[Magellan Spacecraft] [Adivar Crater]

Magellan Mission to Venus

The Magellan spacecraft was launched on May 4, 1989, arrived at Venus on August 10, 1990 and was inserted into a near-polar elliptical orbit with a periapsis altitude of 294 km at 9.5 deg. N. Radio contact with Magellan was lost on October 12, 1994. The primary objectives of the Magellan mission were to map the surface of Venus with a synthetic aperture radar (SAR) and to determine the topographic relief of the planet. At the completion of radar mapping 98% of the surface was imaged at resolutions better than 100 m, and many areas were imaged multiple times. The image at the top of the page shows the 30-km diametar crater Adivar, with a jet-like streak extending off to the left. The streak, which measures over 500 km in length, is probably the result of the initial crater-forming impact. (This image is from C1-MIDR 15N077;1, framelet 52, Magellan CD-ROM MG_0019.) The mission was divided up into "cycles", each cycle lasted 243 days (the time necessary for Venus to rotate once under the Magellan orbit - i.e. the time necessary for Magellan to "see" the entire surface once.) The mission proceeded as follows:

04 May 1989  -  Launch
10 Aug 1990  -  Venus orbit insertion and spacecraft checkout
15 Sep 1990  -  Cycle 1:  Radar mapping (left-looking)
15 May 1991  -  Cycle 2:  Radar mapping (right-looking)
15 Jan 1992  -  Cycle 3:  Radar mapping (left-looking)
14 Sep 1992  -  Cycle 4:  Gravity data acquisition
24 May 1993  -  Aerobraking to circular orbit
03 Aug 1993  -  Cycle 5:  Gravity data acquisition
30 Aug 1994  -  Windmill experiment
12 Oct 1994  -  Termination experiment - loss of signal
13 Oct 1994  -  Presumed loss of spacecraft

More detailed information about the cycles is available. A total of 4225 usable SAR imaging orbits was obtained by Magellan. Each orbit typically covered an area 20 km wide by 17,000 km long, at a resolution of 75 m/pixel. This raw SAR data was processed into image strips called full-resolution basic image data records (F-BIDRs). Adjacent F-BIDRs were then assembled into full-resolution mosaicked image data records (F-MIDRs). These images were then compressed once (by a factor of 3), twice (9), or 3 times (27), to give C1-, C2-, and C3-MIDRs. The MIDRs are available on the Magellan MIDR CD-ROMs from NSSDCA. More details about using Magellan CD-ROM's are also available, as are answers to frequently asked questions about the CD-ROMs and MIDRs. In addition, a CD-ROM Browser is available courtesy of the PDS Microwave Subnode. Other data was also collected by Magellan and is available at the NSSDCA. Altimetry and radiometry composite data records (ARCDR) are available on the ARCDR CD-ROMs. Magellan also collected radar emissivity, radar reflectivity, slope, and topographic data, available on the GxDR CD-ROMs, and gravity and radio occultation data. The USGS has also produced a set of full-resolution mosaics called FMAPs. All the Magellan CD-ROMs mentioned above have been produced under the auspices of the Planetary Data System, and have PDS formats and labels. Below is shown a global map of radar reflectance.

[global reflectance map] The Magellan mission scientific objectives were to study land forms and tectonics, impact processes, erosion, deposition, chemical processes, and model the interior of Venus. Magellan showed us an Earth-sized planet with no evidence of Earth-like plate tectonics. At least 85% of the surface is covered with volcanic flows, the remainder by highly deformed mountain belts. Even with the high surface temperature (475 C) and high atmospheric pressure (92 bars), the complete lack of water makes erosion a negligibly slow process, and surface features can persist for hundreds of millions of years. Some surface modification in the form of wind streaks was observed. Over 80% of Venus lies within 1 km of the mean radius of 6051.84 km. The mean surface age is estimated to be about 500 My. A major unanswered question concerns whether the entire surface was covered in a series of large events 500 My ago, or if it has been covered slowly over time. The gravity field of Venus is highly correlated with the surface topography, which indicates the mechanism of topographic support is unlike the Earth, and may be controlled by processes deep in the interior. Details of the global tectonics on Venus are still unresolved.
[Petal Volcano]

Shown here is a section of a Magellan radar image of a 40 x 60 km "petal" type volcano in eastern Aphrodite Terra, centered at 7.5 S, 200.5. This image is taken from F-MIDR 10S200, framelets 6 and 7, CD-ROM MG_0027. Clicking on the image will give the full-resolution view as it appears on the F-MIDR.
[Magellan Spacecraft]

Other views of Venus are available at the NSSDCA Image Catalog and Photo Gallery.

Detailed Information on the Mission - NSSDCA Master Catalog

Magellan CD-ROMs at NSSDCA

Venus FMAPs - Full resolution Venus mosaics
F-MIDRs and C-MIDRs - Full resolution and compressed Venus images
ARCDRs - Altimetry and radiometry data
GxDRs - Global topography, slope, emissivity, and reflectivity maps
Pre-Magellan - Earth-based radar images of Mercury, Venus, Moon, and Mars.
LOSAPDR - Magellan line-of-sight gravity data
Using Magellan CD-ROM's
LOSAPDR - On-line at the PDS Geosciences Subnode
Magellan Online CD-ROMs - PDS Geosciences Node

Magellan Online Books

The Venus Geologic Mappers Handbook - mapping the surface from Magellan radar
Guide to Magellan Image Interpretation - information on the radar images
Magellan: The Unveiling of Venus - overview of mission plans

Magellan Data Available at NSSDCA
Magellan Fact Sheet
Venus Fact Sheet
Frequently Asked Questions on Venus Data
Magellan Related Resources on WWW
Magellan Images of Venus

Other Venus-related resources
NSSDCA Planetary page

Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771

NASA Official: Dave Williams, david.r.williams@nasa.gov
Last Updated: 28 February 2005, DRW