Engineering topics

Mccarthy, S. G.

Publications and source records attributed to Mccarthy, S. G..

4 records

NASA NTRS1978

Infrared detector performance in the Shuttle Infrared Telescope Facility /SIRTF/

The limitations imposed on infrared detectors for SIRTF are quite different from those imposed on ground-based, balloon-borne, or aircraft-borne systems. The paper examines the limitations and provides performance predictions corresponding to SIRTF conditions. Detector parameters typical of an infrared camera are used. The detector size is taken to be of the order of the diffraction-limited spot, frequency response is taken to correspond to a fraction of a second or less time constant, and spectral definition is provided by multilayer dielectric filters, inductive or capacitive grids, intrinsic absorption, or a combination of these. A nominal 10-micron bandwidth is assumed. The discussion covers atmospheric absorption and emission, zodiacal dust radiance, Shuttle contaminants, telescope self-emission, charged particle radiation, clear environment detector performance, and trapped radiation effects. It is concluded that the SIRTF design and operating conditions will allow current and near-term state-of-the-art detectors to reach their performance limits with SIRTF at a temperature of 10-12 K.

Mccarthy, S. G.↗

NASA NTRS1976

Shuttle/Spacelab - Platform for a cooled infrared astronomical telescope

The Shuttle IR telescope facility is planned to provide a major advance in sensitivity and observations across an IR spectrum from 1 micron to 1 mm. To accomplish this it will operate in a low earth orbit, above most of the atmosphere. The described analysis of revised designs and operations shows that the volume and weight capacity of the Shuttle is adequate for the telescope requirements. Contamination from Shuttle effluents will be significant only in the band between 20 and 30 microns, where it will degrade performance by a factor of 1.7. (The degradation will occur only with the evaporators operating.) With the addition of the telescope's fine stabilization system, the Spacelab instrument pointing and stabilization system will provide the pointing freedom and stability necessary for the telescope to reach its design goals.

Mccarthy, S. G.↗

NASA NTRS1976

Shuttle Infrared Telescope Facility

The Shuttle Infrared Telescope Facility (SIRTF) will combine high sensitivity with the flexibility offered by the Space Transportation System. A recently completed study has generated a preliminary design which demonstrates the feasibility of SIRTF. The 1.0 to 1.5 meter aperture, f/8 Gregorian telescope will be cooled to 20 K by a stored supercritical helium system. The telescope will be pointed and stabilized at two levels: the European-developed Instrument Pointing System provides primary pointing and stabilization; and an internal star tracker senses residual errors and drives a folding mirror inside the telescope to null the errors. The folding mirror can also be driven by square or triangular waves to provide space chopping or small-area scanning.

Mccarthy, S. G.↗

NASA NTRS1975

A large cooled infrared telescope facility for Spacelab

An optimized cooled IR telescope of 1 m aperture diameter will offer sensitivities over the 1 micron to 1 mm spectrum at least 1000 times greater than can be achieved from the ground in the atmospheric windows, and comparable sensitivities at wavelengths that are outside the windows. A study has shown that a cryogenically-cooled telescope of up to 1.6 m aperture diameter for Spacelab is feasible without new technology, although some development of detectors and scientific instruments to take advantage of the extreme sensitivity is indicated.-

Mccarthy, S. G.↗