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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

BRAMS: The Belgian RAdio Meteor Stations

In the last months, the Belgian Institute for Space Aeronomy has been developing a Belgian network for observing radio meteors using forward scattering technique. This network is called BRAMS for Belgian RAdio Meteor Stations. Two beacons emitting a circularly polarized pure sine wave toward the zenith act as the transmitters at frequencies of 49.97 and 49.99 MHz. The first one located in Dourbes (Southern Belgium) emits a constant power of 150 Watts while the one located in Ieper (Western Belgium) emits a constant power of 50 Watts. The receiving network consists of about 20 stations hosted mainly by radio amateurs. Two stations have crossed-Yagi antennas measuring horizontal and vertical polarizations of the waves reflected off meteor trails. This will enable a detailed analysis of the meteor power profiles from which physical parameters of the meteoroids can be obtained. An interferometer consisting of 5 Yagi-antennas will be installed at the site of Humain in order to determine the angular detection of one reflection point, allowing us to determine meteoroid trajectories. We describe this new meteor observing facility and present the goals we expect to achieve with the network.

Lamy, H.↗
NASA NTRS1978

Winds from the Atlanta /34 deg N, 84 deg W/ radio meteor wind facility

A brief description of the Georgia Tech radio meteor wind facility is followed by a tabular presentation and discussion of winds measured over Atlanta (34 deg N, 84 deg W) for the first three intervals of the URSI/IAGA Cooperative Tidal Observations Program (CTOP). The pervailing zonal wind measured during August 1974, being easterly, is significantly different from that measured during October 1975 and January 1976, and is not typical of winds measured in August 1975 and August 1976, when westerlies predominated. The complicated tidal picture is detailed, but is not easily summarized.

Roper, R. G.↗
NASA NTRS1976

Theoretical and experimental studies of atmospheric structure and dynamics, using high altitude chemical release, Radio meteor, and meteorological rocket network and other data

Data collected by the Georgia Tech Radio Meteor Wind Facility during the fall and winter of 1975 are analyzed indicating a relationship between lower thermospheric circulation at mid latitudes and polar stratospheric dynamics. Techniques of measurement of mixing processes in the upper atmosphere and the interpretation of those measurements are described along with a diffusion simulation program based on the Global Reference Atmosphere program.

Edwards, H. D.↗
NASA NTRS1973

Atmospheric motion investigation for vapor trails and radio meteors

The dynamics are investigated of the lower thermosphere through comparison of optical observations of motions of ejected vapor trails with radar observations of motions of ionized meteor trails. In particular, the winds obtained from a series of vapor trail observations which occurred at Wallops Island, Virginia during the night of 14-15 December 1970 are to be compared with wind data deduced from radar observations of meteor trails during the same period. The comparison of these data is considered important for two reasons. First, the most widely used methods of measuring winds in the lower thermosphere are the vapor trails and the radar meteors. However, the two techniques differ markedly and the resultant sets of data have been analyzed and presented in different formats. Secondly, and possibly of greater immediate concern is the fact that the radar meteor method appears to be an appropriate approach to the synoptic measurement of winds. During the night of 14-15 December 1970, five vapor trails were ejected from Nike Apache rockets over Wallops Island, Virginia from 2208 EST through 0627 EST. The wind data which were obtained from these trails are presented, and features of the wind profiles which relate to the radar meteor trails results are discussed.

Bedinger, J.↗
NASA NTRS1979

A comparison between radio meteor and airglow winds

A comparison between the winds near an altitude of 97 kilometers has been made from observations of the 17,924-K (5577-A) O I emission line at Fritz Peak Observatory (39.8 deg N, 195.5 deg W) and with a meteor radar facility at Atlanta (34 deg N, 84 deg W), from August 1974 to November 1975. Since the optical emission measurements are made only at night, the nighttime meteor radar measurements have been used, weighted by an airglow emission-rate profile. The results show general agreement in both the zonal and meridional wind vectors, but with the variations in the amplitude of the meridional winds at the northernmost station (Fritz Peak Observatory) larger than those at Atlanta. This is a result of the smoothing inherent in producing the meteor winds.

Hernandez, G.↗
NASA NTRS1976

Statistical model of meteor streams. IV - A study of radio streams from the synoptic year

The paper gives a detailed description of a search procedure for radio meteor streams and reports the detection of 275 streams in a synoptic-year sample of 19,698 radio meteors observed by the radar system of the Radio Meteor Project at Havana, Illinois. The orbital elements and related parameters of the detected streams are presented, the two parameters of the D-distribution of the streams are determined, and their mean radiants are plotted. Possible associations between the streams and possible parent objects are identified; it is found that streams may be associated with seven periodic comets, five other comets, at least nine asteroids (especially Adonis), and several fireballs. The mean space density in the streams is found to be much lower than the sporadic density, although the central density may be considerably greater than the sporadic density. It is shown that the derived absolute stream-density values are in agreement with the order of magnitude of the space densities estimated from cometary production rates for solid material of comparable particle size.

Sekanina, Z.↗
NASA NTRS1973

Ablation in meteors

A comparison of theoretical calculations with the results of radar meteor observations shows that the theory of radio meteors satisfactorily represents observational data. Radar meteor observations are incompatible with the idea of low density for small meteoroids in the ablation process. The main mechanism of ablation is evaporation. During intensive evaporation, small meteoroids have a density close to that of usual stone meteorites.

Lebedinets, V. N.↗
NASA NTRS1975

The measurement of meteor winds over Atlanta /34 N, 84 W/

An all-sky, continuous wave radio meteor wind facility has been installed in Atlanta. A double sideband suppressed carrier CW transmitter, operating at around 32.5 MHz, with an rms output of 2 kW, has been installed, and a receiving site was established at 27 km away. Details of the equipment, together with height/time profiles of mean wind circulation and tides between 80 and 100 km, measured from August 9 to September 4, 1974, are presented.

Roper, R. G.↗
NASA NTRS1984

Meteor wind results from Atlanta, USA, and Ramey, Puerto Rico

Results obtained using the French (CNET) meteor wind radar at Ramey, Puerto Rico, and the Georgia Tech radio meteor wind facility in Atlanta, U.S.A., are presented and compared. Prevailing wind, diurnal, and semidiurnal wind amplitudes are considerably larger over Ramey than over Atlanta, but the mean zonal circulation over Atlanta is more characteristic of the equatorial circulation than winds measured by stations at higher midlatitudes. The value of continuous observations, with a height resolution of + or - 2 km, is emphasized, as is the need for the application of several techniques, groundbased, in situ and satellite, if projects such as the MAP GLOBMET are to succeed in delineating the global meteorology of the mesopause.

Roper, R. G.↗