Cryogenic performance test results for the flight model JWST fine guidance sensor

Rowlands, Neil; Delamer, Sandra; Haley, C. S.; Harpell, Eric; Vila, M. Begona; Warner, Gerry; Zhou, Julia

doi:10.1117/12.926672

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…The FGS flight instrument underwent cryogenic performance testing from November 2011 to February 2012 [9]. The test was performed with the FGS instrument and custom Optical Ground Support Equipment (OGSE) installed in the TV3 chamber at the Canadian Space Agency's David Florida Laboratories in Ottawa Ontario (Figure 2-1).…”

Section: Fine Guidance Sensor Test Environmentsmentioning

confidence: 99%

Asymmetry in the noise equivalent angle performance of the JWST fine guidance sensor

Rowlands

Warner

et al. 2014

SPIE Proceedings

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The James Webb Space Telescope Fine Guidance Sensor makes use of three 2048x2048 five micron cutoff H2RG HgCdTe detectors from Teledyne Imaging Systems. The FGS consists of two Guider channels and a Near-InfraRed Imager and Slitless Spectrograph (NIRISS) channel. We report here on detailed tests results from the Guider channels originating in both instrument level performance testing and from recent Guider performance testing with the FGS integrated into JWST's Integrated Science Instrument Module (ISIM).A key performance parameter is the noise equivalent angle (NEA) or centroiding precision. The JWST requirement flowed down to the Guiders is a NEA of 4 milli-arcseonds, equivalent to approximately 1/20 th of a detector pixel. This performance has been achieved in the testing to date. We have noted a systematic asymmetry in the NEA depending on whether the NEA in the row or column direction is considered. This asymmetry depends on guide star brightness and reaches its maximum, where the row NEA is 15% to 20% larger than the column NEA, at the dim end of the Guide star brightness range.We evaluate the detector level characteristics of spatially correlated noise and asymmetric inter-pixel capacitance (IPC) as potential sources of this NEA asymmetry. Modelling is used to estimate the impact on NEA of these potential contributors. These model results are then compared to the Guider test results obtained to date in an effort to isolate the cause of this effect. While asymmetric IPC can induce asymmetric NEA, the required magnitude of IPC is far greater than observed in these detectors. Thus, spatially correlated noise was found to be the most likely cause of the asymmetric NEA.

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Section: Fine Guidance Sensor Test Environmentsmentioning

confidence: 99%

Asymmetry in the noise equivalent angle performance of the JWST fine guidance sensor

Rowlands

Warner

et al. 2014

SPIE Proceedings

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“…The operation of the guider has been extensively verified both by analysis, in simulators and testing with the flight hardware and simulated optical sources to confirm it does generate a centroid position every 64 ms, with a latency of 40 ms -latency being defined as the time between the middle of the integration in the detector and the time when the centroid is picked up on the next 64 ms Spacecraft minor cycle. 10,11,12,13 The performance of the ACS has been verified by analysis and on simulators and the operation of the FSM testing at lower level.…”

Section: Fine Guidance Control Functionalitymentioning

confidence: 99%

JWST cryo fine guidance closed loop test results

Vila

Lambros²,

Diaz

et al. 2018

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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Keywords: Fine Guiding, Closed Loop, Attitude Control, Pointing, Stability, Control, James Webb Space Telescope, Line of SightThe James Webb Space Telescope uses the Fine Guidance Controller to achieve pointing accuracy to a millionth of a degree needed for its scientific observations. This closed loop controller includes the Fine Guidance Sensor instrument, the Attitude Control System, and the Fine Steering Mirror, all working together to generate precise attitude updates every 64 ms to stabilize and point the Observatory. It was exercised for the first time with the flight hardware during the cryogenic test at Johnson Space Center. We provide a top level summary of the test, the results, and its performance in preparation for on-orbit operations.

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