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A cockpit situation display of selected NAS/ARTS data

December 15, 1970
  |
Technical Report
Author:
Francis X. Brady
…
Published in:
MIT Lincoln Laboratory Report TN-1970-39
Topic:
air traffic control
R&D area:
R&D group:

Summary

By the mid-1970's, the evolving NAS/ARTS ground environment will provide the air traffic controllers with high quality computer-processed traffic situation displays. We believe it would be useful, particularly in busy terminal areas, to display some of this data in the cockpit. Systems with this objective have been constructed and flight tested at least 3 times during the past 25 years, but these earlier systems could not benefit from: 1) a source of computer-processed data of the quality to be available from NAS/ARTS; 2) aircraft altitude information; 3) contemporary digital data link techniques; and 4) airborne equipment capable of automatically selecting and displaying only information relevant to a particular airplane. It is believed that an effective cockpit display would permit pilots, under IFR conditions, to retain some of the station-keeping and navigation functions they perform during VFR conditions and thereby improve the efficiency of terminal area operation. The goals of the proposed program are: a) to evaluate the effectiveness of this class of system in reducing pilot and controller work loads, and b) to determine its potential for expediting traffic flow in busy terminal areas. A simulated cockpit display has been developed and experienced pilots and controllers who have "flown" it have endorsed enthusiastically the desirability of evaluating this class of system in an operational environment.
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Summary

By the mid-1970's, the evolving NAS/ARTS ground environment will provide the air traffic controllers with high quality computer-processed traffic situation displays. We believe it would be useful, particularly in busy terminal areas, to display some of this data in the cockpit. Systems with this objective have been constructed and flight...

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A cockpit situation display of selected NAS/ARTS data

Measurement of clear air turbulence in the lower stratosphere using the Millstone Hill L-Band Radar

November 1, 1970
  |
Conference Paper
Author:
Robert K. Crane
Published in:
14th Conf. on Radar Meteorology, 17-20 November 1970, pp. 101-106.
Topic:
radar
R&D area:
R&D group:

Summary

Radar measurements of thin turbulent layers in the clear atmosphere have been extensively reported in the literature and have recently been summarized by Hardy and Katz (1969). The majority of the thin turbulent layer detections reported have been for layers in the lower troposphere. Using the high power radar facilities at Wallops Island, Atlas, et al (1966) have detected layers at heights up to the tropopause. In this paper, layer detections at heights above the tropopause are discussed. The detection of layers in the lower 10 km of the stratosphere is made possible by using a radar system which has approximately 10 dB more sensitivity than the Wallops Island radars for the detection of turbulent layers. The program of radar measurements of thin turbulent layers was undertaken to provide basic information about the structure of scattering layers in the upper troposphere and lower stratosphere for use in the prediction of troposcatter field strengths. The radar measurements were accompanied by radiosonde soundings. For a limited series of measurements, a U-2 aircraft was also used to probe for turbulent layers.
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Summary

Radar measurements of thin turbulent layers in the clear atmosphere have been extensively reported in the literature and have recently been summarized by Hardy and Katz (1969). The majority of the thin turbulent layer detections reported have been for layers in the lower troposphere. Using the high power radar facilities...

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Measurement of clear air turbulence in the lower stratosphere using the Millstone Hill L-Band Radar

A comparison between monostatic and bistatic scattering from rain and thin turbulent layers

October 6, 1970
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TN-1970-29
Topic:
weather
R&D area:
R&D group:

Summary

Simultaneous measurements were made of the backscatter cross section and the bistatic scattering cross section of rain and thin turbulent layers. The radar measurements were made at a frequency of 1.3 GHz using the Millstone Hill Radar. The bistatic scattering measurements were made using CW transmission at 7.7 GHz with a 145-km separation between transmitter and receiver. The receive station was the Westford Communication Terminal with a 60-foot antenna. The transmitter was van-mounted and used either a 6-foot antenna or a standard gain horn. Stable frequency sources were used to allow Doppler shift measurements on the bistatic scattering link. The measurements were made by fixing the pointing angles of the transmit antenna and scanning both the receive antenna and the radar to investigate the dependence of the scattered signals both on scattering angle and on the location of the scatterers. The measurements of the scattering cross section of the thin turbulent layers were made in the near forward direction, the measurements of rain at a large number of scattering angles. System sensitivities allowed the measurement of scattering from turbulent layers at a 10-km height with a thickness, Cn^2 product of 10^-13 N^2 m^1/3 and from rain with a 0.1 mm/hr. rate. Comparisons between the radar and bistatic measurements were in good agreement with the appropriate scattering theories.
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Summary

Simultaneous measurements were made of the backscatter cross section and the bistatic scattering cross section of rain and thin turbulent layers. The radar measurements were made at a frequency of 1.3 GHz using the Millstone Hill Radar. The bistatic scattering measurements were made using CW transmission at 7.7 GHz with...

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A comparison between monostatic and bistatic scattering from rain and thin turbulent layers

Air Traffic Control quarterly technical summary, May 1970

May 15, 1970
  |
Technical Report
Author:
Herbert G. Weiss
Published in:
MIT Lincoln Laboratory Report ATC-QTS-05-70
Topic:
air traffic control
R&D area:
R&D group:

Summary

This is the first report in the Quarterly Technical Summary series covering the Air Traffic Control activities at Lincoln Laboratory. The previous work on ATC was included in the General Research Quarterly Technical Summary. Because the allowable effort on ATC is comparatively small, it has been focused on only one facet of the problem; namely, on the data acquisition and communications task. The new group has started to make significant progress in several study aspects of the problem and has also obtained experimental L-band multipath data from an experimental airground test system. When additional support is received, the program will be expanded to include over-all system design studies and the investigation of radar improvements and multilateration systems, both ground- and satellite-based.
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Summary

This is the first report in the Quarterly Technical Summary series covering the Air Traffic Control activities at Lincoln Laboratory. The previous work on ATC was included in the General Research Quarterly Technical Summary. Because the allowable effort on ATC is comparatively small, it has been focused on only one...

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Air Traffic Control quarterly technical summary, May 1970

Monostatic and bistatic scattering from thin turbulent layers in the atmosphere

September 18, 1968
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TN-1968-34
Topic:
radar
R&D area:
R&D group:

Summary

Measurements were made of the scattering properties of thin turbulent layers at and above the tropopause. The Millstone Hill L-band radar was used to measure the backscatter cross section per unit volume of these layers as a function of time and space. An X-band forward scatter link was set up between Wallops Island, Virginia and Westford, Massachusetts to observe scattering from these layers. Although the radar could not provide observations of the common volume of the forward scatter link, for days where no clouds were observed in the vicinity of the tropopause, the radar observations of layers near the tropopause showed horizontal uniformity of height and backscatter cross section, and the radiosonde data taken near the radar and near the common volume showed similar wind and temperature structure near the tropopause, the signal strength on the forward scatter link and its dependence on scattering angle behaved in accordance with the prediction of turbulent scattering theory using the radar data as an input. The radar observations have shown that on each day measurements were made, layers were detected near and above the tropopause. Turbulent layers in the stratosphere have been detected at heights up to 22 km. These layers provide one of the mechanisms for weak, long-distance troposcatter propagation.
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Summary

Measurements were made of the scattering properties of thin turbulent layers at and above the tropopause. The Millstone Hill L-band radar was used to measure the backscatter cross section per unit volume of these layers as a function of time and space. An X-band forward scatter link was set up...

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Monostatic and bistatic scattering from thin turbulent layers in the atmosphere

Simultaneous radar and radiometer measurements of rain shower structure

September 18, 1968
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TN-1968-33
Topic:
radar
R&D area:
R&D group:

Summary

Simultaneous measurements of the backscatter cross section per unit volume and the sky temperature were made for limited volumes of rain showers using an L-band radar and an X-band radiometer. The object of the measurements was to provide data to validate the method used to compute attenuation and sky temperature given weather radar data as an input and to investigate the spatial changes in rainfall intensity and in the attenuation cross section per unit volume. The sky temperature was calculated using the radiative transfer equation and the distribution of attenuation cross section per unit volume estimated from the weather radar data. An empirical relationship between attenuation and backscatter cross sections was used based upon the results of a large number of Mie theory computations using measured raindrop size distributions. The results of the comparisons between calculated and measured sky temperature show good agreement. The discrepancies between the measured and calculated values are due to the difference in the antenna beamwidths for the two systems (0.6° for the L-band radar, 0.07° for the X-band radiometer). From these discrepancies the spatial distances over which the attenuation cross section can change significantly can be estimated. The results show that for the rain showers investigated, the attenuation cross section per unit volume can change an order of magnitude in 400 meters and the integrated attenuation along a horizontal line-of-sight can change an order of magnitude for a 1. 5km horizontal translation of the path.
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Summary

Simultaneous measurements of the backscatter cross section per unit volume and the sky temperature were made for limited volumes of rain showers using an L-band radar and an X-band radiometer. The object of the measurements was to provide data to validate the method used to compute attenuation and sky temperature...

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Simultaneous radar and radiometer measurements of rain shower structure

Rain attenuation at millimeter wavelengths

January 1, 1968
  |
Conference Paper
Author:
Robert K. Crane
Published in:
IEEE Int. Convention Digest, 1968, p. 65.
Topic:
communications
R&D area:
R&D group:

Summary

The major propagation problem confronting the use of millimeter waves for line-of-sight communication links operating through the atmosphere is hydrometeor scattering. Rain, hail, sleet, snow, and fog all can cause severe attenuation at millimeter wave frequencies. The severest problem is that of attenuation by rain. Attenuations in excess of 1 db/km are computed for frequencies in excess of 45 GHz (6.7 mm) and rain rates in excess of 0.1"/hr (2.5 mm/hr). Light rain of this intensity occurs on the average of 80 hrs/year in the New York area and is generally wide spread, completely covering typical line-of-sight ground link distances. This means that for a ground link of 50 km extent the attenuation would exceed 50 db 0.9 percent of the time for frequencies above 45 GHz.
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Summary

The major propagation problem confronting the use of millimeter waves for line-of-sight communication links operating through the atmosphere is hydrometeor scattering. Rain, hail, sleet, snow, and fog all can cause severe attenuation at millimeter wave frequencies. The severest problem is that of attenuation by rain. Attenuations in excess of 1...

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Rain attenuation at millimeter wavelengths

Cooperative scattering by dielectric spheres

July 6, 1967
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TN-1967-31
Topic:
RF technology
R&D area:
R&D group:

Summary

The problem of scattering of electromagnetic waves by a small number of closely spaced dielectric spheres is considered as a boundary value problem. The solution to this problem is obtained in a series form using partial spherical vector waves. An approximate solution is also obtained for spheres separated sufficiently far for waves scattered by one sphere and incident on another to be considered plane waves with an amplitude given by the solution to the single scattering problem. The use of both solutions is discussed.
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Summary

The problem of scattering of electromagnetic waves by a small number of closely spaced dielectric spheres is considered as a boundary value problem. The solution to this problem is obtained in a series form using partial spherical vector waves. An approximate solution is also obtained for spheres separated sufficiently far...

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Cooperative scattering by dielectric spheres

Coherent pulse transmission through rain

December 27, 1966
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TN-1966-63
Topic:
weather
R&D area:
R&D group:

Summary

The problem of received signal degradation for coherent pulse transmission through a rain scattering volume was investigated for large bandwidth transmission at 4.0, 8.0, 15.5 and 34. 86GHz. Calculations of pulse length and total pulse energy were made for different path lengths through the rain volume. The calculations were made for models of heavy and extreme rainfall, using rain rates 49.0 and 196.3 mm/hr. The results of the computations show that for the rain rates considered, the dominant cause of signal degradation is attenuation. Negligible pulse lengthening was noted at 34.86 GHz. For rain rates above 196 mm/hr. and frequencies of 15.5 and 8.0 GHz, measurable values of pulse lengthening were calculated for bandwidths above 2.0 GHz. At 4.0 GHz, measurable values of pulse lengthening were obtained for both rain rates considered.
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Summary

The problem of received signal degradation for coherent pulse transmission through a rain scattering volume was investigated for large bandwidth transmission at 4.0, 8.0, 15.5 and 34. 86GHz. Calculations of pulse length and total pulse energy were made for different path lengths through the rain volume. The calculations were made...

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Coherent pulse transmission through rain

Microwave scattering parameters for New England rain

October 3, 1966
  |
Technical Report
Author:
Robert K. Crane
Published in:
MIT Lincoln Laboratory Report TR-426
Topic:
radar
R&D area:
R&D group:

Summary

Scattergrams of attenuation coefficient, effective reflectivity factor, single-scattering albedo, and radio refractivity vs liquid-water content, rain rate, and reflectivity factor are presented for a raindrop temperature of 0.0 degrees celsius and frequencies of 1.29, 2.80, 8.0, 9.35, 15.5, 35.0, 70.0, and 94.0 GHz. The scattergrams were computed using Mie theory to compute the scattering parameters for single raindrops, and single-scattering theory to compute the integrated scattering effects of an ensemble of raindrops. Measured drop-size distributions were used to generate the scattergrams.
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Summary

Scattergrams of attenuation coefficient, effective reflectivity factor, single-scattering albedo, and radio refractivity vs liquid-water content, rain rate, and reflectivity factor are presented for a raindrop temperature of 0.0 degrees celsius and frequencies of 1.29, 2.80, 8.0, 9.35, 15.5, 35.0, 70.0, and 94.0 GHz. The scattergrams were computed using Mie theory...

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Microwave scattering parameters for New England rain
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