International Global Navigation Satellite Systems Association
IGNSS Symposium 2018
Colombo Theatres, Kensington Campus, UNSW Australia
7 - 9 February 2018
An Adaptive Window for Stare Processing of Delay Doppler
Maps
Benjamin J. Southwell and Andrew G. Dempster
ABSTRACT
GNSS-R is the use of reflected Global Navigation Satellite System (GNSS) sig-
nals for remote sensing. Stare processing is a technique which focuses on a fixed
point on the ocean surface as it traverses through contiguous Delay Doppler Maps
(DDM). As the stare point moves through the DDM and spatial domain, the foot-
print of its ambiguity function varies. This is analyzed and shown to be suboptimal.
In this paper a variable length window in the DDM which provides an improved
spatial footprint is introduced. The window is varied in length along the delay di-
mension as the spatial footprint becomes delay limited when the stare point moves
away from the specular point. The cross-track resolution is found to be sensi-
tive to the variable delay window whilst a Doppler resolution of 500Hz causes the
along-track resolution to be insensitive to the variable delay.
KEYWORDS: GNSS-R, Reflectometry, Stare Processing
1 INTRODUCTION
Global Navigation Satellite Systems (GNSS) signals reflected off the Earth were first proposed for
remote sensing applications in 1993 by Martin-Neira [Martin-Neira, 1993]. This is known as GNSS
Reflectometry (GNSS-R). Multiple applications of GNSS-R have been proposed and experimental
results obtained for altimetry [Martin-Neira, 1993], ocean surface wind vector determination [Glea-
son, 2006] , soil moisture content measurement from both ground based [Rodriguez-Alvarez et al.,
2009, Arroyo et al., 2014] and spaceborne receivers [Camps et al., 2016] in addition to sea ice
detection [Schiavulli et al., 2017] amongst others.
Ocean scatterometry with spaceborne receivers for the retrieval of mean square slopes (MSS) of
the sea surface and surface wind speeds is an active area of research. Currently the TechDemoSat-1
(TDS-1) [Foti et al., 2015] and CYGNSS [Ruf et al., 2012] satellite provide MSS and wind speed
