The last of the Atlas 2AS launchers blasted off on August 31st, carrying a U.S. spy satellite (exact details of which were classified). The Atlas was one the first American ICBMs, but was retired in the late 1960s and many of the missiles were converted to satellite launchers. Fitted with an additional four solid fuel booster rockets, the Atlas 2AS could put 8.6 tons into low orbit (favored for spy satellites), and 3.8 tons into a high, stationary orbit (used for communications satellites.) The Atlas 2AS, one of the later modifications of the basic Atlas design, has been used 30 times since 1993. It is being replaced by a new rocket using Russian technology (which is inexpensive, reliable and robust.) Other versions of the Atlas have long been used for satellite launches. The 197 ton Atlas 2AS was the most powerful of the Atlas launchers. The earliest one, like the 1960 Atlas Agena, weighed 124 tons, and could only put about 2.2 tons into low orbit.