Fractions are not simple

Collisions between satellites and other events flood space with millions of fragments. Who will monitor the waste surrounding the earth?

On February 10, 2009, the American Iridium 33 spacecraft, which was part of a low-orbit communications satellite array, and the Russian Cosmos 2251, an inactive satellite, collided. This collision between two satellites in space, in which a normal satellite was also destroyed, was the first ever recorded.

The collision created a huge cloud of space debris (Space Debris), and raised public awareness of the dangers of space debris and old uncontrolled satellites.

The field known as Space Situational Awareness (SSA) is a technology-rich field, the goal of which is to create a situational picture and awareness as accurate as possible of what is happening in space close to the Earth. These are active and used satellites, missile parts, fragments of space vehicles and anti-satellite combat systems.

The awareness of the situation in space is a condition for operating satellite systems and diverse space missions, including manned missions, in space that is increasingly filled with man-made objects. The topic of awareness of the situation in space also touches on the research field of "space weather" and especially in solar activity and its interaction with the earth's magnetic field (although its importance for satellites is great, we will not deal with it this time).

The destruction of the Chinese satellite

In January 2007, China tested an anti-satellite weapon. It launched from its surface a missile equipped with an explosive warhead towards its old and inactive meteorological satellite, which was sailing at an altitude of about 800 km above the earth. He launched the missile at his target, and when he reached it, it exploded near the target satellite.

The result of the experiment was the worst space debris creation event in history since the launch of Sputnik 1 into space in 1957. It is estimated that as a result of the Chinese experiment, about a million pieces of space debris were created, of which thousands endanger satellites and spacecraft. Furthermore, due to the height at which the fragments are located, a significant part of them will remain in space for over 100 years.

These two cases are the tip of the iceberg of smaller collision cases, random explosions of old satellites, malfunctions that disable the ability to control satellites, and satellites deviating from their orbits.

It should be remembered that close to 1,100 active satellites currently orbit the Earth, along with over 3,000 inactive satellites, thousands of missile parts, and millions of tiny man-made pieces - which are badly damaged - due to the orbital speed at which they move (about eight kilometers per second ).

Tracking space debris from Earth

The field of situational awareness in space has led to the placement of surveillance facilities that are deployed globally and they include telescopes, cameras (operating in the visible light range as well as in the infrared range), passive radio detectors and large radar arrays.

According to open publications, the various tracking facilities are able to detect and track objects as small as ten centimeters. This means that millions of smaller fragments are not tracked, and can cause serious damage.

The North American Aerospace Defense Command (known by its acronym NORAD) and the US Space Command maintain a constantly updated catalog of active and inactive satellites, missile parts and space debris of various types. This catalog is also available online, although highly accurate information is provided by the US to its allies at discretion.

An important element in the ground tracking of satellites and space debris is the surveillance network operated by the US Strategic Command, the US Army, the US Air Force and the US Navy combined. This network is called the Space Surveillance Network, and it started in 1957, when the first object identified and followed by the first satellites was Sputnik 1 from the USSR.

Today the network tracks 8,000 orbital objects, the vast majority of which are inactive satellites. Three tracking facilities equipped with cameras and telescopes are located in New Mexico, Hawaii and Diego Garcia Island in the Indian Ocean. They are operated by the US Air Force.

The American tracking networks for satellites and objects in space have many tasks, and these are: predicting the decay of satellite orbits and estimating when and where satellites and missile parts will fall; Differentiating between falling space fragments and ballistic missiles, and preventing false alerts of the US air defense systems (such a false alert could be extremely dangerous as it is a primary factor in the chain of alert activities for the launch of missiles with a nuclear warhead).

Additional tasks: mapping all objects moving in orbits around the earth and predicting their future trajectory; distinction and identification of new satellites launched into space; Management of an updated catalog for the various objects surrounding the earth; Identifying the countries to which bodies (satellites and missile parts) that are about to fall on Earth belong; and informing the US space agency about space debris that could endanger the space shuttle, the International Space Station or the agency's satellites.

A more modest aspect of the American system is its integration into the command and control systems of the various commands, including the bodies that operate satellites (including NASA, the Oceanic and Atmospheric Administration, and various intelligence bodies) and its ability to support and assist the US's space warfare capabilities.

Such assistance includes the possibility of identifying a hostile satellite and assessing the damage that would be caused by an anti-satellite weapon, as well as assessing the impact of a space weapon that might be used against American or fellow satellites.

Tracking space debris using satellites

In recent years, satellites have begun to be developed to track satellites and debris. These satellites will circle the Earth and look towards the low orbits - at an altitude of hundreds of kilometers, the densest area in terms of satellites - and the area of ​​activity of manned spacecraft and the International Space Station.

It was also noted that these satellites will be able to monitor what is happening in the geostationary belt, home of the communication satellites, at an altitude of 36,000 km above the Earth's equator. It is understood that the ability to track small objects will be better in the low orbits.

The US Department of Defense chose Boeing to characterize and develop the first generation of surveillance satellites to create situational awareness in space. The official definition of the need for this system as formulated by the Ministry of Defense is to "fundamentally change the field of situational awareness in space by means of flexible and adaptive sensors. This ability is a key element for the future space activity of the USA".

The plan is that the first SBSS (Space Based Space Surveillance) satellite will fly into space in July 2010 and a second satellite, with improved capabilities, will join it in 2015.

Future

As the rate of launching satellites into space increases and the number of inactive objects continues to increase, the probability of destructive collisions in space will increase. Estimates by NASA scientists from the Johnson Space Center are not positive, and they claim that in order to preserve the current situation today, at least four used satellites must be taken out of orbit in space per year.

The technologies for lowering bodies from orbit have not yet been tested, and the costs of cleaning space from man-made debris are very heavy. By the time the crowded orbits are cleared and cleaned, the importance of the awareness of the situation in space and of the warning mechanisms for satellite operators arising from it will increase greatly.