Several new Motorola Iridium satellites suffered attitude control failures about the same time. During heightened solar activity, the added energy puffs the atmosphere up like a balloon, increasing atmospheric friction on LEO objects. One result has been the premature demise of such satellites as the Solar Maximum Mission in 1990 and Skylab in 1979. The planned International Space Station, also designed for LEO, will have to be periodically reboosted in orbit to avoid the same fate. Its assembly will involve 1,200 hours of spacewalks, mostly between 2000 and 2002 during the peak of the sunspot cycle.
Atmospheric friction causes other headaches.
During the Quebec blackout in March 1989, the U.S. Space Command had to recompute orbits for more than 1,300 objects affected by momentarily increased air resistance. Nonetheless, LEO is considered prime orbital real estate for the latest generations of communication satellite networks. With the next solar maximum nearly underway, many institutions are responding. To safeguard the power grid, electric companies have begun to hire space weather forecasters and use advanced warning of inclement geospace conditions. Many new commercial satellites, however, may be more susceptible to solar storm damage than their less sophisticated predecessors only a decade older because they lack adequate shielding and radiation-hardened circuitry.