| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This is a regeneration of the Voyager 2 images from Neptune,
in multiple versions including decompressed raw, cleaned,
calibrated and geometrically corrected forms. It has been
derived from the earlier PDS data set VG2-N-ISS-2-EDR-V1.0,
which appeared on volumes VG_0009-VG_0012.
The information covers Voyager 2 at Neptune (1989),
including the planet, its satellites and rings. Pointing
information is not included in this data set.
The data set is organized chronologically for each Voyager
encounter. Volumes VGISS_8201-8210 contain Voyager 2 images.
For each Voyager image, the following files are included:
RAW - The decompressed raw image.
RESLOC - A table of reseau locations.
GEOMA - A table of tiepoints describing the geometric
correction of the image.
CLEANED - The raw image with various spikes, blemishes and
reseau markings removed.
CALIB - The calibrated image, in which data numbers are
directly proportional to reflectivity.
GEOMED - The geometrically corrected version of the calibrated
image.
All images and binary tables are provided in VICAR format, as
defined by JPL's Multimission Instrument Processing Laboratory
(MIPL). A VICAR file begins with an ASCII header describing the
structure of the file. ASCII text versions of the binary tables
are also included.
Processing Level Id : {2, 3, 4, 6}
Software Flag : N
Processing Start Time : 2011-12-01
Processing Stop Time : 2012-02-01
Overview of the Data Set from the Original DATASET.CAT
------------------------------------------------------
This Voyager 2 Neptune data set is available on CD-ROM and
magnetic tape.
NASA's Voyager Project and the Planetary Data System (PDS) have
created an archive of planetary digital images acquired by the
twin Voyager spacecraft (Voyager 1 and Voyager 2).
This data set includes images acquired by Voyager 2 as it
passed by the planet Neptune, its' satellites and rings.
Important to note is the fact that while geometry information
and calibration files exist for all these data sets, they do
not exist in the Experiment Data Record (EDR) data set but are
available separately through the Imaging Node. Neither does
the data set include starfields, calibrations, Plasma Radio
Astronomy (PRA), or Plasma Wave Spectrometer (PWS)
image-formatted information.
The Voyager Neptune archive resides on magnetic tape in EDR
format (this format is explained in the Multimission Image
Processing Laboratory (MIPL) Real-Time Processing Subsystem
Software Design Document (1985), an internal JPL document
available from JPL vellum files) and also on three CD-ROM
volumes.
In addition to the images, supplemental information exists on
the CD-ROMs. This includes documentation providing a user with
information about the organization and contents of the disk.
Software source code is included to provide programmers with
tools to process the image files. There are browse images,
sub-sampled versions of the full-resolution images, which allow
users to rapidly view the archive collection with their
interactive display.
Finally, there are image index files containing information
about all the images stored in the archive.
The set of images on the magnetic tapes are raw; no processing
has been performed other than organizing the original telemetry
into raster-formatted files. The set of images on CD-ROM are
also raw, however they have been compressed using a Huffman
encoding algorithm.
Detail Target Clarification:
There are two targets which may prove to be confusing for the
unfamiliar user; PLAQUE and CAL LAMPS, both are used as
calibration targets. PLAQUE is an image of a flat piece of
metal illuminated by the sun. CAL LAMPS are lamps inside the
camera used for illumination.
The target DARK is a dark current image when the camera mode is
BODARK and the exposure is zero. DARK SKY and SKY are
shuttered images, non-zero exposures looking at dark sky.
SCAT_LIGHT images are used to measure how much light is
scattered in a particular direction.
Definition Clarification:
Planetodetic latitude of a point on the planet surface is the
angle between the surface normal and the equatorial plane. For
a spherical body, the latitude is incidental to the
planetocentric latitude.
The p5 point is one of 6 static points on all images. It is
the point located in the center of the image. The p1 point is
located in the top left corner, p2 top right corner, p3 bottom
left corner, p4 bottom right corner, p5 center, p6 center right
edge. If the target is not on the p5 point then that point
does not have latitude and longitude coordinates associated
with it nor does the target have a p5 point.
The spacecraft coordinate system is a coordinate system defined
by the spacecraft structure. The antenna points alone the +z
axis, the booms are along the +y and the -y axes, creating a
unique coordinate system for each spacecraft.
The Canopus coordinate system is the coordinate system defined
by one axis pointing at Canopus, one pointing at the Sun and
one pointing somewhere else.
These systems are not used for describing images or points on
images. Because our interest is in where the pixels lie, not
relative to the spacecraft or stars but relative to the
target's own system.
Processing Level Id : 2
Software Flag : N
Processing Start Time : 1988-08-01
Processing Stop Time : 1990-04-01
Parameters
==========
Data Set Parameter 'DATA NUMBER'
--------------------------------
Data Number is an integer expressing the digital value of each
pixel in an image.
Sampling Parameter Name : PIXEL
Data Set Parameter Name : DATA NUMBER
Data Set Parameter Unit : DIMENSIONLESS
Data Set Parameter 'PIXEL COORDINATE'
--------------------------------
Pixel coordinate is a real value expressing the horizontal or
vertical location in an image. Coordinates are numbered in
units of image pixels, beginning at one.
Sampling Parameter Name : PIXEL
Data Set Parameter Name : PIXEL COORDINATE
Data Set Parameter Unit : DIMENSIONLESS
Source Instrument Parameters
============================
Instrument Host ID : VG2
Data Set Parameter Name : DATA NUMBER
Instrument Parameter Name : RADIANCE
Important Instrument Parameters : 1
Processing
==========
Processing History
------------------
Source Data Set ID : VG2-N-ISS-2-EDR-V1.0
Software : VGRCDCOPY
Product Data Set ID : RAW IMAGE
Source Data Set ID : RAW IMAGE
Software : VGRFILLIN
Product Data Set ID : VGRFILLIN IMAGE
Source Data Set ID : VGRFILLIN IMAGE
Software : RESLOC
Product Data Set ID : {RESEAU TABLE, TIEPOINT TABLE}
Source Data Set ID : {VGRFILLIN IMAGE, RESEAU TABLE,
BLEMISH TABLE}
Software Name : RESSAR77
Product Data Set ID : RESSAR77 IMAGE
Source Data Set ID : RESSAR77 IMAGE
Software Name : DESPIKE
Product Data Set ID : CLEANED IMAGE
Source Data Set ID : {CLEANED IMAGE, DARK CURRENT
IMAGE, CALIBRATION MODEL}
Software Name : FICOR77
Product Data Set ID : CALIBRATED IMAGE
Source Data Set ID : {CALIBRATED IMAGE, TIEPOINT
TABLE}
Software Name : GEOMA
Product Data Set ID : GEOMETRICALLY CORRECTED IMAGE
Software 'VGRCDCOPY'
--------------------
VICAR routine VGRCDCOPY decompresses a raw, EDR image as
archived in PDS data set VG2-N-ISS-2-EDR-V1.0. It creates
the RAW version of the image with a VICAR header.
Source Data Set ID : COMPRESSED RAW IMAGE
Software Name : VGRCDCOPY
Product Data Set ID : RAW IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'VGRFILLIN'
--------------------
VICAR routine VGRCDCOPY fills in incomplete lines with the
average of the adjacent lines.
Source Data Set ID : RAW IMAGE
Software Name : VGRFILLIN
Product Data Set ID : VGRFILLIN IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'RESLOC'
-----------------
VICAR routine RESLOC locates the reseau markings within the
Voyager image.
Source Data Set ID : VGRFILLIN IMAGE
Software Name : RESLOC
Product Data Set ID : {RESEAU TABLE, TIEPOINT TABLE}
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'RESSAR77'
-------------------
VICAR routine RESSAR77 erases reseau markings and blemishes by
replacing them with an average of the adjacent images.
Source Data Set ID : {VGRFILLIN IMAGE, RESEAU TABLE,
BLEMISH TABLE}
Software Name : RESSAR77
Product Data Set ID : RESSAR77 IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'DESPIKE'
-------------------
VICAR routine DESPIKE erases spikes in the images by
replacing them with an average of the adjacent images.
Source Data Set ID : RESSAR77 IMAGE
Software Name : DESPIKE
Product Data Set ID : CLEANED IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'FICOR77'
------------------
VICAR routine FICOR77 subtracts a dark current and rescales
the image into calibrated values.
Source Data Set ID : {CLEANED IMAGE, DARK CURRENT
IMAGE, CALIBRATION MODEL}
Software Name : FICOR77
Product Data Set ID : CALIBRATED IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
Software 'GEOMA'
------------------
VICAR routine GEOMA resamples a Voyager image to remove its
intrinsic geometric distortion.
Source Data Set ID : {CALIBRATED IMAGE, TIEPOINT
TABLE}
Software Name : GEOMA
Product Data Set ID : GEOMETRICALLY CORRECTED IMAGE
Software Type : N/A
Software Release Date : UNK
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : MIPL
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