A new propagation prediction tool for earth-space geometries for the advanced refractive effects prediction system (AREPS)

Abstract

AREPS is the U.S. Navypsilas designated software tool ** for radar performance simulation and analysis. For well over 20 years it has been used to provide accurate propagation predictions in realistic refractive environments for terrestrial radar systems from VHF (~100 MHz) to Q-band (~60 GHz). Recently, the range of applications for AREPS has been extended by the addition of a communications prediction capability at high frequencies (HF, ~2 MHz - 30 MHz) which includes both surface wave and ionospheric sky wave coverage for beyond line-of-sight propagation paths. In this paper we describe the latest addition to AREPS, which uses refractive height profile input along with a newly developed ray trace capability to provide signal strength estimates for earth-to-satellite communications. By including atmospheric refractivity the model becomes especially useful for determination of antenna pointing angles in strongly refracting environments and for low-elevation satellites for which ray paths through the atmosphere may be very long. The model includes an orbital location prediction capability which uses two-line element sets (TLE) which are widely available on the Internet for non-classified systems and generally available for classified systems for designated users. The model provides a transparent homing procedure which determines the launch angle for the direct ray connecting transmitter to satellite and, in some situations, for the earth reflected mode. Possible ray blockage by terrain for low elevation satellites can be investigated by including DTED terrain elevation data in the analysis.