Science: The Second Tiros

Among the satellites so far shot into orbit, perhaps the most useful to man was Tiros I, the "weather eye," whose pictures of the earth's cloud pattern gave a valuable overall view of global weather. Last week the U.S. launched Tiros II, to improve on the work of its predecessor. The 280-lb., drum-shaped satellite, spangled with 9,260 solar cells, went into a nearly circular orbit about 400 miles above the earth. All except one of its instruments worked fine; only the wide-angle TV camera for photographing large-scale cloud cover was out of kilter.

Tiros II has two cameras. Both are water-glass size, containing midget tubes that impress electronic photographs on magnetic tape. The pictures are sent down to earth on command from stations in California and New Jersey.

The wide-angle camera was designed to cover an area about 750 miles on a side, the exact figure depending on the altitude of the satellite and the slant at which it is viewing the earth. The narrow-angle camera covers an area 75 miles on a side. Its job is to observe cloud formations in fine detail, showing individual thunderclouds and other weather minutiae.

When Tiros II went into orbit, the narrow-angle camera started right off to take good pictures, but the wide-angle camera balked. There is some chance that it will take better pictures later, or that it can be "repaired" by deft electronic twiddling from stations on earth. Even if it never does function properly, the narrow-angle camera alone will yield valuable weather information. But the scientists who interpret the cloud pictures will have to take special pains to identify the places around the earth that are covered by its Rhode Island-size snapshots.

Tiros stands for Television and Infra-Red Observation Satellite, but in Tiros I the infra-red instruments were omitted.

Tiros II has five detectors that measure different kinds of infra-red radiation coming up from the earth. They are working splendidly, and their reports will give new information about the earth's albedo (reflectivity) and about the temperature and humidity of the upper layers of the atmosphere. This sort of data is precious to meteorologists.

Tiros I misbehaved in an unexpected way. Its internal electrical circuits reacted with the earth's magnetic field and made the satellite's axis swing slowly away from the desired direction. To keep this from happening again. Tiros II has turns of aluminum wire running around its girth. On signal from the earth an electric current can be shunted through the wire. This will modify the effect of the earth's magnetism and should keep the satellite's axis pointing properly.