Current Programmes

It's useful to list those radars currently operational with on-going programmes. Some radar facilities are able to operate with different geometries but here we list them according to their major operating role.

3.1. Transverse reflection

3.1.1. Measuring individual orbits

The Advanced Meteor Orbit radar (AMOR) operates at 26.2 MHz radiating 100 kW peak pulse power. The facility uses three ~ 8 km spaced stations to provide time-offlight measurements of echoes to give velocity components while elevation is secured via a dual baseline interferometer. The antenna system is specifically designed [2] to have narrow (1.6°) azimuthal beams and broad in elevation. FM UHF data channels provide links between stations. The facility is in continuous operation in programmes devoted to: the distribution of solar system dust from heliocentric orbit surveys; the identification of interstellar dust in the inner solar system; the dynamical structuring of cometary and asteroidal streams; and the measurement of atmospheric winds and turbulence.

The 45.6 MHz MU radar at Shigaraki near Kyoto Japan has a programme mainly devoted to middle atmospheric dynamical work but the system can sense individual meteor radiants by rapid beam switching with meteoroid speeds determined from Doppler pulse compression characteristics. An array of 475 crossed Yagi antennas is used for transmitting and receiving with each being driven by individual transmitter units. The system antenna beam has a half-power width of 3.7° and target zenith angles of up to 30° can be accessed. Astronomical projects concentrate on the times of major streams [3].

3.1.2. Echo directions but no individual orbits

The Chung-Li radar in Taiwan operating at 52 MHz employs a transmitter array providing a ~ 10° width vertical pointing beam with echo direction determined by relative phases measured using a 0.86A spacing triple Yagi array The meteor programme has focused principally on the Leonid shower influx [4].

In Canada stream parameters have been measured using a 40.68 MHz 10 kW facility. This system (CLOVAR) consists of single transmitter Yagi combined with five Yagis as a multi-spacing interferometer of spacing 2.0 and 2.5 A to determine echo directions to ~ 2°. Stream meteors are identified according to the directions with respect to the expected shower radiant [5].

The Adelaide Buckland Park facility in Australia operates at 54.1 MHz using a TX/RX square antenna filled array sides 16 A giving a full width half power radiation beam of 3.2°. Antenna element phasing can tilt the beam 30 east or west of zenith and accurate 0.8 %) meteor speeds can be determined. The programme has been devoted to stream flux characteristics and the probing the velocity distribution within stream population (e.g. [6]).

One of the most sustained radar surveys has been that carried out at the Ondrejov facility in the Czech republic. The 37 MHz operation employs a steerable antenna 36° beam and has maintained flux measurements of the major streams for several decades. Range-time plots yield valuable longitude cover for fine structure in streams, long term rates influenced by atmospheric changes and data on head echoes (see e.g. [7]).

In South Africa the 28 MHz Grahamstown radar with echo position determined by 4-antenna phase comparisons and with large angular sky coverage but lacking range and velocity information has been able to provide maps of apparent sporadic sources after subtraction of the major streams [8].

Was this article helpful?

0 0

Post a comment