HST Keyword Dictionary

Space Telescope Science Institute

3700 San Martin Drive

Baltimore, MD 21212

_____________________________________________________

Keyword Definitions for the

This is version 11.4, dated 16-NOV-1987

_____________________________________________________

ABSHFILE
absolute flux header file 
Datatype: CHARACTER*18        
Units:    FILENAME
The absolute sensitivity scale files contain data that are used to perform HRS absolute flux calibration. These files are used in conjunction with the HRS wavelength net files that specify the wavelength net (grid) used for interpolation of absolute sensitivity scale values. Absolute sensitivity files contain two groups of data that correspond to the large and small apertures of the HRS. Because the HRS wavelength net files contain the wavelength net corresponding to these sensitivity values it is not assumed that the spacing between wavelength values is uniform. Data in the absolute sensitivity files are stored in REAL*4 format.

Source :

ADC_CORR
application of dispersion constants 
Datatype: CHARACTER*08        
Units:
Convert the sample positions on the photocathode to wavelengths by applying the dispersion constants using tables ccr5, ccr6, ccr7, and ccrc containing spectral order, dispersion, and thermal constants. This routine computes spectral orders and wavelengths. For first order gratings, the spectral order is set to 1. For echelle gratings the spectral order is computed by the following formula: 
		order = NINT( numerator/ denominator)                                         
		numerator = b*A*sin((C-carpos)/B)                                             
		denominator = ydef-a-d*A(sin((C-carpos)/B)                                    
	Where:                                                                         
		NINT  is the nearest integer,                                                 
		A,B,C  are in table ccr5,                                                     
		a,b,d are in table ccr5,                                                      
		carpos  is the carrousel position, and                                        
		ydef is the Y-deflection adjusted for the proper aperture                     
	And:                                                                           
	The wavelengths are computed by solving the dispersion relation for            
	wavelength using Newton's iterative method. The dispersion relation is         
	described by the following equation:                                           
		s = a0 + (a1*m*w) + (a2*(*m*w)**2) + (a3*m) + (a4*w) +                        
		    (a5*m*2*w) + (a6*m*w**2) +(a7*m**3*w**3)                                  
	Where:                                                                         
		m  is the spectral order,                                                     
		w  is the wavelength,                                                         
		a0,a1,..  are the dispersion coefficients, and                                
		s  is the sample position.

Source :(calguide)

APERTURE
aperture name 
Datatype: CHARACTER*08        
Units:
The name of the aperture used for the observation. The possible values are: 
	SSA                                                                            
	LSA                                                                            
	SC1                                                                            
	SC2                                                                            
	blank - No aperture was in use.

Source :

APER_FOV
Aperture field of view (arcsec),N/A for calib 
Datatype: CHARACTER*18        
Units:
The field of view of the aperture in use for the current observation. If not specificed or "N/A", then an aperture which doesn't view the sky is in use, or no aperture is in use.

Source :

BCK_CORR
background removal 
Datatype: CHARACTER*08        
Units:
Subtract the background counts from the raw counts of the diode array. This routine subtracts the background by one of four methods. The first applicable method is used. (1) Subtract sky spectra (header keyword BINID of 5 or 6). For this case the background is smoothed by a median filter followed by a mean filter. (2) Subtract interorder from main diode array. (header keyword BINID of 3 or 4). For this case, the background is smoothed by a median filter followed by a mean filter. (3) Use background diodes from separate substep bins with header keyword BINID between 8 through 15. The diodes to use are selected on the basis of the value of BINID. (4) Use all background diodes from

Source :

BINID
binid 
Datatype: INTEGER*4           
Units:    none
The source bin id number of the current line of science data. The GHRS maintins seven "bins" or arrays for the accumulation of science data. This value indicates from which of these bins the science data came from.

Source :

BRIGHT
upper threshold for star presence (counts) 
Datatype: REAL*4              
Units:    counts
A parameter of the spiral search phase of target acquisition. A valid acquired target must have counts less than specified by BRIGHT.

Source :

BUNIT
brightness units 
Datatype: CHARACTER*18        
Units:
The units of the science data. For the GHRS, valid values are "COUNTS", "COUNTS/S", or "ERGS/CM**2/S/A".

Source :

CARPOS
carrousel position 
Datatype: INTEGER*4           
Units:    encoder units
The position of the GHRS grating carrousel for the observation. Values range from 0 to 65535.

Source :

CCG2
paired-pulse correction table 
Datatype: CHARACTER*18        
Units:    FILENAME
Paired-pulse correction table. Deadtime constants are used to correct for the non-linear channel response of each diode. These constants are not expected to change during the lifetime of the FOS, or GHRS. Analysis of prelaunch data indicate that the same constants can be used for both FOS detectors. They are also applicable to the GHRS.

Source :(calguide)

CCR1
photocathode line mapping parameters table 
Datatype: CHARACTER*18        
Units:    FILENAME
A CDBS table containing the coefficients of the line mapping function that relates Y-deflection to line position in the photocathode.

Source :

CCRA
echelle non-interpolation constants table 
Datatype: CHARACTER*18        
Units:    FILENAME
A CDBS table containing further constants used in the echelle ripple correction. These constants are used to compute the normalized grating efficiency as a function of grating/echelle mode.

Source :

CCRB
scattered light correction factors 
Datatype: CHARACTER*18        
Units:    FILENAME
A CDBS table containing the coefficients for determining the contribution of scattered light to the background. Records contain four scattered light coefficients and are organized by aperture, grating/echelle mode and spectral order. The four coefficients (a_scat, b_scat, c_scat, and d_scat) are used in the following equation to determine the background spectrum: 
	    B(i) = 0.5 * [a_scat*U(i) + b_scat*L(i)] - c_scat*N(i) + d_scat*N          
	    where:                                                                     
		N(i) = O(i) - 0.5*[U(i) + L(i)]                                               
		U(i)  is the upper interorder count rate per diode                            
		L(i)  is the lower interorder count rate per diode                            
		N(i)  is the net on-order count rate per diode                                
		O(i)  is the gross object spectrum count rate per diode                       
		N     is the average net on-order count rate per diode                        
			averaged over all science diodes                                             
		i     is the science diode index

Source :

CCRC
global wavelength coefficients table 
Datatype: CHARACTER*18        
Units:
This table contains the coefficients for the global wavelength solution method of finding the dispersion constants for a particular position of the carrousel. It also contains the zero-point temperatures used for thermal motion calculations of the wavelengths.

Source :

COMB_ADD
comb-addition (NO, TWO, FOUR, DSTWO, DSFOUR) 
Datatype: CHARACTER*06        
Units:
Indicates what mode of comb-addition is used for the observation. Comb-addition is a method of smoothing out diode-nonuniformities in the science data. A particular wavelength can be observed by one, two, or four different diodes. The response of each of these diodes is summed into a single memory location. The meaning of each of the options are as follows: 
	NO	- One diode contributes to the response.                                    
	TWO	- Two adjacent diodes contribute to the response.                          
	FOUR	- Four adjacent diodes contribute to the response.                        
	DSTWO	- "Double space"- Two diodes, separated by a diode,                      
		  contribute to the response.                                                 
	DSFOUR  - Four diodes, each separated by a diode, contribute                   
		  to the response.

Source :

DECAPER1
declination of the aperture (deg) 
Datatype: REAL*8              
Units:    DEGREES
The declination, in degrees, of the sky where the center of the aperture is looking at.

Source :

DEC_APER
declination of aperture (deg) 
Datatype: REAL*8              
Units:    DEGREES
The declination, in degrees, of the sky where the center of the aperture is looking at.

Source :

DELTAS
delta sample position 
Datatype: REAL*4              
Units:    sample per pixel
The linear coefficient of the pixel-to-sample space function. This defines the size of a science pixel in sample units. The formula for converting between pixel and sample position is as follows, if pixels are counted from 1: 
	sample = SAMPLE + DELTAS * (pixel - 1)

Source :

DELTA_X
x increment for map (deflection units) 
Datatype: INTEGER*2           
Units:
This defines the resolution of a map in the X deflection direction. Adjacent "pixels" of a map are separated by DELTA_X deflection units.

Source :

DELTA_Y
y increment for map (deflection units) 
Datatype: INTEGER*2           
Units:
This defines the resolution of a map in the Y deflection direction. Adjacent "pixels" of a map are separated by DELTA_Y deflection units.

Source :

DETECTOR
detector in use (1-2) 
Datatype: INTEGER*2           
Units:
Which detector, side 1 or side2, that is in use.

Source :

DIOHFILE
diode response header file 
Datatype: CHARACTER*18        
Units:    FILENAME
Non-uniformities in diode responses for HRS detectors require science data to be normalized using data from the diode response files. Diode response data files contain a single group of normalization data with 512 entries corresponding to the 512 diodes of each HRS detector. Diode responses are stored in real*4 format.

Source :

DIO_CORR
diode response correction 
Datatype: CHARACTER*08        
Units:
Divide the count value by the diode's response to correct for diode non-uniformity using the diode response file, diohfile. This routine corrects for diode response by dividing the input data by the diode response values. When comb-addition is used, a smoothed diode response array is computed using a weighted average of diode responses. Data with a diode response value less than the minimum value are set to 0.0.

Source :(calguide)

DOPMAG
doppler shift scaling correction magnitude 
Datatype: REAL*4              
Units:
See DOPPLER for a more complete description.

Source :

DOPPLER
on-board doppler compensation (ON, OFF) 
Datatype: CHARACTER*03        
Units:
An onboard doppler correction update can be performed once each minute at at the beginning of each observation. The update consists of computing a small correction factor to be added to each X-deflection as it is generated. The generated form of the correction is given by: 
		dX = C*sin(2*pi*(t-t0)/P)                                                     
	where:                                                                         
		dX:	Correction Factor;                                                        
		C:	DOPMAG: constant made up of a scale factor and the                         
			cosine of the orbital latitude - from OCT;                                   
		P:	orbital period - built into table of sines;                                
		t:	current time - from spacecraft clock;                                      
		t0:	DOPZER: time of the doppler correction - from OCT;

Source : ST-ICD-08(III-80)

DOPZER
doppler shift zero phase time (Mod Julian Date) 
Datatype: REAL*8              
Units:
See DOPPLER for a more complete description.

Source :

DOP_CORR
doppler compensation 
Datatype: CHARACTER*08        
Units:
Correct for on-board Doppler compensation when removing photocathode nonuniformities and vignetting. This routine computes the percent of time spent at each Doppler offset. These are computed by dividing the observation into time segments and computing the deflection offset for each segment. The SHP packet time is used as the start of the readout and the packet time of the first science packet is used as the ending time of the readout.

Source :(calguide)

DQIHFILE
data quality initialization header file 
Datatype: CHARACTER*18        
Units:    FILENAME
The HRS data quality initialization files contain a priori information concerning the effect of the HRS's diode arrays on the quality of output data values. Data quality initialization data files contain a single group of data with 512 entries corresponding to the 512 diodes of each HRS detector.

Source :

DQI_CORR
data quality initialization 
Datatype: CHARACTER*08        
Units:
Apply data quality initialization using the reference file, dqihfile. This routine performs the data quality initialization by flagging each data value with the values in the data quality initialization file. The file contains a data quality value for each diode. If the data quality value of the data is larger than the data qualify initialization file value for the diode, it is left unchanged. Quality values are never decreased.

Source :(calguide)

ECH_CORR
correction for echelle ripple 
Datatype: CHARACTER*08        
Units:
If one of the echelle gratings is used, divide the flux value by the normalized grating efficiency to remove the echelle ripple using tables ccr9 and ccra, which contain echelle ripple constants. This routine performs the echelle ripple removal by dividing the flux by the following echelle ripple function: 
		ripple = gnorm sinc(a*x+b)^^2                                                 
	Where:                                                                         
		gnorm = cos(A+B+C)/cos(A+B-C+e)                                               
		x = [pi]*m*cos(A+B+C)*sin(A+e/2)/sin(A+C+e/2)                                 
	And:                                                                           
		e is arctan ( (samp-280.0)/f ),                                               
		m is the spectral order,                                                      
		samp is the photocathode sample position,                                     
		A is (r0 - carpos)*2*pi/65536.0,                                              
		r0, B, C, f   are grating parameters in table ccra, and                       
		 a and b  are coefficients from table ccr9.

Source :(calguide)

EXPOSURE
exposure time (seconds) 
Datatype: REAL*4              
Units:    SECONDS
The time, in seconds, that each pixel in the science data, accumulated light.

Source :

EXP_CORR
division by exposure time 
Datatype: CHARACTER*08        
Units:
Convert to count rates. This routine converts the input data to count rates by dividing by the exposure times. The exposure time is computed for each bin as 0.05*NCOADD*INTPER, where NCOADD is the number of coadds to the bin and INTPER is the integration period in 0.05 second intervals. If either value contains fill, no exposure time can be computed and the entire bin is flagged as unusable.

Source :(calguide)

FAINT
lower threshold for star presence (counts) 
Datatype: REAL*4              
Units:
A parameter of the spiral search phase of target acquisition. A valid acquired target must have counts greater than specified by FAINT.

Source :

FINCODE
observation termination code 
Datatype: INTEGER*2           
Units:
ZFINCOD: a status code giving the reason for the dump of the HRS Unique Data Log. Thse codes are given in Section 3.8.3 of SE-01: 
		101: Observation Processing initiated                                         
		102: Observation pattern complete                                             
		103: Under-exposure termination                                               
		104: Over-exposure termination                                                
		105: Bad-data termination                                                     
		106: Observation time-out

Source :

FLUXFND
flux measurement for map with greatest flux 
Datatype: REAL*4              
Units:
This contains the flux measurement, in counts, of the dwell point with the greatest flux in a return-to-brightest target acquisition.

Source :

FLX_CORR
absolute flux calibration 
Datatype: CHARACTER*08        
Units:
Convert the object spectra to absolute flux units. The object spectra are converted to flux units by multiplying by the inverse sensitivity vector. This routine requires the inverse sensitivity file iv1file. A second inverse sensitivity file, iv2file, is required for paired- aperture or spectropolarimetry observations. This calibration step converts the count rates to units of ergs/cm^^2/sec/Angstrom. This step is a spectroscopy mode calibration step.

Source :(calguide)

FP_SPLIT
fp-split (NO, TWO, FOUR, DSTWO, DSFOUR) 
Datatype: CHARACTER*06        
Units:
FP_SPLIT is a possible observation mode of the GHRS used to reduce the effects of photocathode response nonuniformities. A particular wavelength is collected by one, two, or four different diodes, whose responses are collected into different bins. The data can be recombined after calibration. The carrousel is moved to shift the wavelength to each of the different diodes. The meaning of the values are as follows: 
	NO	- One carrousel position is used.                                           
	TWO	- Two adjacent carrousel positions are used.                               
	FOUR	- Four adjacent carrousel positions are used.                             
	DSTWO	- "Double Space", Two carrousel positions, separated                     
		  by a carrousel position, are used.                                          
	DSTWO	- "Double Space", four carrousel positions, each separated               
		  by a carrousel position, are used.

Source :

GRATING
grating, echelle or mirror in use 
Datatype: CHARACTER*09        
Units:
GRATING -- grating/echelle mode: 
		Spectral Element	Grating		Detector                                            
		G140M			G-1		Digicon 1                                                        
		G160M			G-2		Digicon 2                                                        
		G200M			G-3		Digicon 2                                                        
		G270M			G-4		Digicon 2                                                        
		G140L			G-5		Digicon 1                                                        
		ECH-A			E-A		Digicon 1                                                        
		ECH-B			E-B		Digicon 2                                                        
		SAFE1			SAF		Digicon 1                                                        
		SAFE2			SAF		Digicon 2                                                        
		MIRROR-N1		MN1		Digicon 1                                                     
		MIRROR-A1		MA1		Digicon 1                                                     
		MIRROR-N2		MN2		Digicon 2                                                     
		MIRROR-A2		MA2		Digicon 2                                                     
					NDF                                                                  
         	(NDF = NOT DEFINED, ERR = ERROR)

Source :[qexposure.grating]

GWC_CORR
use global wavelength coefficients 
Datatype: CHARACTER*08        
Units:
When set to "PERFORM", this indicates to the pipeline calibration to use the global coefficients found in reference table CCRC to determine the wavelength coefficients for an observation instead of the information found in CCR6. See ADC_CORR for more information.

Source :

HEL_CORR
conversion to heliocentric wavelengths 
Datatype: CHARACTER*08        
Units:
Convert wavelengths to heliocentric coordinate system. This routine corrects for the Earth's motion around the Sun.

Source :(calguide)

HOFFi
horizontal offset bin i+1 
Datatype: INTEGER*4           
Units:
The horizontal deflection offset to use during an observation pattern that accumulates data into bin i+1. This offset is added to the initial deflection, when data is being accumulated into bin i+1.

Source :

IAC_CORR
incidence angle correction 
Datatype: CHARACTER*08        
Units:
Adjust the zero-point of the wavelength scale for the large science aperture and the two spectral lamp apertures using table CCR8 containing incidence angle coefficients. This routine adjusts the wavelenght array for the difference in incidence angle of apertures LSA, SC1 and SC2 from the SSA. Table CCR8 is searched for the correct grating, spectral order, aperture, and carrousel position to obtain two coefficients, A and B. Interpolation of the coefficients (in carrousel position) is used if an exact match is not found. These coefficients are then used to compute an offset using the following formula: 
		w = w + (A+B*s)/m                                                             
	Where:                                                                         
		w  is the wavelength,                                                         
		A and B  are coefficients in ccr8,                                            
		s  is the photocathode sample position, and                                   
		m  is the spectral order.

Source :(calguide)

INFOB
deflection pairs/substep pattern 
Datatype: INTEGER*2           
Units:
The number of deflection pairs used for the current observation pattern.

Source :

INFOC
largest repeat code in the substep pattern 
Datatype: INTEGER*2           
Units:
The largest repeat code in the substep pattern. See the RPTCDi keywords for the individual repeat codes for each bin.

Source :

INTOBS
expected number of intermediate readouts 
Datatype: INTEGER*4           
Units:
The number of intermediate readouts expected from the current observation before the final science accumulation readout occurs.

Source :

IXDEFi
initial x deflection 1 
Datatype: INTEGER*4           
Units:    deflection units
The set of X deflections to use while accumulating data into each bin of science data. This the amount of deflection used for comb-addition for each part of the comb-addition.

Source :

IYDEFi
initial y deflection 1 
Datatype: INTEGER*4           
Units:    deflection units
The set of Y deflections to use while accumulating data into each bin of science data.

Source :

KZDEPLOY
COSTAR deployed for the HRS (T or F) 
Datatype: LOGICAL*1           
Units:    TRUE/FALSE
The logical DEPLOY keywords are to be set to True only if the COSTAR arm for that SI has been deployed. There are two conditions under which this keyword should be set to False. Before the servicing mission, a database flag will have to be set to instruct PODPS not to extract the COSTAR mirror positions from the SHP (the telemetry positions will still correspond to HSP data), set the DEPLOY keywords to False and set the mirror position keywords to a default value (99999). Once COSTAR is installed in HST, the database flag will be set to indicate that the COSTAR SHP entries are valid. PODPS should then populate the DEPLOY keywords based on the SHP position telemetry values. If any of the telemetered values for a given SI are the default value (99999), then the DEPLOY keyword for that SI should be set to false. This will allow for the possibility of deploying some COSTAR arms and not others.

Source :

LINE
line positions 
Datatype: INTEGER*4           
Units:    line units
The line position on the photocathode that the diodes are looking at during the observation.

Source :

LOCATE
do a locate after the spiral search 
Datatype: CHARACTER*08        
Units:
Flag to indicate whether a locate is performed after the spiral search phase of a target acquisition. Possible values are "YES" and "NO".

Source :

MAP
dwell points at which to image the aperture 
Datatype: CHARACTER*10        
Units:
Which dwell points of a spiral search that should produce a map. Current values are: 
	NONE	      - No maps are to be produced during the spiral                      
			search                                                                       
	END-POINT     - Produce a map when the spiral search phase has                 
			completed and has moved to the point where the                               
			search was successful                                                        
	ALL-POINTS    - Produce a map at each dwell point of the                       
		      	spiral search.

Source :

MAPFND
map found to have greatest flux 
Datatype: INTEGER*4           
Units:
The dwell point/map where the greatest flux was found during a return-to-brightest target acquistion. The flux of this point is found in FLUXFND.

Source :

MAP_CORR
mapping function 
Datatype: CHARACTER*08        
Units:
Perform the photocathode mapping function using tables ccr1 and ccr2 containing the photocathode line mapping and sample parameters. This routine computes the mapping function for each of the substep bins using the following formulae: 
		SAMPLE(bin) = x0 + b*XD + c*XD^^2                                             
		DELTAS(bin) = e                                                               
		LINE(bin)   = L0 + A*YD                                                       
	Where:                                                                         
		SAMPLE -- is the sample position of the first diode,                          
		DELTAS-- is the spacing between sample positions,                             
		LINE -- is the line position of the diodes,                                   
		XD -- is the X-deflection minus 2048,                                         
		YD -- is the Y-deflection minus 2048,                                         
		s0, b, c and e are coefficients in ccr2, interpolated for                     
			the given Y-deflection, and                                                  
		L0, and A -- are coefficients in ccr1.

Source :(calguide)

MAP_NUM
mosaic map number 
Datatype: CHARACTER*          
Units:
The dwell point number where this map was taken at.

Source :

MAXGSS
maximum substep patterns/observation 
Datatype: INTEGER*4           
Units:
read from the value telemetered in the HRS Unique Data Log (UDL): ZMAXGSS.

Source :

MAXWAVE
maximum wavelength (angstroms) 
Datatype: REAL*4              
Units:    ANGSTROMS
The maximum wavelength represetned by the current line of science data.

Source :

MDF_CORR
median filter of background spectra 
Datatype: CHARACTER*08        
Units:
Use a median filter on the background. This routine performs a median filter of the background with a user-specified (i.e., specified in the table) filter width. The edge points are filled with the value of the closest position that can be filtered.

Source :(calguide)

MERGED
number of merged spectra in this pattern 
Datatype: INTEGER*2           
Units:
The number of bins that contain data that should be merged together.

Source :

MER_CORR
use global wavelength coefficients 
Datatype: CHARACTER*08        
Units:
Merge the substep bins. This routine merges the spectral data. Unmerged output data is just a copy of the input data. Both the input and output data arrays are 2-dimensional arrays treated as 1-dimensional arrays by this routine. The input is treated as 1-dimensional to make copying faster (2-dimensional copying takes longer) and the output array is treated as 1-dimensional because this routine computes its dimensions.

Source :(calguide)

METER
exposure meter enabled 
Datatype: CHARACTER*01        
Units:
Flag indicating whether the onboard exposure meter is enabled or not. Values are "N" and "Y" for no and yes respectively.

Source :

MINWAVE
minimum wavelength (angstroms) 
Datatype: REAL*4              
Units:    ANGSTROMS
The mimimum wavelength of the current line of science data.

Source :

MIR_REVR
is the image mirror reversed 
Datatype: LOGICAL*4           
Units:
Flag indicating whether the map is mirror-reveresed or not.

Source :

MNF_CORR
mean filter of background spectra 
Datatype: CHARACTER*08        
Units:
Use a mean filter on the background. This routine performs a mean filter of the background with a user-specified (i.e., specified in the table) filter width. The edge points are filled with the value of the closest position that can be filtered.

Source :(calguide)

NBINS
number of substep bins in this pattern 
Datatype: INTEGER*2           
Units:
The number of science bins used by the substep pattern.

Source :

NETHFILE
absolute flux wavelength net header file 
Datatype: CHARACTER*18        
Units:    FILENAME
The wavelength net files contain data that are used to perform HRS absolute flux calibration. These data provide the non-uniform interpolation net (grid) used to compute an absolute sensitivity scale from data in the HRS absolute sensitivity files. Wavelength net files contain two groups of data that correspond to the large and small apertures of the HRS. Because the HRS absolute sensitivity files contain the absolute sensitivities corresponding to the wavelength net values, these two sets of files have exactly the same structure. Data in the wavelength net files are stored in REAL*4 format.

Source :

NINIT
number of initial deflections 
Datatype: INTEGER*2           
Units:
The number of initial deflections defined. The initial deflections are found in IXDEFi and IYDEFi.

Source :

OBSINT
intermediate readout number 
Datatype: CHARACTER*          
Units:
The number of the intermediate readout from which the current science data came from.

Source :

OBSMODE
observation mode 
Datatype: CHARACTER*18        
Units:                        
	obsmode				Proposed Mode                                                       
	------------------	------------------------------------------                  
	DIRECT READOUT 		RAPID,ENGINEERING, PULSE-HEIGHT, THRESHOLD;                   
	ACCUMULATION   		ACCUM,OSCAN,WSCAN, PHOTOSCAN;                                 
	TARGET ACQUISITION  	ACQ,IMAGE,DEFCAL, ACQ/PEAKUP.

Source : (tguide 7.0-12)

OBSRPT
observation repeat number 
Datatype: CHARACTER*          
Units:
A number representing at which "repeat" of the substep pattern the current science data came from.

Source :

ORIENTAT
the orientation of the image (deg) 
Datatype: REAL*4              
Units:
The orientation angle of the map, measured in degrees, east of north.

Source :

PHCHFILE
photocathode response header file 
Datatype: CHARACTER*18        
Units:    FILENAME
Non-uniformities in the responses of the photocathodes of the HRS detectors require science data to be normalized using data from the photocathode response files. Photocathode response files contain multiple groups of responses. Each group contains the responses for a particular line position. Within the group, responses are ordered by equally spaced sample positions determined by the keywords SAMPBEG and SAMPOFF. Photocathode responses are stored as REAL*4 values.

Source :

PHC_CORR
removal of photocathode nonuniformity 
Datatype: CHARACTER*08        
Units:
Remove photocathode nonuniformity by dividing the count value by the photocathode response contained in the phchfile file. This routine removes the photocathode granularity using a reference file that has a granularity map. This map has a granularity vector for multiple line positions. At each line position the granularity is tabulated with a constant starting sample for all lines and a constant delta sample. To compute the response for the data's line and sample, bilinear interpolation is used within the reference file. If Doppler compensation is specified, the response is smoothed by a weighting function describing the motion of the data samples along the photocathode. (This calibration will only be known initially for a very few selected wavelength ranges. Using FPSPLITS will generally be required for high S/N work.)

Source :(calguide)

PKTFMT
packet format code 
Datatype: INTEGER*4           
Units:    code                
	101:   Launch Configuration                                                    
	102:   Aliveness Test                                                          
	103:   PDMaps                                                                  
	104:   Other Ground Cmd-generated Data                                         
	111:   ZMETEST: Reset Test                                                     
	112:   ZMETEST: Deflection/Carrousel Test                                      
	113:   ZMETEST: Integration Test                                               
	114:   ZMETEST: Anti-coincidence/Pulsar Test                                   
	115:   ZMETEST: Lamp/Door/Shutter Test                                         
	116:   Configurations and Mode Transitions                                     
	117:   Other Stored Command Tests                                              
	118:   ZMATEST: Aliveness Test                                                 
	121:   Standard PHA                                                            
	122:   Ion Test                                                                
	123:   Other PHA data                                                          
	131:   Configurations                                                          
	132:   Darks (Accumulation Mode)                                               
	133:   Y scans                                                                 
	134:   X scans                                                                 
	135:   Wavelength Calibrations (SC lamps)                                      
	136:   Software and Other Functional Tests                                     
	137:   Mask Scan                                                               
	138:   Rapid Readout Mode: Wavelength Calibration                              
	139:   Rapid Readout Mode: Flatfield and Darks                                 
	141:   Large Aperture Target Acquisitions                                      
	142:   Small Aperture Target Acquisitions                                      
	143:   Image Mode Field Maps (Mirrors and Gratings)                            
	144:   Software and Other Functional Tests                                     
	151:   Calibrations                                                            
	152:   Rapid Readout Mode (External Source)                                    
	153:   Accumulation Mode                                                       
	154:   FP-Split Observations

Source : iminfo.x

PLY_CORR
polynomial smoothing of background spectra 
Datatype: CHARACTER*08        
Units:
Fit a polynomial to the calculated background and subtract this fit from the science data instead of the background itself. The order of the fit comes from the CCR3 table.

Source :

PPC_CORR
paired-pulse correction 
Datatype: CHARACTER*08        
Units:
paired pulse correction: Correct the raw count rates for saturation in the detector electronics using table coccg2r, which contains the paired-pulse correction table. On the first call, the paired pulse parameters are read from table ccg2. The following equation is used: 
		x = y/(1-yt)                                                                  
	Where:                                                                         
		x -- is the true count rate,                                                  
		y -- is the observed count rate,                                              
		t = q0 if y is less than or equal to F, and                                   
		t = q0 + q1 * (y - F) if  y is greater than F.                                
		q0, q1, and F are coefficients in ccg2r.
This is a standard calibration step.

Source :(calguide)

PRECISN
number of diodes used to map (HIGH=1,NORMAL=2) 
Datatype: CHARACTER*08        
Units:
The number of diodes used to map the apertures. If "HIGH", one of the focus diodes is used. If "NORMAL", two focus diodes are used.

Source :

RA_APER
right ascension of aperture (deg) 
Datatype: CHARACTER*          
Units:    DEGREES
The right ascension of the reference position of the aperture used for the group data. For WFPC group data, the aperture is indicated by the value of the group keyword DETECTOR. For other SIs the aperture is that indicated by the standard header packet keyword APEROBJ.

Source :

RPTCDi
repeat code bin 2 (0 = no def offset) 
Datatype: INTEGER*2           
Units:    CODE
The repeat code determines how often a bin is used during a substep pattern. 
		0 = no def offset,                                                            
		1 = every time,                                                               
		2 = every 2nd time,                                                           
		4 = every 4th time,                                                           
		8 = every 8th time.

Source :

RPTOBS
expected number of observation repeats 
Datatype: INTEGER*4           
Units:    COUNT
The number of times to repeate the substep pattern for the observation. This effectively repeats the observartion for RPTOBS number of times.

Source :

RTBRIGHT
BRIGHT=RETURN used 
Datatype: LOGICAL*1           
Units:
For target acquistions, this flag indicates whether the return-to-brightest mode was used.

Source :

SAMPLE
sample position 
Datatype: CHARACTER*          
Units:    sample units
The sample position of the first pixel of the science data. See DELTAS for more information.

Source :

SCIDMP
intermediate data dump (-1 = nodump) 
Datatype: INTEGER*4           
Units:
Number of substep patterms between intermediate data dumps (-1 for no intermediate dumps) SE-01p3-267

Source :

SCLAMP
spectral calibration lamp 
Datatype: INTEGER*2           
Units:
The calibration lamp in use. 0 for none.

Source :

SPORDER
spectral order 
Datatype: INTEGER*2           
Units:
The spectral order represented by the science data. For the first order gratings, this is one. For the echelles, the values can range between 18 and 51.

Source :

SRCHSIZE
width of spiral-search in dwell points 
Datatype: INTEGER*2           
Units:
The number of dwell points on a side of a spiral search.

Source :

STEPPATT
step pattern sequence 
Datatype: INTEGER*2           
Units:
Flag indicating the step pattern sequence to use. See the GHRS instrument handbook for more information.

Source :

STEPTIME
exposure time at each dwell point (seconds) 
Datatype: REAL*4              
Units:
The exposure time at each dwell point of a target acquisition.

Source :

VAC_CORR
vacuum to air correction 
Datatype: CHARACTER*08        
Units:
Apply vacuum-to-air correction to the wavelengths. This routine converts vacuum wavelengths to air wavelengths above 2000 Angstroms.

Source :(calguide)

VIGHFILE
vignetting response header file 
Datatype: CHARACTER*18        
Units:    FILENAME
The removal of vignetting and wavelength-dependent photocathode variations is done using data from the vignetting files. Vignetting correction files contain multiple groups of responses. Each group contains the responses for a particular carrousel position and line position. Within the group, responses are ordered by equally spaced sample positions determined by the keywords, SAMPBEG and SAMPOFF. Data in the vignetting correction data files are stored in REAL*4 format.

Source :

VIG_CORR
removal of vignetting nonuniformity 
Datatype: CHARACTER*08        
Units:
Remove vignetting and wavelength-dependent photocathode variations by dividing each count value by the vignetting response contained in the vighfile file. This routine removes the vignetting and low frequency photcathode response using a reference file that has a vignetting map. This map is has a vignetting vector for multiple line position and carrousel positions. At each line position the granularity is tabulated with a constant starting sample for all lines and a constant delta sample. To compute the response for the data's line and sample, tri-linear interpolation is used within the reference file over carrousel position, line position and sample position. If Doppler compensation is specified, the response is smoothed by a weighting function describing the motion of the data samples along the photocathode.

Source :(calguide)

VOFFi
vertical offset bin 2 
Datatype: INTEGER*4           
Units:
The vertical deflection offset to use during an observation pattern that accumulates data into bin i+1. This offset is added to the initial deflection, when data is being accumulated into bin i+1.

Source :

XDEF
horizontal deflection 
Datatype: CHARACTER*          
Units:
The X deflection used to accumulate the current line of science data.

Source :

YDEF
vertical deflection 
Datatype: CHARACTER*          
Units:
The Y deflection used to accumulate the current line of science data.

Source :

ZLCOEF1
line mapping function L0 
Datatype: REAL*4              
Units:
The L0 coefficient of the deflection to line mapping function. The function is: 
	line = L0 + a * y-deflection

Source :

ZSCOEFi
first coefficient of sample mapping 
Datatype: CHARACTER*          
Units:
These are the coefficients used for the deflection-to-sample mapping function. The function is: 
	sample = s0 + b*x-def + c*(x-def)**2 + e*diode
The mappings between the coefficients and the keywords are: 
	ZSCOEF1	     s0                                                                
	ZSCOEF2	     b                                                                 
	ZSCOEF3	     c                                                                 
	ZSCOEF4	     e

Source :

HST Keyword Dictionary: 3/15/94: (rose@stsci.edu)