Enhanced Sky Coverage

The technique employs narrow fan antenna radiation patterns confined to the geographic meridian for the elevation-finding dual-spacing interferomEter.

The location of echo targets within the narrow main beam is unnecessary since the main beam azimuthal width of 1.6° (FWHP) is comparable with the elevation accuracy ~ 0.5° and both uncertainties are comparable with the angular errors arising from the uncertainties in the velocity vector determined from the orthogonal velocity components measured from time-of-flight. However this N-S fan of echo coverage does results in a bias in sampling the celestial sphere. Enhanced sky sampling is now (operational since Jan 2000) provided by an additional orthogonal radar sampling direction in the E-W meridian: one result is that those influxing meteoroids with radiants near the local zenith (declinations ~ —46°) produce target ionisation trails which are sampled more fully.

A new antenna system providing orthogonal transmitter and receivers (six co-linear arrays in total) have been installed with underground ducted coaxial cables feeding time-switched receivers from the elevation-finding dual interferometer (see Figure 1).

The radar system samples in orthogonal directions by switching at regular (~ 10 min.) intervals with transmitter, receivers and remote site directional switching carried out by GPS time synchronisation.

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