Comstar Experiment: The Crawford Hill 7-Meter Millimeter Wave Antenna

Chu, Tianshu; Wilson, R. W.; England, Richard; Gray, D. A.; Legg, W. E.

doi:10.1002/j.1538-7305.1978.tb02099.x

Cited by 38 publications

(12 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Transients during these large phase changes cause uncertainty in calculating the location of the symmetry axis. Since a 90 ø rotation would not 1974; Cox, 1978;Chu et al, 1978; (This signal polarization is aligned with the more nearly vertically polarized 19-GHz Cornstar signal. ), (2) measurement of the depolarization of a 12-GHz circularly polarized signal transmitted from the Communications Technology Satellite (CTS) (Hermes) satellite (This signal is received with elevation 27 ø and azimuth 234 ø at Crawford Hill by a 6-m antenna and receiver [Rustako, 1978].…”

Section: Most Step Changes In Depolarization Are Increases; However mentioning

confidence: 99%

Observations of rapid changes in the orientation and degree of alignment of ice particles along an Earth‐space radio propagation path

Cox¹,

Arnold²

1979

J. Geophys. Res.

View full text Add to dashboard Cite

Rapid changes (<• s) have been observed in the depolarization of earth-space radio signals propagating through ice clouds. This paper presents the first observations of the rapid changes in the degree of alignment and in the orientation of the anisotropy axis of the ice particles producing the depolarization. The ice particles appear to be aligned by the intense electric field in thunderstorms and appear to realign rapidly with the new field directions existing after lightning discharges. INTRODUCTION It has become generally accepted that the anisotropy of aligned ice particles in clouds along earth-space propagation paths causes significant depolarization of centimeter wavelength radio waves. [Cox and Arnold, 1976; McEwan et al., 1977; Shutie et al., 1977a, b,' Cox et al., 1977; Cox et al., 1978; Haworth et al., 1977; Arnold and Cox, 1977; Rustako, 1977; Rustako, 1978]. Early investigators of this ice depolarization reported occasional rapid changes in the depolarization magnitude that was sometimes coincident with lightning strokes [McEwan et al., 1977; Shutie et al., 1977a; Haworth et al., 1977; Arnold and Cox, 1977; Rustako, 1977; and Rustako, 1978]. These rapid changes were attributed to rapid changes in the degree of alignment or the orientation of the alignment of small ice crystals that were observed with radar by Hendry and McCormick [1976]. This paper presents the first observations of rapid changes in the degree of alignment and in the orientation of the anisotropy axis for ice particles producing depolarization on an earth-space radio path. The observations were made using a 19-GHz Cornstar satellite beacon [Cox, 1974; Cox, 1978] and the Bell Laboratories Crawford Hill receiving site [Cox, 1974; Cox, 1978; Chu et al., 1978; Arnold et al. , 1978]. The unique feature of this experiment that makes these observations possible is the measurement of differential phase between two copolarized received signals that have orthogonal polarizations. An example is shown also of rapid changes observed simultaneously in the atmospheric electric field and in the depolarization of linearly polarized 19-and 28-GHz satellite signals and circular polarized 12-GHz satellite signals [Rusteko, 1978]. THE EXPERIMENT The experimental equipment is described in detail by Cox [ 1978], Chu et al. [ 1978], and Arnold et al. [ 1978]. Briefly, a 19-GHz carrier is switched at a 1-kHz rate between two orthogonal linearly polarized antennas on a geosynchronous Comstar satellite. These signals are received with a 7-m antenna and narrow band receiving system at the Crawford Hill, New Jersey, receiving site. Amplitudes and phases are measured and recorded digitally for the two received signal components that are copolarized with the transmitted signals and for the two signal components that are cross polarized to the transmitted signals. The propagation path is at an azimuth of 210.5 ø and an elevation of 38.5 ø from Crawford Hill. The clear air received signal polarizations are rotated 21 ø from horizontal and vertical. (The horizontal ...

show abstract

Section: Most Step Changes In Depolarization Are Increases; However mentioning

confidence: 99%

Observations of rapid changes in the orientation and degree of alignment of ice particles along an Earth‐space radio propagation path

Cox¹,

Arnold²

1979

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…In such cases, the residual is not readily predictable, so residual removal is not very effective. In order to facilitate unambiguous, accurate depolarization measurements, special antennas have been designed with low (<-40 dB), slowly varying residuals throughout the 3-dB beam-width of the antenna [Cox et al, 1977a;Chu et al, 1978].…”

Section: Measurement Of Depolarizationmentioning

confidence: 99%

“…A comprehensive depolarization experiment has been run at 19 GHz using the polarization switched beacon on a COMSTAR satellite and a precision antenna and receiving system designed specifically to minimize measurement errors [Cox, 1974[Cox, , 1978Chu et al, 1978;Arnold et al, 1978]. This experiment measures the following parameters for two orthogonal linearly polarized signals at the same frequency: (1) copolarized signal attenuation, (2) depolarization magnitude and phase, and (3) phase difference between copolarized signals.…”

Section: Measurement Of Depolarizationmentioning

confidence: 99%

Depolarization of radio waves by atmospheric hydrometeors in earth‐space paths: A review

Cox¹

1981

Radio Science

View full text Add to dashboard Cite

A reviewMany measurements of earth-space radio wave depolarization from 10 to 30 GHz have been made in recent years. This review relates the results from these measurements within the framework of theoretical relationships derived from rain and ice depolarization models. The review includes measured statistical relationships between depolarization and rain attenuation and contains cumulative statistics showing the relative frequencies of occurrence of rain and ice depolarization. Depolarization is usually strongest for circular polarizations and for fixed linear polarizations oriented 45 ø from vertical and horizontal. Depolarization is usually minimized for fixed vertical and horizontal polarizations. For frequencies up to 30 GHz and elevation angles ranging from 10 ø to 50 ø, amplitude ratios of ice and rain depolarization are approximately proportional to frequency and to cos 2 0/sin 0, where 0 is the path elevation angle.

show abstract

“…The main receiving system electronics 3 were operated for a short period in parallel with this system, while awaiting completion of the Crawford Hill millimeter-wave antenna. 4 The interim receiving system is presently observing the beacon located at 128°W longitude. The propagation path from Crawford Hill to the beacon has an azimuth of 244.7° and an elevation of 18.5°.…”

Section: Introductionmentioning

confidence: 99%

Comstar Experiment: The 19-GHz Receiving System for an Interim Comstar Beacon Propagation Experiment at Crawford Hill

Arnold¹,

Cox²,

Gray³

1978

Bell System Technical Journal

Self Cite

View full text Add to dashboard Cite

This paper describes the antenna and receiving electronics for the Bell Laboratories Crawford Hill 19-GHzCOMSTAR Interim Experiment. This experiment has collected essentially continuous 19-GHz atten uation data on the earth-space path to the COMSTAR A satellite since May 25,1976. The receiver operates unattended, automatically reac quiring the beacon signals after deep rain-induced signal fades. A re ceiver bandwidth of 10 Hz allows accurate measurement of fade depth to the 40-dB level.

show abstract

Comstar Experiment: The Crawford Hill 7-Meter Millimeter Wave Antenna

Cited by 38 publications

References 4 publications

Observations of rapid changes in the orientation and degree of alignment of ice particles along an Earth‐space radio propagation path

Observations of rapid changes in the orientation and degree of alignment of ice particles along an Earth‐space radio propagation path

Depolarization of radio waves by atmospheric hydrometeors in earth‐space paths: A review

Comstar Experiment: The 19-GHz Receiving System for an Interim Comstar Beacon Propagation Experiment at Crawford Hill

Contact Info

Product

Resources

About