A partial 45 MHz sky temperature map obtained from the  observations of five ST radars

Campistron, Bernard; Despaux, Gilbert; Lothon, Marie; Klaus, V.; Pointin, Y.; Mauprivez, Michel

doi:10.5194/angeo-19-863-2001

Cited by 17 publications

(24 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A theoretical estimate for the limiting meteor sensitivity of the radar is obtained using the minimum detectable power P noise at the antenna determined from a sky noise map for 45 MHz at 69 • N (Campistron et al, 2001) after Eqs. (1) and (2), where k is Boltzman's constant.…”

Section: The Radar Instrument: Its Parameters and Sitesmentioning

confidence: 99%

Diurnal and annual variations of meteor rates at the arctic circle

Singer¹,

Zahn²,

Weiss³

2004

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. Meteors are an important source for (a) the metal atoms of the upper atmosphere metal layers and (b) for condensation nuclei, the existence of which are a prerequisite for the formation of noctilucent cloud particles in the polar mesopause region. For a better understanding of these phenomena, it would be helpful to know accurately the annual and diurnal variations of meteor rates. So far, these rates have been little studied at polar latitudes. Therefore we have used the 33 MHz meteor radar of the ALOMAR observatory at 69 • N to measure the meteor rates at this location for two full annual cycles. This site, being within 3 • of the Arctic circle, offers in addition an interesting capability: The axis of its antenna field points (almost) towards the North ecliptic pole once each day of the year. In this particular viewing direction, the radar monitors the meteoroid influx from (almost) the entire ecliptic Northern hemisphere.We report on the observed diurnal variations (averaged over one month) of meteor rates and their significant alterations throughout the year. The ratio of maximum over minimum meteor rates throughout one diurnal cycle is in January and February about 5, from April through December 2.3±0.3. If compared with similar measurements at midlatitudes, our expectation, that the amplitude of the diurnal variation is to decrease towards the North pole, is not really borne out.Observations with the antenna axis pointing towards the North ecliptic pole showed that the rate of deposition of meteoric dust is substantially larger during the Arctic NLC season than the annual mean deposition rate. The daylight meteor showers of the Arietids, Zeta Perseids, and Beta Taurids supposedly contribute considerably to the June maximum of meteor rates. We note, though, that with the radar antenna pointing as described above, all three meteor radiants are close to the local horizon but all three radiants were detected.

show abstract

Section: The Radar Instrument: Its Parameters and Sitesmentioning

confidence: 99%

Diurnal and annual variations of meteor rates at the arctic circle

Singer¹,

Zahn²,

Weiss³

2004

Atmos. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…Note that (S sys + S sky ) must be evaluated at the same time resolution as the measurements of P r , while S cal is a single number evaluated as an average of measurements with the noise-injection source in place, or as an average of the daily variation of the natural noise over several days. (Calibration using galactic noise is also discussed in Campistron et al, 2001, but the method there is slightly different since it is mainly concerned with passive, rather than active, measurements) An indication of the degree to which radar scatter may be described by the Fresnel and volume scatter models can be given by the aspect sensitivity, φ s , where the polar diagram of the scatter can be described by the expression…”

Section: Radar Scattering Modelsmentioning

confidence: 99%

Fresnel scatter revisited – comparison of 50 MHz radar and radiosondes in the Arctic, the Tropics and Antarctica

et al. 2010

View full text Add to dashboard Cite

Abstract. High-resolution radiosondes and calibrated radars operating close to 50 MHz, are used to examine the relationship between the strength of radar scatter and refractive index gradient. Three radars are used, in Kiruna in Arctic Sweden, at Gadanki in southern India and at the Swedish/Finnish base Wasa/Aboa in Queen Maud Land, Antarctica. Calibration is accomplished using the daily variation of galactic noise measured at each site. Proportionality between radar scatter strength and the square of the mean gradient of potential refractive index, M 2 , is found in the upper troposphere and lower stratosphere at all three sites, confirming previously reported results from many VHF radars. If the radar scatter is interpreted as Fresnel scatter, the constant of proportionality between radar scatter and M 2 is found to be the same, within the calibration uncertainties, for all three radars. The radiosondes show evidence of distinct layering with sharp gradients, extending over 10s of kilometers horizontally, but the scatter is found to be two orders of magnitude weaker than would be expected from true Fresnel scatter from such layers. Using radar reflectivities resolved to a few 100 ms, we show that this is due to strong temporal variability in the scattering conditions, possibly due to undulations of the scattering layers. The constancy of the radar scatter -M 2 relationship between the different sites suggests an unexpected uniformity in these perturbations between very different regions of the globe.

show abstract

“…During the last few decades observations of cosmic noise emissions have been carried out to calibrate various atmospheric radar systems (see e.g. Czechowsky et al, 1984;Palmer et al, 1996;Zecha, 1999;Campistron et al, 2001;Carey-Smith et al, 2003;Fukao et al, 2003;Swarnalingam et al, 2009a,b;Renkwitz et al, 2011). The purpose of these studies has been e.g.…”

Section: Introductionmentioning

confidence: 99%

Validation of the radiation pattern of the Middle Atmosphere Alomar Radar System (MAARSY)

et al. 2012

View full text Add to dashboard Cite

The Middle Atmosphere Alomar Radar System (MAARSY) allows studies with high spatial and temporal resolution in the troposphere/lower stratosphere and in the mesosphere/lower thermosphere of the Arctic atmosphere. The monostatic radar is operated at 53.5 MHz with an active phased array antenna consisting of 433 Yagi antennas. Each individual antenna is connected to its own transceiver with independent phase control and a scalable power output of up to 2 kW, which implies high flexibility of beam forming and beam steering. During the design phase of MAARSY several model studies have been carried out in order to estimate the radiation pattern for various combinations of beam forming and steering. However, parameters like mutual coupling, active impedance and ground parameters have an impact on the radiation pattern, but can hardly be measured. Hence, experiments need to be designed to verify the model results. For this purpose, the radar has occasionally been used in passive mode, monitoring the noise power received from both distinct cosmic noise sources like e.g. Cassiopeia A and Cygnus A, and the diffuse cosmic background noise. The analysis of the collected dataset enables us to verify beam forming and steering attempts. These results document the current status of the radar during its development and provide valuable information for further improvement.

show abstract

A partial 45 MHz sky temperature map obtained from the observations of five ST radars

Cited by 17 publications

References 20 publications

Diurnal and annual variations of meteor rates at the arctic circle

Diurnal and annual variations of meteor rates at the arctic circle

Fresnel scatter revisited – comparison of 50 MHz radar and radiosondes in the Arctic, the Tropics and Antarctica

Validation of the radiation pattern of the Middle Atmosphere Alomar Radar System (MAARSY)

Contact Info

Product

Resources

About