Magellan Fact Sheet *** Mission Summary *** The Magellan spacecraft, named after the sixteenth-century Portuguese 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 data also measured the surface topography and electrical characteristics. During subsequent cycles the map will be completed, filling gaps in coverage from the first cycle and imaging the south polar region for the first time. Precision radio tracking of the spacecraft will measure Venus' gravitational field to show the planet's internal mass distribution and the forces which have created the surface features. Magellan's data will permit the first global geological understanding of Venus, the planet most like Earth in our solar system. *** Venus *** Distance from Sun: 1.1 x 108 km Orbit Period: 225 Earth days Radius: 6051 km Rotational Period (sidereal): 243 Earth days Average Density: 5.2 g/cm3 Surface Gravity: .907 times that of Earth (8.87 m/s2) Surface Temperature: 850 F (730 K) Surface Atmospheric Pressure: 90 times that of Earth (90 q 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 May 15, 1991 Orbit Period: 3.25 hours Orbit Inclination: 86 degrees Radar Mapping Per Orbit: 37.2 minutes Planetary Coverage: 84% Extended Mission Plan: May 16, 1991 to May 15, 1993 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 *** 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 - James F. Scott, Project Manager - R. Stephen Saunders, Project Scientist - Douglas G. Griffith, Mission Directory 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 msec - 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 C Operating parameters controlled by ground command *** Key Scientific Results *** A preliminary assessment 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. *** For More Information on Data *** Photographic images, digital data (CD ROMs) and display software, and videotapes showing computer-generated flights over Venus are available to researchers, educators, and the public through the National Space Science Data Center, Goddard Space Flight Center, Mail Code 933.4, Greenbelt, MD 20771, (301) 286-6695, Fax: (301) 286-4952. 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. Photographic imagery, CD-ROMs, and videotapes are available for browsing at NASA's 15 Regional Planetary Image Facilities. For additional information, call Mary Ann Harger at the Lunar and Planetary Institute at (713) 486-2136 or -2172, Fax: (713) 486-2153. Teachers can obtain information about Magellan, including copies of the videotapes, through NASA's Teacher Resource Centers. For more information, call the Jet Propulsion Laboratory's Teacher Resource Center at (818) 354-6916, Fax: (818) 354-8080.