NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

VG1/VG2 SR/UR RSS RESAMPLED RING OCCULTATION V1.0 (PDS)

NSSDCA ID: PSRI-00017

Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1980-11-01 to 1986-02-01

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

This data set contains radio occultation data obtained during the Voyager 1 Saturn encounter and the Voyager 2 Uranus encounter. Only highly processed ring occultation data is included. Ring profiles are archived in a variety of formats, from the source files as provided to the Rings Node to calibrated and resampled optical depth profiles. Processing software, geometry solutions and calibration models are also provided.

Parameters

Data files contain ring normal opacity and phase shift of the X-band (3.6 cm) and S-band (13 cm) signals as they passed through the ring plane on their transit from Voyager to Earth. Some files contain the complex transmissivity of the ring, which is based on the change in the complex field strength of the coherent radio signal due to the crossing of the ring. Specifically, it is the complex ratio of the field strength after crossing the ring to the field strength that would have been received in the absence of a ring. Complex transmissivity is related to ring opacity and phase shift as follows: tau = normal opacity phi = phase shift T_norm = exp(-tau/mu0) = amplitude of the transmissivity T_re = T_norm * cos(phi) = real component of the transmissivity T_im = T_norm * sin(phi) = imaginary component of the transmissivity Here mu0 is the cosine of the incidence angle.

Processing

These data files are already highly processed, as summarized by [MAROUFETAL1986] for Saturn and [GRESHETAL1989] for Uranus. Further processing involves conventional resampling and smoothing.

Data

A variety of data files are included on this volume. Source data (S_RINGS/SORCDATA and U_RINGS/SORCDATA directories) --------------------------------------------------------------The data files as contributed to the Rings Node by several investigators. These files are provided for documentation purposes and are not otherwise supported. Low-level data (S_RINGS/LOWDATA and U_RINGS/LOWDATA directories) ---------------------------------------------------------These files contain essentially the same data as are found in the SORCDATA directory, but in easier to use, PDS-compliant formats. They contain the material from which the Rings Node generated its derived products. Edited data (S_RINGS/EDITDATA and U_RINGS/EDITDATA directories) --------------------------------------------------------------Edited versions of the low-level data, which in this case entails conversion from opacity and phase to complex transmissivity. The latter is more appropriate for smoothing and resampling. Derived profiles (S_RINGS/EASYDATA and S_RINGS/EASYDATA dirs) ------------------------------------------------------------Easy-to-use ASCII data files containing ring opacity, phase and their uncertainty vs. radial location in a ring system. Files are included at a variety of radial resolutions. Because the rings of Uranus are narrow and inclined, there are separate profiles for each Uranian ring.

Ancillary Data

Several different types of ancillary data files are provided to describe the geometry and calibration during each occultation. Geometry models (S_RINGS/GEOMETRY, S_RINGS/GEOMETRY directories) ---------------------------------------------------------------ASCII data files, containing a description of the ring intercept geometry, indexed to locations in the corresponding edited data files. Because the rings of Uranus are inclined, there are separate geometry files for each ring of these planets. Calibration models (S_RINGS/CALIB and S_RINGS/CALIB directories) ---------------------------------------------------------------ASCII data files, containing the modeled free space signal and noise power, indexed to locations in the corresponding edited data files. Ephemeris files (SPICE directory) --------------------------------Voyager ephemeris files for each of the planetary encounters, in SPICE format. For more information about SPICE data and toolkits, consult the PDS Navigation and Ancillary Information (NAIF) Node at: http://pds.jpl.nasa.gov/naif.html

Coordinate System

All geometric quantities appearing in the labels are in J2000 coordinates. In this coordinate frame, the z-axis points northward along the Earth's J2000 rotation axis and the x-axis points toward the First Point of Aries. Some values are also provided in B1950 coordinates.

Software

Included on this disk is the source code for several libraries of software tools designed to be used with this and other ring occultation data sets. Light Label Library (SOFTWARE/OAL directory) -------------------------------------------A toolkit supported by the PDS Central Node for reading and writing PDS labels. Object Access Library (SOFTWARE/OAL directory) ---------------------------------------------A toolkit supported by the PDS Central Node for reading and writing data objects described by PDS labels. Built atop the Light Label Library. Profile Library (SOFTWARE/PROFILE directory) -------------------------------------------A toolkit supported by the PDS Rings Node for manipulating one-dimensional profiles of planetary rings. Built atop the Light Label Library and the Object Access Library. Also included are the software tools to generate calibrated ring profiles at arbitrary resolution. These are the tools used to populate the EASYDATA subdirectories. These tools make full use of the above libraries.

Media/Format

This data set is archived on compact disc (CDROM) media. Organization and formats are according to PDS and ISO 9660 level 1 standards. Binary data files are provided in native formats for most platforms. Also, note that the software tools provided on this volume handle binary conversions on the fly if this is necessary.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-rings.seti.org/holdings/volumes/VG_28xx/VG_2803/

Alternate Names

  • VG1/VG2-SR/UR-RSS-4-OCC-V1.0

Discipline

  • Planetary Science: Rings

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Mark R. ShowalterGeneral ContactSETI Institutemshowalter@seti.org
[USA.gov] NASA Logo - nasa.gov