The Mariner IV spacecraft last night was buffeted about in interplanetary space between the orbits of Earth and Mars when it apparently crossed the path of a stream of micrometeoroids.
The 575-pound spacecraft, which was launched in November, 1964, and photographed Mars in July, 1965, was pelted with at least 17 pieces of meteoric matter during a seven-minute period beginning at 7:54 p.m. Pacific Daylight Time.
Numerous other bits could have occurred, project officials pointed out, in addition to those observed acoustically by the microphone portion of Mariner IV's cosmic dust detector.
The spacecraft apparently was not damaged by the encounter with the interplanetary debris. Mariner responded to a routine command which was being prepared before the hits occurred and was transmitted when the disturbance ended. No loss of power from the solar panels was noted, and the on-board attitude control system was able to stabilize the rocking motion of the spacecraft.
Other data received in the Mariner command center at the Jet Propulsion Laboratory during the meteor shower included:
...Unusual brightness observed by the spacecraft's Canopus sensor indicating the sensor may have been following light reflected from micrometeorites or hair-thin particles knocked loose from Mariner during one or more hits.
...A slight drop in the level of Mariner IV's radio signal received at the Deep Space Network station at Goldstone, Calif., at 8 p.m. -- the instant that a cluster of five hits was recorded.
...A disturbance in the pitch and yaw axes of the spacecraft which required nearly an hour for the attitude control system to overcome by firing spurts of nitrogen gas.
...A slight drop in spacecraft temperatures -- about one degree -- appeared in the telemetry during the same time frame indicating Mariner's thermal shield may have been altered by minute particles.
When the disturbance occurred, Mariner IV was about 29.6 million miles from Earth and had completed nearly 1.4 billion miles of flight in 1020 days since launch.
During the past few months, Mariner IV has been tracked in a combined operations effort with its sister ship, Mariner V, now enroute to a flyby of the planet Venus next October 19.
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