Solar active regions at millimeter wavelengths
Solar active regions at millimeter wavelengths, discussing brightness temperature, background radiation, electron density, optical thickness, polarization and chromospheric magnetic fields
Kundu, M. R.↗
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Contributions to X-ray physics in space
Background radiation in space and synchrotron X radiation in galaxy and pulsars
Schocken, K.↗
Diffuse cosmic X- and gamma radiation - The isotropic component
Isotropic diffuse cosmic X rays and gamma radiation background origin
Silk, J.↗
Instrumentation for radio astronomy measurements aboard the IMP-I spacecraft
The design considerations and performance parameters of a satellite-borne instrumentation system are discussed. The system is designed to make radio astronomy measurements at eight discrete frequencies from 50 kHz to 3.53 MHz. These measurements are to detect solar and Jovian radio frequency bursts and to determine the average cosmic background radiation level down to 50 kHz. Procedures used for preflight and inflight calibration of the radiometer and the ground support equipment used for preflight testing are described.
Haddock, F. T.↗
Gravitation research
Balloon measurements were made of the far infrared background radiation. The radiometer used and its calibration are discussed. An electromagnetically coupled broadband gravitational antenna is also considered. The proposed antenna design and noise sources in the antenna are reviewed. A comparison is made between interferometric broadband and resonant bar antennas for the detection of gravitational wave pulses.
Weiss, R.↗
X-ray emission from white dwarfs.
It is suggested that both the 250-eV background radiation and the recently observed variations in the optical emission from certain white dwarfs may be due to thermal bremsstrahlung from hot coronae surrounding such stars. The X-ray flux from the variable white dwarfs is predicted and in the most favorable case, R548, is sufficiently large to allow an observational test of the model. The possibility that the variations observed in strong X-ray sources are due to pulsations in the coronae surrounding degenerate stars, rather than in stars themselves, is also discussed. For the white dwarfs, both pulsation and rotation of the central star are found to be adequate sources of coronal energy, with pulsation being subject to relatively easy observational test. The energy requirements for the strong X-ray sources are briefly discussed.
Strittmatter, P. A.↗
Extragalactic X-ray sources.
The extended X-ray sources associated with the Virgo, Perseus, and Coma clusters of galaxies can best be explained as a result of the Compton scattering of relativistic electrons (generated in the radio sources which are present in each of these clusters) on the microwave background radiation. The same physical process involving microwave infrared or optical photons generated in the nuclei of active galaxies may account for the more compact X-ray sources. Thermal bremsstrahlung of hot gas in clusters of galaxies is a less likely source of X-rays.
Brecher, K.↗
On the estimation and detection for optical turbulent channels.
Consideration of the problem of filtering and detecting signals received through a turbulent channel at optical frequencies. Adopting the semiclassical method of quantum mechanics, application is made to the direct detection of a single-path optical communication channel where the received field is assumed to be the coherent signal field degraded by the atmospheric turbulence with a signal-independent, additive, zero-mean Gaussian background radiation.
Harger, R. O.↗
Simultaneous Raman and laser velocimeter measurements
The feasibility of performing Raman and laser velocimeter measurements simultaneously is demonstrated, and it is shown that the background radiation associated with the Mie scattering and large particulate concentrations does not saturate or distort the relatively weak rotational Raman signals. Under stringent conditions of low static gas densities and large particulate concentrations, Raman density and temperature measurements agree to within plus or minus 5% of the calculated values.
Hillard, M. E., Jr.↗
Investigation of electron dynamics in the magnetosphere with electron beams injected from sounding rockets
This paper describes an empirical study of the basic mechanisms by which electrons precipitate from the geomagnetic field to produce 'auroral X rays' during periods of geomagnetic activity. The study was based on data obtained by the Echo satellites. Echo I, launched in 1970, injected 40 keV, 0.1 amp electron pulses at low latitude (L ? 2.6) and successfully measured the returning pulses from the conjugate region. Electric fields and multiple Coulomb scattering were studied. Echo II, launched in 1972 from high latitude (L ? 8) studied the interaction of the beams with background radiation and the detailed motion of the beams near the rocket. Evidence for a beam plasma instability was obtained. Echo III launched in April 1974, (L ? 5.5) detected a series of conjugate echoes during the presence of a strong convective field in the magnetosphere. It was shown that the electric field measurement in the ionosphere using the incoherent backscatter radar and detectors on the rocket was transferred to the equatorial plane as though field lines were equipotentials.
Winckler, J. R.↗
Measurement of the spectrum of the submillimeter cosmic background
The spectrum of the night sky has been measured in the wave number range from 3 to 40 per cm using a fully calibrated liquid-helium-cooled balloon-borne spectrophotometer at an elevation of 39 km. A model based on the known molecular parameters was used to subtract the atmospheric emission. In the range from 4 to 17 per cm, the spectrum of the background radiation is that of a blackbody with a temperature of about 2.99 K.
Woody, D. P.↗
Investigation of electron dynamics in the magnetosphere with electron beams injected from sounding rockets
The Electron Echo experiments are described which were conducted with three sounding rockets to study the basic mechanisms by which electrons precipitate from the geomagnetic field to produce auroral X-rays during periods of geomagnetic activity. Echo I (1970) injected electron pulses at low latitude and successfully measured the returning pulses from the conjugate region. Echo II (1972) was launched from high latitude, studied the interaction of electron beams with background radiation as well as beam motion near the rocket, and obtained evidence for a beam plasma instability. Echo III (1974) detected a series of conjugate echoes during the presence of a strong convective field in the magnetosphere and conducted an unsuccessful search for beam bunching at the local plasma frequency. It is shown that the electric field measurement in the ionosphere, using incoherent backscatter radar and detectors on the rocket, was transferred to the equatorial plane as though field lines were equipotentials.
Winckler, J. R.↗
Dirac cosmology
The large numbers hypothesis (LNH) linking the magnitude of large dimensionless ratios in physics (on the order of 10 to the 40th power) to cosmic time is examined. The LNH is checked against evidence on 3K background radiation of the universe and the (log N, log S)-relation for radio galaxies. Earlier criticisms of LNH by Gamow and Teller are examined, and alternative hypotheses put forth by Dicke and Carter (1974) are discussed. The discussion covers: continuous (additive or multiplicative) creation of matter, the Einstein metric and the atomic metric, and general cosmological and local astronomical implications of LNH. LNH is also viewed in relation to solar evolution and pulsar physics.
Canuto, V.↗
Gamma rays and the case for baryon symmetric big-bang cosmology
The baryon symmetric big-bang cosmologies offer an explanation of the present photon-baryon ratio in the universe, the best present explanation of the diffuse gamma-ray background spectrum in the 1 to 200 MeV range, and a mechanism for galaxy formation. In the context of an open universe model, the value of omega which best fits the present gamma-ray data is omega equals approx. 0.1 which does not conflict with upper limits on Comptonization distortion of the 3K background radiation. In regard to He production, evidence is discussed that nucleosynthesis of He may have taken place after the galaxies were formed.
Stecker, F. W.↗
Baryon symmetric big-bang cosmology
The framework of baryon-symmetric big-bang cosmology offers the greatest potential for deducing the evolution of the universe as a consequence of physical laws and processes with the minimum number of arbitrary assumptions as to initial conditions in the big-bang. In addition, it offers the possibility of explaining the photon-baryon ratio in the universe and how galaxies and galaxy clusters are formed, and also provides the only acceptable explanation at present for the origin of the cosmic gamma ray background radiation.
Stecker, F. W.↗
Apollo-Soyuz pamphlet no. 3: Sun, stars, in between
The structure of the sun and its surface temperature and brightness are discussed as background for explaining the ASTP joint experiment to photograph the solar corona from Soyuz while the Apollo spacecraft created an artificial eclipse by blocking out the sun. Stellar spectra, stellar evolution, and the Milky Way galaxy are explored in relation to the MA-083 experiment to survey the sky for extreme ultraviolet sources and background radiation. Interstellar gas and the spectrum of helium are discussed in relation to the MA-088 experiment designed to detect interstellar helium entering the solar system and to measure its density and motion.
Page, L. W.↗
Far infrared polarization of the Kleinmann-Low Nebula in Orion
Elongated dust grains aligned by local magnetic fields are though to absorb background radiation and produce linear and circular polarization which exhibit strong wavelength dependence in the near infrared. The NASA Kuiper observatory 91 cm infrared telescope was used to observe polarization characteristics of the Kleinmann-Low nebula in four far infrared wavelength bands in order to detect emission from these same oriented grains at longer wavelengths, and determine whether this radiation shows a direction of polarization perpendicular to that seen in the near infrared. The polarization, if any, that characterized the radiation in the three longest wavelength filter positions (28-48 micron, 44-72 micron, and 70-115 micron) is small. The noisiest measurements were obtained in the 16-33 micron filter position. Possible explanations for the low polarization observed at long wavelengths are explored.
Gull, G. E.↗
A comparative study of optimum and suboptimum direct-detection laser ranging receivers
A summary of previously proposed receiver strategies for direct-detection laser ranging receivers is presented. Computer simulations are used to compare performance of candidate implementation strategies in the 1- to 100-photoelectron region. Under the condition of no background radiation, the maximum-likelihood and minimum mean-square error estimators were found to give the same performance for both bell-shaped and rectangular optical-pulse shapes. For signal energies greater than 100 photoelectrons, the root-mean-square range error is shown to decrease as Q to the -1/2 power for bell-shaped pulses and Q to the -1 power for rectangular pulses, where Q represents the average pulse energy. Of several receiver implementations presented, the matched-filter peak detector was found to be preferable. A similar configuration, using a constant-fraction discriminator, exhibited a signal-level dependent time bias.
Abshire, J. B.↗