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Approximation of normalized point source sensitivity using power spectral density and slopes of wavefront aberration
Byoung-Joon Seo1, Carl Nissly, Mitchell Troy
1Jet Propulsion Laboratory, Pasadena, California 91109, USA. Byoung-Joon.Seo@jpl.nasa.gov
Applied Optics
|June 14, 2013
Summary
Two new methods approximate telescope optical performance (PSSN). The β approximation offers high accuracy for the Thirty Meter Telescope, while SlopeRMS provides a simple worst-case estimate, aiding mirror specifications.
Area of Science:
- Optical engineering
- Telescope optics
- Metrology
Background:
- The normalized point source sensitivity (PSSN) is a key optical performance metric for advanced telescopes.
- Accurate estimation of PSSN is crucial for telescope design and manufacturing.
Purpose of the Study:
- To investigate and compare two novel approximation methods for estimating PSSN.
- To evaluate the suitability of these methods for large telescope projects like the Thirty Meter Telescope (TMT).
Main Methods:
- Developed and analyzed the 'β approximation' based on wavefront error power spectral density (PSD).
- Developed and analyzed the 'SlopeRMS approximation' based on the root-square-sum of wavefront slopes.
- Assessed approximation accuracy and applicability under different aberration conditions.
Main Results:
- The β approximation shows low uncertainty (<1x10⁻³) for TMT when PSSN > 0.95, assuming accurate PSD estimation.
- The SlopeRMS approximation effectively estimates worst-case PSSN for low-frequency aberrations.
- SlopeRMS is identified as a practical method for mirror surface specifications.
Conclusions:
- Both β and SlopeRMS approximations are valuable tools for PSSN estimation in telescope optics.
- The SlopeRMS approximation is particularly useful for setting mirror polishing specifications for vendors.
- TMT plans to implement the SlopeRMS approximation for M2 and M3 mirror polishing standards.
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