1. M2 and Transfer Optics Thermal Control 25 August 2003 ATST CoDR Dr. Nathan Dalrymple Air Force Research Laboratory Space Vehicles Directorate

2. M2 & Transfer Optics Thermal Control Function: Mitigate mirror seeing Function: Reduce thermally- induced figure errors seeing

3. Requirements 1.Minimize mirror seeing a.Racine experiment:  = 0.38  T M - T e ) 1.2 b.Iye experiment:  greatly reduced by flushing c.IR HB aerodynamic analysis:  =  T  V,  d.Bottom line: requirements on surface-air  T and wind flushing 2.Minimize thermally-induced figure error Ref: Racine, Rene, “Mirror, dome, and natural seeing at CFHT,” PASP, v. 103, p. 1020, 1991. Iye, M.; Noguchi, T.; Torii, Y.; Mikama, Y.; Ando, H. "Evaluation of Seeing on a 62-cm Mirror". PASP 103, 712, 1991

4. Error Budgets (nm) Error budgetDescription 50020 nm Diffraction- limited 16000.05 arcsec Seeing- limited 10000.05 arcsecCoronal Must share this allocation with M1. Most of the budget will be given to M1.

5. Diffraction-Limited Error Budget (10 nm rms, est.) Blue contours: rms wavefront error (nm) Acceptable operating range Note: No AO correction assumed Green range is larger with AO correction. = 500 nm Sign must be reversed for M2, which is inverted.

6. Seeing-Limited Error Budget (0.02 arcsec, est.) Blue contours: 50% encircled energy (arcsec) Acceptable operating range = 1600 nm

7. Coronal Error Budget (0.02 arcsec, est.) Blue contours: 50% encircled energy (arcsec) Acceptable operating range = 1000 nm

8. Thermal Loads Mirror Total Absorbed Flux (watts) Peak Irradiance (watts/m 2 ) Peak Absorbed Irradiance (watts/m 2 )Footprint (mm) Mean Absorbed Irradiance (watts/m 2 ) M11,382.31,100110 4,000  4,000 110 M230.41,182118 584  596 111 M327.240,3904,039 100  140 2,474 M424.57,022702 316  314 314 M522.110,9211,092 175  178 903 M619.99,276928 231  189 580 Compare with 0.25 W on the DST tip-tilt mirror

9. Thermal Loads (cont.) M2 irradiance (nearly the same as M1) M3 irradiance (34x larger than M2)

10. Thermal Loads (cont.) M4 irradiance (6x larger than M2) M5 irradiance (9x larger than M2)

11. Thermal Loads (cont.) M6 irradiance (8x larger than M2)

12. M2 Thermal Control System Concept Air jets inserted in backside cells SiC

13. M2 Cooling System Flow Loop Insert diagram here

14. 3D NASTRAN Model

15. 3D NASTRAN Results for M2 Enhanced Cooling Temperature Profile (˚C above Ambient) Temperature Range of Approximately 0.14˚C Peak-to-Valley. No coolant under mount point

16. 3D NASTRAN Results for M2: Time History

17. M2 Thermal Control System Specs Next steps: Fan and system curves Heat exchanger specs Chiller specs Time response of fluid volume

18. M3, M4, and M6 Thermal Control System Concept High-k Edge cooling of conductive substrate

19. M3, M4, and M6 Cooling System Flow Loop Insert diagram here

20. M3, M4, and M6 Thermal Control System Performance M3 M4M6 All have surface to coolant  T’s of less than 4 ˚C. Relatively easy to obtain good temperature control.

21. M5 (DM) Thermal Control System Concept Force flow of air or dielectric liquid (Freon) past actuator array on the rear of the faceplate. Must work with the DM manufacturer to integrate cooling scheme. Q = 22.1 W q = 903 W/m 2 Need: h = 90 W/m 2 -K  T = 10 K

22. M5 Cooling System Flow Loop Insert diagram here

23. Summary 1.With highly conductive substrates, we do not expect major difficulties controlling surface temperatures of M3, M4, or M6. 2.M2 performs well thermally with air jet array cooling. 3.Cooling flow option: use the same primary coolant for M1, M2, M3, M4, M5, and M6 (and maybe HS). Use shunts and throttling valves for each load.