There may be a way to ensure that space telescopes fly in ultra-precise formations around our planet. According to a physicist, this is possible by combining the push of laser light with the pull of tethers. The issue is important because even if giant telescopes and sensitive detectors usually could do the job, they are expensive to make and to maintain plus they are also burdensome to launch.

Now, several next generation space missions propose to use more than one, in some cases dozens, of smaller spacecraft flying in formation to cover the area between them. A good example of this is NASA's Micro-Ascend X-ray Imaging Mission (MAXIM) and the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS).

The former, envisions as many as 33 satellites flying in concert to create a massive, X-ray interferometer with a resolution high enough to image black holes. The latter, on the other hand, calls for three satellites with a spacing of 1 km. apart to study the first galaxies that were formed in the Universe.

The problem now is how would astronomers maintain the configurations that are needed to make the separate spacecraft move and behave as one. Physicist Young Bae, is now proposing a system that will rely on lasers and tethers, according to the good physicist, "with these two working in combination, we can achieve nanometer accuracy over a kilometer in formation".

The concept will work in this way, lasers are beamed between pairs of spacecraft within a formation. Mirrors on each satellite reflect the laser beams back and forth, providing an energy-efficient thrust. This outward push is balanced by the inward pull of tension in Kevlar tethers linking the satellites. The system also uses the laser beams to measure and maintain the desired distance between satellites very accurately. Bae also added that “the alignment accuracy cannot be achieved by any other means”.

The NASA Institute for Advanced concepts funded Bae's research, but according to NASA officials, Bae's idea is not the only idea that they are entertaining. There are others suggesting the use of electromagnets rather than traditional thrusters to control the pointing of the individual satellites.