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Redding, D. C.

Publications and source records attributed to Redding, D. C..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Wavefront sensing and control for large space optics

Large space optical systems will require on-orbit wavefront sensing and control systems to correct misalignments and figure errors incurred during manufacture, launch and deployment.

NGST wavefront sensing wavefront control segmented↗
NASA NTRS2002

Phase retrieval camera for testing NGST optics

The NGST Phase Retrieval Camera (PRC) is a portable wavefront sensor useful for optical testing in high-vibration environments. Primary applications of the PRC are testing and experimenting with NGST technology demonstrator mirrors, along with exploring other wavefront sensing and control problems not easily studied using WCT. An overview of the hardware and testing results will be presented.

NGST↗
NASA NTRS1990

Calibration and operation of a large space-based optical interferometer

The on-orbit calibration of the optics, structure, and control systems of the CSI Focus Mission Interferometer (FMI) is described. The calibration involves the estimation and propagation of both positional and rotational parameters and the propagation of both positional and rotational parameters at the nanometer/nanoradian level. It is shown that, given a nanometer class metrology system to monitor positional changes of critical optical elements, this calibration procedure should enable the FMI to perform 50 picoradian astrometry. The same Kalman filter that implements the initializing calibration of the interferometer baselines and internal pathlengths will also participate in the astrometric measurements of stellar positions.

Laskin, R. A.↗
NASA NTRS1986

Linear-quadratic stationkeeping for the STS Orbiter

An automatic controller for Space Shuttle Orbiter stationkeeping or formationkeeping is presented. The controller uses a feed-forward loop for precise control at non-equilibrium set points, and a discrete-time linear quadratic regulator for disturbance rejection. Selection of sample time and quadratic cost matrices is done to provide good limit cycling performance in the presence of sensor noise and a control threshold nonlinearity. Large position changes are effected by feed-forward of a minimum fuel or straightline maneuver path. Results show that 20 ft precision can be achieved using current sensors, and that 2 ft precision would be possible with enhanced sensors.

Redding, D. C.↗
NASA NTRS1985

An optimized rotation-axis model-following controller for STS orbiter attitude maneuvers

This paper describes a new controller for automatic attitude maneuvers of the Space Shuttle Orbiter. The controller incorporates a new solution algorithm for partially linearized, fuel-optimal maneuvers for RCS jet controlled spacecraft. These solutions provide model trajectories and jet commands that are easily tracked using a feed-forward, feedback controller structure. The result is a substantial performance improvement over the current Orbiter attitude maneuver controller. The paper discusses optimal maneuvers for this type of vehicle, giving detail of the solution algorithm. Closed-loop controller design and implementation is discussed. Detailed performance results are presented.

Redding, D. C.↗