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Detection of Celestial Sources at Far-Infrared Wavelengths
Abstract
Celestial sources far IR radiation detection using balloon-borne telescope
Fig. 1 Portion of observed solar spectrum between 40 and 54 cm"1, Pikes Peak, April 13,1971. Intensity in arbitrary units.
The preparation of high-pass inclusion filters for the far-infrared spectral range is described. Rejection factors (1/T) better than 103–104 in the visible and near infrared together with a high transmittance (T = 70–80%) in the far infrared up to ∼300 μ, have been obtained.
These filters are used in high altitude experiments on far-infrared detection of extraterrestrial sources.
A retrospective is given on infrared sky surveys from Thomas Edison’s proposal in the late 1870s to IRAS, the first sensitive
mid- to far-infrared all-sky survey, and the mid-1990s experiments that filled in the IRAS deficiencies. The emerging technology
for space-based surveys is highlighted, as is the prominent role the US Defense Department, particularly the Air Force, played
in developing and applying detector and cryogenic sensor advances to early mid-infrared probe-rocket and satellite-based surveys.
This technology was transitioned to the infrared astronomical community in relatively short order and was essential to the
success of IRAS, COBE and ISO. Mention is made of several of the little known early observational programs that were superseded
by more successful efforts.
During a high-altitude balloon flight, sources of far-infrared radiation have been detected with apparent fluxes greater than or about equal to 3 pW/sq cm in the spectral band from 50 to 500 microns. While the sources are not uniquely identifiable with any well-known class of celestial objects, two associations should be noted. Many of the objects lie close to local stars; there is also a tendency to cluster around the ecliptic plane. Alternatively, a new class of celestial objects may have been observed.
A description is given of a simple and reliable system for recording information which in a postflight analysis will make it possible to determine the orientation of the telescope beam for any arbitrary time during the flight. The system provides a continuous in-flight photographic reference to the pole star. Questions of system design are considered and instrumental details are presented. Attention is also given to aspects of calibration and postflight analysis.
IR radiation sources, discussing intermediate and early stars, galactic nucleus and extragalactic sources
Far IR source in galactic center detected at 100 microns, noting thermal emission of interstellar dust grains as possible mechanism
WE have measured the radiation from the region of the Crab nebula (Taurus A) in a waveband centred at 1.2 mm (250 GHz) in the far infrared. Our equipment was an indium antimonide detector of the Rollin1 type cooled by liquid helium at the cassegrain focus of the 98 inch Isaac Newton telescope of the Royal Greenwich Observatory. The observations were made with the aid of a rapid-scan unit, comprising an oscillating mirror which scanned in declination 13.7′ of arc on the sky either side of its axial point with a period of 1.2 s. The effect of the rapid scanning is to increase the discrimination of the system against v-1 components in both sky background and detector electronic noise2. The scans were synchronized, stored digitally and averaged by means of an "enhancetron" digital analyser, which provided a visual display and chart recorder readout.
Infrared flux densities have been measured over the last 5 years for a number of galaxies. The continuum out to 25 μ, the existence of large variations, and estimates of total infrared luminosities are presented.
Cosmic IR radiation sources, discussing galactic and stellar masses
A series of far-infrared surveys of the sky is searching for thermal radiation from interstellar grains and for other localized
sources of far-infrared radiation. A balloon-borne germanium bolometer, cooled by liquid helium, is used in association with
a telescope and spectral filters. During two initial flights the response to a black-body source was mainly between 300 and
360 microns. Approximately half the celestial sphere was surveyed, including most of the northern Milky Way. The angular resolution
was 2 degrees. Moon was the only source of thermal radiation detected. The upper limit on the differential flux, relative
to background, from other sources was 2 x 10-23 watt per square centimeter per hertz, corresponding to an antenna temperature of 0.6°K in the Rayleigh-Jeans approximation,
or 10°K for a black body.
IR luminosity of galactic nucleus from far IR observations, noting considerations favoring nonthermal model consisting of multiple sources
IR radiation sources /irtrons/ accounting for energy releases by continuous matter and antimatter creation