Advanced Technology Solar Telescope ENCLOSURE Error Budgets Rob
Advanced Technology Solar Telescope ENCLOSURE Error Budgets Rob Hubbard January 2006
Leaving the Dark Side and Coming to the Light – 1 The best seeing does not occur at minimum airmass Morning 10/21/2021 January 18, 2006 Enclosure Error Budgets Afternoon 2
Leaving the Dark Side and Coming to the Light – 2 We work in the daytime The ATST enclosure without active thermal control when the seeing is likely the best. 10/21/2021 January 18, 2006 Enclosure Error Budgets 3
Leaving the Dark Side and Coming to the Light – 3 For some use cases we must observe faint objects very close to a very bright object (the sun) SRD: “The total instrumental scattered light (dust plus mirror roughness) shall be 25 millionths or less at 1000 nm and at 1. 1 radii. ” 10/21/2021 January 18, 2006 Enclosure Error Budgets 4
Leaving the Dark Side and Coming to the Light – 4 Many solar telescopes do not have domes 10/21/2021 January 18, 2006 Enclosure Error Budgets 5
Telescope Performance and the Enclosure Stray Light Control (Dust Infiltration) Delivered Image Quality n n Pick an excellent site Use solar adaptive optics 10/21/2021 January 18, 2006 Enclosure Error Budgets 6
Telescope Performance and the Enclosure Stray Light Control (Dust Infiltration) Delivered Image Quality n n Pick an excellent site Use solar adaptive optics 10/21/2021 January 18, 2006 Enclosure Error Budgets 7
Image Quality – Self Seeing Contributing to the problem 10/21/2021 January 18, 2006 Enclosure Error Budgets 8
Image Quality – Self Seeing Contributing to the solution Shading of complex telescope structures Prevent wind shake and mirror buffeting by throttling high winds Allow wind flushing of the mirrors and structures Active ventilation under low-wind conditions 10/21/2021 January 18, 2006 Enclosure Error Budgets 9
Delivered Image Quality Seeing Limited Coronal Off-pointing up to 1. 5 solar radii, wavelength 1 micron, excellent seeing conditions: r 0 (1 micron) 50 cm… The Telescope shall deliver the following image quality: 50% Encircled Energy Diameter < 0. 7 arcsec Seeing Limited On-Disk [For] excellent seeing conditions, (r 0 at 1. 6 micron 100 cm)… Minimum requirement: 50% Encircled Energy Diameter < 0. 15 arcsec. Diffraction Limited The ATST shall provide diffraction-limited observations (at the detector plane) with high Strehl (S>0. 6 required, S>0. 7 goal) at 630 nm during excellent conditions (r 0 (630 nm) > 20 cm) and S > 0. 3 at 500 nm during good seeing (r 0 (500 nm) = 7 cm). 10/21/2021 January 18, 2006 Enclosure Error Budgets 10
Mitigation of Error Each case gets a separate error budget 10/21/2021 January 18, 2006 Enclosure Error Budgets 11
Seeing-Limited Coronal Error Budget 10/21/2021 January 18, 2006 Enclosure Error Budgets 12
Seeing-Limited On-Disk Error Budget 10/21/2021 January 18, 2006 Enclosure Error Budgets 13
Diffraction-Limited Error Budget 10/21/2021 January 18, 2006 Enclosure Error Budgets 14
Some Definitions… Top-down error budget values: The earliest values placed into the error budget cells based on relevant performance of similar systems implemented in other telescopes. Bottom-up error budget values: Values based on analysis of our specific design or performance measurements of our manufactured systems. 10/21/2021 January 18, 2006 Enclosure Error Budgets 15
Flow Down Science Requirements to Design Specifications 50% EE (arcsec) T Point Spread Function 10/21/2021 January 18, 2006 Enclosure Error Budgets 16
Convert to 50% EE The Seeing Estimator 10/21/2021 January 18, 2006 Enclosure Error Budgets 17
Probability/fraction of time Monte Carlo Simulation Seeing Limited (Case 2) 0. 15 arcsec 50% EE 50% Encircled Energy (Arcsec) 10/21/2021 January 18, 2006 Enclosure Error Budgets 18
Good Seeing with Low Wind All Data 10/21/2021 January 18, 2006 Excellent Seeing Enclosure Error Budgets 19
Conservative Top-Down Spec Tw. r. t. ambient 10/21/2021 January 18, 2006 + 0°C = 4°C Enclosure Error Budgets 20
- Slides: 20