Science: Cloud Satellite

Like a high-strung thoroughbred finally cured of its jitters, the much-criticized Vanguard ran a perfect race last week. Of seven earlier Vanguard firings, six had been failures, and the seventh put only a grapefruit-sized, 3.25-lb. satellite in orbit. Last week’s shot was perfect. All three stages of the 72-ft., pencil-slim rocket fired without a hitch. The satellite, which had the full design weight of 21.5 Ibs., settled into an orbit slightly higher than had been expected. Its perigee (lowest point) is 347 miles above the earth; its apogee (highest point) is 2,065 miles. Its batteries will go dead in about two weeks. But unless some future space-cleaning agency removes it as a menace to astronavigation, Vanguard II itself will probably orbit silently for at least a century.

The reason for this shining success after so many failures is buried in Washington’s jungle of bureaucracy. The firing was postponed from December to February on orders of Dr. Keith Glennan, head of the newly formed National Aeronautics and Space Administration, which took the program over from the Navy. Every detail of the launching vehicle was examined critically, but whether major changes were made is not clear. There were few changes of personnel. Long-suffering Dr. John P. Hagen, director of the Vanguard program from its beginning, remained in charge. When he reported to the House space committee on the day after the launching, a Congressman remarked: “You look about ten years younger.”

The launching crew at Cape Canaveral showed a new confidence, which spread to unofficial bird watchers. For the first time during a Vanguard launching, the newsmen did not organize a poker game to kill time during expected delays. In fact, there was only one 25-min. hold, which was due to a balky tracking instrument. The bird itself was raring to go.

Weather Scanner. Vanguard’s new satellite is probably the most sophisticated bit of spaceware to leave the ground so far. Its job is to scan a broad belt around the earth, reporting on the cloud patterns that indicate the trend of the earth’s weather. Ordinary meteorological methods keep accurate track of the weather over only 5% of the earth’s surface. Vanguard II will raise this figure toward 25%, giving hope of understanding how worldwide weather works.

The satellite, a magnesium sphere with a surface of silicon monoxide to keep it at proper temperature in sun or shadow, was put into a spin of about 50 r.p.m. The spin made it act like a gyroscope, keeping its axis always pointing in the same direction in space. At its perigee, the axis is parallel to the earth’s surface. But a quarter of a revolution later the axis points vertically at the earth (see diagram). At apogee, the axis is parallel again.

The electronic scanning apparatus, consists of two reflecting telescopes made by

Perkin Elmer Corp. of Norwalk, Conn. Each “eye” is 3 in. in diameter but weighs only 3.5 oz. The telescopes are not producing photographic images, but are capable of detecting contrasts of light (clouds are usually brighter than land, land brighter than oceans).

The two telescopes are set at 45° angles to the satellite’s spin axis. At perigee. one of them will look ahead, the other astern of the satellite’s orbital motion. Each telescope’s field is about 1.1° wide. As the satellite spins, each will scan a line seven miles wide and about 600 miles long across the earth below. With the satellite simultaneously moving forward on its orbit, successive scannings will cover a broad path, acting much like the fine horizontal lines that build up a TV picture. The ends of the 600-mile lines are pretty much distorted, so the Army Signal Corps, which put together the satellite’s instruments, plans to use only the central 300 miles in drawing its cloud-pattern pictures.

Recorder & Playback. To record what the telescopes see, the light that reaches them is concentrated on a wafer of lead sulphide which produces an electrical response proportionate to the strength of the light. A tiny recorder transfers these fluctuations to a magnetic tape 75 ft. long. The tape runs for about 50 min., is timed to cover the period when the satellite is in a favorable attitude near perigee and is over the sunlit part of the earth. When it swings into darkness, small solar batteries sense the lack of light and stop the recorder to save electric current. When the satellite reaches sunlight again on the other side of its orbit, the batteries switch the recorder on again.

A featherweight radio receiver is rigged to listen for a coded signal from the earth. When the satellite swings around to the dark side of the earth, the nearest control station triggers the receiver, which starts the tape running rapidly in reverse. In less than 60 sec. the receiver plays the cloud-pattern data into a transmitter, which radios its data to earth. Simultaneously, the receiver erases the tape and makes it ready to record another cloud picture on the satellite’s next swing through daylight.

No Bugs. Soon after launch, Dr. Hagen reported that this complicated, incredibly light but rugged apparatus was “working very fine, with no bugs so far.” Six monitoring stations in the U.S., Latin America and Australia had queried the satellite’s transmitter and got an answer. Masses of cloud-pattern data were headed for the Signal Corps laboratory at Fort Monmouth, N.J. but it may be two weeks before a crude cloud picture can be put together. Said crew-cut William G. Stroud Jr., head of the Fort Monmouth team that developed the weather eye: “We’re grinning from ear to ear.”

The Vanguard, almost derided to death, has revived.