'COMPLETE'           / Set individual photon flags                    
GTI__COR= 'COMPLETE'           / Determine good-time intervals                  
TIME_COR= 'OMIT    '           / Modify photon arrival times (HIST only)        
AIRG_COR= 'COMPLETE'           / Flag events in airglow regions                 
BPIX_COR= 'COMPLETE'           / Flag events in bad-pixel regions               
PHA__COR= 'COMPLETE'           / Pulse-height screening                         
FIND_COR= 'COMPLETE'           / Find spectra on detector                       
YMOT_COR= 'COMPLETE'           / Track motion of Y centroid                     
GRAT_COR= 'COMPLETE'           / Grating motion correction                      
FPA__COR= 'COMPLETE'           / FPA offset correction                          
MIRR_COR= 'COMPLETE'           / Mirror motion correction                       
JITR_COR= 'COMPLETE'           / Satellite jitter correction                    
YCNT_COR= 'COMPLETE'           / Y centroid of corrected data                   
CHID_COR= 'COMPLETE'           / Final channel assignment                       
TCRT_COR= 'COMPLETE'           / Calculate target count rate                    
ASTG_COR= 'COMPLETE'           / Astigmatism correction                         
WAVE_COR= 'COMPLETE'           / Assign wavelength to photons                   
DOPP_COR= 'COMPLETE'           / Heliocentric reference frame                   
FLAT_COR= 'OMIT    '           / Flat-field correction                          
FLUX_COR= 'COMPLETE'           / Flux-calibrate each photon                     
COMB_COR= 'PERFORM '           / Generate observation-level spectrum

SCIENCE DATA PROCESSING CALIBRATION FILES: These keywords indicate the names of the SDP calibration files and the ancillary files used by the calibration software. Knowing these filenames is important if one is considering reprocessing the data. Since no flat field or worm corrections were applied to the data these fields always remain empty.

              SCIENCE DATA PROCESSING CALIBRATION FILES                         
AEFF1CAL= '     ' / Effective-area curve #1                        
AEFF2CAL= '     ' / Effective-area curve #2                        
AIRG_CAL= '     ' / Geocoronal line locations                      
ASTG_CAL= '     ' / Astigmatism correction                         
BCHR_CAL= '     ' / Background characteristics                     
BKGD_CAL= '     ' / Background/scattered-light model               
BPM_CAL = '' / Bad-pixel map for this exposure         
CHID_CAL= '     ' / Windows for spectral extraction                
DIGI_CAL= '       ' / Reference file for digitizer values            
ELEC_CAL= '       ' / Detector parameters                            
FLAT1CAL= '        '           / Flat-field correction #1                       
FLAT2CAL= '        '           / Flat-field correction #2                       
GEOM_CAL= '     ' / X and Y geometric corrections                  
GRAT_CAL= '       ' / Grating motions                                
HSKP_CAL= '' / Housekeeping data                            
JITR_CAL= '' / Spacecraft jitter data                       
MIRR_CAL= '       ' / Mirror motions                                 
PARM_CAL= '     ' / Master parameter file                          
PHAH_CAL= '     ' / Pulse height map for HIST data                 
PHAX_CAL= '     ' / Low-pulse-height X distortion                  
QUAL_CAL= '     ' / Quality flag (bad pixel) map                   
RATE_CAL= '     ' / Y stretch with count rate                      
SAAC_CAL= '       ' / SAA contours for data screening                
SCRN_CAL= '     ' / Parameters for data screening                  
SPEC_CAL= '       ' / Spectrograph parameters                        
STIM_CAL= '     ' / Default thermal drift parameters               
TMXY_CAL= '     ' / Temporal X and Y corrections                   
VOLT_CAL= '     ' / Detector bias voltages and dates               
WAVE_CAL= '     ' / Wavelength calibration                         
WGTS_CAL= '     ' / Pixel weights for extraction                   
WORM1CAL= '        '           / Worm correction #1                             
WORM2CAL= '        '           / Worm correction #2

SCIENCE DATA PROCESSING KEYWORDS: This section collects other data which are relevant to the calibration. These keywords are populated by OPUS and/or by CalFUSE. Some of these keywords (e.g., limb angle; pulse height) reflect screening limits used when CalFUSE was executed (see The CalFUSE Page).

              SCIENCE DATA PROCESSING KEYWORDS                                  
OPUSVERS= '2.7               ' / FUSE OPUS version number                       
CF_VERS = '3.2.1   '           / CALFUSE pipeline version number                
HKEXISTS= 'yes     '           / Housekeeping data file exists                  
DAYNIGHT= 'BOTH    '           / Use only DAY, NIGHT, or BOTH                   
BRITLIMB=                  15. / [deg] Bright limb avoidance angle              
DARKLIMB=                  10. / [deg] Dark limb avoidance angle                
ORBPERID=                5998. / [s] Estimate of orbital period                 
PHALOW  =                    2 / Pulse height screening low limit               
PHAHIGH =                   24 / Pulse height screening high limit              
OPT_EXTR=                   10 / Number of optimal extraction iterations        
STIM_L_X=             256.5767 / X centroid of left stim pulse                  
STIM_L_Y=             749.4218 / Y centroid of left stim pulse                  
STIM_R_X=             16144.58 / X centroid of right stim pulse                 
STIM_R_Y=             772.1562 / Y centroid of right stim pulse                 
FPADXLIF=           -0.1579872 / [pixels] Correction for FPA position (LIF)     
FPADXSIC=            -5.317671 / [pixels] Correction for FPA position (SIC)     
WPC     =                0.013 / [A] Wavelength increment per pixel             
W0      =                 900. / [A] Wavelength of first pixel                  
DET_DEAD=             1.005887 / Mean detector deadtime correction factor       
IDS_DEAD=                   1. / Mean IDS deadtime correction factor            
TOT_DEAD=             1.005887 / TOTAL deadtime correction factor

MEASURED SPECTRAL CENTROIDS: This section gives the position of the centroids of the spectra determined by CalFUSE. The quality keyword is set to HIGH if the centroid is measured from the target spectrum, MEDIUM if it is measured from airglow features, and LOW if it is taken from a reference file (see Dixon et al. (2007) for more details).

              MEASURED SPECTRAL CENTROIDS                                       
YCENT1  =             688.1578 / [pixels] Y centroid of LIF HIRS spectrum       
YCENT2  =             809.5578 / [pixels] Y centroid of LIF MDRS spectrum       
YCENT3  =             558.6619 / [pixels] Y centroid of LIF LWRS spectrum       
YCENT5  =             193.9905 / [pixels] Y centroid of SIC HIRS spectrum       
YCENT6  =             321.1906 / [pixels] Y centroid of SIC MDRS spectrum       
YCENT7  =              60.5411 / [pixels] Y centroid of SIC LWRS spectrum       
YQUAL1  = 'MEDIUM  '           / Quality of Y centroid value (LIF HIRS)         
YQUAL2  = 'MEDIUM  '           / Quality of Y centroid value (LIF MDRS)         
YQUAL3  = 'HIGH    '           / Quality of Y centroid value (LIF LWRS)         
YQUAL5  = 'MEDIUM  '           / Quality of Y centroid value (SIC HIRS)         
YQUAL6  = 'MEDIUM  '           / Quality of Y centroid value (SIC MDRS)         
YQUAL7  = 'HIGH    '           / Quality of Y centroid value (SIC LWRS)

BACKGROUND SAMPLE REGIONS: This section provides the details of the regions on the detectors used to determine the backgrounds used by CalFUSE (see Chapter 7).

              BACKGROUND SAMPLE REGIONS                                         
BKGD_NUM=                    3 / Number of background regions specified         
BKG_MIN0=                  160 / [pixels] bkgd sample region 0 - lower limit    
BKG_MIN1=                  665 / [pixels] bkgd sample region 1 - lower limit    
BKG_MIN2=                  891 / [pixels] bkgd sample region 2 - lower limit    
BKG_MIN3=                    0 / [pixels] bkgd sample region 3 - lower limit    
BKG_MIN4=                    0 / [pixels] bkgd sample region 4 - lower limit    
BKG_MIN5=                    0 / [pixels] bkgd sample region 5 - lower limit    
BKG_MIN6=                    0 / [pixels] bkgd sample region 6 - lower limit    
BKG_MIN7=                    0 / [pixels] bkgd sample region 7 - lower limit    
BKG_MAX0=                  450 / [pixels] bkgd sample region 0 - upper limit    
BKG_MAX1=                  890 / [pixels] bkgd sample region 1 - upper limit    
BKG_MAX2=                  930 / [pixels] bkgd sample region 2 - upper limit    
BKG_MAX3=                    0 / [pixels] bkgd sample region 3 - upper limit    
BKG_MAX4=                    0 / [pixels] bkgd sample region 4 - upper limit    
BKG_MAX5=                    0 / [pixels] bkgd sample region 5 - upper limit    
BKG_MAX6=                    0 / [pixels] bkgd sample region 6 - upper limit    
BKG_MAX7=                    0 / [pixels] bkgd sample region 7 - upper limit

ENGINEERING KEYWORDS: A fair amount of the detector engineering snapshot data (engineering telemetry) is included in the FITS headers. The values included are shown below. Except for the Active Image Counters, only those values from the relevant detector segment are inserted into the header. The example keywords below are for segment 1B. For a description of the counters and masks, see the Instrument Handbook (2009). The counter information is used by CalFUSE (see Dixon et al. (2007)).

              ENGINEERING KEYWORDS                                              
THERMCON= 'ON                ' / Thermal control flag                           
FESSRC  = 'FES A             ' / Source of FES dump data                        
FESCENT = 'FES A             ' / Source of FES centroid data                    
GMODE   = 'IDENTIFIED_TRACKING ' / Guidance mode                                
TRACKON = 'OFF               ' / Moving target tracking on                         
ATCMDATT= 'AT COMMANDED ATTITUD    ' / At commanded attitude                    
              Segment 1B Counters                                               
C1BSIC_B=             14101192 / SIC counter at beginning of integration        
C1BSIC_E=             14175036 / SIC counter at end of integration              
C1BLIF_B=             11704586 / LIF counter at beginning of integration        
C1BLIF_E=             12032091 / LIF counter at end of integration              
C1BDE_B =             13969564 / Digitized events counter at beginning of integr
C1BDE_E =             14391379 / Digitized events counter at end of integration 
C1BAS_B =             15180958 / Autonomous shutdown (SAA) counter at beginning 
C1BAS_E =             15182787 / Autonomous shutdown (SAA) counter at end of int
C1BFE_B =              3527277 / Fast event counter at beginning of integration 
C1BFE_E =              3954788 / Fast event counter at end of integration       
C1BFE_CR=           394.019348 / Count rate from fast event counter             
              Active Image Counters                                             
CTIME_B =   5.182961006944E+04 / [MJD] Time of first engineering snapshot       
CTIME_E =   5.182962262731E+04 / [MJD] Time of last engineering snapshot        
C1AAI_B =             10760595 / Seg 1A at beginning                            
C1AAI_E =             11259319 / Seg 1A at end of integration                   
C1BAI_B =             13894835 / Seg 1B at beginning                            
C1BAI_E =             14316651 / Seg 1B at end of integration                   
C2AAI_B =              1067178 / Seg 2A at beginning                            
C2AAI_E =              1679155 / Seg 2A at end of integration                   
C2BAI_B =              2067772 / Seg 2B at beginning                            
C2BAI_E =              2341339 / Seg 2B at end of integration                   
              Detector 1 parameters                                             
DET1ETMP=              25.9103 / DET1 electronics temperature                   
DET1PTMP=              18.1937 / DET1 Baseplate temperature                     
DET1ASCL=                 17.0 / DET1 segment A  Time (X) image scale factor    
DET1BSCL=                 91.0 / DET1 segment B  Time (X) image scale factor    
DET1AXOF=                183.0 / DET1 segment A  Time (X) image position offset 
DET1BXOF=                107.0 / DET1 segment B  Time (X) image position offset 
DET1TEMP=              18.4255 / DET1 Detector temperature                      
DET1HVMT=              24.5318 / DET1 High Voltage Module temperature           
DET1HVFT=              20.9761 / DET1 High Voltage Filter temperature           
DET1AMAT=              26.3947 / DET1 segment A Amplifier temperature           
DET1AMBT=              26.3947 / DET1 segment B Amplifier temperature           
DET1TDAT=            21.386000 / DET1 TDC A  temperature                        
DET1TDBT=               21.792 / DET1 TDC B  temperature                        
DET1HVA =                 57.0 / DET1 MCP A Bias Current                        
DET1HVB =                 48.0 / DET1 MCP B Bias Current                        
DET1AUCT=                227.0 / DET1 TDC-A Upper Charge Threshold setting      
DET1BUCT=                228.0 / DET1 TDC-B Upper Charge Threshold setting      
DET1ABWK=                165.0 / DET1 TDC-A Begin CFD Walk setting              
DET1BBWK=                139.0 / DET1 TDC-B Begin CFD Walk setting              
DET1AEWK=                165.0 / DET1 TDC-A End CFD Walk setting                
DET1BEWK=                125.0 / DET1 TDC-B End CFD Walk setting                
DET1ABSL=                227.0 / DET1 TDC-A charge Baseline threshold setting   
DET1BBSL=                228.0 / DET1 TDC-B charge Baseline threshold setting   
DET1ALCT=                  7.0 / DET1 TDC-A Lower Charge Threshold setting      
DET1BLCT=                  6.0 / DET1 TDC-B Lower Charge Threshold setting      
DET1ALTT=                169.0 / DET1 TDC-A Lower Time Threshold setting        
DET1BLTT=                143.0 / DET1 TDC-B Lower Time Threshold setting        
DET1HVGR=                  1.0 / DET1 Grid High Voltage Status                  
DET1HVPW=                  1.0 / DET1 Bias High Voltage Status                  
DET1STIM= 'OFF               ' / DET1 Stimulation Lamp Status

ARCHIVE SEARCH KEYWORDS: Finally, keywords used by the archive, and those necessary to associate the exposures that make up an observation are included.

              ARCHIVE SEARCH KEYWORDS                                           
BANDWID =             99.99597 / [Angstroms] Bandwidth of the data              
CENTRWV =              949.998 / [Angstroms] Central wavelength of the data     
WAVEMIN =                 900. / [Angstroms] Minimum wavelength of the data     
WAVEMAX =              999.996 / [Angstroms] Maximum wavelength of the data     
PLATESC =                1.163 / [arcsec/pixel] Plate scale                     
              ASSOCIATION KEYWORDS                                              
ASN_ID  = 'A1330147000       ' / Unique identifier assigned to association      
ASN_TAB = '  ' / Name of the association table                
ASN_MTYP= 'EXPOSURE          ' / Role of the exposure in the association

6.2 Engineering Data File Headers

Subsets of the DATA DESCRIPTION keywords, PROPOSAL INFORMATION keywords, and TARGET INFORMATION keywords are also included in the housekeeping and jitter file headers. In addition, their headers contain unique keywords which are described in this section.

Housekeeping Keywords: The HDU1 header for the housekeeping files contains some of the keywords defined above plus a set of engineering housekeeping time keywords (shown below). These specify the start time of the engineering telemetry contained in the file, and are measured quantities. The TIME_ENG keyword value is normally about one-half to one minute before the actual start time of the science exposure.

              ENGINEERING HOUSEKEEPING TIME                                     
HSKPVERS= '3.2               ' / Housekeeping version number                    
DATE_ENG= '2000-09-27        ' / start date (yyyy-mm-dd)                        
TIME_ENG= '11:03:16          ' / start time (hh:mm:ss)

The HDU2 headers of the housekeeping files simply contain definitions of the housekeeping variables listed in Appendix D, so they are not repeated here.

Jitter Keywords: The HDU1 headers for the jitter files contain the engineering housekeeping time keywords described above, as well as a unique set of jitter keywords. The jitter data are computed from the housekeeping data. Most of the jitter keywords reflect the results of that analysis, and are intended as indicators of the overall quality of the pointing during the science exposure.

              JITTER KEYWORDS                                                   
JIT_STAT=                    0 / Status of jitter data is good                  
JIT_VERS= '3.5     '           / cf_jitter version number                       
QREF_SRC= 'TELEMETRY'          / Source of reference quaternion                 
QREF_0  =  -0.0168658437405577 / Reference quaternion                           
QREF_1  =    0.318041029256893                                                  
QREF_2  =    0.908345046651746                                                  
QREF_3  =    0.271062212872567                                                  
EXP_DUR =                 668. / [s] duration of jitter data                    
KNOWNTRK=                   1. / fraction of exp in known track                 
ACSTRK  =                   0. / fraction of exp in ACS track                   
NOGDEINF=                   0. / fraction of exp with no guiding info           
NGS_USED=                    6 / number of guide stars used                     
GS1_USED=                   1. / fraction of exp using known guide star 1       
GS2_USED=                   1. / fraction of exp using known guide star 2       
GS3_USED=                   1. / fraction of exp using known guide star 3       
GS4_USED=                   1. / fraction of exp using known guide star 4       
GS5_USED=                   1. / fraction of exp using known guide star 5       
GS6_USED=                   1. / fraction of exp using known guide star 6       
KTRKFINE=                   1. / exp fraction, err < 15 arcsec, known stars     
ATRKFINE=                   0. / exp fraction, err < 15 arcsec, ACS             
TOTLFINE=                   1. / exp fraction, err < 15 arcsec, total           
GS_INUSE=                   1. / fraction of exp tracking on guide stars        
SLEWFLG =                   -1 / Slew commanded during obs (if > 0)             
SLEWTIME=                    0 / time spent slewing (sec)                       
POSAVG_X=           0.02662656 / [arcsec] mean DX during known track            
POSAVG_Y=          -0.01711245 / [arcsec] mean DY during known track            
X_JITTER=             0.326723 / [arcsec] sigma of DX during known track        
Y_JITTER=             0.136007 / [arcsec] sigma of DY during known track        
XJIT_15 =             0.326723 / [arcsec] sigma of DX for err < 15 arcsec       
YJIT_15 =             0.136007 / [arcsec] sigma of DY for err < 15 arcsec       
X_JITLRG=           0.03892216 / frac of DX more than 2-sigma from POSAVE_X     
Y_JITLRG=           0.05239521 / frac of DY more than 2-sigma from POSAVE_Y

is set to 0 for good jitter data, 1 if there were problems with the jitter data, 2 if the AT_CMD_ATT flag was not set, 3 if the commanded ACS quaternions were not available, 4 if there was no field information, and 5 if there were problems with the tabulated starting time of the exposure.

is the CalFUSE jitter routine version number used to generate the jitter file. Values less than 3.1 will produce an error in CalFUSE.

gives the source of the reference quaternion.

are the values of the reference quaternions (see Instrument Handbook (2009).

is the duration of telemetry in the jitter file. The telemetry in the housekeeping data is specified to start 0.5-1.0 minute before the start of the associated science exposure, and to end 1 minute after the end of the associated science exposure. Thus, the jitter EXP_DUR should be 90-120 s longer than the science exposure time EXPTIME.

is the fraction of EXP_DUR when the IDS was using known guide stars to compute a guiding solution. In known tracking, the pointing position is the aperture.

is the fraction of EXP_DUR when the IDS was using unknown stars to compute a guiding solution. In unknown tracking, stars are used to control the pointing of the spacecraft, but the identity of these stars is not known. The target may or may not be at the desired place in the aperture, depending on preceding events.

is the fraction of EXP_DUR for which there was no ACS guidance mode information available.

gives the number of guide stars used to track.

is the fraction of EXP_DUR when guide star n was contributing to the guiding solution computed by the IDS. Normally, 3 to 6 guide stars are used for an observation. Rarely as few as 1 or 2 are scheduled. Values of 0 are assigned to any star not scheduled to be used. Any star with a severe problem preventing use may have a value of 0 for this keyword. In general, these keywords indicate a problem if: (1) the keyword value differs significantly for the guide stars in use during a single exposure; (2) a lower-numbered guide star is 0 while a higher-numbered guide star is non-zero, or; (3) the number of guide stars in use changes among the jitter files in the same observation.

is the fraction of the exposure using known guide stars when the errors were < 15″

is the fraction of the exposure using the ACS when the errors were < 15″

is the fraction of the total exposure when the errors were < 15″

is the fraction of EXP_DUR when the IDS was using stars for guiding, whether Known or Unknown.

is the fraction of EXP_DUR when the spacecraft was executing a commanded slew. A non-zero value may indicate a guiding problem during the exposure, except in certain cases. A non-zero value is not a problem for science exposures for which scans were purposely executed, including M112's, M114's, and certain other calibration observations. There are two other cases where a non-zero value may not be a problem. Because the jitter "exposure" starts 30-60 s before the science exposure, a slew that completed prior to the science exposure may be included in the housekeeping data. Certain science exposures are more likely to be affected by this mis-match: the first exposure following the guide star acquisition; and the first exposure following a peakup.

is the time spent slewing (sec).

is the average of DX[Y] during the exposure, where DX[Y] are defined in Section 5.2.

is the standard deviation of DX[Y] in the telemetry file. This value gives some indication of the orbital variation.

, if present, is the standard deviation of DX[Y] during the observation time when the pointing was within 15″ of nominal. Hence, this value measures the stability while the target was within the LWRS aperture.

is fraction of EXP_DUR for which DX[Y] is more than 2σ from the average.

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