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Mariner 10

By Marty McDowell/NASA

On November 3, 1973, the United States launched Mariner 10. Mariner 10, though launched after Pioneer 11, was the first craft to successfully complete multiple planetary flybys. It was also the first to encounter Mercury.

Mariner 10 was the seventh successful launch in the Mariner series, the first spacecraft to use the gravitational pull of one planet (Venus) to reach another (Mercury), and the first spacecraft mission to visit two planets. Mariner 10 was the first (and as of 2003 the only) spacecraft to visit Mercury. The spacecraft flew by Mercury three times in a retrograde heliocentric orbit and returned images and data on the planet. Mariner 10 returned the first-ever close-up images of Venus and Mercury. The primary scientific objectives of the mission were to measure Mercury's environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity-assist mission.
Spacecraft and Subsystems

The spacecraft structure was an eight-sided forger magnesium framework with eight electronics compartments. It measured 1.39 m diagonally and 0.457 m in depth. Two solar panels, each 2.69 m long and 0.97 m wide, were attached at the top, supporting 5.1 sq m of solar cell area. Fully deployed the spacecraft measured 8.0 m across the solar panels and 3.7 m from the top of the low-gain antenna to the bottom of the heat-shield. A scan platform with two degrees of freedom was mounted on the anti-sunward face. A 5.8 m long hinged magnetometer boom extended from one of the octagonal sides of the body. Total launch mass was 502.9 kg, of this 29 kg were propellant and attitude control gas. The total mass of instruments onboard was 79.4 kg.

The rocket engine was a 222-N liquid monopropellant hydrazine motor situated below a spherical propellant tank which was mounted in the center of the framework. The nozzle protruded through a sunshade. Two sets of three pairs of orthogonal reaction nitrogen gas jets, mounted on the tips of the solar panels, were used to stabilize the spacecraft on three axes. Command and control were the responsibility of an on-board computer with a 512 word memory augmented by ground commands

Mariner 10 carried a motor driven high-gain dish antenna, a 1.37 m diameter aluminum honeycomb-disk parabolic reflector, which was mounted on a boom on the side of the spacecraft. A low-gain omnidirectional antenna was mounted at the end of a 2.85 m boom extending from the anti-solar face of the spacecraft. Feeds enabled the spacecraft to transmit at S- and X-band frequencies, data could be transmitted at a maximum rate of 117.6 kilobits per second. 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. The sunshade was deployed after launch to protect the spacecraft on the solar-oriented side. Louvered sides on five of the eight electronics compartments also helped control the interior temperatures.

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

Mission Profile

Mariner 10 (also known as Mariner Venus Mercury 1973) was placed in a parking orbit after launch for approximately 25 minutes, then placed in orbit around the Sun en route to Venus. The protective cover of the sunward-facing electrostatic analyzers did not open fully after launch, and these intruments, part of the Scanning Electrostatic Analyzer and Electron Spectrometer experiment, could not be used. It was also discovered that the heaters for the television cameras had failed, so the cameras were left on to prevent low temperatures from damaging the optics.


Mariner 10, shown in this artist's rendering, was the last in a series of Mariner missions designed to survey other planets in the solar system.

Image courtesy of NASA.


A trajectory correction maneuver was made 10 days after launch. Immediately following this manuever the star-tracker locked onto a bright flake of paint which had come off the spacecraft and lost lock on the guide star Canopus. An automated safety protocol recovered Canopus, but the problem of flaking paint recurred throughout the mission. The on-board computer also experienced unscheduled resets occasionally, which would neccesitate reconfiguring the clock sequence and subsystems. Periodic problems with the high-gain antenna also occurred during the cruise. In January 1974 Mariner 10 made ultraviolet observations of Comet Kohoutek and another mid-course correction was made on 21 January. The spacecraft passed Venus on February 5, 1974, at a closest range of 5768 km at 17:01 UT and returned the first close-up images of Venus. This also marked the first time a spacecraft used a gravity assist from one planet to help it reach another.

Enroute to Mercury an attitude control anomaly occurred for the second time, using up attitude control gas. Some new procedures were used from that point on to orient the spacecraft, including Sun-line maneuvers and the use of solar wind on the solar panels to orient the spacecraft. Mariner 10 crossed the orbit of Mercury on March 29, 1974, at 2046 UT, at a distance of about 704 km from the surface. A second encounter with Mercury, when more photographs were taken, occurred on September 21, 1974, at an altitude of 48,069 km. Unfortunately the lighted hemisphere was almost the same as the first encounter, so a large portion of the planet remained unimaged. A third and last Mercury encounter at an altitude of 327 km, with additional photography of about 300 frames and magnetic field measurements occurred on March 16, 1975. Engineering tests were continued until March 24, 1975, when the supply of attitude-control gas was depleted and the mission was terminated.

Mariner 10 results showed a Hadley-type circulation existed in Venus' atmosphere and showed that Venus had at best a weak magnetic field, and the ionosphere interacted with the solar wind to form a bow shock. At Mercury, it was confirmed that Mercury had no atmosphere and a cratered, dormant Moon-like surface was shown in the images. Mercury was shown to have a small magnetic field and a relatively large iron-rich core. Total research, development, launch, and support costs for the Mariner series of spacecraft (Mariners 1 through 10) was approximately $554 million. The total cost of the Mariner 10 mission was roughly $100 million.

Source: NASA.


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Space References (Books):
Dickinson, Terence. Nightwatch: A Practical Guide to Viewing the Universe. Firefly Books, 1998.
Greene, Brian. Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. Vintage, 2000.
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Hawking, Stephen. Theory of Everything: The Origin and Fate of the Universe. New Millenium, 2002.
Hawking, Stephen. The Universe in a Nutshell. Bantam, 2001.
Kaku, Michio. Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps and the Tenth Dimension.
Kranz, Gene. Failure Is Not an Option: Mission Control from Mercury to Apollo 13 and Beyond. Berkley Pub Group, 2001.
Sagan, Carl; Druyan, Ann. Comet, Revised Edition. Ballantine, 1997
Sagan, Carl. Cosmos, Reissue Edition. Ballantine, 1993
Sagan, Carl. Pale Blue Dot: A Vision of the Human Future in Space. Ballantine, 1997

Space References (Videos):
Cosmos. PBS, 2000.
Stephen Hawking's Universe. PBS, 1997.
Hyperspace. BBC, 2002.
Life Beyond Earth PBS, 1999.
The Planets
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Understanding The Universe. A&E, 1996.



Mosaic of Mercury taken by the Mariner 10 spacecraft during its approach on March 29, 1974

Courtesy of NASA

Launched: November 3, 1973

Destination: Venus & Mercury

Arrival: February 4, 1974 & March 29, 1974


Nation: U.S.

Mission: Fly-bys

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