February 18, 2003
Wanted: Traffic Cops for Space
By ANDREW C. REVKIN


After decades of relatively ungoverned exploration and exploitation, rules of the road may be coming to the final frontier.

They resemble some of the norms already long established for travelers on Earth: don't litter and stay in your lane.

On Monday in Vienna, a panel of scientists from space agencies around the world will submit to the United Nations Office for Outer Space Affairs recommendations for designing and flying space vehicles to reduce the amount of debris they produce and cut their chances of colliding with one another.

The proposals, the result of eight years of negotiation, are in effect the first international attempt to establish pollution and air traffic controls in orbit.

The shift is driven by growing awareness that, in space, litter and erratic movements can kill. Recent years have seen a marked increase in space debris, everything from used rocket boosters to paint chips, much of it from the increasing numbers of privately launched spacecraft, like communication satellites.

Because the material is moving at such high speeds, even a small chunk can cause potentially lethal damage. A collision with a small piece of space junk remains high on NASA's list of possible explanations for the puncture that apparently led to the disintegration of the space shuttle Columbia as it re-entered the atmosphere.

Even a one-centimeter pellet, the width of a fingertip, can destroy a spacecraft traveling at a typical orbital speed of 20,000 miles per hour or more, experts say. And the best military radars and telescopes can reliably track only debris that is at least 10 times as large, or roughly bigger than a softball.

In interviews, officials from space agencies around the world said that the risks of a catastrophic collision remain very low. Air Force radars and telescopes routinely sweep a 30-mile box ahead of spacecraft carrying astronauts for any intersecting orbits of tracked objects. And space is so vast, even in the confines relatively near Earth, that it is unlikely that two speeding objects will collide.

Insurance rates for satellites still mainly reflect launching risks, not collisions. Experts note that so far only one active spacecraft — Cerise, a French electronic surveillance device — has been hit by a tracked piece of debris. In that 1995 case, Cerise survived because the debris lopped off only a long strut.

Still, hints of the debris hazard have come up throughout the shuttle program's history.

"Almost every time the shuttle goes up, it returns with small nicks in its windows and tiles that were caused by impacts with small particles on orbit," says a NASA Web site on the debris risks, at hitf.jsc.nasa .gov/hitfpub/problem/index.html.

In the next two decades the risks could substantially rise as the number of satellites continues to grow.

"It's a classic environmental problem," said Nicholas L. Johnson, chief scientist for orbital debris research at NASA's Johnson Space Center in Houston. "If you don't do anything about this for the next 10 or 20 years, then it's too late."

Mr. Johnson, who is the top American official in the scientific group that will brief the United Nations next week, said, "The best way to prevent this from becoming a big problem is to stop making more debris, or make sure it's short-lived or bring things out of orbit."

Although discussions are intensifying now, this is an issue that has loomed large in the minds of astronauts since the early days of the shuttle program.

Nearly 20 years ago, on the third day of his first space shuttle mission, Capt. Frederick H. Hauck of the Navy settled into the co-pilot's seat and glanced idly up at a window to his right.

"I was just sitting there doing something, and I noticed this splatter mark, almost like a bug," he recalled. "Except I could see a little tiny chip embedded."

A closer look revealed radiating webs of damage in the outermost of three layered panes of heavy glass.

When the window was removed back on Earth, the embedded mote was found to contain traces of aluminum and titanium.

It was a fleck of paint, most likely from a derelict rocket casing.

If it had been slightly heavier, the window could have imploded, killing the crew, experts concluded.

Meteoroids also pose a slight threat but in low Earth orbit are outnumbered at least 10 times over by space junk, according to several analyses.

The threat to the shuttle or the International Space Station from orbiting debris has been highlighted in several reports by NASA and the National Academy of Sciences, but it has also been manifested in several close calls.

On Nov. 21, 2001, for example, a Russian satellite monitoring naval activity, Cosmos 2367, broke apart in an orbit just 18 miles above that of the space station, spewing 300 bits of debris large enough to be tracked on radar and presumably a blizzard of smaller motes.

About 40 percent of the tracked pieces ended up in orbits intersecting that of the orbiting laboratory.

NASA scrambled debris specialists to judge the threat to the station and an impending shuttle flight. They did so by poring over data collected by the Air Force's First Space Control Squadron, which tracks debris and missile launchings by integrating data from a host of orbiting and land-based radars and telescopes.

In that case, the risks were judged to be within acceptable limits, and no dangerous debris struck either spacecraft.

In the early days of the space race, few people considered the consequences of jettisoning rocket components, beyond trying to avoid having things fall to the surface. But the problem is now glaringly apparent.

In 1961, sensitive American and Soviet radar watching for World War III detected only 50 manufactured objects, burned-out rocket stages and the like, circling the globe.

The list of orbiting objects tracked by an array of military radars and telescopes now tops 10,000, but these are only the bits large enough to be routinely tracked — things larger than a softball.

There are an estimated 150,000 to 300,000 additional bits and pieces with dimensions ranging from 1 to 10 centimeters.

The best spacecraft shielding can stop only those things smaller than a centimeter. Debris in orbits higher than 500 miles or so can take decades or even centuries to drop into the atmosphere and burn up.

"Because it is so hard to clean up once it's out there, you have to do whatever you can to prevent it before you leave Earth," said Joanne I. Gabrynowicz, the director of the National Remote Sensing and Space Law Center at the University of Mississippi.

She cited a 1967 treaty on activities in outer space, which says that countries exploring space should do so in ways that avoid "harmful contamination and also adverse changes in the environment of the Earth."

But space, she said, is now dominated by private companies selling digital television or phone service or navigation aides, and none of them are directly addressed in a document drawn up when only the Soviet Union and the United States were launching things into orbit.

Over all, the orbits of the space station and shuttle, between 180 miles and 240 miles up, are relatively safe because they are periodically swept, in a way, by atmospheric changes resulting from the 11-year solar cycle.

In periods of high magnetic storm activity on the surface of the Sun, Earth's atmosphere expands farther out into the heavens. This relatively dense air creates greater friction with space debris, dragging it down until it is destroyed in a fiery descent to Earth.

But three regions in space that are growing very popular with companies lofting commercial satellites are particularly vulnerable to a continuing buildup of space junk, according to analyses by NASA and other researchers: the band from 480 to 600 miles up, another 840 to 900 miles up, and finally the special zone 22,300 miles from the Equator, called geosynchronous orbit, where satellites can remain nearly stationary over a spot on the surface.

That region already has some 320 satellites parked in coveted spots, with dozens more planned as space-based enterprises continue to expand.

Several large spacecraft have broken up in that region in recent years, including an American Titan rocket stage and a Russian satellite. Debris there, just like the satellites, goes nowhere and can create highly dangerous zones.

Some NASA and private scientists have proposed ways to use ground-based lasers, tethers or space tugs to sweep away dangerous debris, but these options are many years from being employed, experts say.

The United States, starting in the 1990's, became the first country to adopt strict national standards for cutting risks that space activities would add to debris-collision risks. The regulations apply both to NASA and military launchings and to any company seeking the federal licenses required to launch or operate a satellite.

Europe and Japan are following suit, but most of the 65 countries that either launch or own satellites have no such standards.

The guidelines that Mr. Johnson and other space scientists will propose have not been made public, but several scientists familiar with them say they are nearly identical to those already established in the United States.

They include physical changes like designing covers for cameras and other equipment that do not pop off and float away — once a common occurrence — but instead are tethered.

Another recommendation is dumping any leftover fuel or draining batteries to avoid explosions that can turn one derelict item into a cloud of thousands of deadly bits.

The scientists are also calling for planning the trajectories of launchings or timing the releases of rocket stages so that ejected components settle in orbits so that they will drop into the atmosphere in no more than 25 years.

One of the biggest continuing threats in space comes from a steady buildup of abandoned rocket stages, and many of them spontaneously explode, sometimes years or even decades after they were used.

The breakup of rocket stages, according to NASA and European officials, is responsible for about 40 percent of all the tracked debris circling Earth.

Some experts say that voluntary guidelines, even if adopted, will not be enough, particularly as space becomes increasingly dominated by private ventures lofting satellites for navigation, imaging, communication and other enterprises.

Altogether, about 700 functioning satellites now orbit Earth, but that number is expected to rise to 2,000 or more in coming decades.

Without a binding international standard, experts say, companies may simply shift their operations to countries without standards, avoiding the extra costs of making flights safer.

Alby Fernand, who directs orbital debris policy for the French National Center for Space Research, said the result could mirror a problem with ship registration: owners can register their vessels under "flags of convenience" to avoid strict laws elsewhere.

The motivation to skirt rules lies in money. One of the biggest expected costs to commercial satellite owners from the proposed standards will be holding in reserve some of the fuel that is used to keep certain satellites precisely positioned.

The standards will require those satellites, toward the end of their useful lives, to be boosted into "graveyard orbits," said Dr. Phillip D. Anz-Meador, a physicist and NASA consultant in Houston who has done many studies of the debris problem.

This could cost some companies hundreds of millions of dollars in lost revenue from the abbreviated missions of their equipment.

Dr. Anz-Meador and many other space scientists here and in Europe said they expected a long fight before binding international standards were adopted, mainly because spaceflight involves a host of questions that have hardly been debated.

"There are huge issues," Dr. Anz-Meador said. "Think about space salvage," he said. "Who owns a piece of debris? Who is liable if there's an accident? What about trade secrets, national security?"

Indeed, several experts pointed to the dozens of classified military and intelligence satellites roving space as a daunting issue. The positions of these devices are not provided to the public or other countries by American and Russian military agencies that track debris and satellites.

If an uncharted satellite breaks up and threatens a private satellite or a spacecraft, experts asked, will that information be released?

Like Mr. Fernand, Dr. Anz-Meador compared the situation in space to practices on the high seas, but with one big difference. At sea, a wrecked ship sinks; in space its remains may linger for decades or centuries.

Worse yet, as orbiting fragments break up through internal explosions or collisions with other debris, clouds of potentially lethal junk continue to grow denser.

As long as more debris is being generated than is falling into the atmosphere, Dr. Anz-Meador said, navigating space will be increasingly perilous.

"Imagine if all the boats that have ever sailed the world's oceans were primarily still out there," he said. "The crews might be dead and gone, but they're still sailing around. You could launch a new supertanker and be rammed by a Greek trireme. That may be what we're headed for."

Indeed, he and other experts noted, such a collision has already happened.

The piece of debris that struck the French Cerise satellite, which was launched on an Ariane rocket in 1995, came from the exploded upper stage of an Ariane rocket, one launched in 1986.





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