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

Overview : This data set represents a complete collection of images from Voyager 2 Uranus encounters beginning with the Observatory Phase. The image processing history represents our best understanding of the cameras circa the early 1990's. The programs used to process the images have not been updated in any significant way since the Voyager 2 Neptune encounter in 1989. Absolute calibration is probably accurate to the level of 5-10%; relative calibration of images through the same camera and filter is better. Absolute calibration of the Voyager 2 data set is probably somewhat more accurate due to results from the subsequent Uranus and Neptune encounters. Zero values in the images are based on a dark current subtraction; these values are probably accurate to the level of a few data numbers. Comparison of reference dark current images taken close in time can be used to estimate the systematic variations.