Way of a Satellite

The earth's first man-made satellite is nearing the end of the planning stage. Last week the National Academy of Sciences released information about the small, short-lived artificial moon that will be shot into an orbit during the International Geophysical Year (1957-58). The launching vehicle will be a three-stage rocket. The first stage, whose rocket motor will have 27,000 lbs. of thrust, will take off from the Air Force's missile test base at Cape Canaveral, Fla. About two minutes after takeoff, it will have traveled about 40 miles, and will be traveling 3,000 to 4,000 m.p.h. Then the second rocket stage will take over, reaching 11,000 m.p.h. at about 130 miles altitude. When it has risen 300 miles, the final rocket will fire, raising the satellite to "orbiting" speed of 18,000 m.p.h.

The orbit selected for the satellite is 40DEG from the equator, and the rocket will be fired toward the southeast to take advantage of the earth's rotation. Instead of following a true circle, which would keep it at a single level in the earth's high atmosphere, the satellite will move in an ellipse (oval), rising to 800 miles altitude, then descending to 200 miles. It will pass around the earth every 90 minutes, and since the earth will be turning beneath it, the satellite will pass over different areas during each circuit. It will eventually cover all parts of the earth between 40DEG north and 40DEG south (see map).

The satellite itself will be a sphere about 30 in. in diameter weighing approximately 21.5 Ibs., half of which will be instruments for reporting by radio to the earth below. Observations to be attempted with the first satellite:

P:Air density. The satellite's rate of slowdown and change of orbit will yield information about the high atmosphere.

P: Temperature. Instruments will report on the sun's heating effect and about heat and light coming up from the earth.

P:Crust of the earth. Variations in the earth's gravitational pull will distort the orbit slightly. Thus irregularities in the earth's crust and the slight bulge at the earth's equator can be determined more accurately.

P: Internal pressure. The satellite will contain a gas whose pressure will indicate leakage. If the skin is punctured by a meteorite, the gas will register shock waves and a quick loss of pressure.

P:Micrometeorites. Very small meteoritic particles will not puncture the skin, but impact detectors will report when they hit and will give an idea of their size and speed.

P: Ultraviolet. Most of the sun's ultraviolet radiation does not pass through the atmosphere, but the satellite can measure it in space.

P: Cosmic rays. The satellite can observe cosmic-ray particles before they hit the atmosphere, which destroys them or changes their energy.

Organized amateur astronomers will be called on to track the satellite with binoculars or modest telescopes during its first revolutions, which will not be exactly predictable. When it settles down in its orbit, the professionals will take over. Eventually, the satellite will be slowed by air drag, will swing lower and lower, meeting more air and more drag. At last will come the wild moment when it plunges back into the atmosphere and turns into a streak of fire. As this stage approaches, the amateur satellite-watchers will be needed again. The orbit will be changing too fast for the professionals to follow it.

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