Voyager ISS Neptune Data Set Description
Index
- Data Set Overview
- Parameters
- Source Instrument Parameters
- Processing History
- Confidence Level Note
- References
Click for the original DATASET.CAT file (text format).
Data Set Overview
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
Sampling Parameter Name : PIXEL
Data Set Parameter Name : DATA NUMBER
Data Set Parameter Unit : DIMENSIONLESS
Data Number is an integer expressing the digital value of an experiment’s telemetry data.
Source Instrument Parameters
Instrument Host ID : VG2
Data Set Parameter Name : DATA NUMBER
Instrument Parameter Name : RADIANCE
Important Instrument Parameters : 1
Processing History
Source Data Set ID : FRAMSINK
Software : VIMBUILD
Product Data Set ID : UNPROCESSED DATA RECORD
Source Data Set ID : UNPROCESSED DATA RECORD
Software : MERGE
Product Data Set ID : RAW DATA RECORD
Source Data Set ID : RAW DATA RECORD
Software : EDRGEN
Product Data Set ID : VG2-N-ISS-2-EDR-V1.0
Software ‘VIMBUILD’
The functions of VIMBUILD include: 1) to receive, reconstruct, and format high rate telemetry data into ‘images’ 2) decompress data and fill edited data as required, and 3) extract and store selected spacecraft and sensor engineering data from telemetry.
Source Data Set ID : FRAMSINK
Software Name : VIMBUILD
Product Data Set ID : UNPROCESSED DATA RECORD
Software Type : N/A
Software Release Date : 1985-10-01
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : NOT ACCESSIBLE THROUGH PDS CATALOG
- CONTACT IMAGING NODE.
Software ‘MERGE’
The MERGE program creates a new Voyager image from all version of a specified image. This program is part of the VICAR system (see VICAR).
Source Data Set ID : UNPROCESSED DATA RECORD
Software Name : MERGE
Product Data Set ID : RAW DATA RECORD
Software Type : N/A
Software Release Date : 1989-09-01
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : NOT ACCESSIBLE THROUGH PDS CATALOG
- CONTACT IMAGING NODE.
Software ‘EDRGEN’
The EDRGEN program generates Voyager EDR formatted tapes. This program is a part of the VICAR system (see VICAR).
Source Data Set ID : RAW DATA RECORD
Software Name : EDRGEN
Product Data Set ID : VG1/VG2-S-ISS-2-EDR-V2.0
Software Type : N/A
Software Release Date : 1989-09-01
Node ID : IMAGING
Cognizant Engineer : SUSAN K. LAVOIE
Software Access Description : NOT ACCESSIBLE THROUGH PDS CATALOG
- CONTACT IMAGING NODE.
Confidence Level Note
This data set represents a complete collection of raw images from the Voyager 2 Neptune encounter beginning with the Observatory Phase. To make full scientific use of the image collection, it is necessary to obtain (from the Imaging Node) and understand the radiometric and geometric properties of the camera system and perform corrections to the data. Geometry and basic pointing information is included for all Image Observation Types including Calibration, Stars, and very small Satellites (or ‘Rocks’). Non primary planetary bodies, like rocks may have geometry that refers to the primary planetary body (NEPTUNE, TRITON and NEREID).
We recommend obtaining a copy of the ‘Software Interface Specification, ISS PI SEDR Processor, Rev.b, SIS 4-7008-2’, an internal JPL document available from the JPL vellum files for reference while using this data set. This document will clarify some questions which may arise when using the geometry data, particularly for non primary planetary bodies. For example; the original predict Supplemental Experiment Data Record (SEDRs) had a target for each image. Some targets have been changed as information about that particular image has been refined. However the geometry still refers to the original target from the SEDR. We suggest contacting the Imaging Node for more information, clarification or assistance.
The values for emissions and incidence angles contain errors and were received that way on the original set of SEDR tapes. We intend to update these values when the entire set of SEDR tapes are regenerated.
While using more than one Voyager data set some confusion can occur due to duplications in the Flight Data Subsystem(FDS) counts (a.k.a. spacecraft clock times). This is due first to the fact that Voyager 1 and 2 flew concurrently, so there is inter-spacecraft duplication, and second because of spacecraft clock resets and rollovers that occurred, causing duplication within data sets. Users are cautioned therefore, that the FDS count is not a unique identifier for an image. A unique query must include the spacecraft ID, the FDS count, and the target.
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 in bodark and the exposure is zero. SKY is a shuttered image, non-zero exposure looking at dark sky.
