Venus

Pioneer Venus

1. Does NSSDC have PVO data on CD-ROM?

Some preliminary gravity and radar data were archived on the Pre-Magellan CD-ROM to support Magellan activities, but complete sets of these data on CD-ROM have not yet been produced.
Data on CD-ROM from some of the particles and fields experiments on the Pioneer Venus Orbiter are currently being produced by the Planetary Data System's Planetary Plasma Interactions (PPI) node. The first set of CD-ROMs contains 24 s and high-resolution data from the magnetometer (OMAG) and electric field detector (OEFD) experiments on the orbiter as well as ephemeris data. Once this set is completed (about 55-60 volumes), other fields and particles experiments will begin to arrive on separate CD-ROM series.
More information on CD-ROMs available from the NSSDC can be found in the NSSDC CD-ROM Catalog.URL: http://nssdc.gsfc.nasa.gov/cd-rom/

2. Does NSSDC have digital image models (DIMs) of Venus?

Yes, in the form of the Magellan C3-MIDRs. These are sinusoidal equal area projections of compressed Magellan radar images, and are available on the Magellan CD-ROMs (NSSDC Data Set PSPG-00175). More information on these DIMs and DIMs of other planets and satellites is available on the Digital Image Models Page.URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Magellan

1. What is meant by "Cycle 1" data?

The Magellan project for convenience divided up the observing periods for Magellan delineated by the time it took the orbiter to cover 360 degrees of longitude. This time is equal to the sidereal day of Venus, ~243 Earth days, or roughly eight months. Magellan arrived at Venus in mid-August 1990 and, due to normal spacecraft and instrument checkout activities as well as initial problems with communications, cycle 1 began officially on 15 September 1990 and lasted until 15 May 1991.

2. What kind of observations were made by Magellan during the various cycles?

During the first three cycles, Magellan made primarily radar, altimeter, and radiometer observations of Venus' surface. Subsequent cycles were dedicated primarily to gravimetric observations. The orbit was circularized by aerobraking between cycles 4 and 5. Other kinds of observations (solar corona, atmospheric, etc.) were also made during some of these cycles.

3. What exactly are Magellan F-BIDRs, F-MIDRs and C-MIDRs?

Magellan raw Synthetic Aperture Radar (SAR) data is processed to create Basic Image Data Records or BIDRs. F-BIDRs are simply Full-resolution (~75 m/pixel) Basic Image Data Records, which look like long, thin strips of radar imagery, representing one pass of the Magellan spacecraft. These are difficult to use for geologic interpretation because they are only about 20 Km wide by 17,000 Km long, so a mosaic of these images is produced, a Full-resolution Mosaicked Image Data Record, or F-MIDR.
The F-MIDRs are high resolution radar "pictures" of the surface of Venus. An F-MIDR has the same resolution as the F-BIDRs (~75 m/pixel), but covers an area approximately 5 degrees on a side. (One degree on Venus is approximately 105 Km at the equator.) These F-MIDRs have been compressed (an averaging of 9 pixels down to one) to form lower resolution but larger area Compressed Mosaicked Image Data Records or C-MIDRs. Three levels of compression have been done: Compressed once (C1-MIDRs), 15 degrees on a side and 225 m resolution; Compressed twice (C2-MIDRs), 45 degrees on a side and 675 m resolution; and, Compressed thrice (C3-MIDR's), 120 by 80 degrees and 2025 m resolution.
There are also products called Polar Mosaicked Image Data Records, or P-MIDRs, which cover from 80 degrees latitude to the pole.

4. What do the numbers on the MIDRs indicate?

Each MIDR has an identification number of the form t-MIDR.xxHyyy;C, where t is the data type: F, C1, C2, or C3; xx is the approximate latitude of the center of the mosaic, H is the hemisphere (N or S); yyy is the approximate longitude of the center of the mosaic; and C gives the cycle and version number. For cycle 1, C is a one digit number giving the version number. For cycles 2 and 3, C is a three digit number, with the first digit being the cycle number and the last the version number. For example, F-MIDR.15S140;301 is a full-resolution mosaicked image data record, centered at 15 degrees south latitude and 140 degrees longitude, from the third data cycle, version 1.