Heath Yardley

The Soil Moisture Active Passive Experiments (SMAPEx): Toward Soil Moisture Retrieval From the SMAP Mission

NASAs Soil Moisture Active Passive (SMAP) mission will carry the first combined spaceborne L-band radiometer and Synthetic Aperture Radar (SAR) system with the objective of mapping near-surface soil moisture and freeze/thaw state globally every 2-3 days. SMAP will provide three soil moisture products: i) high-resolution from radar (~3 km), ii) low-resolution from radiometer (~36 km), and iii) intermediate-resolution from the fusion of radar and radiometer (~9 km). The Soil Moisture Active Passive Experiments (SMAPEx) are a series of three airborne field experiments designed to provide prototype SMAP data for the development and validation of soil moisture retrieval algorithms applicable to the SMAP mission. This paper describes the SMAPEx sampling strategy and presents an overview of the data collected during the three experiments: SMAPEx-1 (July 5-10, 2010), SMAPEx-2 (December 4-8, 2010) and SMAPEx-3 (September 5-23, 2011). The SMAPEx experiments were conducted in a semi-arid agricultural and grazing area located in southeastern Australia, timed so as to acquire data over a seasonal cycle at various stages of the crop growth. Airborne L-band brightness temperature (~1 km) and radar backscatter (~10 m) observations were collected over an area the size of a single SMAP footprint (38 km × 36 km at 35° latitude) with a 2-3 days revisit time, providing SMAP-like data for testing of radiometer-only, radar-only and combined radiometer-radar soil moisture retrieval and downscaling algorithms. Airborne observations were supported by continuous monitoring of near-surface (0-5 cm) soil moisture along with intensive ground monitoring of soil moisture, soil temperature, vegetation biomass and structure, and surface roughness.

A practical bistatic passive radar system for use with DAB and DRM illuminators

Digital broadcasts provide powerful illuminators of opportunity with waveforms that produce excellent radar ambiguity functions. An experimental program to investigate the possibility of such broadcasts for target tracking radar is described. In addition, the atmospheric monitoring possibilities for such broadcasts are discussed.

DAB based passive radar: Performance calculations and trials

This paper investigates the potential performance of an experimental passive bistatic radar that uses target illuminations by digital audio broadcasts. The work predicts that the current system has the potential to detect targets at distances of over 30 km and this has been verified by an experimental campaign using the radar. Possibilities for improvement of the system are identified.

Bistatic Radar Based on DAB Illuminators: The Evolution of a Practical System

Digital audio broadcasting (DAB) has massive potential for the development of passive bistatic radar. A project to build DAB based radar is described, together with its advantages and disadvantages. Several serious obstacles need to be overcome in order to make the system a reality. Most importantly, these include the removal of direct signal interference and the extraction of the illuminating signal in a form suitable for detections. Progress towards the solution of these problems will be described. In addition, some real aircraft detections are included to prove the viability of a practical system.