The Pollution of Space

When the two new satellites were launched last May, NASA hailed them as the latest example of space-age technology benefiting life on earth. One satellite, dubbed AT56 (for Applications Technology Satellite), is relaying educational TV programs to remote regions; the other, SM51 (Synchronous Meteorological Satellite), is a new breed of weather satellite equipped with infrared cameras that can shoot remarkably detailed cloud pictures even at night.

Both satellites are performing splendidly, but both are producing unexpected and undesired side effects: they are creating so much electronic interference that radio astronomers are sometimes virtually "blinded"--unable to distinguish the celestial radio signals so crucial to their work.

"It can cost us time, money and lost observations," grouses Radio Astronomer Frank J. Kerr of the University of Maryland. What makes the situation even worse, he explains, is that the satellites use a portion of the radio spectrum especially important to radio astronomy. SMS-1, for instance, operates near the 18-cm. band, which is the natural wave length of hydroxyl, one of the first molecules discovered in space. It is from the signals of the hydroxyl molecule (which consists of one atom of hydrogen and one of oxygen) that radio astronomers have been learning about star formation and the nature of the clouds of gases between the stars.

AT56 broadcasts near an even more important frequency: the 11-cm. band, which has been specifically set aside by the International Telecommunications Union for the use of radio astronomers in their explorations of quasars, pulsars, distant galaxies and even the sun. Trouble is, the signals from these celestial sources are often so faint that they can be easily overwhelmed by signal spillover from the satellites' powerful radio transmissions, even when the complex craft are in a different part of the sky.

Kerr, who has been studying this new form of electronic pollution for the National Academy of Sciences, echoes the concern of his fellow radio astronomers: "We can perhaps live with one or two satellites, but if they put up 20 or 100 satellites that interfere in this way, it would be catastrophic."

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