Mariner 10 - Credit: NASA. 12,192 bytes. 329 x 214 pixels.

Mariner 10 was the first mission to use the gravitational attraction of one planet to reach another, the first mission with two planetary objectives, and (to date) the only mission ever to perform up close imaging and science at Mercury. The vehicle's first planetary encounter was with Venus on November 3, 1973. Mariner 10 took some 4,000 photos of Venus, which revealed a nearly round planet enveloped in smooth cloud layers. After the Venus flyby, Mariner 10 was sent towards Mercury , which it flew past at 756 km altitude on March 29, 1974. Photographs taken during the pass revealed an intensely cratered, Moon-like surface and a faint atmosphere of mostly helium. After the first flyby, Mariner 10 entered solar orbit, which permitted two more rendezvous with Mercury. On September 21, 1974, the second Mercury rendezvous provided another opportunity to photograph the sunlit side of the planet and the south polar region. The third and final Mercury encounter occurred on March 16, 1975, and yielded primarily fields and particles data. The vehicle was turned off March 24, 1975 after its onboard fuel was depleted. Total mission cost was $100 million.

Spacecraft: The spacecraft structure was an eight-sided framework of magnesium and aluminum with eight electronics compartments. It measured 1.39 m diagonally and 0.457 m in depth. Two solar panels, each 2.7 m long and 0.97 m wide, were attached at the top, supporting 5.1 sq m of solar cell area. The rocket engine was liquid-fueled, with two sets of cold gas thrusters used to stabilize the spacecraft on three axes. It carried a low-gain omnidirectional antenna, composed of a honeycomb-disk parabolic reflector, 1.37 m in diameter, with focal length 55 cm. Feeds enabled the spacecraft to transmit at S- and X-band frequencies. An experimental X-band, high-frequency transmitter was flown for the first time on this spacecraft. The spacecraft carried a Canopus star tracker, located on the upper ring structure of the octagonal satellite, and acquisition sun sensors on the tips of the solar panels. The interior of the spacecraft was insulated with multilayer thermal blankets at top and bottom. A sunshade was deployed after launch to protect the spacecraft on the solar-oriented side. Solar panels produce 540 W max. NiCd batteries (20 AHr). Payload: Instruments on-board the spacecraft measured the atmospheric, surface, and physical characteristics of Mercury and Venus. Cameras, magnetometer, plasma science experiment, charged particle telescope, ultraviolet spectrometer, and infrared radiometer.

Total Mass: 526 kg.

The vehicle's first planetary encounter was with Venus on November 3, 1973. Mariner 10 took some 4,000 photos of Venus, which revealed a nearly round planet enveloped in smooth cloud layers.

Mariner 10 flew past Mercury at 756 km altitude. Photographs taken during the pass revealed an intensely cratered, Moon-like surface and a faint atmosphere of mostly helium.

The second Mercury rendezvous provided another opportunity to photograph the sunlit side of the planet and the south polar region.

The third and final Mercury encounter yielded primarily fields and particles data.

The vehicle was turned off after its onboard fuel was depleted.

• 2 - McDowell, Jonathan, The United Nations Registry of Space Objects, Harvard University, 1997. HTML when accessed: http://hea-www.harvard.edu/QEDT/jcm/space/un/un.html
• 6 - JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. HTML when accessed: http://msl.jpl.nasa.gov/home.html
• 296 - National Space Science Center Planetary Page, As of 19 February 1999.. HTML when accessed: http://nssdc.gsfc.nasa.gov/planetary/planetary_home.html