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Shaw, John

Publications and source records attributed to Shaw, John.

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

WFIRST Low Order WaveFront Sensing and Control (LOWFS/C) performance on line-of-sight disturbances from multiple reaction wheels

In this paper we will describe the LOWFS/C LoS performance test in which the injected LoS disturbances are derived from all six reaction wheels on WFIRST, each with an independent varying wheel speed profile modeled for a typical coronagraph observational scenario. We will describe the LoS disturbances profile and testbed implementation approach. We will present the LOWFS/C LoS feedback and feed forward loops testbed performance under these realistic LoS disturbances in which we have demonstrated the LoS control that meets the CGI requirement.

Shelton, Chris↗
NASA NTRS2018

WFIRST Low Order Wavefront Sensing and Control Testbed Performance under Flight Like Photon Flux

To maintain the required performance for the WFIRST Coronagraph Instrument (CGI) in a realistic space environment, a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem is necessary. The WFIRST CGI LOWFS/C subsystem would use the Zernike wavefront sensor, which has the phase-shifting disk combined with the coronagraph’s focal plane mask, to sense the low-order wavefront drift and line-of-sight (LoS) error using the rejected starlight. The dynamic tests on JPL’s on the Occulting Mask Coronagraph (OMC) Testbed have demonstrated that LOWFS/C can maintain coronagraph contrast to better than 10-8 in presence of WFIRST-like line of sight and low order wavefront disturbances in both Shaped Pupil Coronagraph (SPC) and Hybrid Lyot Coronagraph (HLC) modes. However, the previous dynamic tests have been done using a bright source with photon flux equivalent to stellar magnitude of Mv = -3.5. The LOWFS/C technology development continues on the OMC testbed especially in evaluating and improving the LOWFS/C performance under the realistic photon flux that is equivalent to WFIRST Coronagraph target stars. Our recent testbed tests have demonstrated that the LOWFS/C can work cohesively with the stellar light suppression wavefront control, which brings broad band coronagraph contrast from 1x10-6 to 6x10-9, while LOWF/C is simultaneously suppressing the WFIRST like LoS and low order wavefront drift disturbances on a source that photon flux is equivalent to a Mv = 2 star. This demonstration mimics the CGI initial dark hole establish process on a bright reference star. We also demonstrated on the testbed that LOWFS/C can maintain the coronagraph contrast by suppressing the WFIRST like line-of-sight disturbances on a fainter Mv = 5 star. This mimics scenario of CGI science target observations. In this paper we will present the recent testbed results on LOWFS/C LoS loops and low order wavefront error correction loop performance on the flight like photon flux.

Truong, Tuan↗
NASA NTRS1988

Rotorcraft technology at Boeing Vertol: Recent advances

An overview is presented of key accomplishments in the rotorcraft development at Boeing Vertol. Projects of particular significance: high speed rotor development and the Model 360 Advanced Technology Helicopter. Areas addressed in the overview are: advanced rotors with reduced noise and vibration, 3-D aerodynamic modeling, flight control and avionics, active control, automated diagnostics and prognostics, composite structures, and drive systems.

Shaw, John↗