Engineering topics

Jura, M. A.

Publications and source records attributed to Jura, M. A..

4 records

NASA NTRS1984

Laboratory test results on the High Resolution Spectrograph (HRS) for the Space Telescope (ST)

Some of the laboratory measured performance parameters of the HRS are reported. Then a description is given of three aspects of performance of particular importance to astronomers: (1) the capability of detecting very weak features against a continuum, (2) the capability of producing reliable line profiles, and (3) the capability of assigning accurate wavelengths to spectral features. Specific technical descriptions of the performance of the HRS detectors (Eck and Beaver, this volume), gratings (Bottema et al., this volume), and control and data-handling system (Becker, this volume) are reported separately.

Brandt, J. C.↗

NASA NTRS1982

Ultraviolet images of M101 - Observations of dust and inferences on the metallicity

Since extreme Population I dominates three rocketborne telescope UV images of the Sc I galaxy NGC 5457, the delineation of the spiral structure is sharper than that of ground photographs. The UV pictures, in which the H II regions appear as reflection nebulae and illumine the nearby dust, reveal faint arms which, although correlated with the 21 cm H I radiograph, are only marginally detectable on deep visual photographs. The surface brightness of the arms is explainable in terms of UV light scattering off dust from hot stars and bright H II regions, in which case the dust would have extinction properties and a dust-to-gas ratio similar to that in the solar neighborhood and would in addition suggest that the NGC 5457 outer arm metal content is similar to that of the galaxy.

Stecher, T. P.↗

NASA NTRS1981

Progress report on the high resolution spectrograph for the Space Telescope

The instrument design is complete and many components and subsystems have been manufactured and tested. Solar-blind, multichannel, pulse counting detectors for two ultraviolet spectral bands have been developed and satisfactory flight units have been chosen. A large, lightweight graphite-epoxy optical bench, utilizing fingerplate joints with no metallic parts in order to minimize thermal expansion, has been built. Tests of the engineering model torque-motor-driven grating carrousel indicate that this critical system exceeds tight specifications for accurate and repeatable angular positioning. A complement of large, high-frequency gratings and an echelle is being completed in several laboratories. Software resident in a computer on the spacecraft will control the spectrograph with the capability to alter procedures in response to real-time evaluation of the data.

Brandt, J. C.↗

NASA NTRS1979

High resolution spectrograph for the Space Telescope

The high resolution spectrograph (HRS) for ultraviolet astronomy with the Space Telescope will provide a spectral resolution of approximately 120,000 over a nominal wavelength range of 110-320 nm, together with a spatial resolution of about 0.25 arc seconds. The two detectors will consist of 512-element Digicons with cesium telluride and cesium iodide photocathodes, respectively. Photoelectrons in transit between the photocathodes and the diodes within the Digicons can be deflected in two axes with 12-bit resolution. This feature facilitates a design that emphasizes reliability since (once a hermetic seal is opened in orbit), only two moving parts, a grating carrousel and a shutter, are required for regular operation of the HRS. The instrument will be controlled by a computer in the spacecraft. The scientific objectives of the HRS investigation relate to interstellar matter in our own and nearby galaxies, physical processes of stellar mass loss and mass transfer, chemical abundances, bright quasars and Seyfert galaxy nuclei, and solar system phenomena.

Brandt, J. C.↗