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The results of a high-altitude probing experiment are presented which demonstrate the capability of measuring atmospheric stability at tropopause altitudes using a 940-MHz forward-scatter CW radar system. Vertical profiles of the potential temperature gradient measured by radiosondes launched under the common volume of the radar system are well correlated with profiles of received power from radar data, taken nearly simultaneously. Thus, the tropopause can be located within a few hundred meters and its stability structure can be observed as it evolves.

An experiment is described by which the ephemeris of a near-synchronous satellite was determined from passive range observations. The data consist of the measured times of reception at ground tracking stations of electromagnetic signals which are radiated from the satellite at regular intervals. A comparison of the ephemeris to one obtained from Doppler tracking indicates an accuracy of better than 4.9 mrad rms.

Boundary layer probing by multiple remote sensors can greatly improve the understanding of processes in this complex region. For this purpose one needs to know the unique information each individual sensor can provide. Two promising boundary layer remote sensors, a microwave, frequency-modulated, continuous-wave (FM-CW) radar and a laser radar (lidar), were operated simultaneously to probe a common volume. As expected, the lidar sometimes separately detected aerosol layers, notably cloud bases, and the radar sometimes separately detected refractive layers and insects. Boundaries of aerosol structures were often found to be regions of radar returns such as in layers, convective activity, and breaking waves. In contrast, however, a refractive layer was observed within an apparently well-mixed aerosol layer. The data indicate that the radar may have a characteristic echo which is coincident with cloud and fog tops. This experiment shows that FM-CW radars and lidars can separately sense layering in t...

The antenna elevation control signal and the associated staticequilibrium equations are analyzed for the case of tracking of lowaltitude targets for both monopulse and conical-scanning radar. Three possible equilibrium positions of the radar antenna under static operating conditions are ascertained. The static solutions suggest certain dynamic solutions that are likely to arise under practical conditions. The extreme values of the pointing error are shown in graphical form.

Coherent high-resolution synthetic-aperture radar systems achieve their range resolution by pulse compression and azimuth resolution by compression of naturally generated FM coding due to Doppler shifts as the aircraft flies by the target. If the data is left unprocessed, it is, in effect, a defocused map of the terrain. As such, it should exhibit less dynamic range than if the data is compressed. This paper describes an experimental study to verify the above conjecture. The results of this study indicate that if dynamic range of the data link is a problem, the radar data should be transmitted in its unprocessed form. This might very well be the case for planetary mapping by means of satellites.

Recent developments in airborne Doppler and ground mapping navigation radars and ground and satellite based radio systems are described. Simultaneous lobing and slope tracking techniques can remove the well-known Doppler sea bias error in fast and slowly moving vehicles. Doppler velocity information can be extracted from coherent forward-looking mapping radars, and high position fixing accuracy can be achieved by synthetic aperture radars. In radio navigation systems, such as Loran, Omega, and satellite systems, direct-ranging and differential techniques greatly reduce the geometric dilution and propagation effects which have plagued conventional radio navigation systems. The advantages gained by mixing of the data from these and other navigation sensors in a digital multisensor system are discussed and approaches for processing these data are suggested.

A unique experiment using advanced remote and direct sensing techniques was designed to investigate the detailed evolution and structure of clear-air convection. The measurements involved a high-power, narrow-beam pulse radar, a frequency modulated, continuous wave radar, an acoustic echo sounder, and instrumented aircraft. The various probing methods when used together complement each other and give a compatible and comprehensive description of the spatial and temporal evolution of clear-air convection.

The effect of soil moisture on the radar backscattering coefficient was investigated by measuring the 4-8 GHz spectral response from two types of bare-soil fields: slightly rough and very rough, in terms of the wavelength. An FM-CW radar system mounted atop a 75-ft truck-mounted boom was used to measure the return at 10 frequency points across the 4-8 GHz band, at 8 different look angles ( 0\deg through 70\deg ), and for all polarization combinations. A total of 17 sets of data were collected covering the range 4-36 percent soil moisture content by weight. The results indicate that the radar response to soil moisture content is highly dependent on the surface roughness, microwave frequency, and look angle. The response seems to be linear, however, over the range 15-30 percent moisture content for all angles, frequencies, polarizations, and surface conditions.

Space measurements of electric fields have provided instrumentation for measuring atmospheric parameters and a better basis for understanding the electrical coupling between the magnetosphere and the atmosphere. Applications of an incoherent scatter radar (developed for ionospheric electric field research) to the measurement of atmospheric winds and turbulence and of Langmuir double probes (also developed for space research) for measurement of atmospheric electric fields are described. The increased knowledge of magnetospheric electric fields has focused attention on the electrical coupling between the magnetosphere and the atmosphere with conclusions that should considerably modify previous physical concepts in both domains.

The complex indicated angle technique, applicable to monopulse radars, is being investigated as a means of overcoming the serious degradation of elevation measurement caused by multipath when the target is within a beamwidth or so of the horizon. This technique makes use of the quadrature-phase component of the normalized difference signal, as well as the in-phase component. Results of analysis and computer simulation have been published previously. This paper reports results of a test program using a slightly modified AN/FPS-16 monopulse tracking radar and a simulated target. The results to date indicate a potential for high accuracy, though there are limitations as to the applications for which the technique appears feasible. A computer program has been developed to perform the elevation estimate and to resolve ambiguities.

Good agreement was found between the velocity spectra obtained from Doppler radar measurements of the variations in the mean wind field and the spectra of velocity fluctuations simultaneously measured by an aircraft-borne hot-wire anemometer. This experiment is the first in which such a comparison was attempted where the radar return was from fine-scale refractivity fluctuations due to turbulent mixing and not from precipitation particles of artificial scatterers.

A mathematical model to study target image return frequency spectrums in Doppler radars is described. The model includes the effects of eclipsing, sea surface slope distribution, and surface reflectivity characteristics. The procedure of calculations has been computerized and the analytical results are compared to flight-test values obtained from flights over the ocean. The calculated values of amplitude-frequency spectrums of target image returns correspond reasonably well with the respective recorded flight-test data.

Statistical properties of the field backscattered from a weather radar target are related to the velocity distribution of the scatterers comprising the target. The complete distribution of radial velocity components can be derived from the received radar signal using coherent Doppler techniques. The standard deviation, and in special cases the complete form of this distribution, can be obtained from incoherent radar measurements.

A continuous record of precipitation falling through a fixed volume in space was obtained by means of a vertically-pointing pulsed-Doppler radar during a period of continuous precipitation. The range gate was held fixed at an altitude of 910 m above the ground. The output of the radar gave the power returned in several adjacent velocity intervals, from which the drop size distribution and liquid water content were calculated. Variance spectra for power in selected velocity channels, total liquid water, and reflectivity were computed. The results revealed that despite the uniformity of radar reflectivity at elevations much below the melting layer, a good deal of structure was still evident in the time (space) variations in number of drops of given size. The variance spectra for concentration of drops falling at 7 m sec−1 (about 2 mm drop diameter) revealed significant modes at wavelengths of 2–3 km, and about 350–800 m, which support other evidence of organized atmospheric activity at these scales.

A new technique is described which provides for precision angle tracking of celestial radio sources with a conventional monopulse antenna receiving system. It is shown that this technique is readily adapted to angle tracking radars. The features of conventional monopulse operation are preserved while permitting precise angle tracking of noise sources when signal to noise ratios are much less than unity. Measurements, using a four-horn monopulse feed with a 28-foot parabolic reflector and a "monopulse radiometer" produced the characteristic monopulse angle detection functions when using the sun, the moon, and Cassiopeia A as boresight reference sources. Precision measurements were made to 8 arc second under varying weather conditions using 28-foot radio astronomy antennas. The accuracy of the measurements were limited by the antenna angle encoders, consequently no conclusions are drawn with regard to the absolute accuracy of the measurements. The celestial coordinates of four discrete radio sources and the equations for coordinate transformation to local elevation and azimuth are contained in the Appendixes.

More than 1000 hr of radar records taken with the APS-34 1.25-cm vertical-beam radar during a four-year period have been readily classified into four clearly recognizable types. A limited number of precipitation growth mechanisms are thereby suggested, and the echo types representing them are shown to be well correlated to three basically different classes of synoptic situations. A generalized echo cyclone model is derived. Maximum attainable hourly rates of precipitation are empirically related to the depth of detectable echo. The average vertical distance between the warm-front surface and that of the top of the radar echo above is 12,000 ft with no significant correlation. A marked increase in the frequency of precipitation echoes is found in the temperature interval −11C to −15C.

Through the use of digital radar data measured at successive elevation angles in a storm system, we developed a technique that presents a new dimension in mesoscale analysis. This technique, mapped vertically integrated liquid-water content (VIL), presents the three-dimensional characteristics of a storm system in a two-dimensional display. This analysis technique appears to hold real promise for both severe storm and hydrologic applications.

CAT layer simultaneous radar and instrumented aircraft observations, noting eddy dissipation rate computation from radar reflectivity measurement

An estimate of the integrated liquid water content along radio rays passing through a thunderstorm has been made by using the thermal emission from the storm at 10.7 GHz. The radiometric data, together with supplementary radar, radiosonde, and surface meteorological data are used to determine absorption in the storm, which in turn is used to determine the liquid water content. The results of the technique are illustrated by contour diagrams showing liquid water content of a small storm system and its changes over a period of 2 hr.

This paper reviews the remote sensing of waves and turbulence in statically stable atmospheric layers, utilizing sodar and microwave radar echoes from the small-scale inhomogeneities in gaseous refractive index caused by localized fluctuations in temperature, humidity, and velocity. Scattering theory and sounding methodology are reviewed briefly, and the relative performance of typical radar and sodar systems compared. The main section of the paper takes the form of a summary and discussion of experimental progress since 1969, showing how the echo patterns obtained may be applied to the interpretation of multiple layering, gravity waves, internal fronts and the details of dynamic instability and the genesis of turbulence in stably stratified shear layers. In addition, methods for the measurement of the intensity of the small-scale (∼ λ/2) variability of wind, temperature and water vapor from the observed radar or sodar echo intensities, and the use of Doppler techniques for the measurement of mean velocity and turbulence are discussed.

The use of a two-lobe monopulse radar for measuring slant range to the surface of the earth in the absence of discrete targets is analyzed. It is shown that tracking dispersion can be considered as the resultant of two components. One component is independent of range and results from the finite pulse length and gate length and the random nature of the return signals. The other component is due to receiver noise and increases as the signal-to-noise ratio decreases. The dispersion component independent of range is shown to be proportional to the pulse length and tracking gate length. The variable dispersion is shown to be proportional to the five halves power of the range and the three halves power of the cotangent of the depression angle of the antenna boresight axis. Performance calculations for a specific radar are carried out and compared with experimental data.

Radar has become an important tool for bird migration studies (Eastwood, 1967), but estimating bird densities from echo densities on the radar screen has often been difficult if not impossible. In the following paper I report on the use of the Weather Bureau's new WSR-57 radar for bird migration research. Emphasis is on (1) the direct visual correlation between radar echoes attributed to birds

When reading articles on radar-navigation in various nautical magazines, one is constantly struck by the difficulty of comparing the different targets on the screen and of interpreting the changes that take place in the right way. So plotting becomes still more necessary in order to get: (a) the nearest approach, and (b) the present course and speed of other vessels, before we can manœuvre to avoid collision, especially in thick weather. When plotting, comparisons are hampered by the fact that the echoes must be recorded on a piece of paper or on the reflection-plotter, and that the different distances, courses and speeds must be measured very accurately. And nearly all these tasks depend upon the skill and accuracy of one man.

An analytical technique is proposed for investigating the effect of antenna pattern shape on reentry vehicle radar altimeter performance. Initially, a method is presented that computes the average performance under all roll positions. This method is then extended to allow performance to be determined at each roll position. Some numerical results are included that show roll effects for a typical antenna pattern.

A simple method is described for calibrating a weather radar by means of a standard spherical target, thus permitting the radar to be used for quantitative measurements of storm reflectivity. The t...

Shortly after the development of radar some 25 years ago, it became apparent that bird movements were often discernible on radar screens. These ``radar angels'' in some cases are looked upon as clutter to be eliminated from the radar screen. However, they should be regarded as signals conveying valuable information, since birds can provide a real threat to aircraft, particularly in certain areas and at certain times of the year.

In recent years many sets of experimental data have been obtained on radar reflections from the moon. After analyzing the results, workers tried to determine the scattering properties of the moon at radar wavelengths, and they concluded that rough-scattering laws could be ascribed to the surface. The available evidence no longer appears to support this view.

Many of the severe and persistent hailstorms in Alberta propagate by means of new cloud development on the southern or western flank. A concept is proposed whereby these cumulus towers are seeded with freezing nuclei early in their development. In order to accomplish this a droppable pyrotechnic flare system was developed and tested. A T-33 jet aircraft was used as the seeding platform. It was equipped with a Ku-band weather radar, a flare rack and firing control panel, a 14 channel recorder and a 3-cm transponder. Seven inch pyrotechnic flares were manufactured to the following specifications: delay burn 50 sec, silver iodide burn time 30 sec, and flare output 24 gm of silver iodide producing a total of 2.4 × 1014 freezing nuclei active at −10C. A unique feature was the incorporation of 10-cm radar chaff which was released at the flare burn-out and used as a position marker. Flare performance was evaluated using radar, visual and photographic tracking. Total fall distance as a function of releas...

The determination of the prevailing wind in the 80–100 km region of the upper atmosphere by a new method, involving the simultaneous use of a CW doppler radar at 30.02 Mc/sec and three-station pulsed radars at about the same frequencies, is presented in this paper. This method involves the determination of the exact location of each observed meteor train and the component of the velocity of its horizontal drift in the direction of the azimuth from Ottawa. A 40-minute period during the Geminid shower on the night of Dec. 10/11, 1948, has been selected for this investigation. Theory for the analysis of the body doppler records is briefly outlined. The prevailing wind speed obtained from the body doppler frequencies (fd) is 54 m/sec. The observed linear variation in the average fd with time, in the case of each meteor, has been explained as caused by the effective point of reflection drifting along its train towards the maximum echo duration level. Periodic fluctuations of fd of the order of 1–3 c.p.s., on the average, have also been observed. The above two phenomena can be explained from a postulate of atmospheric turbulence on a scale of about 1 km or above.

A peak in 48.2-Mc/sec echo occurrence is observed at Saskatoon corresponding in time to the period of breakup of quiet arcs into active rayed structures. This is also the time of most frequent occurrence of characteristic "curl" forms in the aurora. If, as Gartlein suggests, the "curl" forms are formed by instabilities in a sheet beam then the primary particles are positively charged.

Radar observation of insects in free flight, noting backscatter and velocity measurement results

This paper gives an account of the radar observations of the Russian earth satellites I and II and of the carrier rocket of satellite I, which have been made with the 250 ft. radio telescope at the Jodrell Bank Experimental Station. When the first satellite was launched on 4 October 1957, the radio telescope was still in an incomplete state. The instrument had already been tested in early August on the reception of the extragalactic radio emissions, but had never been used as a radar instrument. Emergency arrangements were made to connect it with the existing radar installations working in other parts of the establishment. By the night of 9 October the equipment was available for testing and with the telescope in auto­matic motion on the moon satisfactory lunar echoes were obtained. The first radar contacts with the rocket and satellite were obtained during the evening of 11 Octo­ber. The present paper is confined to a discussion of the results up to the date of burn-up of the carrier rocket of satellite I on 1 December 1957 2. Equipment The essential features of the radio telescope have been described by Lovell (1956, 1957 a ). On the frequencies used in the present work (36 and 120 Mc/s) the calculated beam widths and power gains are 8° to half power and 600 on 36 Mc/s, and 2.5° to half power and 6500 on 120 Mc/s. These values have not yet been established by experiment, but the equivalent measured values on frequencies of 160 and 408 Mc/s are very close to the calculated figures. Hence, it is unlikely that the values quoted for 36 and 120 Mc/s are in error. On each frequency the primary feed was a dipole with reflector, mounted at the focal point so that there was cross-polarization between the two feeds.

Preceding the development of a tornado at the ground a fingerline projection developed on the PPI in the SW corner of an echo. This was also visible on the three-dimensional models constructed from...

Long-range surveillance radars use MTI techniques to detect moving targets in a clutter background. The transmitter PRF is usually staggered to eliminate the blind speeds due to aliasing of the target and clutter spectra. A spectral analysis of the target and clutter signals is performed for the case of nonuniform sampling, and it is shown that the clutter spectral density continues to fold over at the basic PRF, but the signal spectrum becomes dispersed in frequency, which means that an MTI rader will never be completely blind to moving targets.

A frequency-modulated, continuous-wave radar seems to be particularly well suited to the observation of auroral ionization, since it provides both range information and a Doppler indication of radial motion. An experimental equipment of this type has been operated for a few months near Ottawa. The system parameters are briefly considered and the radar observations are compared with similar measurements made with higher-powered pulse systems.

Theoretical analyses are made to determine expected relative values of average radar cross section for idealized scatterers above the sea. Horizontal, vertical, and circular polarizations are considered along with various sea states and radar depression angles. The results are considered to be useful for providing insight into effects of the sea on the polarization dependence of rain return. Effects of the earth's curvature and atmospheric refraction are neglected.

The ability of a forward-scatter CW radar to measure cross-path wind speed profiles is demonstrated from the results of a two-week observation period in June 1971. Radar-measured winds are compared with wind speeds measured simultaneously by radiosondes and pibals. It is concluded that forward-scatter CW radar is a sensitive atmospheric probe which can accurately measure atmospheric winds.

The main concern is with the applications of a radar dopplermeter which has recently become available. Laboratory trials have been carried out to investigate its use in the process industries especially as a potential interrogating unit in a control system. Useful features, and some of the disadvantages are exposed and comparisons are made between dapplermeters using radar and laser sources. These and other techniques are under patent application.

It is proposed that the range derivative of the logarithm of the ratio of average echo powers from two (S- and X-band) synchronized and slaved radars would yield a highly reliable indication of the boundaries of hail shafts. In the presence of rain alone, and ignoring fluctuations, this derivative would always be positive and proportional to the incremental difference in attenuation at the smaller wavelength. In general, the derivative has the same sign as the hail concentration gradient and attains negative values on the far side of a hail shaft. Without hail, signal fluctuations are the only possible source of negative derivatives, and so of false alarms. Thus, a small negative threshold level would avoid the identification of the effect of signal fluctuations at the far side of a hail shaft; similarly a large positive threshold would avoid identifying regions of intense rain as the near side of a hail shaft. This approach is capable of detecting smaller concentrations of hail with greater conf...

A new high power radar at Malvern is being used to investigate the ionosphere by the incoherent scatter technique.