The Cosmos 2251 was traveling at about six miles a second when it was struck by Iridium 33 which was traveling at approximately the same speed on February 10, 2009. They were both destroyed over northern Siberia at an altitude of approximately 788 kilometers. Officials at NASA say that neither was responsible because there is no right of way in space.

There were two prior known accidental in-orbit collisions resulting in damage and/or destruction satellites.

• December 1991 Cosmos 1934 and Cosmos 926 junk
• July 1996 French Cerise satellite and debris from an Ariane rocket used to launch Spot 1

There were two deliberate destructions:

• January 2007 Shoot-down of Chinese Feng Yun-1C satellite (anti-satellite test)
• February 2008 Shot-down of NRO L-21 by SM-3 missile (USS Lake Erie, Aegis Ballistic Missile Defense system)

According to SWF, (Secure World Foundation) the solution to the problem concerning this type of accident, is the application of an International Civil Space Situational Awareness System. As things stand, according to Weeden (Technical Consultant for SWF) “The owner or operator of a particular satellite usually has excellent knowledge about the position of that satellite in space, but little to no information about the locations of other objects around them.”

Once in place, this system would provide the tools needed for safe and sustainable activity in Earth Orbit.  The system would consist of sensor data, analytical component and should provide a “data-sharing” capability.

In addition to lack of information about location of objects around satellites, an underlying concern is orbital debris and the threat that it presents to the International Space Station and other functional satellites.  What accurately describes orbital debris? For the past 51 years of our activity in space, a scattered mist of junk surrounds our planet. Its appearance is close to that of a swarm of insects and is composed of miscellaneous fragments, mission related objects, old spacecraft, rocket bodies, operational space craft, 2cm copper needles, and rubbish bags-approximately 17,000 man-made objects (some bigger than 10cm).

How many additional pieces of orbital junk did the most recent collision generate? According to Dr. T. S. Kelso of celestrak.com, “As of today, the SSN (The US Space Surveillance Network) is tracking 217 pieces of debris associated with Iridium 33 and 457 pieces of debris associated with  Cosmos 2251.”

“The graphic shows the current Iridium constellation with the orbits for the operational satellites shown in green, the spares shown in blue, and the inactive satellites shown in red. The Iridium 33 debris is shown in yellow and the Cosmos 2251 debris is shown in orange.”

The threat to the International Space Station according to NASA is considered low. However, experts report that both the Hubble Space Telescope and Earth observation satellites could be at risk of damage because of their closer proximity to the collision point. A major concern is that the debris cloud is in two different orbits, and future tracking has to be accurate.  Large objects are not the only potential threat. Due to the high velocities of objects, small, untracked objects can also damage sensors and spacecraft components.

 Is there a threat to the Earth’s surface? Approximately 24,000 tracked objects have re-entered Earth’s atmosphere. However, NASA reports “most fall harmlessly into the oceans or onto sparsely populated regions such as Siberia, the Australian Outback, or the Canadian Tundra.”  Nevertheless, Paul Maley, project engineer for the Midcourse Space Experiment 1966,  has photos of two large pieces of a Delta rocket carrier that survived reentry, was recovered, and sent to Houston. He also reports that a recoverable, photo-imaging spacecraft-FSW3-3, launched on September 27, 2004 returned to Earth on October 15 suspended on its parachute, crashed through the roof of a house in the village of Penglai, Sichuan province. These are obviously isolated and uncommon incidents and Maley states, “For Earth dwellers, being hit by a piece of reentering space debris is a highly unlikely event”.

What are other fears or concerns of the dangers of orbital debris? The most notable is, that a large spacecraft will be smashed into hundreds of pieces by a speeding bit of orbital debris and that would begin a chain reaction of collisions that would expand for centuries, enveloping the heavens in chaos.

Scientists are growing more anxious with the realization that the number of objects in orbit has surpassed “critical mass” (a point in which a chain reaction becomes inevitable). China’s January 11, 2007 test of an anti-satellite rocket will cause the cascade to start sooner, putting at risk billions of dollars worth of advanced satellites and limiting future space exploration. Termed as the “worst such episode in space history”, and according to observation, the shattered satellite’s 800 pieces of debris will grow to approximately 1,000.  The experts are certain at some point in time that a piece of whirling debris will initiate the cascade.

Donald Kessler, a former head of the orbital debris program at NASA appeared to be somewhat sympathetic about placing the full blame on China.  He stated, “"If the Chinese didn't do the test, it would still happen. It just wouldn't happen as quickly."

China has assumed a growing role in fighting the proliferation of space junk and Beijing's policy was to keep space free of weapons.

No one is blameless for the resulting approaching cascade. In 1996, the fuel tank of an abandoned American rocket engine exploded. The craft broke into 713 detectable fragments. This was a “record” incident until China’s recent event.

Ecological Society of America (ESA) feels that implementation of mitigation measures should begin immediately. They express, “Most importantly, spacecraft and rocket stages have to be de-orbited and returned to Earth after the completion of their mission. They'll burn up in the atmosphere, or splash down in uninhabited ocean areas. In the case of telecommunication and other satellites operating in the commercially valuable geostationary zone, they should boost their satellites to a safe disposal orbit.  There are other measures, like reducing the number of mission-related objects and controlling the risk for reentry, but these are the basics.”

For NASA, the US, and all space-faring nations, mitigation is a high priority. What type of mitigation measures are in place?

·         Curtailing/preventing the creation of new debris

·         Better design of satellites that withstand impact by small debris

·         Provide better avoidance maneuverability 

NASA scientists are diligent in their continuation in the development and upgrading of orbital debris models that analyze the debris environment. For instance, models ORDEM2000 predict debris impact risk assessment and models EVOLVE and LEGEND predicts future debris environment.  These tools will continue to study how various mitigation practices impact evolution of floating space junk and, hopefully, will make operations of current and future spacecrafts free of collision risk.