Mariner 10
First spacecraft to visit Mercury and use gravity assist.
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Mariner 10 was an American robotic space probe launched by NASA on 3 November 1973. It was the first spacecraft to visit Mercury and the first to perform a flyby of multiple planets. It was the last spacecraft in the Mariner program.
Design and trajectory
Mariner 10 was the first mission to use a gravity assist from one planet to reach another, employing Venus to bend its flight path and lower its perihelion to Mercury's orbit. This maneuver was inspired by orbital mechanics calculations of Giuseppe Colombo. The spacecraft used solar radiation pressure on its solar panels and high-gain antenna for attitude control, the first active solar pressure control on a spacecraft. Its components were attached to an octagonal prism hub storing internal electronics.
The navigational system included a hydrazine rocket. NASA imposed a strict US$98 million budget, the first inflexible constraint on a mission, and cost control was achieved by executing contract work closer to launch than normal schedules recommended. The mission ended about US$1 million under budget.
Instruments
Mariner 10 conducted seven experiments at Venus and Mercury, six with dedicated instruments. From forty-six submissions, JPL selected seven experiments costing US$12.6 million, about one-eighth of the total budget. The imaging system consisted of two 15 cm Cassegrain telescopes feeding vidicon tubes, with an 8-position filter wheel and a wide-angle bypass. Exposures ranged from 3 ms to 12 s, with a picture every 42 s at 832 x 700 pixels, 8-bit coded.
After launch, electric heaters on the cameras failed to turn on; engineers found the vidicons could generate enough heat through normal operation to stay above -40 °C, so they advised against turning off the cameras. The heaters started working on 17 January 1974, two months after launch, due to a short circuit elsewhere. The 43.6 kg cameras consumed 67 watts, more than the other five instruments combined, and returned about 7,000 photographs.
Mission profile
Boeing finished building the spacecraft at the end of June 1973, and it was delivered to JPL for testing, then transported to the Eastern Test Range in Florida. Technicians filled a tank with 29 kg of hydrazine and attached squibs for separation. The gravity assist at Venus allowed use of an Atlas-Centaur rocket instead of a more expensive Titan IIIC. The launch period ran from 16 October to 21 November 1973; NASA chose 3 November to optimize imaging at Mercury.
On 3 November at 17:45 UTC, the Atlas-Centaur lifted off from pad SLC-36B. After the Atlas stage burned for about four minutes, the Centaur stage propelled the spacecraft to a parking orbit, then a second burn set it toward Venus. This was the first planetary mission to depend on two separate rocket burns during launch. During its first week, the camera system took five photographic mosaics of Earth and six of the Moon, including the north polar region where prior coverage was poor.
Discoveries
At Venus, Mariner 10 spotted rotating cloud formations and detected a faint magnetic field, capturing images of chevron-shaped clouds with a special ultraviolet filter. The probe made three passes by Mercury, photographing 40 to 45 percent of its cratered, Moon-like terrain in over 2,800 images.
It found Mercury has a thin helium atmosphere, a magnetic field, and a large, iron-rich core. Temperature readings showed a frigid nighttime low of -183 degrees Celsius and a scorching daytime high of 187 degrees Celsius. The data gathered was crucial for designing the later MESSENGER mission.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Mariner 10 (CC BY-SA 4.0).
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