Data were still being received during these final days and the Earth and Sun lock were still being maintained. Although the antenna hinge angle was no longer being automatically readjusted by the spacecraft, commands were sent from the Earth in an attempt to keep the antenna pointed at the Earth, even if the Earth sensor were no longer operating properly. At 2 a.m., EST, January 3, 1963, 20 days after passing Venus, Mariner finished transmitting 30 minutes of telemetry data to Johannesburg and the station shut down its operation. When Woomera’s DSIF 4 later made a normal search for the spacecraft signal, it could not be found. Goldstone also searched in vain for the spacecraft transmissions, but apparently Mariner’s voice had at last died, although the spacecraft would go into an eternal orbit around the Sun. It was estimated that Mariner’s aphelion (farthest point out) in its orbit around the Sun would occur on June 18, 1963, at a distance of 113,813,087 miles. Maximum distance from the Earth would be 98,063,599 miles on March 30, 1963; closest approach to the Earth: 25,765,717 miles on September 27, 1963. THE RECORD OF MARINER The performance record of Mariner II exceeded that of any spacecraft previously launched from Earth: —It performed the first and most distant trajectory-correcting maneuver in deep space, firing a rocket motor at the greatest distance from the Earth: 1,492,000 miles (September 4, 1962). —The spacecraft transmitted continuously for four months, sending back to the Earth some 90 million bits of information while using only 3 watts of transmitted power. —Useful telemetry measurements were made at another record distance from the Earth: 53.9 million miles (January 3, 1963). —Mariner II was the first spacecraft to operate in the immediate vicinity of another planet and return useful scientific information to the Earth: approximately 21,598 miles from Venus (December 14, 1962). —Measurements were made closest to the Sun: 65.3 million miles away (December 27, 1962). —Mariner’s communication system operated for the longest continuous period in interplanetary space: 129 days (August 27, 1962, to January 3, 1963). —Mariner achieved the longest continuous operation of a spacecraft attitude-stabilization system in space, and at a greater distance from the Earth than any previous spacecraft: 129 days (August 27, 1962, to January 3, 1963), at 53.9 million miles from the Earth. CHAPTER 6 THE TRACKING NETWORK Thirty-six million miles separated the Earth from Venus at encounter. Communicating with Mariner II and tracking it out to this distance, and beyond, represented a tremendous extension of man’s ability to probe interplanetary space. The problem involved: