National Geographic : 1972 Apr
would affect you and me the following day. NOAA 1 made such a picture every 260 seconds. Each covered a square some 2,000 miles on a side, an area of four million square miles. Cloud patterns as small as two miles across could be distinguished. As the spacecraft made its orbit, the earth rotated nearly 29 degrees to the east. Thus each successive orbit, and each successive strip of photographs, was displaced west ward. Since the strips overlapped, NOAA 1 captured a progressive portrait of the globe. It scanned every spot on earth at least twice each day. Cloud Pictures Free for the Taking NOAA 1's second camera system, known as APT (Automatic Picture Transmission), did not store its pictures. Instead, the electronic signals were continuously broadcast to earth, free for anyone who wanted to pick them up. Some 550 weather stations all over the world, in 94 countries and territories, have their own APT receivers for picking up these signals and converting them to pictures. Even less advanced nations can afford them. In fact, they are so simple that in Montgomery County, Maryland, high school students put together a receiver. I always find it impressive to watch APT pictures come in. As a wide sheet of paper slides slowly from the machine, an electric needle moves rapidly back and forth, burn ing a pattern of light and dark. The needle makes 600 passes in two and a half minutes to complete each picture-each pass corre sponding to a scan made by the TV camera. The individual lines blend to form a con tinuous picture, just as on a TV screen. The original NOAA was launched December 11, 1970, and unexpectedly went dead last July. Another is scheduled to be put in orbit sometime this spring. In the interval, other weather satellites of an earlier generation have taken over NOAA 1's tasks. Two dozen older weathercraft-most of them smaller and less elaborate-keep the now-silent NOAA 1 company as they circle earth in space. Most are also dead; only five can still send back pictures. In a lower orbit, for example, flies TIROS 1, which excited the world with the first useful television pictures from space in April 1960 and inaugurated a revolution in weather forecasting. More than a million and a half satellite pictures have flooded to earth since that time. ROBERT W. MADDEN The world is his weather station: Dr. Walter Orr Roberts spurs a global meteorological study as President of the University Corporation for Atmo spheric Research in Boulder, Colo rado. The corporation, supported by the National Science Foundation, manages a laboratory in which some 600 scientists and technicians investi gate the atmosphere. An astronomer, Dr. Roberts was elected president of the American Association for the Advancement of Science for 1968. Here he holds the instrument package of a ten-foot GHOST balloon (background) used for charting air movements.