Weather and Aircraft Surveillance Radar Requirements for a 10-cm Wavelength Multi-function Phased Array Radar

WEATHER AND AIRCRAFT SURVEILLANCE RADAR REQUIREMENTS
for a 10-cm wavelength Multi-function Phased Array Radar

Dick Doviak, Mark Weber, and Dusan Zrnić

NOAA National Severe Storms Laboratory

Norman, Oklahoma USA

To free spectral space for commercial use radar engineers will need to move existing surveillance radars from bands they presently occupy. This paper suggests that a 10-cm wavelength phased array radar can meet the two aircraft surveillance functions now met by the ARSR and ASR radars, and the two weather surveillance functions now met by the WSR-88D and the TDWR, while conserving spectrum usage.

Matching the performances of the ARSR-4 and ASR-9/11 for aircraft detection and tracking, and performances of the TDWR and the WSR-88D for weather surveillance, with a 10-cm wavelength Multi-function Phased Array Radar (MPAR), or the Spectrum Efficient National Surveillance Radar (SENSR), using a 4-face Planar Polarimetric PAR (PPPAR) or a 4-sector Cylindrical Polarimetric PAR (CPPAR) is a challenge. Presented are the key requirements of an MPAR or SENSR if either is to meet the present day performances of the existing national network of aircraft and weather surveillance radars.

The ARSR function of the 10-cm MPAR can meet the 20-cm ARSR-4 capability to detect and track aircraft at the longest range with and without precipitation but requires a modest increase of average power if the ARSR-4 precipitation model specified by the FAA for storm systems is used in computing propagation loss. There can be more demanding precipitation conditions typical of lines of storms containing rain or mixtures of rain and hail. But these are relatively rare events that typically occur over central USA. Higher average power would be required during these events if availability requirements are to be met. However, increased power might not be necessary if all MPARS have the same functionality because the MPAR coverage will blanket the continental US and there are likely other MPARs that can detect aircraft if echoes from one MPAR are not detected because of unusual excessive attenuation. Moreover because the MPAR might be a backup system to the upcoming GPS tracking system for the continental USA, the availability requirements might be relaxed.

To match the height resolution of the TDWR for the detection of low altitude wind shear along the approach and departure corridors of an airport, the 10-cm wavelength MPAR should be located closer, by a factor of two, to the airport than present TDWR sites or, since the MPAR also serves the ASR-9/11 function, located on the airport at or near the present site of the ASR-9/11.

The most stringent antenna sidelobe level is set by the performance of the WSR-88D antenna. To match this, it is recommended the specified MPAR two-way sidelobe level be below -64 dB at 2^o decreasing to -100 dB below the mainlobe gain at about 12^o and then decreasing to -110 dB at 20^o and beyond. Any increase in the sidelobe levels of the MPAR over what is effectively present with the WSR-88D would likely increase the incidence of data corrupted by sidelobe coupled power.

Furthermore, polarimetric H and V radiation patterns need to be well matched and to differ by less than 0.5 dB down to the -20 dB level below the peak of the mainlobe.

If time multiplexing of the four surveillance functions described herein proves practical, spectrum utilization might be decreased significantly from that presently allocated for the present day network of four independently operated surveillance radars.