1. Space Junk a.
Natural - Most are fragments from comets or asteroids, while others are collision impact debris ejected from bodies such as the Moon or Mars b. Orbital debris are all man-made objects in orbit about the Earth which no longer serve a useful purpose. Derelict spacecraft and upper stages of launch vehicles, carriers for multiple payloads, debris intentionally released during spacecraft separation from its launch vehicle or during mission operations, debris created as a result of spacecraft or upper stage explosions or collisions, solid rocket motor effluents, and tiny flecks of paint released by thermal stress or small particle impacts 2. Population 3. Measurement a. NORAD NORTH American Aerospace defense command b. Some important data sources have been the U.S. Space Surveillance Network, the Haystack X-Band Radar, and returned surfaces from the Solar Max, the Long Duration Exposure Facility (LDEF), the Hubble Space Telescope (HST) and the Space Shuttle spacecraft c. ESA collaborates primarily with the operators of the German TIRA system (Tracking and Imaging Radar, European Incoherent Scatter Scientific Association EISCAT d. Space Based Sensors have the ability to detect debris, spacecraft, or other distant space objects without interference from weather, atmosphere, or time of day. Space based sensors use optical or infrared sensors which either scan, or quickly focus between targets without having to expend time and fuel to reposition the entire spacecraft. 4. Two recent events a. In January of 2007, the Chinese government conducted an anti-satellite (ASAT) test in which the FengYun 1C satellite was destroyed. This single event resulted in more than 2900 pieces of orbital debris greater than 10 cm in size, many of which are not yet included in the debris catalog. The first unintentional collision of two satellites occurred in February of 2009 when the operational Iridium-33 satellite collided with the inoperative Cosmos 2251. This accident generated more than 1600 pieces of large debris in two separate clouds b. These events taken together represent an increase in the collision risk for operational satellites in orbits between 750 and 900 km altitude 5. Removal a. Why? portions of low Earth orbit have already reached the point where future accidental collisions will produce new debris faster than the debris will fall naturally from orbit, leading to an ever increasing debris population, the well-known Kessler Syndrome b. The Kessler syndrome (also called the Kessler effect,[1][2] collisional cascading or ablation cascade), proposed by the NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) is high enough that collisions between objects could cause a cascadeeach collision generating space debris which increases the likelihood of further collision c. How? Solid Rocket Motors Solid Rocket Motors (SRMs) attached to a debris object have also been considered. The basic concept would be to launch an ADR vehicle containing multiple small thrust stages which could be deployed and attached to large debris objects. The problems inherent with this technique include an increased mass at launch due to the required shell and propellant mass of the SRMs and the difficulty in attaching an SRM to an arbitrarily rotating unprepared surface
d. Lasers - The use of lasers for ADR activities is questionable at best, partially due to a requirement to keep a very focused beam pointed at a rapidly and arbitrarily moving target for a long period of time, such that the surface can be ablated enough to induce an acceleration. Moreover, generating adequate levels of power for a space-based laser is beyond our current space power generation capabilities. Additionally, the use of such lasers in space could be problematic with respect to existing international weapons treaties and UN regulations. Also, many of the objects that could be removed may contain unspent propellant that could explode if heated by a laser, thus causing more debris
