The collision earlier this year between an inoperative Russian military satellite and an Iridium communication satellite led to a lot of speculation about the future of satellites and dealing with such collisions and the debris created in their aftermath. The February 2009 collision apparently created upwards of 500 individual pieces of debris which can potentially threaten other satellites.
Moreover, there is a small chance of a cascading debris failure called the Kessler Syndrome in which debris from one collision causes other collisions which in turn cause other collisions until it is all but impossible to orbit satellites around the Earth.
Fortunately, NASA has a plan — we could always shoot down space debris ranging from 1 to 10cm in size with ground-based lasers. SpaceFuture.com posted a summary of the status of such research published back in 1997,
A recent NASA study sought to determine the feasibility of removing the threat to low-altitude spacecraft by deorbiting nearly all debris objects of primary concern. This would be accomplished by irradiating the objects with a ground laser, which would ablate a thin surface layer of the debris and cause plasma blowoff. The resulting dynamic reaction would change the object’s orbit, decreasing its perigee and causing its rapid reentry. The study, called Orion after the mythological archer, was cosponsored by the USAF Space Command, directed by the author (then at NASA Headquarters), and managed by John Campbell of Marshall.
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Several Orion systems were defined by the team, as were the characteristics and performance of two representative systems. The nearer term system would be able to remove from orbit essentially all of the 30,000 110-cm debris objects at or below about 800-km altitude within three years, for an estimated total cost of $60 million-$80 million, including R&D and operations. The longer term system would be able to remove essentially all of the 125,000 1-10-cm debris objects at or below 1.500-km altitude within two years, for an estimated total cost of $150 million-$180 million.
NASA would focus primarily on the smallest debris which can be hard to detect, opting to simply maneuver around debris larger than 10cm since it is easier to detect and, also, avoid. However, debris less than 1cm still poses a risk but is not reliably detect and would not be targeted by this system.
The article notes this system could not be used as a method of destroying satellites — you’d have to point the laser at a satellite continuously for months to effect its perigree enough to notice, and literally for years before causing major structural damage to a satellite.