83 
Figure 1 The location of the sea off Fukushima and observation sites 
2. ORO/CRL HFOSR system 
ORO/CRL HFOSR adopts frequency moderated interrupt continuous wave (FMICW) 
radar system. The specification of ORO/CRL HFOSR is shown in Table 1. 
Table 1 Specifications of ORO/CRL HFOSR system 
Radar 
Radar Type 
Mean Frequency 
Sweep Band Width 
Frequency Sweep Interval 
Maximum Transmission Power 
Range Resolution 
Velocity Resolution 
Frequency Modulated Interrupted Continuous Wave 
24.515 Mhz 
100 kHz 
0.5 sec 
100 W 
1.5 km 
< 4.78 cm/s 
Antenna 
Antenna Type 
Electronically Steered Phased Array Antenna 
Beam Width 
15 ° 
Beam Scan 
±45° in steps of 7.5° 
The central frequency of the transmitted radio wave is 24.15 MHz, corresponding to 
12.2m in wavelength, which gives the wavelength of the resonant ocean surface wave 
6.1m. The observation time is 128 seconds for each line of sight gives the velocity 
resolving power 4.78 cin/s. Each ORO/CRL HFOSR has a electrically steered phased 
array antenna with 10 elements. The antenna beam has the width 15° and is steered within 
±45° to the normal direction of the radar in steps of 7.5°. The observation time in each 
line of sight takes 10 minutes for the data accumulation and frequency analysis, therefore 
the total time for a survey, 12 beam directions, takes 2 hours.