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

M1 M2 CLU CTM-TM HDM PMU OTA overview: Aplanatic Gregorian Aperture500mmφ Length1500mm Specification: - Strehl > - φ400 ” FOV - λ nm - φ30mm pupil image - minimum polarization - stabilized pointing - unnecessary heat rejected

Tests in the past one year 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 CTM environmental test/CT-CTM combination test Excellent performance of the image stabilization was demonstrated 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 System micro-vibration test Significant vibration of M1/M2 was excited by IRU New M1 support mechanism, optical performance/vibration test Significant improvements of the M1-surface figure was confirmed 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 CLU-FM vibration test/Optical performance Excellent optical performance. No change was found after vibrations OTA Opto-thermal test (on going)

OTA vibration test, Wavefront measurement with OTA tower,

MTM acoustic testMTM vibration test

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

Solar-B in 2nd tower

OTA optical measurement sequence A:Last measurement of OTA 1 st tower  System integration  System vibration/shock test C:Post 1 st tower  System disassembling B: Measurement on 2 nd tower Interferometer measurement System test

RESULTS: A:OTA only B:System C:OTA only 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  m.  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. difference

Micro-vibration transmissivity test x y z plate 0.176“/  m M1 M2 TM CLU plate “/  m Shift 1  m Tilt 1arcsec M M CLU CTM-TM (x) (y) Optical response factor: Image shift (arcsec) /displacement Sources of disturbance: - Momentum Wheel - IRU-A & B - Mechanisms in mission instruments

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

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. 2 nd 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…)

OTA in System-TTM test

19.9 ~ 43.2 C 1.1 ~ 16.3 C  27.8 ~ 4.6 C  1.7 ~ 25.0 C 16.0 ~ 30.0 C 26.2 ~ 45.7 C Predicted OTA temperature in orbit Heater control  21.5 ~ 4.4 C 21.1 ~ 67.3 C Heater control 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 OTA Opto-thermal testing

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

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

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

Point spread function of OTA ～ 500nm OTA pupil Goal of OTA Strehl > 0.8

Budget for the OTA image quality

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

: after system MTM test : just before system MTM test, after cleaning Particle contamination of M1 during MTM test Cleanliness level ~ 1000 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.