Mariner IV, launched two years ago today on its historic Mars photo mission, has flown more than one billion miles in space and continues to operate properly, reporting its condition to Earth three times each week.
The National Aeronautics and Space Administration said the spacecraft, now in its 730th day of flight, has been transmitting data to the Goldstone Space Communications Station in California across a distance of some 206 million miles.
At 4 p.m. Pacific Standard Time today Mariner IV will have flown 1,025,082,830 miles since it was launched from Cape Kennedy on November 28, 1964. It completed its primary mission on August 2, 1965, after transmitting to Earth 22 pictures of the Martian surface recorded July 14 when it flew within 6118 miles of the planet.
By using Goldstone's new high-precision 210-foot-diameter antenna, Mariner Project officials at the Jet Propulsion Laboratory have been able to monitor periodically many of Mariner's subsystems and its scientific instruments.
Recent data from the spacecraft, collected by the "210" and its super-sensitive radio receiver, indicated that the occurrence of an intense solar flare last September caused a slight loss in the total power capability of Mariner's solar panels. The "class three" solar storm, which raged more than a week and reached its peak on September 3-4, was detected also by NASA's Pioneer VI and VII spacecraft in orbit around the sun and Lunar Orbiter I, then revolving the moon.
Because the Mariner IV design allowed for a 20 per cent panel degradation by just such an occurrence, the power loss caused by the flare--probably less than half that allowed for--is not expected to jeopardize the continuing performance of the spacecraft. Mariner was about 116 million miles from the sun when the flare occurred.
Other information derived from analysis of the telemetry data indicates that Mariner's attitude control system has a nitrogen gas supply capable of keeping it stabilized for more than a year, and that temperatures and voltages of all systems including the scientific instruments are as expected.
Having operated continuously for more than 17,000 hours, the spacecraft is approaching 300 per cent of its 6000-hour mission design life.
Mariner IV currently is being tracked by the 210-foot antenna on a time-sharing basis with Pioneer VI which has been in solar orbit for nearly a year and also is beyond the range of the Deep Space Network's 85-foot antennas. If Mariner continues to function until June, 1967, communications with it may be stepped up. Mariner's orbit will bring it to within 30 million miles of Earth in September, 1967, when it is planned to attempt several engineering experiments in addition to receiving interplanetary science information.
The year 1967 will be one increasing solar activity. The presence of Mariner IV and Pioneers VI and VII in orbit around the sun, in addition to another Mariner enroute to Venus during the latter half of the year, will provide an unprecedented opportunity to take scientific advantage of this part of the 11-year solar cycle.
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