Blog 37 How can we see the stars and planets clearly from Earth?
Figure 1. Adaptive Optics can correct for atmospheric distortion
Some adaptive optics use lasers to correct for atmospheric distortion. Thanks to a new adaptive-optics module, the Vary Large Telescope in Chile has a much sharper view of Neptune. Which is clearer to you: the view from the Hubble Space Telescope or the view using VLT Adaptive Optics?
Credit: ESO/P. Weilbacher (AIP)
Figure 2. Each big mirror consists of micro-segments that can be deformed
A deformable mirror can be used to correct wavefront errors in an astronomical telescope as shown in Figure 3. Illustration of a (simplified) adaptive optics system is available; see Wikipedia Adaptive Optics. “The light first hits a tip–tilt (TT) mirror and then a deformable mirror (DM) which corrects the wavefront. Part of the light is tapped off by a beamsplitter (BS) to the wavefront sensor and the control hardware which sends updated signals to the DM and TT mirrors.”
These new technologies use innovative software and hardware. One of the key technologies is microelectromechanical systems (MEMS) deformable mirrors. Another is magnetics concept for deformable mirrors. Perhaps the simplest corrective system is tip-tilt correction, which corresponds to correction of the tilts of the wavefront, which is introduced by the atmospheric distortions and may be greatly improved.
The Very Large Telescope site in Chile use a combination of adaptive optics to correct for atmospheric distortion. Lasers are fired into space to correct these distortions for many optics facilities in astronomy. One wavefront correction method is known as Shack-Hartmann sensor. To be successful in seeing clearly, the shape of the incoming wavefronts must be measured as a function of position in the telescope aperture plane. Sometimes known as “astronomical seeing,” the twinkling or blurring is caused by turbulence in Earth’s atmosphere, which muddies a telescope’s view. Astronomical seeing is why astronomers flock to mountains, because there are fewer distortions at higher elevations.
Figure 3 Comparison showing the amazing result of a complex technology first developed by DARPA, an agency of the US government. DARPA also developed the first internet.
Figure 4. Illustration of how adaptive optics can correct a distortion.
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Dr. Levin was born and grew up in Vermont with many winters spent in Florida as a child. As a teenager he wrote poetry, served as a lifeguard and played football. He currently enjoys sailing, exploring underwater caves, snorkeling, writing science fiction and other pursuits. After working on the Apollo and Mars projects, he returned to school to study under Nobel Laureate Paul Dirac, obtaining his PhD in 2.5 years. Dr. Levin founded two companies and served the science policy apparatus in President Ford’s administration. He has been published over 44 times in scientific literature and was awarded over 32 US patents. The science fiction writer is now emerging with his first work, a trilogy entitled 30th Century. The first award-winning book, 30th Century: Escape, is currently available on Amazon. Book two in the series, 30th Century: Revived, should be released before the end of April 2018.