Search NASA⌕ Search

Engineering topics

Wood, H. J.

Publications and source records attributed to Wood, H. J..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

MTRAP: The Magnetic Transition Region Probe

The Magnetic Transition Region Probe is a space telescope designed to measure the magnetic field at several heights and temperatures in the solar atmosphere, providing observations spanning the chromospheric region where the field is expected to become force free. The primary goal is to provide an early warning system (hours to days) for solar energetic particle events that pose a serious hazard to astronauts in deep space and to understand the source regions of these particles. The required magnetic field data consist of simultaneous circular and linear polarization measurements in several spectral lines over the wavelength range from 150 to 855 nm. Because the observations are photon limited an optical telescope with a large (>18sq m) collecting area is required. To keep the heat dissipation problem manageable we have chosen to implement MTRAP with six separate Gregorian telescopes, each with approx. 3 sq m collecting area, that are brought to a common focus. The large field of view (5 x 5 arcmin(sup 2)) and angular resolution (0.025 arcsec pixels) require large detector arrays and, because of the requirements on signal to noise (10(exp 3)), pixels with large full well depths to reduce the readout time and improve the temporal resolution. The optical and engineering considerations that have gone into the development of a concept that meets MTRAP's requirements are described.

Davis, J. M.↗
NASA NTRS1993

Telescope simulators for Hubble - An overview of optical designs

This paper briefly describes optical design of the Hubble Space Telescope (HST) and overviews three optical design simulators for HST which have been proposed for use as verification tools to characterize the performance of second-generation instruments during ground testing. These simulators are: the Refractive Aberrated Simulator developed at Ball Aerospace, the Optical Simulator developed at Laboratoire Astronomie Spatiale, and the Jet Propulsion Laboratory Stimulus. Relative advantages and disadvantages of each optical configuration are discussed.

Davilla, Pam↗
NASA NTRS1993

Optical design of zero-power Hubble Space Telescope wave-front correctors for null testing

The optical design of the second-generation wide-field/planetary-camera instrument for the Hubble Space Telescope has been modified to compensate for the spherical aberration of the optical telescope assembly (OTA) by introduction of undercorrected spherical aberration into the wave front. This instrument can be tested in a simple manner to ensure that its aberration contribution has the proper sign and magnitude. We present designs for a near-zero power doublet lens that can be used to generate a spherically aberrated wave front that is similar to the OTA wave front. When this lens is used in combination with the instrument, a near-perfect or nulled wave front should be produced, resulting in a high-quality point image on axis. We also present lens designs for a similar test that can be performed on the OTA simulators now being built to verify the other second-generation instruments.

Hannan, Paul G.↗
NASA NTRS1990

The Diffuse Infrared Background Experiment (DIRBE) - Understanding through test and simulation

Optical problems which arose during final integration and testing of the DIRBE instrument in the closed flight dewar before launch are discussed. Simulation based on the optical breadboard and engineering unit components showed that these problems (stray light signals) originated outside the instrument in the dewar dome lid. Excellent performance of the instrument confirmed this fact.

Wood, H. J.↗
NASA NTRS1982

Reconnaissance and recovery of the brighter asteroids. Brief summary of the entire project

An inexpensive method of baking large (8- by 10-inch) IIIa-J plates in 2 percent forming gas was found and successfully tested. The large storage capacity and fine grain structure of the emulsion made the sky fog negligible on plates of one-hour exposure at Link. Plates were taken through the end of October 18, 1981 on various asteroids from the recent critical lists published in the Minor Planet Circulars and the Russian Ephemeris of Minor Planets.

Edmonson, F. K.↗
NASA NTRS1981

Outburst and nuclear breakup of Comet Halley - 1910

Computer processing of five plates of Comet Halley taken during the 1910 apparition shows that on May 24 strong asymmetric (with respect to the tail axis) fountain-like parabolic plumes had developed on the sunward side of the nucleus. Visual observations showed that after an initial fading while passing in front of the sun, the brightness increased to about magnitude 1. On the plates taken May 31, the nucleus is clearly divided into at least three parts of nearly equal brightness. However, the last plate on June 3 shows a symmetrical coma with a small stellar-like nucleus.

Wood, H. J.↗
NASA NTRS1980

Zeeman observations of W Sgr

A new precise method for measuring magnetic fields on Zeeman plates of the southern Cepheid 'W Sgr' is reviewed. Ten plates over the 7.6(d) period of pulsation show two extrema in the measured values of the effective magnetic field. The method has a precision of + or - 0.4 microns in the Zeeman shift corresponding to + or - 50 Gauss (g). A negative spike of -220 g occurred at the time of arrival of the compressional wave of pulsation at the stellar surface. A positive field of +270 g occurred at the phase of most rapid contraction near the temperature minimum of the pulsation cycle.

Wood, H. J.↗