Commands were transmitted from Earth yesterday to two Mariner interplanetary spacecraft operating at widely-separated points in the solar system, the National Aeronautics and Space Administration reported today.
The mission of Mariner V, which flew within 2500 miles of Venus last October 19, was terminated with a command to switch the spacecraft's transmitter from a high-gain directional antenna to a low-gain all-directional antenna.
Its mission at Venus completed, Mariner V is in a solar orbit between the orbits of Venus and Mercury at a position about 74 million miles from Earth and about 60 million miles from the sun.
Ground commands also were sent to Mariner IV, which achieved the first close-up photography of Mars in 1965 and continues to operate after nearly three years in space. The spacecraft was launched November 28, 1964, and has traveled nearly 1.5 billion miles.
Mariner IV, now circling the sun between Earth and Mars, was commanded to once again take TV pictures--this time of black space-- to check out the condition of the spacecraft's camera and the ability of the data storage system to record on magnetic tape after its long exposure to the space environment.
Commands to both spacecraft originated in the Space Flight Operations Facility at the Jet Propulsion Laboratory in Pasadena, Calif., and were radioed from the Deep Space Network station at Goldstone, California.
Both Mariners will remain in solar orbit indefinitely. Mariner IV's nitrogen gas supply, which keeps the spacecraft stabilized, is expected to be depleted during the next few weeks. Reception of data will end thereafter when Mariner drifts to the point where the solar panels no longer face the sun.
It may be possible to renew the Mariner V mission next September when the directional antenna is once again pointed toward Earth.
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