OTA Status Report K.Ichimoto/Y.Suematsu, NAOJ

1. OTA Status Report K.Ichimoto/Y.Suematsu, NAOJ Following institutes/companies are in collaboration. J-side: ISAS (Institute of Space and Astronautical Science) (OTA) NAOJ (National Astronomical Observatory, Japan) MELCO (Mitsubishi Electric Corporation) Genesia Canon U-side: NASA (FPP) Lockheed Martin HAO Solar-B Science Meeting, 3-5 Feb. 2003

2. OTA overview: Aplanatic Gregorian Aperture 500mmφ Length 1500mm Specification: - Strehl > 0.8 @500nm - φ400” FOV - λ380 - 700nm - φ30mm pupil image - minimum polarization - stabilized pointing - unnecessary heat rejected M2 HDM M1 CLU PMU CTM-TM

3. Tests in the past one year 2002.3 OTA alone vibration/shock test/Optical performance Mechanical healthiness of OTA is proved. No change of mirror alignment. Non-negligible stress from the M1 support was discovered. 2002.3-4 CTM environmental test/CT-CTM combination test Excellent performance of the image stabilization was demonstrated 2002.5-6 System MTM test, acoustic/random vibration/shock Mechanical environment was determined OTA pointing axis and wavefront were measured on the S/C. No change in wavefront, 20” change of the pionting on S/C. 2002.7 System micro-vibration test Significant vibration of M1/M2 was excited by IRU. 2002.9 New M1 support mechanism, optical performance/vibration test Significant improvements of the M1-surface figure was confirmed. 2002.10 System TTM test Efficiency of the OTA heat dump path was confirmed. M1/CLU temperature was ~10C lower than expected (good news!). Accurate mathematical model of OTA was established. 2002.12 CLU-FM vibration test/Optical performance Excellent optical performance. No change was found after vibrations. 2003.1-2 OTA Opto-thermal test (on going)

4. OTA vibration test, 2002.3 Wavefront measurement with OTA tower, 2002.4

5. MTM acoustic test MTM vibration test

6. FPP SOT optical testing during the system MTM test - OTA optical performance check (measure WFE) - OTA-FPP alignment check with the Solar-B tower. (2nd OTA tower) flat mirror XRT EIS interferometer

7. Solar-B in 2nd tower

8. OTA optical measurement sequence Interferometer measurement A:Last measurement of OTA alignment @ 1st tower • System integration • System vibration/shock test System test B: Measurement on S/C @ 2nd tower • System disassembling C:Post measurement @ 1st tower

9. RESULTS: A:OTA only B:System C:OTA only difference RMS 105nm (single path) A20=105nmRMS, Other= 6nmRMS RMS 22.5nm(single path) A20=19nmRMS, Other =11nmRMS • Change of distance between M1 and M2 (defocus) ~ +20 mm • .  probably due to temperature/humidity change • Coma and other aberrations were negligibly small. • Change of pointing axis (center of OTA FOV) wrt. OTA cube was ~30” on S/C.

10. Micro-vibration transmissivity test M2 plate scale @f1 0.176“/mm plate scale @f2 0.0456“/mm CLU M1 TM z y x • Sources of disturbance: • Momentum Wheel • IRU-A & B • Mechanisms in mission instruments Optical response factor: Image shift (arcsec) /displacement

11. PSD of image motion due to M2-tilt excited by MW disturbance

13. It was found that the disturbance of IRUs causes a significant pointing error of the OTA. • The degree of pointing jitter is reduced from that initially expected, owing to the efforts of reduction of the IRU disturbance, but still NOT meets the SOT requirement. • To overcome this problem,,, • - System decided to move one of the Gyro (for nominal usage) from the OBU to the bus box.. • OTA will test the counter-weight mechanism to suppress the M2 resonance at 130Hz. • 2nd micro-vibration testing with OTA and S/C is planed in March. • Effects of the shutter or filter wheels in mission instruments are still unknown. • Careful tuning for balancing the moving mechanisms of each instrument is highly appreciated! (It was found that the dumping rate of the OBU structure is extremely small (Q>>100) against the micro-disturbance…)

14. OTA in System-TTM test

15. OTA Opto-thermal testing Predicted OTA temperature in orbit • Aim: to verify the optical performance (image quality) of OTA under the thermal environment in orbit. • Items for evaluation: • Deformation of mirrors by stress from • the mirror supports, • Dimensional change of the truss • structure, • due to temperature change and dryout -1.7 ~ 25.0 C Heater control -21.5 ~ 4.4 C -27.8 ~ 4.6 C 21.1 ~ 67.3 C 1.1 ~ 16.3 C 19.9 ~ 43.2 C 16.0 ~ 30.0 C 26.2 ~ 45.7 C Heater control

16. OTA Opt-thermal test configuration  OTA pointing ax. Upper shroud Theodlite  OTA center of FOV OTA interferometer Dummy OBU Test started 2003.1.28 – on-going Support theodlite  OTA mech.ax. Lower shroud OTA alignment cube flat shroud Flat mirror reference Tilt/shift stage Autocollimator  OTA pointing ax.

18. Test modes: ① In air ② Room temperature in vacuum ③ 0C uniform temperature ④ Temperature gradient (cold case, -50 ~ +23C) operational heater, truss T un-isotropy, ⑤ Temperature gradient (hot case, -50 ~ +50C) ⑥ Room temperature in vacuum today

21. FM Optics Status: CLU-FM was completed (Dec. 2002) Wavefront error ~ 0.015l rms (on-axis) 0.028l rms (140” off-axis) Chromatic aberration theoretical, before/after vibration

22. Point spread function of OTA Goal of OTA Strehl > 0.8 ～ 0.21” @ 500nm OTA pupil

23. Budget for the OTA image quality

24. M1/M2 (test coating) CTM-TM (theoretical) CLU (FM measurement) BFI wavelengths NFI wavelengths

25. Particle contamination of M1 during MTM test 02.04.11: just before system MTM test, after cleaning 02.08.07: after system MTM test Cleanliness level 300? Scattered light should be still negligible, but we plan to make more complete bagging of OTA or S/C during the FM test phase. Cleanliness level ~ 1000