PARIS — More than 600 dead satellites, spent rocket stages and other debris re-entered Earth’s atmosphere in 2014 — more than 100,000 kilograms of mass that caused no reported casualties or sizable property damage, NASA has told a United Nations conference.
The rain of junk was more substantial in 2014 than in previous years because of a peak in solar activity, which expands the atmosphere and captures dead satellites and other garbage that otherwise would have remained in orbit longer.
The low-orbit-cleansing effect of solar activity caused a slight dip in the total number of pieces of debris measuring 10 centimeters in diameter or larger, according to J.C. Liou, chief scientist at NASA’s Orbital Debris Program Office, located at the Johnson Space Center in Houston.
But if the number of pieces was reduced, the total estimated mass of junk resulting from launch activity continued to climb, reaching 6.7 million kilograms by the end of the year. The figure was 5 million kilograms in 2005.
In a presentation to the 52nd session of the Scientific and Technical Subcommittee of the U.N. Committee on the Peaceful Uses of Outer Space (COPUOS), Liou and officials from Europe, Russia and elsewhere gave the United Nations updates on orbital debris tracking.
The conference, held Feb. 2-13 in Vienna, was the occasion for space agencies to assess whether spacefaring nations are getting any better at disposing of their rockets and satellites so as to minimize orbital debris accumulation. Here the news continues to be mixed.
Liou said all five civil/commercial telecommunications satellites registered in the United States and retired from geostationary orbit in 2014 were placed by their owners into graveyard orbits more than 200 kilometers above the geostationary belt some 36,000 kilometers over the equator.
International debris mitigation guidelines accepted by all the major spacefaring nations — but not always honored by these nations — call for geostationary satellites to be raised by at least 200 kilometers, depending on their size, above the geostationary arc.
For satellites in low Earth orbit, the guidelines call for satellites to be disposed of such that they re-enter Earth’s atmosphere within 25 years of retirement. Orbital debris experts agree that this is where the problem is.
Holger Krag, head of the space debris office at the 21-nation European Space Agency, said a large percentage of satellites in low Earth orbit without onboard propulsion capability are operated and then abandoned in orbits from which they will not re-enter the atmosphere within 25 years.
Of the slightly more than 500 satellites launched since 2000 without maneuvering capability, Krag said, fully half were left in “noncompliant” orbits.
There is “a clear and positive trend” in geostationary orbit, Krag said. In low orbit, on the other hand, respect for the rules is “poor in critical altitudes, with no apparent trends.”
And even in geostationary orbit, while the trend toward greater respect for the retirement-orbit guidelines is clear, more than 10 percent of satellites retiring in a given year are either left where they are or moved an insufficient distance from the orbital highway, according to ESA data.
For now, the U.S. Air Force’s Space Surveillance Network of ground- and space-based sensors is the reference for determining what is going on in orbit. But neither the U.S. nor any other satellite tracking service publishes data showing what happens to military satellites.
Liou said the U.S. debris-tracking network’s capabilities will improve late this year when the 1.3-meter Meter-Class Autonomous Telescope (MCAT) enters service on Ascension Island, a British Overseas Territory in the Atlantic Ocean about midway between the horn of South America and Africa.
Located at about 8 degrees south latitude and operated remotely by NASA, the telescope — funded by NASA, the U.S. Air Force and the Air Force Research Laboratory — will boost tracking of objects in low-inclination orbits relative to the equator, at all latitudes, Liou said. For geostationary orbit, the telescope will be able to detect objects as small as 10 centimeters in diameter.
Europe has a much more modest set of ground radars that both ESA and the European Commission have been trying to turn into a network of stations that would enhance Europe’s ability to make its own judgments about orbital phenomena.
Russia operates a network of more than 70 optical ground telescopes at 35 observation facilities in 15 nations — including the United States — as part of the International Scientific Optical Network (ISON).
ISON is operated by the Keldysh Institute of Applied Mathematics, part of Russia’s Academy of Sciences.
Vladimir Agapov of Keldysh told the U.N. session that ISON is the sole source of orbital measurement data for 13.6 percent of active satellites in geostationary orbit — 62 satellites.
Keldysh is attempting to turn its space-tracking ability into a commercial service. Agapov said the institute now uses ISON to perform conjunction analysis — meaning assessments of collision likelihood — on more than 50 operational spacecraft, “including analysis of motion for co-located active geostationary spacecraft operated by noncooperating entities.”
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