Magellan Fact Sheet

A global view of Venus made from a mosaic of radar images from the Magellan spacecraft. This computer-generated globe shows the planet from above the equator at 90 degrees longitude. It shows the coverage of Venus during Magellan's highly successful first mapping cycle, completed in 1991. Magellan continued to gather data until October, 1994.

Mission Summary

The Magellan spacecraft, named after the sixteenth-century Portuguese-born explorer whose expedition first circumnavigated the Earth, was launched May 4, 1989, and arrived at Venus on August 10, 1990. Magellan's solid rocket motor placed it into a near-polar elliptical orbit around the planet. During the first 8-month mapping cycle around Venus, Magellan collected radar images of 84 percent of the planet's surface, with resolution 10 times better than that of the earlier Soviet Venera 15 and 16 missions. Altimetry and radiometry measurements were also made, yielding information about the surface topography and electrical characteristics.

During the extended mission, two further mapping cycles from May 15, 1991 to September 14, 1992 brought mapping coverage to 98% of the planet, with a resolution of approximately 100m.

Precision radio tracking of the spacecraft measured Venus' gravitational field to show the planet's internal mass distribution and the forces which have created the surface features. An aerobraking maneuver circularized the orbit to improve gravity measurements. Magellan's data will permit the first global geological understanding of Venus, the planet most like Earth in our solar system.

For more information on the mission see below and also go to the Magellan Home Page.

A map of the Venus free-air gravity anomaly constructed from data received during cycles 4 and 5.

Venus

Distance from Sun: 1.1 x 10^8 km
Orbit Period: 225 Earth days
Radius: 6052 km
Rotational Period (sidereal): 243 Earth days 
Average Density: 5.2 g/cm3
Surface Gravity: 0.907 times that of Earth (8.87 m/s2)
Surface Temperature: 850 F (730 K)
Surface Atmospheric Pressure: 90 times that of Earth (90 +- 2 bar)
Atmospheric Composition: Carbon dioxide (96%); nitrogen (3+%); trace 
                         amounts of sulfur dioxide, water vapor, carbon 
                         monoxide, argon, helium, neon, hydrogen chloride, 
                         hydrogen fluoride

Major Mission Characteristics

Interplanetary Cruise: May 4, 1989, to August 10, 1990
First Mapping Cycle: September 15, 1990 to September 15, 1991
Orbit Period: 3.25 hours
Orbit Inclination: 86 degrees
Radar Mapping Per Orbit: 37.2 minutes
Planetary Coverage: 98%
Extended Mission: September 15, 1991
Cycle 2: Image the south pole region and gaps from Cycle 1
Cycle 3: Fill remaining gaps and collect stereo imagery
Cycle 4: Measure Venus' gravitational field
Cycle 5: Aerobraking to circular orbit and global gravity measurements
Cycle 6: Global gravity measurements
Windmill experiment
End of Mission - atmospheric entry 12-13 Oct 1994

Mission Objectives

Obtain near-global radar images of Venus' surface, with resolution equivalent to optical imaging of 1 km per line pair.
Obtain a near-global topographic map with 50km spatial and 100m vertical resolution.
Obtain near-global gravity field data with 700km resolution and 2-3 milligals accuracy.
Develop an understanding of the geological structure of the planet, including its density distribution and dynamics.

Magellan Team

NASA/Solar System Exploration Division

Elizabeth E. Beyer, Program Manager
Joseph M. Boyce, Program Scientist
David J. Okerson, Program Engineer

JPL

Douglas G. Griffith, Project Manager
R. Stephen Saunders, Project Scientist

Principal Investigators

Radar: Gordon Pettengill (MIT)
Gravity: William Sjogren (JPL), Georges Balmino (France)

System Contractors

Spacecraft: Martin Marietta/Denver, F. McKinney, Manager
Radar: Hughes Aircraft, B. Dagarin, Manager

Key Spacecraft Characteristics

Single radar instrument operates simultaneously (by interleaving) in Synthetic Aperture Radar (SAR), altimeter, and radiometer modes.
High Gain Antenna (3.7m diameter) is used as both the radar and telecommunications antenna.
X-band downlink data rate of 268.8 or 115 kbps.
Coherent X- and S-band radio subsystem used for gravity field measurement by precision tracking of the spacecraft's orbit.
Spacecraft on-orbit dry mass of 1035 kg.
Monopropellant hydrazine thruster system (0.9 to 445N thrust).
Powered by solar panels with rechargeable batteries.
Three orthogonal electrically powered reaction wheels used for spacecraft pointing control.

Key Radar Characteristics

Synthetic Aperture Radar (SAR)
- Frequency: 2.385 GHz
- Peak Power: 325 W
- Pulse Length: 26.5 microsec
- PRF: 4400-5800 Hz
- Swath Width: 25 km (variable)
- Data Acquisition Rate: 806 kbps
- Downlink Quantization: 2 bits
Operates in SAR, altimeter, and radiometer modes
- SAR Resolution: 150m range/150m azimuth
- Altimeter Resolution: 30m
- Radiometer Accuracy: 2 degree C

Magellan image of a volcano known as the 'tick'. The outer rim of this feature is about 30 km in diameter. The volcano is northeast of Alpha Regio at 18.5 S, 5.6 E. Image taken from F-MIDR 20S003 on CD-ROM MG_0006

Key Scientific Results

Study of the Magellan high-resolution global images is providing evidence to understand the role of impacts, volcanism, and tectonism in the formation of Venusian surface structures.

The surface of Venus is mostly covered by volcanic materials. Volcanic surface features, such as vast lava plains, fields of small lava domes, and large shield volcanoes are common.

There are few impact craters on Venus, suggesting that the surface is, in general, geologically young - less than 800 million years old.

The presence of lava channels over 6,000 kilometers long suggests river-like flows of extremely low-viscosity lava that probably erupted at a high rate.

Large pancake-shaped volcanic domes suggest the presence of a type of lava produced by extensive evolution of crustal rocks.

The typical signs of terrestrial plate tectonics - continental drift and basin floor spreading - are not in evidence on Venus. The planet's tectonics is dominated by a system of global rift zones and numerous broad, low domical structures called coronae, produced by the upwelling and subsidence of magma from the mantle.

Although Venus has a dense atmosphere, the surface reveals no evidence of substantial wind erosion, and only evidence of limited wind transport of dust and sand. This contrasts with Mars, where there is a thin atmosphere, but substantial evidence of wind erosion and transport of dust and sand.

Magellan radar image of the "crater farm", showing the craters (clockwise from top left) Danilova, Aglaonice, and Saskia centered at 27 S, 339 E. Aglaonice is 65 km in diameter. This image is from C1-MIDR 30S333, CD-ROM MG_0002.

For More Information on Data

Detailed catalog information is available to researchers funded by NASA's Solar System Exploration Division through the Planetary Data System, Geosciences Node , Earth and Planetary Remote Sensing Laboratory, Washington University St. Louis, MO 63130-4899, (314) 935-5493, Fax: (314) 935-7361

Three-dimensional view of the "crater farm" (see above) created using Magellan radar images and alimetry data. Saskia is in the foreground. This image is part of a "flyover" sequence available on videotape.

Photographic imagery, CD-ROMs, and videotapes are available for browsing at NASA's 15 Regional Planetary Image Facilities.

Magellan Home Page

Other Venus-related resources

NSSDCA Planetary Home Page

Original html mark-up: Syed S. Towheed, November, 1993
Original text provided by David Okerson, Magellan Program Engineer

Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258