When space debris is poised to strike, NASA turns to a U of M alumnus to divert the
By Gabrielle Maxey
Skylab, NASA’s first space station, had been abandoned and its orbit was severely
decayed. Many feared it could land anywhere on Earth, raining fiery debris on an anxious
population. The station’s demise sparked an international frenzy, with people donning
hard hats, buying t-shirts and wagering on the time and place of re-entry. Scientists
tried several altitude control maneuvers, which they hoped would alter Skylab’s re-entry
path. They nearly succeeded, and most of the station’s fiery pieces fell harmlessly
into the Indian Ocean off the Australian coast in July 1979.
If such a potential risk arose today, a U of M alumnus would be charged with averting
the impending disaster.
Nicholas L. Johnson (BS ‘74) has been NASA’s chief scientist for orbital debris, or
self-described “junk man,” since 1996. Among his tasks, he and his staff keep track
of thousands of objects orbiting the Earth. Their work helps keep expensive satellites
and manned spacecraft from colliding with debris. His efforts also help prevent a
colossal environmental problem in space.
Just as mankind has created mountains of garbage on Earth, there is also a blanket
of junk around the planet. Space debris is defined as anything in orbit that is no
longer serving a useful purpose. This includes spacecraft that have completed their
mission but are still in orbit, solid fuel fragments, paint chips and old rocket bodies
that might spontaneously blow up, creating hundreds of pieces of debris.
“Spacecraft are always throwing things off,” Johnson explains. “Lens covers, straps,
springs, explosive bolts.”
Another problem is that even debris can break up. Explosions or collisions blast objects
into small pieces, increasing the amount of garbage in space.
|Computer generated images of objects in Earth orbit that are currently being tracked.
Approximately 95 percent of the objects are orbital debris. The dots represent the
current location of each item.
Since the first satellite, Sputnik 1, was launched in 1957, thousands of space probes, satellites and telescopes have
been shot into space. There have been more than 4,600 space missions launched from
around the world, with about 60 to 70 occurring annually.
Johnson estimates there are some 19,000 large pieces of debris (more than 4 inches)
and as many as 500,000 objects from a half inch to 4 inches still in orbit. The Department
of Defense tracks the larger objects while NASA keeps tabs on the smaller pieces.
Any piece of debris has the potential to damage or demolish any spacecraft in orbit,
Johnson says. Although most bits are small, they are traveling extremely fast, up
to 20,000 miles per hour. NASA has had to replace windows of the Space Shuttle damaged
by objects as tiny as a fleck of paint. If a rock caused a ding that small in a car
windshield, the driver could probably ignore it; in the Shuttle, it’s dangerous.
Even debris as small as a centimeter traveling at that speed could conceivably puncture
a spacecraft, Johnson says. “They carry so much energy, they’re going so fast they
have the potential to destroy any satellite they come in contact with.”
The International Space Station is the most heavily protected vehicle ever launched,
but even it is vulnerable to space debris. “The International Space Station’s shields
cannot handle anything larger than a half inch,” Johnson says. “Anything bigger would
be like hitting it with a hand grenade.”
Johnson’s teams are conservative as they work to keep manned spacecraft away from
known debris hazards. “We calculate the possibility of a collision. If it’s greater
than one in 10,000, we make a maneuver to get out of the way,” he says.
It’s a critical task. NASA has had to adjust the flight path of space shuttles at
least eight times to avoid collisions. Some time after 2020, the Hubble Space Telescope
could fall back to Earth in an uncontrolled manner with many of its elements expected
to survive re-entry. NASA will revisit ideas for bringing Hubble down harmlessly over
the Pacific Ocean.
“An Orion mission (NASA’s next-generation crew exploration vehicle) would go to Hubble
and attach an engine and re-enter it in a controlled manner,” Johnson says.
How much of a risk does space debris actually pose to people on Earth? Johnson says
not much. “We’ve had thousands of re-entries and no one has been hurt.”
Most objects burn up in the atmosphere; the surviving components, like those made
of titanium or stainless steel, are likely to land where they won’t hurt people or
“The Earth is still two-thirds water,” Johnson says. “The odds are it would land in
the Pacific Ocean or a desolate region like Siberia or the Australian desert.”
|Left, top: 70m Goldstone antenna located near Barstow, Calif. One of many such installations,
when operated as a bi-static radar, Goldstone is capable of detecting 2mm debris at
altitudes below 1,000km.
Left, bottom: Johnson, at right, receiving an award from the Department of Defense
for helping destroy an out-of-control satellite. The U.S technical expert at the United
Nations in matters related to orbital debris, Johnson has also been recognized with
NASA’s Exceptional Achievement Medal for his substantial contributions to the agency.
Right, top: Johnson, second from right, leads the American delegation to the Inter-Agency
Space Debris Coordination Committee, a forum comprised of the world’s 11 leading space
agencies, including the European Space Agency, Russia, China and Japan. The members
share information on the location and risks of space debris. Images courtesy of NASA
Orbital Debris Program Office.
Johnson enlisted in the Air Force in 1968 with his high school classmate, Mary Elizabeth
“Beth” Porter (BSEd ’74). They married soon after they enlisted. The couple was assigned
to Keesler Air Force Base, where he was an aviation electronics technician and she
was an administrative specialist and human relations adviser. He later served a one-year
tour of duty in Vietnam.
After his discharge from the Air Force, Johnson enrolled at then-Memphis State University,
majoring in physics. As a senior, Johnson was assigned to track sunspots for Dr. Albert
Wollett’s astronomy class.
“I would daily carry a telescope up to (and back down from) the roof of the physics
building (Manning Hall),” he remembers. “I had no idea that solar activity, which
I was studying as a special project, would be so important to my future work for NASA
and other U.S. government organizations. As it turns out, solar activity today is
abnormally low, which allows debris to collect in the Earth’s orbit, posing risks
to operational spacecraft.”
Overall, he says, “MSU gave me the basic foundations of physics and math which I have
used throughout my subsequent 30-year career in the field of orbital debris.”
A few years after graduating, Johnson developed an interest in the Russian space program.
His research inspired articles and two books, Handbook of Soviet Lunar and Planetary Exploration and Handbook of Soviet Manned Space Flight.
In 1979 Johnson joined Teledyne Brown Engineering, where he helped assess the capability
of the Soviet Union’s spacecraft, provided assistance in space surveillance and worked
on such projects as the Space Defense Initiative, known as “Star Wars.” Ironically,
for someone who has made a career of preventing damage from space debris, one of his
tasks was devising a plan for blowing up Soviet satellites if war broke out. Says
Johnson, “My sole purpose was in creating debris.”
In 2008 Johnson received the Department of Defense’s Joint Meritorious Civilian Service
Award and the Distinguished Service Medal, NASA’s highest civilian award, for his
contributions to intercepting and destroying an uncontrolled satellite before it could
strike Earth. The crippled satellite contained a large amount of a hazardous propellant
that would have survived re-entry into the atmosphere. The intelligence satellite,
launched in December 2006, failed almost immediately. “We knew the material could
be exceptionally hazardous to human health,” he says.
Johnson was NASA’s representative to the large government interagency group charged
with assessing the threat posed by the satellite and dealing with it. He found himself
visiting the U.S. Strategic Command in Omaha, meeting with the President’s science
adviser and attending a deputies’ meeting of the National Security Council at the
An order from President George W. Bush ended the danger. “We struck it with a missile
launched from a Navy ship north of Hawaii and blew it up,” Johnson recalls. “We completely
eliminated the threat.”
As a space environmentalist, Johnson works with the aerospace industry to limit the
clutter orbiting Earth by designing debris-free spacecraft and improving their operations.
“If space gets too cluttered to send up satellites, they’re out of business,” he observes.
Johnson likens environmental problems in space to air or water pollution on Earth.
“It’s a classic if not high-tech environmental issue,” he says. “We want to ensure
the environment in space doesn’t get any worse than necessary, and we’ve been very
successful. We recognized the potential for pollution in space long before it has
gotten out of hand.”