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It is shown that the Kleinmann-Low nebula continues to radiate like a 70-deg-K blackbody at 69 microns, as it does at shorter wavelengths, but that most of the 69-micron flux from Ori A (M42) comes from an extended emission that roughly follows the free-free radio emission. Nearby sources also detected include the nebula M43 and the molecular cloud OMC-2.
Localized sources of far infrared radiation (approximately 50 microns) have been detected during a high altitude balloon flight with a 40 cm telescope and silicon detectors. The flight system is described and preliminary results are presented. A large area of the sky has been scanned for localized sources of far infrared radiation, using a balloon-borne system that was sensitive to wavelengths beyond about 55 microns. Two Molectron silicon bolometers were used, with a Newtonian telescope having a 40 cm primary. The telescope was driven in azimuth at a fixed elevation; this mode of scanning was carried out for the duration of each of two balloon flights. The flight system is described.
Passive radio observations are discussed from 1 mm to 2 cm wavelengths. The interferometric technique was used to observe the brightness of the rings. The reflectivity and disk temperature are also considered. The differences between radio and radar observations are examined and discussed.
The gf values for 265,587 atomic lines selected from the line data used to calculate line-blanketed model atmospheres are tabulated. These data are especially useful for line identification and spectral synthesis in solar and stellar spectra. The gf values are calculated semiempirically by using scaled Thomas-Fermi-Dirac radial wavefunctions and eigenvectors found through least-squares fits to observed energy levels. Included in the calculation are the first five or six stages of ionization for sequences up through nickel. Published gf values are included for elements heavier than nickel. The tabulation is restricted to lines with wavelengths less than 10 micrometers.
A detailed gravimetric geoid was computed for the Northwest Atlantic Ocean and Caribbean Sea area in support of the calibration and evaluation of the GEOS-C altimeter. This geoid, computed on a 15 ft. x 15 ft. grid was based upon a combination of surface gravity data with the GSFC GEM-6 satellite derived gravity data. A comparison of this gravimetric geoid with 10 passes of SKYLAB altimeter data is presented. The agreement of the two data types is quite good with the differences generally less than 2 meters. Sea surface manifestations of numerous short wavelength (approximately 100 km) oceanographic features are now indicated in the gravimetric geoid and are also confirmed by the altimetry data.
The fixed 20/30 GHz ground terminal is described in detail; it is being used for path diversity measurements in the ATS-6 millimeter wavelength propagation experiment. The current status and summary of operations are reviewed.
The design, fabrication, and testing of a radiative cooler are described. This cooler is an engineering model suitable for bench testing in the laboratory as a part of the 10-micrometer wavelength engineering model receiver, and conforms to the standard radiative cooler configuration, except that the inner stage and its support system were redesigned to accommodate the larger, heavier SAT detector. This radiative cooler will cool the detector to cryogenic temperature levels when the receiver is in a space environment or in a suitable thermal vacuum chamber. Equipment specifications are given along with the results of thermal tests, vibration tests, and electrical integrity tests.
From short wavelength interferometry of Venus interpreted on the basis of the physical structure and bulk composition of its atmosphere as given by spacecraft measurements, evidence for the presence of a source of opacity in addition to CO2 is found. This opacity presumably is due to unknown minor constituents of the atmosphere of Venus.
Construction and mode of operation are described for a sounding rocket spectroheliometer used to establish the sensitivity of the EUV spectroheliometer on the Skylab Apollo Telescope Mount (ATM). The sounding rocket instrument was calibrated immediately before and after two flights and the calibration was transferred when the rocket and ATM instruments simultaneously measured the average intensity emitted by a quiet area of the solar disk. Descriptions are presented for the payload assembly and flight sequence, the optical system (telescope, spectrometer, and pointing reference camera), the vacuum pumping system, and the instrument electronics. Results obtained from the two flights in August and December 1973 are discussed, which included unambiguous determinations of the absolute intensity emitted by a region of the quiet solar disk over the wavelength range from 1350 to 300 A on two separate occasions and the establishment of photometric accuracy to that of laboratory calibration procedures.
The significant aspects of the NASA MAT (measurement of atmospheric turbulence) program are described. A principal objective of the project is to determine if the Von Karman equation is appropriate for clear-air turbulence in various meteorological conditions, and if so, to define the appropriate L-values in the equation. The current work is primarily a status report describing the measurement system and analysis procedure, some meteorological aspects, and several preliminary results. Measurements of gust velocity will be made over a wide altitude range and in different meteorological conditions. Power spectral density values will be obtained for the three components of gust velocity to wavelengths of 30,000 ft and greater. Principal meteorological parameters of interest include the jet stream, mountain waves, and flight at low altitude (or in the earth's boundary layer).
Data are presented on type II and type III radio bursts observed at hectometric and kilometric wavelengths in the interplanetary medium by IMP-6. Thirty-two discrete frequencies were recorded which ranged from 4.9 MHz down to 30 kHz. Intensity contours are plotted for the data, and it is noted that the type II emission was observed at both the plasma frequency characteristic of its point of origin in the corona and the second harmonic of that frequency. It is suggested that hectometric and kilometric type III bursts are observed at twice the plasma frequency of the source.
The area in the vicinity of the H II region W3 is mapped at an effective wavelength of 69 microns with high angular resolution (1 min) using the 102-cm balloon-borne telescope. The main continuum source, W3, shows a partially resolved complex structure with a FWHM size of 1.8 min. The radio sources W3(OH) and G133.8 + 1.4 are also observed as well as three faint sources not associated with known radio emission.
The Ohio State University participation in the ATS-6 Millimeter Wavelength Propagation Experiment is summarized. Attenuation was measured simultaneously at 20 and 30 GHz on earth space propagation paths to two ground terminals located at Columbus, Ohio. In addition, 20 and 30 GHz radiometric temperatures were measured along the same propagation paths; and the 20 GHz radiometric temperature was also measured at a third ground terminal. The results of these measurements are presented, and diversity gains for the four pairs of propagation paths are discussed. The scintillation characteristics of the received signals are also presented.
Observations made during a series of meter-wavelength very-long-baseline (VLBI) experiments conducted during 1971-1973 are reported. A wide variety of objects was observed, including many extragalactic sources known to have compact components, several strong pulsars (especially the Crab nebula pulsar), and a selection of supernova remnants. The experiments are discussed in detail, and tests made to check the consistency of the results are described. The measured correlated flux densities are presented for each source as a function of interferometer baseline and observing frequency. An assessment is made of the measurement errors and of the possibility of confusion within the interferometer beam. The results show that all sources except the pulsars, which are known to have intrinsically small sizes, are resolved on the longest baseline. We also conclude that no supernova remnants except the Crab nebula and Cassiopeia A gave evidence of compact components.
A study of the asteroid 433 Eros using 3.5 and 12.6 cm radar waves indicates that the surface is very much rougher than any planetary or lunar surface observed by this method. A surface completely covered with sharp edges, pits, subsurface holes, or embedded chunks with scale sizes on the order of our wavelengths seems to be indicated. A model based on a rough rotating triaxial ellipsoid having radii in the rotation equator of 18.6 and 7.9 km agrees well with our data, although a strong wobble in the apparent center frequency of the spectra as rotation progresses indicates that one side may be more reflective than the other, or more likely, that the projected axis of rotation does not equally divide the projected area.
Observations of pulsars, especially the Crab Nebula pulsar, made in very long baseline interferometry (VLBI) experiments are discussed. Based on a crude 144 MHz visibility curve which is consistent with a Gaussian brightness distribution, the measured visibilities at 196, 111, and 74 MHz were interpreted to yield apparent angular diameters (at half-power) of about 0.03 sec, 0.07 sec, and 0.18 sec, respectively. These sizes scale approximately as wavelength-squared, and the 74 MHz size agrees with recent observations using interplanetary scintillation techniques. The total flux densities lie on the extrapolation from higher frequencies of the pulsing flux densities. Variations in the total flux density up to 25 per cent were observed. A lack of fine structure other than the pulsar in the nebula is indicated by the simple visibility curves. The pulse shapes are similar to single-dish measurements at 196 MHz but reveal a steady, nonpulsing component at 111 MHz. The ratio of pulsing to total power was approximately equal to one-half but varied with time. It was found that four strong, low-dispersion pulsars were only slightly resolved.
Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.
Analysis of the O I /5577-A wavelength/ airglow observations conducted on board the Atmosphere Explorer C satellite yields the following results when combined with simultaneous measurements of ion and neutral composition. A volume emission rate profile derived after sunset requires the production of an O(1S) atom in 8% of the O2(+) recombinations. Photoelectric impact on atomic oxygen and the dissociative recombination of O2(+) are important sources of O(1S) in the dayglow; however, the airglow measurements require a large additional production of O(1S) below 200 km in addition to these. The reaction N + O2(+) yielding NO(+) + O(1S) can provide the missing O(1S) source if the rate coefficient is near 2.5 times 10 to the minus 11th cu cm per sec.