vlev1 Documentation

vlev1 - Level 1 processing for Viking and Voyager data
The VLEV1 procedure updates the spacecraft positional (SPICE)
information on the image labels for VIKING data.  For both
Viking and Voyager it removes reseau marks, removes noise,
and applies the radiometric correction.  The input to this
procedure is a raw EDR image frame which has been converted
to the ISIS image format. The default for the output image
is a 32-bit image file containing radiance factor values.
The default can be changed to 16-bit by specifying otype=2
and orange=(min/max range of output).

VLEV1 is a TAE procedure which executes a series of programs:

For Viking only:
   SPICELAB - Stores geometry information on the labels.
	The EXT parameter specifies the source and type of
	SPICE geometry file.  If you specify the rmb spice
	file, be aware that not all the VIKING
	data set are included in this spice file.  For Viking,
        VLEV1 will first check the rmb spice file, if the record is
	not found it will automatically get the information
	from the gem spice file.  The rmb spice file has
	adjusted camera angle information, gem contains the
        complete set of predicted values supplied by JPL.
        For Voyager, it is assumed that the user has applied
        either spicelab and/or naiflab previous to this process.

For both Viking and Voyager:
   FINDRX - Finds and stores reseau positions in the image
	keyword label area. The reseau locations are used in
	subsequent processing steps.

   BOXFILTER - Two is used for two purposes:
	(1) Removes noise spikes and/or random noise.  The user
	specified NOISE parameter defines the relative amount
	of random noise (HIGH or LOW).  The standard deviation
	filter is used to replace a "noisy" pixel with the
	average value within a specified box or pixel area.
	(2) Replaces missing data.  Applies a low-pass filter to
	replace NULL pixel values introduced by remrx if
        ACTION=NULL.

   REMRX  - Removes the reseaus.  The reseau marks are replaced
	with averages of the neighborhood pixels (default box
	is 9x9).  The ACTION parameter determines which method
	to use, bilinear or null, the default is null.

   VIKCAL - Performs radiometric corrections to planetary images
	acquired by the Viking orbiter cameras. VIKCAL performs a
	radiometric correction in two steps. First, VIKCAL corrects
	for the varying response of the vidicon across the field of
	view of the camera.  Multiplicative and additive correction
	coefficients, as a function of line and sample position,
	are applied to an image array to produce the results of an
	'ideal' camera.  VIKCAL converts the image data to radiance
	factor values.  The radiance factor is defined as the ratio
	of the observed radiance and the radiance of a white screen,
	normal to the incident rays of the sun.
	See VIKCAL.pdf for further information.

        For a discussion of the radiance factor value, see "Planets
        and Satellites", Volume 3,  edited by G. P. Kuiper and B. M.
        Middlehurst, Chapter 6, Photometry of the Moon, by M.
        Minnaert, The University of Chicago Press, 1961.

For VOYAGER only:

    VOYCAL - Performs the radiometric correction of Voyager data
         similar to the description for VIKCAL above.
	 See VOYCAL.pdf for further information.


     TRIM - Trims the edges of the input file by 20 pixels.
        This is trimming off noise and camera distortions where the
        correction is limited.

     CIRCLE - Trims the corners of the input file with a radius=480.
        This is to remove the worst case
               camera distortions.

   *NOTE* - The output of VOYCAL is kept in order to allow the user
            to use the untrimmed version of the input Voyager file
            if desired. The output file name is "FROM".cal

PROGRAMMER: Ella Mae Lee, U.S.G.S., Flagstaff, AZ Original Version
            Jun 29, 1999 Tammy Becker, revisions for Voyager

Input cube file name
 (Default extension is .cub)

NONE

Output cube file name
 (Default extension is .cub)

NONE

SPICE geometry file extension
(gem,rmb)

rmb

Level of random noise in image
LOW = low to moderate noise
HIGH = high noise levels
NONE = no noise

LOW

Use look up table
(OPTIONAL)

0.0

Saturation flag in radcal
(OPTIONAL)

NO

Which way to remove reseaus -
  (BILINEAR or NULL)

"NULL"

Output pixel type
 NULL = input type
    1 = 8 bit
    2 = 16 bit
    3 = 32 bit (default)

3

Output min/max data range

0.0,1.0

Number of samples to remove
  around each reseau

9

Number of lines to remove
  around each reseau

9

ADDITIONAL NOTES:

Parm	Description
FROM	Input cube file name. If the file extension is omitted, then ".cub" will be assumed.
TO	Output cube file name. If the file extension is omitted, then ".cub" will be assumed.
EXT	For Viking: The extension of the SPICE geometry file name. Valid values are rmb and gem. This parameter will be used to select a SPICE file based on the extension entered. The *.rmb files were created by the cartographic group in Flagstaff and the *.gem files are the original files released by JPL during and after each mission. (It is assumed that Voyager has had spicelab/naiflab applied previously).
NOISE	There are two noise removal modes in VLEV1. This parameter specifies which noise removal scheme to utilize. Use the mode NOISE=LOW (default) for images which have a low to moderate amount of data drop outs and noise. For extreme noise levels in the data, use the NOISE=HIGH mode of VLEV1. NOISE=LOW utilizes less computer time than NOISE=HIGH. Use NOISE=HIGH sparingly because it is more destructive to real data. The great majority of raw images can utilize the NOISE=LOW option. NOISE=NONE will skip this process and indicates that the input file does not need the noise removal.
OFFT	VIKCAL or VOYCAL -- Time dependent offset correction value. The offset of the camera changes with time. This value is ADDED to the image. This value is usually extracted from the RADOFF.CAL file. When specified, this parameter will override the value in RADOFF.CAL.
SAT_FLAG	VIKCAL or VOYCAL -- The saturation flag is meant to be used only by the expert image processing analyst. This flag is normally set to NO. If the SAT_FLAG=YES then the output file will contain saturation flags (HIS or HRS) wherever the input values are saturated. ** Use this flag at your own risk!
ACTION	There are 2 ways the program can remove the reseaus. BILINEAR will use bilinear interpolation to create new DN values for the pixels inside the SDIM x LDIM box. NULL will simply replace each DN value inside the SDIM x LDIM box with the ISIS NULL value. The NULL data is then replaced with the average of neighboring pixels using the program "BOXFILTER".
OTYPE	Output pixel data type. Permitted values are: NULL = output type is same as input file pixel type 1 = 8-bit (integer with type conversion parameters) 2 = 16-bit (integer with type conversion parameters) 3 = 32-bit (floating point) When processed data are being written back into the input file, the output pixel type must be the same as the existing pixel type in the input file.
ORANGE	Output pixel data range. If ORANGE is NULL, then the CORE_BASE and CORE_MULTIPLIER in the output file will be set to represent the same range of data as the input file. If OTYPE=1 (8-bit) or OTYPE=2 (16-bit), then the CORE_BASE and CORE_MULTIPLIER in the output file will be set to values that allow representing the specified range of output values. Output values outside this range will be stored as a special "representation saturation" value. The ORANGE parameter is ignored if OTYPE=3 (32-bit) since the CORE_BASE and CORE_MULTIPLIER are not applicable to floating point pixel values.
SDIM	Number of samples to replace around each reseau location. The area inside the SDIM x LDIM box will be changed to remove the reseau. If the number entered is not an odd number, 1 will be added to it to make the dimension an odd number.
LDIM	Number of lines to replace around each reseau location. The area inside the SDIM x LDIM box will be changed to remove the reseau. If the number entered is not an odd number, 1 will be added to it to make the dimension an odd number.