The Ostsee-Wind-Radar OSWIN

From September 1997 to September 1998 a VHF-radar was operating at Kühlungsborn (54.1°N; 11.8°E) for the investigation of the dynamics and structure of the tropo-, strato-, and mesosphere. The transmitting and receiving technique was transported to Andenes/Norway (69.01°N; 16.03°E) and is continuously and unattended working there since 12 October 1998 as the Alomar Wind Radar ALWIN) (Latteck et al, 1999).

During summer 1999 a new VHF-radar (OSWIN) was installed at Kühlungsborn using the existing antenna field and new transmitting and receiving units. Height profiles of the 3-D wind vector and of the radar reflectivity can continuously and unattended be derived by the Spaced-Antenna (SA) and the Doppler-Beam-Swinging (DBS) method.

 

The system is composed of different modules shown in the block diagram The tube transmitter of the company ATRAD consists of six units each with 15 kW transmitting power. The signals of each unit are transferred through a passive transmitting-receiving-switch  to the antenna steering unit thus allowing an automatic operation of the transmitting/receiving antenna system in SA- and DBS-mode.

 

Technical Parameters

Frequency

53,5 MHz

Peak power

90 kW

Mean power

4,5 kW (@ 5% Duty Cycle)

3dB-Beam width

6°

Pulse length

1 ... 32 µs

Pulse repetition frequency

< 50 kHz

Height Ranges

(0,4) 1 ... 18 km (65 ... 95 km)

Height resolution

150 m, 300 m, 600 m, 1000 m

Time resolution

~ 1 min

Transmission signal

Single pulse, Complementary codes

Pulse form

Rectangle  modified Gauss (for maximum power)

The transmitting/receiving antenna consists of 144 four-element-Yagi antennas grouped in quadratic subsystems of four antennas each and arranged in a 6x6 matrix. The distance between the individual antennas is λ/√2. The antennas are aligned by an angle of 45° concerning the North-South-axis thus ensuring that an identical antenna characteristic can be used in DBS-mode for zonal (East-West) and meridional (North-South) direction. In case of the SA-mode the antenna field for reception is subdivided in 6 individual fields consisting of 6 subsystems each. These 6 individual fields can be connected with maximum 6 receiving channels. In DBS-mode it is possible to swing the antenna beam in three zenith angles (7°, 13°, 20°) in the four directions North, South, East, and West. Such steering is made by a phase delayed feeding of the six antenna rows or columns in transmission case and in case of reception by a software supported post-beam steering (PBS).

The receiving system consists of 6 channels where the signals are pre-processed into their quadrature components. The following analysis of the row data can be carried out online or as post process at the integrated host PC or at every other internet connected computer.

By use of single and coded pulses in a combined mode continuous wind profiles from 1 to 18 km can be estimated. In principle also measurements are possible within the boundary layer above 400 m by use of a modified SA-method.

In the mesosphere the OSWIN-VHF-Radar is mainly used for investigations of mesospheric radar echoes in summer (MSE) and in winter (MWE).

Since 2002 the OSWIN-VHF-Radar has the additional possibility to make investigations during selected measuring campaigns at ionisation traces caused by invading meteoroids using a separate transmitting antenna and spatially separated receiving antennas. From the echo amplitude, the radial velocity and the life time of such echoes the wind field between about 80 and 110 km as well as the temperature at about 87 km can be estimated.