Surveyor I, on its 220th day on the moon since it landed in the Ocean of Storms June 1, 1966, was turned on last Friday and communicated with Earth stations for approximately twelve hours. The objective for activating the transmitters aboard the spacecraft was to obtain scientific data on the motion of the moon. Analysis over the weekend of the information obtained shows that this objective was met.
The information that can be extracted from the radio signal is the doppler effect on the radio frequency. Doppler is a change in frequency due to motion. In this case the motion of the moon in its orbit alters the radio frequency from the spacecraft. When accumulated over a period of time this data allows a refining of the moon's distance from the Earth, its position in orbit at a given time, constants of its physical and optical libration and aid in the determination of the exact location of Surveyor I on the surface of the moon.
One of the spacecraft's two transmitters was turned on by a command from the Canberra, Australia, tracking station of the Deep Space Net at 10:22, a.m., PST, Friday. Although the signal received from the spacecraft was very faint, the tracking station established a two-way lock with the spacecraft throughout the day and was successful in alternating between the two transmitters on the spacecraft. Later in the day communication with the spacecraft was transferred from the Canberra station to the Johannesburg, South Africa, tracking station. Doppler data was recorded continuously until sunset on the moon in the area of the Surveyor spacecraft, at approximately 11:22 p.m., PST.
The objective of the reawakening of the spacecraft was to obtain the doppler information and no attempt was made to activate the camera or other systems aboard the spacecraft.
Surveyor returned more than 11,000 pictures of the lunar surface during June and July last year and has been successfully reawakened in October and November of last year for short periods. It is now in its eighth lunar night.
The Surveyor project is assigned to the Jet Propulsion Laboratory by the National Aeronautics and Space Administration. The Surveyor spacecraft was designed and manufactured under contract to JPL by the Hughes Aircraft Company in Culver City, California.
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