HST Keyword Dictionary

Space Telescope Science Institute

3700 San Martin Drive

Baltimore, MD 21212

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Keyword Definitions for the

dated 14-APR-94

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ACCPDATE
proposal acceptance date (yyyyddd) 
Datatype: CHARACTER*07        
Units:    DATE
Date that proposal became an approved program.

Source : PEP

AFFILIAT
proposal class (eg: GO, IDT, OS) 
Datatype: CHARACTER*03        
Units:    NONE
Obtained directly from the cover page of the proposal form: 
		GO  = general observer,                                                       
		AR  = archival researcher,                                                    
		IDT = investigation definition team,                                          
		IS  = interdisciplinary scientist,                                            
		SCI = ST Science staff,                                                       
		ESA = european space agency,                                                  
		MOC = mission operation contractor. 	(qpersonnel)

Source : PEP

CALIBRAT
calibrate data flag 
Datatype: CHARACTER*01        
Units:    Y/N
The default is Y which provides routine calibration for the archive.

Source : TRANS

CALIBTYP
calibration type : E, I or Blank 
Datatype: CHARACTER*01        
Units:    TYPE                
		I = internal,                                                                 
		E = external.                                                                 
               otherwise not a calibration observation

Source : TRANS

CDBSDATA
cdbs notification flag: 'CAL' or 'FALSE' 
Datatype: CHARACTER*05        
Units:    NONE
An operational flag used to control routine science data processing.

Source : PODPS

DATE-OBS
UT date of start of observation (dd/mm/yy) 
Datatype: CHARACTER*08        
Units:    DATE
See TIME-OBS. Note that this is not necessarily the start of the exposure. For example, the WFPC observation starts on a major frame pulse, while the exposure actually starts 16.4 seconds later following a memory erase. See EXPSTART.

Source : HST

DEC_TARG
declination of the target (J2000) 
Datatype: REAL*8              
Units:    DEGREES
Position in J2000 system. For fixed targets, proper motion data is evaluated in SCS, at the epoch of the target position for the predicted start time of the observation. For spatial scans, the target position is evaluated at the end of the scan for science observations but at the beginning of scans for target acquisition observations. The value does not change for any observation in the spatial scan. For moving target, the SPSS Chebyshev Interpolating Polynomials for are evaluated at the predicted timem that may be a few minutes different than the actual start observation time. (Fixed target - Heliocentric, moving target - Geocentric)

Source : SPSS and SCS

EQUINOX
proposal equinox of the target coordinate system 
Datatype: CHARACTER*08        
Units:    DATE
Target position equinox of the celestial coordinate system: 
         EYYYY.F where                                                          
                 E = J or B,                                                    
                 YYYY = year,                                                   
                 F is tenth of year.

Source : PEP

EXPACKET
expected number of source packets 
Datatype: INTEGER*4           
Units:    COUNTS
This is a minimum value used to estimate completeness of telemetry for science instrument data. It is used to determine whether data collected by PODPS data partitioning is complete. The estimate includes science data, unique definition log, and science header packets.

Source : SCS

EXPEND
exposure end time (Modified Julian Date) 
Datatype: REAL*8              
Units:    MJD                 
	 WFPC: EXPEND = EXPSTART + EXPTIME                                             
	 FOS:  EXPEND = FPKTTIME

Source : HST

EXPFLAG
Exposure interruption indicator 
Datatype: CHARACTER*13        
Units:                        
	 If any EXPTIME from UDL is fill, then                                         
           EXPFLAG = 'UNKNOWN'.                                                 
	 else if no EXPTIME from UDL is fill, then                                     
	    If software cannot retrieve a planned exposure time, then                  
		EXPFLAG = 'INDETERMINATE'                                                     
	    else if 'close shutter' is missing, then                                   
               EXPFLAG = 'UNCERTAIN'.                                           
	    else if 'close shutter' is present and there are more than                 
	             two open/close times, then                                        
               EXPFLAG = 'INTERRUPTED'.                                         
	    else if 'close shutter' is present and there are no more                   
	             than two open/close times, then                                   
               EXPFLAG = 'NORMAL'.

Source : PODPS

EXPSTART
exposure start time (Modified Julian Date) 
Datatype: REAL*8              
Units:    MJD                 
   	WFPC and WFPC2: Calculated as follows:                                      
    	   EXPSTART = UTC0 + (CLKRATE * T) + (CLKDRFTR * T**2)/2  + DELAY          
	     where:                                                                    
    	        T        = (WEXPTMHI*2**16 + WEXPOTIM) - SPCLINCN                  
               SPCLINCL = spacecraft ticks since UTC0                           
    		DELAY    = 16.4 seconds if non-NSCC-1 controlled exposure                 
		           (generally means, the NSCC-1 didn't have                           
                           to take over because of loss of PCS lock.)           
          	         = 16.5 seconds if NSCC-1 controlled exposure                
		           (rather than WFPC micro-processor controlled.)                     
	 FOS:                                                                          
	    EXPSTART = FPKTTIME - (EXPTIME + EXPDEADTM)                                
	      where:                                                                   
	        EXPDEADTM=  DEADTIME*7.8125E-6*INTS*                                   
                           NXSTEPS*OVERSCAN*YSTEPS*SLICES*                      
                           NPAT*NREAD*NMCLEARS                                  
       	   NOTE: EXPSTART only gives the start time of the                      
                        FIRST group of data in the final PODPS product.

Source : HST and PODPS

EXPTIME
exposure duration --calculated 
Datatype: REAL*4              
Units:    SEC
WFPC & WFPC2: If the WFPC exposure was a DARK FRAME, the exposure time code in WEXPORTH is used to obtain EXPTIME from the WFPC Exposure Time Table. Otherwise, the exposure time code in WEXPOCMD is used to obtain EXPTIME from that table. In addition, if the number of shutter closures (NSHUTA17) was greater than 1, the WFOCTIME values are used to calculate the amount of time that the shutter was closed: 
            EXPTIME = EXPTIME - shutter_closed_time
When EXPFLAG is set to PREDICTED, EXPTIME was set to the predicted exposure time.
FOS: EXPTIME reflects the total accumulator open time (livetime): 
        	EXPTIME= (LIVETIME*7.8125E-6)*INTS*NXSTEPS*OVERSCAN*                   
                         YSTEPS*SLICES*NPAT*NREAD*NMCLEARS
Misleading exposure time: This gives the total time the accumlation of photons took even though that time includes independent pixels (nxsteps) and separate spectra (ysteps) and is the sum of ALL groups.

Source : HST and PODPS

FGSLOCK
commanded FGS lock (FINE,COARSE,GYROS,UNKNOWN) 
Datatype: CHARACTER*07        
Units:    NONE
Keyword source is the field qbs_obset.scenario_acq which is translated into simpler terms.

Source : TRANS

LINENUM
PEP proposal line number 
Datatype: CHARACTER*15        
Units:    LINE NUMBER
The proposal line number (floating point) of the exposure specification before expansions by the Proposal Entry Processor. See PEPEXPO.

Source : PEP

MOONANGL
angle between Moon and V1 axis 
Datatype: REAL*4              
Units:    DEGREES
Computed from the spherical trig formula: 
       cos(moonangle) = sin(declmoon) * sin(declnv10 +                          
             cos(declmoon) * cos(declnv1) * cos(rtasmoon - rtascnv1)

Source : SCS

OBSERVTN
observation number 
Datatype: CHARACTER*02        
Units:    BASE 36 (0-9,A-Z)
The unique sequential number of the observation within an observation set. A two-digit base 36 number allows for 1295 observations.

Source : SCS

OBSET_ID
observation set id 
Datatype: CHARACTER*02        
Units:    BASE 36 (0-9,A-Z)
The observation set id, these are numbered sequentially throughout the proposal. A two-digit base 36 number allows for 1295 observation sets.

Source : TRANS and SPSS

OPFORMAT
output product format specification 
Datatype: CHARACTER*18        
Units:    NONE
Specification for routine science data processing.

Source : TRANS and PODPS

PEP_EXPO
PEP exposure identifier including sequence 
Datatype: CHARACTER*15        
Units:    NONE
The expanded proposal line number of the exposure specification. PEP appends #nnn to replicate exposures at proposal exposure LINENUM.

Source : PEP

PRODTYPE
output product medium type 
Datatype: CHARACTER*18        
Units:    NONE
Specification for routine science data processing.

Source : TRANS and PODPS

PROGRMID
program id 
Datatype: CHARACTER*03        
Units:    BASE 36 (0-9,A-Z)
For a proposal that has been accepted. (1-46,655 possible ids)

Source : PEP

PROPOSID
PEP proposal identifier 
Datatype: INTEGER*4           
Units:    NONE
A sequence number assigned for every proposal.

Source : PEP

PR_INV_F
first name of principal investigator 
Datatype: CHARACTER*18        
Units:    NAME
Proposal description data.

Source : PEP

PR_INV_L
last name of principal investigator 
Datatype: CHARACTER*18        
Units:    NAME
Proposal description data.

Source : PEP

PR_INV_M
middle initial of principal investigator 
Datatype: CHARACTER*01        
Units:    NAME
Proposal description data.

Source : PEP

RA_TARG
right ascension of the target (J2000) 
Datatype: REAL*8              
Units:    DEGREES
Position in J2000 system. For fixed targets, proper motion data is evaluated in SCS, at the epoch of the target position for the predicted start time of the observation. For spatial scans, the target position is evaluated at the end of the scan for science observations but at the beginning of scans for target acquisition observations. The value does not change for any observation in the spatial scan. For moving target, the SPSS Chebyshev Interpolating Polynomials for are evaluated at the predicted timem that may be a few minutes different than the actual start observation time. (Fixed target - Heliocentric, moving target - Geocentric)

Source : SPSS and SCS

SEQLINE
PEP line number of defined sequence 
Datatype: CHARACTER*15        
Units:    NONE
Blank if exposure specification in proposal does not use a PEP define/use sequence. Otherwise, the proposal line number of the sequence. See SEQNAME.

Source : PEP

SEQNAME
PEP define/use sequence name 
Datatype: CHARACTER*15        
Units:    NONE
Blank if exposure does not reference a define sequence. Otherwise, the proposal name of that sequence.

Source : PEP

SUNANGLE
angle between Sun and V1 axis 
Datatype: REAL*4              
Units:    DEGREES
Computed from the spherical trig formula: 
       cos(sunangle) = sin(declsun) * sin(declnv10 +                            
             cos(declsun) * cos(declnv1) * cos(rtassun - rtascnv1)

Source : SCS

SUN_ALT
altitude of the Sun above Earth's limb 
Datatype: REAL*4              
Units:    DEGREES
The algorithm calculates the altitude using the rectangular coordinates of HST and the coordinates of the Sun from the SHP header. For a long exposure, this wouldn't be as useful as, say, the maximum altitude of the Sun during the exposure. The other problem of this algorithm is that it assumes a spherical earth, which results in an error of about 0.4 degrees. Another effect is that it ignores atmospheric refraction. This will be very small at high altitudes but can be as large as one degree near the horizon.

Source : SCS

TARGNAME
proposer's target name 
Datatype: CHARACTER*30        
Units:    NAME
The target name specified in the proposal. The unique target id is TARG_ID.

Source : PEP

TIME-OBS
UT time of start of observation (hh:mm:ss) 
Datatype: CHARACTER*08        
Units:    TIME
PODPS calcuted time using packet times generated at the spacecraft at the time of the data measurement. The seconds place is not always accurate as the fractions of a section information is discarded rather than used for rounding.
FOS: merely the FPKTIME translated from MJD (keeping only whole seconds) see EXPSTART for relation to shutter opening.
WFPC: Note that this is not necessarily the start of the exposure. For example, the WFPC observation starts on a major frame pulse, while the exposure actually starts 16.4 seconds later following a memory clear. See EXPSTART.

Source : HST

HST Keyword Dictionary: 14-APR-94: (rose@stsci.edu)