Although adaptive optics technology is becoming more advanced, powerful lasers that are often used in the technique are at odds with the U.S. Air Force. For every astronomy campaign that requires the use of lasers, an application must be sent days ahead of time to the Laser Clearing House at Vandenberg Air Force base, Calif. In the past, this was just a routine requirement, but more recently restrictions have become very tight, impacting the science that is being carried out.
The most commonly used laser shines on a volume of the atmosphere at an altitude of 90 km (56 miles), refracting off a layer of sodium atoms. The resulting light creates an artificial star that can be used by astronomers to calibrate their equipment and gain a measure of atmospheric turbulence. Turbulence data can then be fed into the adaptive optics system and any atmospheric interference can be removed from the observations, thus making images sharper.
Although the lasers are not powerful enough to damage the hull of spacecraft, they could burn out sensitive optics looking down on Earth (although the risk of this happening is not known).
Currently, there are four such lasers operating in the U.S. with plans for more. Although the "black out" periods may only last for a few seconds or minutes, the increasing number of interruptions in observing time is impacting some studies. Also, astronomers argue, these tightening restrictions are preventing observatories, such as the Gemini Observatory on Maunakea, Hawai'i, from reacting to sudden astronomical events like supernovae, as requests for observing time have to be submitted before the campaign.
Astronomers respect the need for protecting orbiting satellites and abide by all the rules, but as orbital traffic gets increasingly busy, interruptions in the use of laser star guides can only increase.