Laser guide star

Adaptive optics (AO) systems require a wavefront reference source of light called a guide star.

This star can be positioned anywhere the telescope desires to point, opening up much greater amounts of the sky to adaptive optics.

[11] Important output features of the tunable lasers mentioned here include diffraction-limited beam divergence and narrow-linewidth emission.

[6] The sodium laser guide star for use in adaptive optics to correct for atmospheric distortions is believed to have been invented by Princeton physicist Will Happer in 1982, as part of the Strategic Defense Initiative, but it was classified at the time.

[12] Laser guide star adaptive optics is still a very young field, with much effort currently invested in technology development.

Other observatories developing laser AO systems as of 2006 include the Large Binocular Telescope and Gran Telescopio Canarias.

The laser guide star system at the Very Large Telescope started regular scientific operations in June 2007.

The 4LGSF helps astronomers to test devices for the E-ELT,[21] which will have a similar system to support the adaptive optics of the telescope.

For sodium laser guide stars, there are three main challenges to overcome: Larmor precession, recoil, and transition saturation.