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Environmentalism in the space age.

Environmentalism in the Space Age

The scientists meeting in Washington, D.C., this week to discuss pollution, debris and noise had a different set of concerns than the usual environmental issues. Instead of PCBs in a river, it was stray light in the dark; the debris was pieces of orbiting space hardware; the noise was electromagnetic, interfering with the sensitive instruments that "hear" for radio astronomers.

The gathering was the first colloquium on the subject sponsored by the International Astronomical Union. It was headed by David Crawford of Kitt Peak national Observatory in Tucson, Ariz., whose first direct involvement with the problem of space pollution came from light pollution that can ruin telescopic observations of faint stars and other astronomical objects.

"People have become so accustomed to bad lighting that they think there's no lighting unless there's some glare," Crawford says.

The famous 200-inch Hale Telescope on Palomar Mountain, 100 miles from the lights of Los Angeles, went into use in 1948. By the 1960s, spectral measurements made with the instrument were already showing emission lines of the element mercury due to street lights. Today's sky over Palomar, says Robert Brucato, assistant director of the observatory, is about 0.mk magnitude brighter -- around twice as bright -- as it would be without light pollution.

The problem has been eased somewhat around both Palomar and Kitt Peak in the 1980s by the installation of low-pressure sodium streetlamps. Many Arizona counties, in fact, now require them.

NASA has been studying debris hazards to (and caused by) spacecraft for a decade, and there is a host of international organizations involved with the dense thicket of regulations governing radio-frequency interference.

Luo Xianhan of Beijing, China, reports that several observations of apparent solar microwave bursts have proved to be radio-frequency interference from sources as diverse as radar and sparks from automobile ignition systems. Michael M. Davis of the Arecibo radio observatory in Puerto Rico notes that a system of tethered, balloon-borne transmitters planned for use in battling drug smugglers had threatened studies of natural hydorgen radio emissions, which are important in understanding galactic evolution. Fortunately, he says, intervention by the National Science Foundation and the Puerto Rican government led to radio-frequency changes that made the transmitters "less intrusive on astronomical work."

Of particular concern is debris -- not only meteorites and space dust but also fragments of satellites that break up in orbit, leaving smaller but vastly more shards of what amounts to orbiting shrapnel. As of last week, says Sidney van den Bergh of the Dominion Astrophysical Observatory in Victoria, British Columbia, some 7,300 pieces of human-made debris were being tracked in orbit, moving at velocities of about 20,000 miles an hour. "In another century," he adds, "if the trend continues, a lethal layer will develop," posing a risk to astronauts.

Also of concern are satellites powered by nuclear reactors, such as the Soviet Cosmos 1900, expected to reenter the atmosphere late next month. About 70 percent of Earth's surface is ocean, so most satellite debris that reaches the ground should fall there, but in 1978 one satellite strewed debris over thousands of square miles of northern Canada.

Scientists at the meeting discussed the oft-mentioned possibility of a huge radio-telescope on the far side of the moon, never facing Earh, where the moon itself woudl block out terrestrial radio emissions. But even with that distant and protected outpost, Crawford says, "the polluters ae going to get there first. And they're better funded."
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Author:Eberhart, Jonathan
Publication:Science News
Date:Aug 20, 1988
Words:578
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