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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A very high frequency radio interferometer for investigating ionospheric disturbances using geostationary satellites. Determination of changes in exospheric electron content by a comparison of group delay and Faraday rotation

The theory and development of a VHF correlation radio interferometer for investigating ionospheric disturbances are discussed. The system was developed to receive signals from the geostationary Applications Technology Satellites. Amplitude and phase variations of the signal passing through the ionosphere can be detected by this instrument. The system consists of two superheterodyne receivers separated by a distance known as the baseline of the system. Since the system is a phase sensitive instrument, the local oscillators of the two receivers must be phase coherent. This is accomplished by using phase-locked loops for generating the local oscillators. The two signals from the separate receivers are cross-correlated by multiplying the two signals together and then time averaging the result. The sensitivity of the instrument is increased by off-setting one of the local oscillators by a small amount.

Terry, R.↗
NASA NTRS1972

Tracking of the ATS-3 synchronous satellite by the Very Long Baseline Interferometer (VLBI) technique

During 1971, a series of very long baseline interferometer observations were made of the C-band (6 cm) radio signals from the ATS-3 communications satellite which is in a synchronous, near-equatorial orbit. The first series of observations were conducted during May-June 1971 from Rosman, North Carolina (NASA/ATS Station 85' dish) and Mojave, California (NASA/ATS Station, 40' dish). The second series of observations were conducted during August-September, 1971 from Rosman, North Carolina (NASA/ATS Station, 85' dish), Owens Valley, California (Cal Tech, 130' dish) and Agassiz, Massachusetts (SAO Agassiz Radio Observatory, 84' dish). The ATS-3 Spacecraft position was determined with a precision of 70-100 meters and its velocity with a precision of less than a mm/sec. The ATS-3 orbital elements were computed using the GEODYN program and the derived values are consistent with those derived from conventional tracking data.

Ramasastry, J.↗
NASA NTRS1971

The use of the transmission windows of the Fabry-Perot interferometer in the detection of Raman scattered radiation from atmospheric gases.

Demonstration that the use of the Fabry-Perot interferometer as a filter with transmission windows occurring at regular intervals in wave numbers provides a highly sensitive method for detection of atmospheric gases using their rotational Raman spectra excited by a suitable laser. Some of the operating advantages include signal gains of several orders of magnitude, a simple direct interpretation of the results in terms of the density and types of the gaseous constituents, size and weight reductions from conventional apparatus, ease of operation, and relative freedom from interference from other molecules in the scattering volume. This method is compared with the techniques that have been discussed in the literature by other workers in the field.

Smith, W. H.↗