Abstract
Land-reflected signals from a geosynchronous communication satellite
broadcasting in P-band (367.5 MHz) were captured in low Earth orbit
using a simple dipole antenna. A delay-Doppler map (DDM) was generated
through autocorrelation. Estimates of the specular point delay were
obtained from the lag of the second peak in the DDM with a bias of 239.4
m and a standard deviation of 44 m (12 m over a frozen lake) with
respect to a predicted orbit model. Relative magnitudes of the first and
second DDM peaks fell within the range of values predicted using
dielectric models for the frozen ground and lake. Lastly, retrievals of
surface reflectivity were generated using a range of realistic values
for the transmitter link budget G/T, these also fell within the range of
possible values for the antenna gain pattern. Given the lack of
calibration and the large uncertainties in the receiver orbit and
attitude, this agreement is sufficient to conclude a successful
demonstration of the fundamental principle of single-antenna
reflectometry in P-band. P-band reflectometry may offer a new approach
to remote sensing of sub-canopy and root-zone soil moisture.