Engineering topics
Publications and source records attributed to Sterk, A. A..
The detailed optical design of the Solar Maximum Mission-Ultraviolet Spectrometer and Polarimeter is discussed in conjunction with the scientific objectives that led to the design. The instrument consists of a 1.8-m effective focal length aplanatic Gregorian telescope followed by a 1-m Ebert spectrometer. The design of the Stokes polarimeter is also discussed.
The instrument observes spectral line intensity, Doppler motions, and polarization parameters. First Dopplergrams of the sun showing mass motion of prominences have been obtained. The instrument consists of a telescope, a spectrometer, a polarimeter, and five detectors. Spectral range extends from 1150 to 3600 Angstroms. The telescope is an alphanatic Gregorian capable of scanning a 256 x 256 arcsecond raster. The spectrometer is an Ebert-Fastie mount with exchangeable slits for intensity measurements and spectroscopy. Detectors are photomultipliers operating in the pulse-counting mode.
It is demonstrated that a photoinitiated emulsion polymerization can be carried out to a significant conversion in a SPAR rocket prototype polymerization vessel within the six minutes allowed for the experiment. The percentage of conversion was determined by both dilatometry and gravimetric methods with good agreement. The experimental results lead to the following conclusions: (1) emulsion polymerizations can be carried out to conversions as high as 75%, using a stable micellized styrene-SLS system plus photoinitiator; (2) dilatometry can be used to accurately determine both the rate and conversion of polymerization; (3) thermal expansion due to the light source and heat of reaction is small and can be corrected for if necessary; (4) although seeded emulsion polymerizations are unfavorable in photoinitiation, as opposed to chemical initiation, polymerizations can be carried out to at least 15% conversion using 7940A seed particles, with 0.05% solids; and (5) photoinitiation should be used to initiate polymerization in the SPAR rocket experiments because of the mechanical simplicity of the experiment.
The results of a program directed toward the definition of an EUV and X-ray spectroheliograph which has significant performance and operational improvements over the OSO-7 instrument are documented. The program investigated methods of implementing selected changes and incorporated the results of the study into a set of drawings which defines the new instrument. The EUV detector performance degradation observed during the OSO-7 mission was investigated and the most probable cause of the degradation identified.
A complex scientific instrument was designed, fabricated, tested, and calibrated for launch onboard OSO-H. This instrument consisted of four spectroheliographs and an X-ray polarimeter. The instrument is designed to study solar radiation at selected wavelengths in the X-ray and the extreme ultraviolet ranges, make observations at the H-alpha wavelength, and measure the degree of polarization of X-ray emissions.