Around the Moon

By orbiting the moon last April, Russia's Luna 10 achieved a first that the U.S. is striving to match. The Soviet spacecraft apparently lacked photographic equipment, and the U.S. now aims to take the lead by orbiting the moon with five picture-taking satellites in a row. Last week Lunar Orbiter 1 soared up from Cape Kennedy and successfully zeroed in on its 237,500-mile, 92-hour trip to the moon.

The orbiter's prime mission is to transmit some 350 medium-and high-resolution pictures of nine possible landing sites for U.S. astronauts near the lunar equator. It will also take an admiring look at Surveyor 1, which now sits silently on the moon's Ocean of Storms after prodigiously transmitting more than 11,000 close-up pictures last June. After dry-developing its own film, Lunar Orbiter 1 will use a light scanner one-twentieth the thickness of a human hair to send pictures back to earth for kinescope reproduction.

Groping for Gravity. Last Wednesday the orbiter's Atlas-Agena boosters lofted the 850-lb. craft into a parking orbit, where it coasted for 28 minutes while ground computers honed its next course. Then, high above the Indian Ocean, the second-stage Agena engine reignited and kicked the orbiter into its precise moon-bound path. Two antennas and four solar-power panels snapped out, giving the space craft a windmill look. Guidance sensors aligned it with the sun; some six hours later, a star tracker began hunting for Canopus. When the sensor repeatedly failed to lock onto the guidance star, ground controllers made do by using the moon instead.

By week's end, the orbiter was scheduled to reach a crucial point 550 miles away from the moon. There, plans called for firing its retrorocket for 9 1/2 minutes and cutting its speed from 6,000 m.p.h. to 2,000 m.p.h. Purpose: to let the moon's gravity capture the spacecraft and pull it into "loose lunar orbit" on an elliptical course ranging from 120 to 1,150 miles above the moon.

Pay-Dirt Passes. If all this works, the spacecraft will then be tracked for three to seven days in order to determine whatever variations exist in the moon's gravitational field. At the same time, the orbiter's systems will be checked out by transmitting pictures of the moon's previously unphotographed right edge. After the orbit has been determined, a blast from the spacecraft's 100-lb.-thrust engine is scheduled to lower it as close as 28 miles above the lunar surface. Then, zooming around the moon at a relative speed of 4,500 m.p.h. at its lowest point, the orbiter will snap its pay-dirt pictures during a week of low passes.

From launching to final picture transmission will take 35 days. At the same time, Lunar Orbiter 1 will continue its other chores--measuring radiation and detecting micrometeorites in its scouting mission for the astronauts yet to follow.

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