Mariner 10 [NASA]

Mariner 10 was the seventh successful launch in the Mariner series and the firstspacecraft to use the gravitational pull of one planet (Venus) to reach another (Mercury).The spacecraft flew by Mercury three times in a heliocentric orbit and returned images anddata on the planet. Mariner 10 is the only spacecraft to have visited Mercury.

The spacecraft structure was an eight-sided framework with eight electronicscompartments. It measured 1.39 m diagonally and 0.457 m in depth. Two solar panels, each2.7 m long and 0.97 m wide, were attached at the top, supporting 5.1 sq m of solar cellarea. The rocket engine was liquid-fueled, with two sets of reaction jets used tostabilize 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 55cm. Feeds enabled the spacecraft to transmit at S- and X-band frequencies. The spacecraftcarried a Canopus star tracker, located on the upper ring structure of the octagonalsatellite, and acquisition sun sensors on the tips of the solar panels. The interior ofthe spacecraft was insulated with multilayer thermal blankets at top and bottom. Asunshade was deployed after launch to protect the spacecraft on the solar-oriented side.

Instruments on-board the spacecraft measured the atmospheric, surface, and physicalcharacteristics of Mercury and Venus. Experiments included television photography,magnetic field, plasma, infrared radiometry, ultraviolet spectroscopy, and radio sciencedetectors. An experimental X-band, high-frequency transmitter was flown for the first timeon this spacecraft.

Mariner 10 was placed in a parking orbit after launch for approximately 25 minutes,then placed in orbit around the Sun en route to Venus. The orbit direction was opposite tothe motion of the Earth around the Sun. Mid-course corrections were made. The spacecraftpassed Venus on 5 February 1974, at a distance of 4200 km. It crossed the orbit ofMercury on 29 March 1974, at 2046 UT, at a distance of about 704 km from the surface. TheTV and UV experiments were turned on the comet Kohoutek while the spacecraft was on theway to Venus. A second encounter with Mercury, when more photographs were taken, occurredon 21 September 1974, at an altitude of about 47,000 km. A third and last Mercuryencounter at an altitude of 327 km, with additional photography of about 300 photographsand magnetic field measurements occurred on 16 March 1975. Engineering tests werecontinued until 24 March 1975, when the supply of attitude-control gas was depleted andthe mission was terminated.

Total research, development, launch, and support costs for the Mariner series ofspacecraft (Mariners 1 through 10) was approximately $554 million.

A back-up probe named Mariner-K was built and stood ready on a "borrowed"Atlas Centaur launch vehicle, in case the Mariner 10 launch failed. This probe was laterdonated to the Smithsonian and the launch vehicle was used for its original purpose.

References:

• NSSDC Master Catalog:Mariner 10

• Mariner 1, 2
• Mariner 3, 4
• Mariner 5
• Mariner 6, 7
• Mariner 8, 9
• Mariner 10
• Mariner Jupiter/Saturn A, B

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