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310Satellites at low Earth orbit LEO are in many different orbital planes providing global coverage and the 15 orbits per day typical of LEO satellites result in frequent approaches between object pairs After space debris is created the orbital plane s direction will change over time and thus collisions can occur from virtually any direction This leads to a cascading e3ect DEBRIS AT HIGHER ALTITUDES At higher altitudes where atmospheric drag is less signi cant orbital decay takes much longer This issue is especially problematic in the valuable Geostationary Earth Orbit GEO where satellites are often clustered to share the same orbital paths It has been estimated that at least one close approach within 50 metres takes place every year On a positive note relative velocities in GEO are low compared to LEO about 1 5 kmps This means that the debris field from such a collision will not have the drastic effects as that of LEO at least over a short term TRACKING OF SPACE DEBRIS Radar and optical detectors such as LIDAR Light detection and Ranging are the main tools used for tracking space debris Radio waves have been recently used These waves are transmitted into space and they bounce o3 space junk back to the origin that will detect and track the object Space telescopes and ground based radar facilities are also used to track the debris CLEANING UP OF SPACE DEBRIS Some methods for cleaning up of space debris are ElectroDynamic Tethers Giant Lasers Space Balloons Self Destructing Janitor Satellites Wall of Water Space Pods Tungsten Micro dust Space Garbage Trucks Recycling Satellites Laser Brooms Solar Sails Space nets and collectors Sticky Booms LASER BROOMS
The laser broom uses a powerful ground based laser to ablate the front surface o3 of debris and thereby produce a rocket like thrust that slows the object With continued application the debris will eventually decrease their altitude enough to become subject to atmospheric drag Additionally momentum of photons in the laser beam could be used to impart thrust on the debris directly The current technology used is the Hydrogen 9uoride chemical energy powered laser Although this thrust would be tiny it may be enough to move small debris into new orbits that do not intersect those of working satellites SOLAR SAILS The solar sails uses the pressure from sunlight to navigate an object just like a naval sail uses wind This way debris can be navigated out of orbit and burn into the atmosphere The only problem with the solar sail is that it is very hard to navigate the junk into the ocean and hence might be pretty dangerous SPACE NETS AND COLLECTOR SATELLITES Space nets or umbrellas are satellites which eject a huge net that collects the debris and is later disposed o3 into a graveyard orbit The most commonly used collector satellite is the sling sat It has two extended arms which collect the debris as it is in motion SPACE BALLOONS The GOLD Gossamer Orbit Lowering Device system uses an ultra thin balloon which is in9ated with gas to the size of a football eld and then attached to large pieces of space debris The GOLD balloon will increase the drag of objects so that the space debris will enter the Earth's atmosphere and burn up SELF DESTRUCTING JANITOR SATELLITES Clean space one a small satellite developed by Swiss researchers at Federal Institute of Technology which is then grab onto space junk with jelly sh like tentacles The device would then plummet back towards Earth where both the satellite and the space debris would be destroyed during the heat and friction of re entry
WALL OF WATER A new idea for cleaning up space junk from James Hollopeter of GIT Satellite is to launch rockets full of water into space The rockets would release their payload to create a wall of water that orbiting junk would bump into slow down and fall out of orbit The Ballistic Orbital Removal System is said to be able to be put into action inexpensively by launching water on decommissioned missiles MEASUREMENT OF DEBRIS LDEF Long duration exposure facility satellite EURECA European retrievable carrier STS 61 Endeavour STS 109 Columbia