Status: Operational 1973. First Launch: 1973-11-03. Last Launch: 1973-11-03. Number: 1 . Gross mass: 526 kg (1,159 lb).
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 3 November 1973. Mariner 10 took some 4,000 photos of Venus, which revealed a nearly round planet enveloped in smooth cloud layers. The Venus flyby deflected Mariner 10's trajectory towards Mercury , which it flew past at 756 km altitude on 29 March 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's solar orbit permitted two more rendezvous with Mercury. On 21 September 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 16 March 1975, and yielded primarily fields and particles data. The vehicle was turned off on 24 March 1975 after its onboard fuel was depleted. Total mission cost was $100 million.
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 maximum and recharged NiCd batteries (20 AHr). Instruments on board the spacecraft measured the atmospheric, surface, and physical characteristics of Mercury and Venus. These included cameras, a magnetometer, a plasma science experiment, a charged particle telescope, an ultraviolet spectrometer, and an infrared radiometer.
NASA NSSDC Master Catalog Description
Mariner 10 was the seventh successful launch in the Mariner series and the first spacecraft to visit Mercury. It was also 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. 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.
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/s. 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.
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 instruments, 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.
A trajectory correction maneuver was made 10 days after launch. Immediately following this maneuver 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 necessitate 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 05 February 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.
En route 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 29 March 1974, at 20:46 UT, at a distance of about 704 km from the surface. A second encounter with Mercury, when more photographs were taken, occurred on 21 September 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 16 March 1975. Engineering tests were continued until 24 March 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.
Credit: Manufacturer Image
An Atlas/Agena D launched Mariner 10 (Mariner Venus-Mercury) from the Eastern Test Range. The spacecraft was scheduled for Venus f lyby in February 1974 and Mercury in March 1974 - it would be the first space probe ever to approach Mercury. Mariner 10 was the first spacecraft to reach Mercury. Mariner 10 was placed in a parking orbit for 25 minutes after launch, then accelerated to a trans-Venus escape trajectory. The television and ultraviolet experiments were trained on the comet Kohoutek while the spacecraft was en route to its destination. The vehicle's first planetary encounter was with Venus on February 5, 1974, at a distance of 4200 km. Mariner 10 took 4,000 photos of Venus, which revealed a nearly round planet enveloped in smooth cloud layers. The gravity of Venus bent the orbit of the spacecraft and sent it towards Mercury. It crossed the orbit of Mercury on March 29, 1974, at 20:46 GMT, at a distance of 704 km from the surface. 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, at an altitude of about 47,000 km, provided another opportunity to photograph the sunlit side of the planet and the south polar region. The third and final Mercury encounter on March 16, 1975, at an altitude of 327 km, yielded 300 photographs and magnetic field measurements. The vehicle was turned off March 24, 1975 when the supply of attitude-control gas was depleted.