Extreme ultraviolet imaging spectrometer for thermospheric emissions.

One of the instruments that has been developed to fly on the Space Shuttle is the Imaging Spectrometric Observatory, an array of five imaging spectrometers to cover the 300-12,000-A wavelength range. In this paper we describe the spectrometer designed to operate in the extreme ultraviolet (300-1200 A). The instrument is intended for studies of the thermosphere and magnetosphere and support of various plasma experiments to be performed from the Shuttle. The design is modular so that various components such as gratings and detectors can be changed and optimized for a range of specific studies following the first survey mission. The detector is an intensified 2-D CCD which permits simultaneous spectral and spatial imaging. The spectral multiplexing gives the spectrometer a considerable speed advantage. The instrument has a small field of view (0.65 degrees ) and is thus capable of obtaining much needed scale height information on the atmospheric EUV emissions. Operating from the Shuttle, global and temporal coverage will be obtained, and the EUV data will be enhanced by the simultaneously acquired UV, visible, and near-IR observations.

Detection of Lyman agr Emission from the Saturnian Disk and from the Ring System.

A rocket-borne spectrograph detected H I Lyman alpha emission from the disk of Saturn and from the vicinity of the planet. The signal is consistent with an emission brightness of 700 rayleighs for the disk and 200 rayleighs for the vicinity of Saturn. The emission from the vicinity of the planet may be due to a hydrogen atmosphere associated with the saturnian ring system.

Sensitive far uv spectrograph with a multispectral element microchannel plate detector for rocket-borne astronomy.

An evacuated high transmission prism spectrograph using a microchannel plate detection system with resistive strip readout was flown behind a precision pointing telescope on a sounding rocket. The construction, preparation, flight performance, and calibration stability of the system are discussed. Despite the adverse environmental conditions associated with sounding rocket flights, the microchannel detector system performed well. Far uv spectra (1160-1750 A) of stellar and planetary objects were obtained; spectral features with fluxes as low as 0.06 photons cm(-2) sec(-1) were detectable. This was achieved by operating the plates at lower than normal gains, using sensitive pulse counting electronics with both upper and lower limit discriminators, and maintaining the spectrograph and detector at a pressure of ~10(-6) Torr until reaching altitude.

Small LiF Prism Spectrometer for Space Applications.

A small LiF prism constant deviation spectrometer of the Czerny-Turner type is described. The transmission in the vacuum uv is at least twice that of a typical Ebert plane grating spectrometer. Although designed for planetary astronomy, it is also useful for airglow experiments and interplanetary missions where compactness and low weight are desirable. Without a drive, it weighs 850 g and is roughly 17 cm x 10 cm x 7 cm. However, it is mechanically rugged with high wavelength stability in flight ( 1 A). With 0.5-mm entrance and exit slits the spectral resolution is 16 A at 1216 A.