Real-time atmospheric turbulence profile estimation using modal covariance measurements from multiple guide stars

N. Mark Milton, Michael Lloyd-Hart, Jessica A. Bernier, Christoph Baranec

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


An accurate and timely model of the atmospheric turbulence profile is an important input into the construction of tomographic reconstructors for laser tomography adaptive optics (LTAO) and multi-conjugate adaptive optics (MCAO) using multiple guide stars. We report on a technique for estimating the turbulence profile using the correlations between the modal reconstructions of open-loop wavefront sensor (WFS) measurements from natural or laser guide stars. Laser guide stars can provide an estimate of the turbulence profile along the line of sight to any suitable science target. Open-loop WFS measurements, acquired at the MMT telescope, have been analyzed to recover an estimate of the Cn2 profile. This open-loop WFS data can be used to yield turbulence estimates in near real-time, which can be used to update the tomographic reconstructor prior to closed-loop operation. This method can also be applied in closed-loop, using telemetry data already captured by multi-guide star adaptive optics (AO) systems, by computing estimates of the wavefront modal covariances from the closed-loop WFS residual error signals and the deformable mirror (DM) actuator positions. This will be of particular value when implemented with accurate position feedback from the AO system's DMs, rather than the input actuator commands, as is possible with an adaptive secondary mirror. We plan the first tests of the technique with the MMT's adaptive secondary and five Rayleigh laser guide stars.

Original languageEnglish (US)
Title of host publicationAstronomical Adaptive Optics Systems and Applications III
StatePublished - 2007
EventAstronomical Adaptive Optics Systems and Applications III - San Diego, CA, United States
Duration: Aug 29 2007Aug 30 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherAstronomical Adaptive Optics Systems and Applications III
Country/TerritoryUnited States
CitySan Diego, CA


  • Adaptive optics
  • Atmospheric turbulence
  • Tomography

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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