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
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OTA Status Report K.Ichimoto/Y.Suematsu, NAOJ Following institutes/companies are in collaboration. J-side:ISAS (Institute of Space and Astronautical Science)
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OTA Status Report
K.Ichimoto/Y.Suematsu, NAOJ
Following institutes/companies are in collaboration. J-side: ISAS (Institute of Space and Astronautical Science)
2002.3 OTA alone vibration/shock test/Optical performanceMechanical 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 testExcellent performance of the image stabilization was demonstrated
2002.5-6 System MTM test, acoustic/random vibration/shockMechanical environment was determinedOTA 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 testSignificant vibration of M1/M2 was excited by IRU.
2002.9 New M1 support mechanism, optical performance/vibration testSignificant improvements of the M1-surface figure was confirmed.
2002.10 System TTM testEfficiency 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 performanceExcellent optical performance. No change was found after vibrations.
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.
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…)
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 cubeLower 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 2003.1.28 – on-going
Test modes:
① In air ② Room temperature in vacuum③ 0C uniform temperature④ Temperature gradient (cold case, -50 ~ +23C)
operational heater, truss T un-isotropy, ⑤ Temperature gradient (hot case, -50 ~ +50C)