OTA Status Report K.Ichimoto/Y.Suematsu, NAOJ
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Transcript of OTA Status Report K.Ichimoto/Y.Suematsu, NAOJ
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)
GenesiaCanon
U-side: NASA (FPP) Lockheed Martin
HAOSolar-B Science Meeting, 3-5 Feb. 2003
M1
M2
CLU
CTM-TM
HDM
PMU
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
Tests in the past one year
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.
2003.1-2 OTA Opto-thermal test (on going)
OTA vibration test, 2002.3
Wavefront measurement with OTA tower, 2002.4
MTM acoustic test MTM vibration test
FPPFPP
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)
EIS
XRT
interferometer
flat mirror
Solar-B in 2nd tower
OTA optical measurement sequence
A:Last measurement of OTA alignment @ 1st tower
System integration
System vibration/shock test
C:Post measurement @ 1st tower
System disassembling
B: Measurement on S/C @ 2nd tower
Interferometer measurement
Sys
tem
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 scale @f10.176“/m
M1
M2
TM
CLU
plate scale @f20.0456“/m
Shift 1m Tilt 1arcsec
M1 0.176 2
M2 0.222 0.565
CLU 0.046 0
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.
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)
⑥ Room temperature in vacuum
today
Wavefront error ~ 0.015 rms (on-axis)0.028 rms (140” off-axis)
chromatic aberration of CLU- FM befor/ after vibration
- 50
- 40
- 30
- 20
- 10
0
10
20
350 400 450 500 550 600 650 700 750
wavelength [nm]
Bes
t Fo
cus[
μm
]
振動試験【前】
設計値
振動試験【後】
Chromatic aberration theoretical, before/after vibration
FM Optics Status: CLU-FM was completed (Dec. 2002)
Point spread function of OTA
~ 0.21” @ 500nm
OTA pupil
Goal of OTAStrehl > 0.8
Budget for the OTA image quality
CLU (FM measurement)
M1/M2 (test coating)
CTM-TM (theoretical)
NFI wavelengths
BFI wavelengths
02.08.07: after system MTM test
02.04.11: 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.