Mitigation of orbital debris

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Orbital Debris: The Problem

Orbital debris is a form of space pollution – junk produced by orbital launches and spacecraft operations. Each orbital launch places temporary and permanent payloads into space. Each time a vehicle goes into orbit, junk is produced. Fuel tanks are discarded, screws come loose, paint chips flake off and, of course, satellites die. The Space Surveillance Network (SSN), operated by the United States, tracks 17,300 artificial objects in space bigger than 10 centimeters. About 800 of these are operational satellites. The SSN tracks only a fraction of the estimated 300,000 total objects, ranging in size from one to ten centimeters also orbit the Earth, including such things as foil scraps, bolts, and other material. Finally, there are billions of bits and pieces smaller than one centimeter circling our planet, each following its own orbit. All of this material orbits the Earth at high velocities, usually between seven and ten kilometers per second, speeds that can produce considerable injury to astronauts and damage to equipment. To give a recent example, during an eight-year period ending in 2002, the solar panels of the Hubble Space Telescope (HST) were struck 725,000 times. Five thousand of these impacts were large enough to be seen by the naked eye, with several hundred being up to 3.5 millimeters in diameter.

The lifespan of orbital debris is directly related to its altitude. Debris in lower orbits undergoes greater atmospheric drag which acts naturally to speed its decay into the Earth’s atmosphere. At this point, it is not technically or economically feasible to remove long-lived debris from higher orbits. Debris at high altitudes can stay in orbit for decades or even centuries, accumulating over time. All sizes of orbital debris, even down to less than a millimeter, can have a devastating effect on anything they hit because of their high relative impact velocities. While overall levels of space debris are somewhat manageable at this time, we face a looming problem with escalating amounts of debris in the most heavily used orbits. This scenario will sharply increase the probability of damaging collisions between space debris and operational spacecraft.

For an idea of how serious this level of interplay can be, the debris shielding for the International Space Station (ISS) is designed to shield the ISS only from debris one millimeter to one centimeter in thickness. A hit in a critical area by larger objects would cause significant and serious damage. Most space systems do not even have this level of shielding, because of the added weight and launch costs, and thus are highly vulnerable to loss of service from debris impacts. In time, as the quantity of space debris grows within popular orbits, debris fragments will begin colliding with each other more frequently, creating a cascade effect leading to increasing amounts of threatening debris.

A recent study conducted by the National Aeronautics and Space Administration (NASA) forecast a 10-fold increase in the probability of collision with debris over the next 200 years. While this forecast is a cause for concern in itself, it is considered an underestimate because for modeling purposes the study’s forecast was based on the assumption that no further launches would be undertaken during this period. Since orbital launches are expected to continue, the probability of future collisions with orbiting debris will almost certainly be higher. This forecast was also made prior to the January 11, 2007 Chinese ASAT test, which deposited more than 2,300 pieces of debris larger than 10 centimeters into some of the most heavily used orbits where the world’s weather and climate monitoring satellites reside.

In order to manage international problems that will naturally develop as the space environment surrounding Earth becomes more crowded, we must begin on the creation of space resource management mechanisms to reduce the creation of new debris. Our continued ability to maintain a secure and safe space environment depends on it.

What is the Secure World Foundation doing about orbital debris?

While no existing international agreements ban the deliberate creation of debris, consensus is building within the scientific and academic community on the need to develop tighter controls on orbital debris creation. The voluntary United Nations (UN) Space Debris Mitigation Guidelines, created by the Inter-Agency Space Debris Coordination Committee (IADC), will be implemented by the national mechanisms of individual nations. In addition to ensuring that they are implemented fully on a national basis, it will be important for all space faring nations to view the guidelines as one important part of the solution and not the entire solution.

Adoption of a debris mitigation resolution by the United Nations General Assembly (UNGA) will be insufficient to fully protect the space environment. It is essential that space faring nations, the IADC, the UN Committee on the Peaceful Use of Outer Space (COPUOS) and others continue to monitor scientific and technological developments, with particular emphasis on developing new ways to reduce the propagation of debris and exploring debris mitigation.

To this end, the Foundation and its partners work closely with the IADC and UNCOPUOS with the following objectives:

• A conference should be convened to discuss necessary next steps in the mitigation of orbital debris. This should include a discussion of data sharing (for example, an international space situational awareness system) and appropriate allocation of responsibilities.
• The UN Space Debris Mitigation Guidelines should be leveraged to justify and support the beginning of work on space traffic management (STM).
• All space faring nations must be encouraged to pass national mechanisms to implement the IADC debris mitigation guidelines and to report on their status at annual COPUOS sessions.
• COPUOS, the IADC, and the commercial space industry should work together to strengthen the space debris mitigation norms now in place. This will enable new technological developments to be incorporated into the international approach to mitigating space debris.
• The passage of the UN Space Debris Mitigation Guidelines should be followed by a program of review and continued negotiations towards a strengthened set of debris mitigation guidelines.
• Research into technologically and economically feasible methods of removing debris from orbit should be continued.

Be sure to visit the links above to learn more about orbital debris in International Space Policy Documents, Reports, Fact Sheets, Links, and Papers and Articles.