1 or 2 input files.
The required first file is an input picture containing the
target body. The maximum size is 1400 by 1400.
The optional second file (IBIS tiepoint format) contains GEOMA
parameters for geometrically correcting the input picture.
0-3 Output Files:
The LAST output file contains GEOMA parameters which the user can use
as a secondary input to GEOMA (along with the input image to FARENC) to
produce an image with the target body centered on NL/2.,NS/2.
This file will have the format of an IBIS tiepoint file and will contain the
GEOM parameters necessary to translate the picture to the center of the
output picture. If the second input is provided, geometric correction
will be included in the translation. Since for GLL project there are
no reseaus the geometric correction is included for all inputs
not already corrected.
(See parameter GEOM)
In addition 2 optional output files may be specified: CURVE and POINTS:
CURVE must be the first output data set, if it is desired. It is the
size of the input picture, and displays all of the limb fitted curves
superimposed on the target body.
POINTS must be the the second output data set, if it is desired. It
is a byte image the size of the input picture containing a display of
all limb points.
All limb points used in the fitting are in black.
All candidate limb points not used in the fit are in white.
Note: If the input image has a map3 perspective label placed there by
the PERSLAB program Farenc will ignore the sedr/spice and
will write the planet center to an output file called: FARENC.POS
This file is a Vicar image, has 1 line & 2 samples with the
real values line,sample.
4 INTEGERS - A Vicar SIZE field which is ignored unless the GEOM is specified, then Number-of-lines and Number-of-samples refer to the size of the output file containing the translated image.
INTEGER - Starting line in the input file to be processed
INTEGER - Starting sample in the input file to be processed
INTEGER - Number of lines in the input file to be processed
INTEGER - Number of samples in the input file to be processed
('HALF or 'BYTE) - Specifies the Input picture, the Curve data set
and the GEOMed image are to be in halfword or byte format.
Default is to read the format parameter in the VICAR label.
A keyword which specifies that SEDR file information is to be ignored. The default is to read the SEDR file.
The maximum permitted error in the SPICE/SEDR location of the planet center in pixels. This range is used to restrict farenc in it's search for the planet center from the predicted SPICE planet center location. Default is 400 for VGR and 250 for GLL. If no sedr/spice available it defaults to the picture size. Range is the diameter of the error circle. Does not apply if an unconstrained circle is used.
Real, 2 values representing the initial line,samp location of the planet center. The default is to consult the sedr/spice. If no sedr/spice is available this will default to the image center. Ignored for the unconstrained circle. This is an object space coordinate. Example: initcen=(256.,256.)
INTEGER - All pixels whose DN's are less than DNTHRESH will be ignored. No activity value will be computed for such pixels and they will never be considered as a potential target body limb position. Default is DNTHRESH = 30 for byte and 200 for halfword. See AUTO keyword.
INTEGER - All pixels whose activity value is less than ACTIVITY will be ignored. If 'AUTO keyword is NOT used: Default is ACTIVITY = 55. See AUTO keyword.
INTEGER - Each column and row through out the picture is searched for two maximum activity values. The values must be at least DISTANCE apart. If no two acceptable values occur at a separation of at least DISTANCE pixels, the value with the least activity measure will be discarded. This value is used to assure both sides of the target body are represented. Default is DISTANCE = 10
REAL - The maximum accepted ratio between the activity values of the second and first maximum on each line and column. A HEIGHT of 1 would indicate that the second largest value must be at least equal to the largest value. This would virtually preclude a second value. Default is HEIGHT = 0.60.
At least one of the adjacent 8 pixels must lie at or below the value BELOW. To use this parameter the value of BELOW must be above the dark current. Default is 30 for byte and 200 for halfword pictures. See AUTO keyword.
'AUTO -
AUTOmatically resets ACTIVITY
AUTOmatically resets DNTHRESH
AUTOmatically resets BELOW
depending on the maximum DN in the picture. The maximum
DN is determined by computing a certain percentage of the
way down from the top of the histogram (See PERCENT).
If this value is MAXDN then the following defaults are
evaluated:
ACTIVITY = (MAXDN-OFFSET)/7
DNTHRESH = (MAXDN-OFFSET)/7+OFFSET
BELOW = (MAXDN-OFFSET)/7+OFFSET
Parameters override all defaults and auto values.
For the case of halfword pictures, DN
values above 14000 will be truncated to 14000.
This parameter is a user-supplied estimate of the fraction of the target body that is contained in the image. It is only used in the AUTO algorithm (see parameter AUTO), in estimating the lowest DN on the planet. Its most reliable usage is when the entire planet is in view, in which case the user would specify FRACTION=1.0 in order to enable this algorithm. (Estimating the fraction of a partially covered target body may lead to erroneous results, and should be done with care.) Note that the default value of 0.0 does NOT mean that by default the target body is 100% off the image, but merely serves to disable this algorithm: by default, the AUTO algorithm will not attempt to take account of the size of the target body in the image.
INTEGER _ Specified when a Dark Current OFFSET has been added to the picture. The offset is used only in computing the new ACTIVITY value in the AUTO mode. Default is OFFSET = 0.
REAL - The PERCENTage to bypass at the top of the histogram for AUTO. Default is 0.20. NOTE PERCENT is ignored if AUTO is not specified.
INTEGER - The interval between lines to be read for computing the AUTO histogram. Default is 5. LINC is ignored if AUTO is not specified.
2 INTEGERS - (C1,C2) - The half-width of a box in pixels (C1) and the minimum number of limb points to be contained within the box(C2). For each candidate limb point, a check is made of the number of other points lying within a box of dimension 2*C1 pixels centered at the point. If the number is less than C2, the point in question is rejected from the set of possible limb points. Rejected points do not appear as white on the points display data set of FARENC. Default is C1 = 30, C2 = 24. ( C1 > C2)
4 INTEGERS - (Starting-Line, Starting-Sample, Number-of-Lines, Number-of-Samples) - The search for candidate limb points will only be performed within the specified area. Default is to search the entire image. Points located will be with respect to L=1, S=1.
ODD INTEGER - The filter width. If specified , each picture line will be low pass filtered. The median filter has the advantage of passing unchanged all samples which are monotonic within MEDIAN pixels Default is to perform no filtering.
KEYWORD - ('LCIRCLE) - Causes the candidate limb points to be
selected from the extremum ends of each row and column, i.e., the
furthest left and right on the line and the furthest top and bottom
on the column. LCIRCLE is to be used with RING.
REAL - One pass is made through the initial set of potential limb points in order to reject all values of activity which deviate from the mean activity by more than SIGACT activity. Default is SIGACT = 2.5.
REAL - In order to eliminate spurious points the program will iterate, each time rejecting points which give an error in radius from the last least squares fit of a circle by more than +/-SIGMA * sigma where sigma is the standard deviation of all the errors. The process ceases when all points lie within +/- TOLERANCE. Default is SIGMA = 1.70.
REAL - A final solution for the target body center and radius requires all points on the limb must lie within +/-TOLERANCE of a least square radi (see operation) Default is TOLERANCE = 1.0.
REAL - The direction of the sun in degrees measured about the target body center clockwise from up. If SEDR is available SUNANGLE will be computed automatically. SUNANGLE allows FARENC to reject terminator points for low phase angles.
KEYWORD - ('PRINT) - Causes a listing of line, sample and radial
error of all points which were used to compute the target body center.
INTEGER - The maximum number at points on any video line which can be usd in the line fit . This eliminates the use of a bad line in the fit. Default is MAXNUM = 10.
REAL - Specifies the ratio of the desired target body diameter (major axis) in pixels to the smallest picture dimension (obtained from the size field). RESCALE provides a magnification effect if GEOM is also specified. Default is no magnification. NOTE: if rescale > 1 the planet will exceed the picture size !
KEYWORD - Specifies that the SPICE kernel/SEDR data will be updated.
REAL - Specifies the rotation angle ( in degrees ) of the minor
axis of the ellipse measured clockwise from up about the ellipse
center.
Or the north angle of the projected spin axis of the target body
into the picture measured clockwise from up about the target body
center in degrees.
REAL - Specifies the rotation angle ( in degrees ) of the minor
axis of the ellipse measured clockwise from up about the ellipse
center.
Or the north angle of the projected spin axis of the target body
into the picture measured clockwise from up about the target body
center in degrees.
REAL - Specifies the semimajor axis of the ellipse in the picture in pixels.
REAL - The semiminor axis of the ellipse in the picture in pixels.
REAL - The camera focal length in millimeters.
REAL - The camera focal length in millimeters.
REAL - The scale in pixels/mm. of the picture.
REAL - The number of pixels per millimeter in the camera focal plane.
REAL - The polar and equatorial radius of the target body in kilometers
REAL - The target body equatorial radius in kilometers.
REAL - The target body polar radius in kilometers.
REAL - The distance between the target body center and the spacecraft measured in kilometers. Default is -400.
REAL - The distance between the target body center and the spacecraft measured in kilometers. Default is -400.
REAL - the geocentric latitude of the subspacecraft point in degrees.
REAL - the geocentric latitude of the subspacecraft point in degrees.
REAL - The radius of Saturn's ring (km). If RING is specified, REQUATOR and RPOLAR are unnecessary. This causes a fit to be made to the ring rather than to the target body. (see LCIRCLE)
REAL - The geocentric longitude of the subspacecraft point in degrees.
2 REALS - (Solar-Latitude, Solar-Longitude) - Subsolar latitude and longitude.
KEYWORD - This parameter selects the name of a solar system object.
Specification of any of these keywords sets the polar and
equatorial radii to the values currently stored in the Vicar
subroutine GETPLACON. (The values returned are in km.)
The program default values indicating "no data available" are:
Polar radius = Equatorial radius = -400.0 km.
Percentage of the initial limb candidate points required to fall within 1 pixel of the limb fit function (circle or ellipse). Only used in the 'NEW mode of FARENC (as opposed to 'OLD mode). If this condition fails then the program reduces the percentage by 10 percent and tries the fit all over again. Eventually the percentage may get down from BEGIN to 10 percent, the lowest permitted percentage. If there still is no solution the solution for the smallest residual is returned. Defaults to 80 percent.
FDS=integer overrides the FDS number in the input image label.
SERNO=integer overrides the camera serial number in the input image label.
CENTER=(line,sample) causes the center of the target in the output image to be set to the specified coordinates. The default is to put the center at the center of the output image.
PUTNORTH=(real) causes the pole of the target body in the output image to be rotated to the PUTNORTH position. The coordinates are clockwise from up. The pole must be positioned such that the total rotation is < 45 degrees PUTNORTH=0. puts the pole vertical in the output image.
Ex: TARGET=GANYMEDE specifies that GANYMEDE is the target in the input image. The TARGET may be a planet, satellite, or asteroid. A complete list of valid target names is located in the ASCII file assigned the logical name (or environmental variable) BODY_IDS. If defaulted, the target is retrieved from the VICAR label or other TBD means.
SPICEMODE=LOCAL specifies that SPICE data is to be accessed from local SPICE kernels. SPICEMODE=REMOTE specifies that SPICE data is to be accessed via the SPICE server. If SPICEMODE is defaulted, the logical name (or environmental variable) DEFAULTSPICE is used to determine whether LOCAL or REMOTE is used. Note that if SPICE data is not found in LOCAL or REMOTE mode, the other mode is attempted in order to retrieve SPICE data. However, when improved camera pointing data is stored, only the specified or default mode is used.
CKNAME is a four character string specifying the C-kernel to be used in reading camera pointing data: CKNAME C KERNEL -------- ------------- DAVI MIPS_DAVI.CK NAV MIPS_NAV.CK FARE MIPS_FARENC.CK NAV2 MIPS_NAV2.CK NEAR MIPS_NEAR.CK AMOS MIPS_AMOS.CK NAIF the best NAIF kernel is used If defaulted, the kernels are searched in the above order.
CKID is an alternative way to specify the prefered C-kernel for reading
camera pointing data (see CKNAME parameter):
CKID CKNAME C KERNEL
---- -------- -------------
M906 DAVI MIPS_DAVI.CK
M905 NAV MIPS_NAV.CK
M904 FARE MIPS_FARENC.CK
M903 NAV2 MIPS_NAV2.CK
M902 NEAR MIPS_NEAR.CK
M901 AMOS MIPS_AMOS.CK
varies NAIF there are a large number of these files
Ex: CKID=M901 specifies the four character ID which uniquely identifies the
C-kernel MIPS_AMOS.CK.
A complete list of the C-kernel IDs is located in the ASCII file assigned the
logical name (or environmental variable) KERNELDB.
If specified, CKID overrides the CKNAME parameter.
INSTITUTE is a four character string identifying the facility which creates
the improved (C-Smithed) camera pointing. If defaulted, the value of the
logical name (or environmental variable) VICAR_SITE is used.
Ex: INSTITUTE=ASU identifies ASU as the creator of the improved camera
pointing.
PURPOSE is a four character string identifying the purpose of the observation or the purpose of processing. For example, PURPOSE=MOSA identifies the image as part of a mosaic sequence PURPOSE=COLO identifies the image as part of a color sequence
REQUNUM is a four character string identifying the IPL request number for which the camera pointing was created. REQNUM must contain exactly 4 digits. Ex: REQNUM=0123 identifies (somewhat) request number R000123
Date and time the camera pointing was created in the form 'YEARMMDDHHMM'.
The date string must contain exactly 12 digits.
Ex: CDATE=199602291200 specifies that the pointing was created at noon
on February 29, 1996.
If defaulted, the current date and time is used.
GROUPID is a three character string which identifies the group of the user running this program to store improved camera pointing. (The user ID is automatically determined by the program). Ex: GROUPID=040 identifies group 040 as the creator of the camera pointing. On VMS, this parameter is ignored since the program automatically determines the group ID of the current user. If GROUPID is defaulted on Unix, the program uses the value of the environmental variable GROUPID. Note that GROUPID is not a system-defined variable, and should be defined in your .cshrc as in the following example: Ex: setenv GROUPID 040
NAME--OPTIONAL Specifies the name of a TCL variable to contain the derived planet center line.
NAME--OPTIONAL Specifies the name of a TCL variable to contain the derived planet center sample.