AIRBORNE FOREST MONITORING DURING SMAPEX-3 CAMPAIGN C.Vittucci(1), L.Guerriero(1), P.Ferrazzoli(1), R. Rahmoune(1), M.Tanase(2), R.Panciera (2), A.Monerris(3), C. Rüdiger(3), J.P.Walker(3) (1) DICII, Tor Vergata University, Roma, Italy, Email: vittucci@disp.uniroma2.it (2) CRC-SI, University of Melbourne, Melbourne, Australia (3) Department of Civil Engineering, Monash University, Clayton, Australia ABSTRACT This study investigates the potentialities offered by active and passive simultaneous acquisitions at L band for monitoring of soil moisture in forested areas. Airborne data, acquired over the moderately dense Gillenbah forest in the framework of SMAPEx-3 project, have been analyzed to derive the sensitivity of emissivity and backscattering coefficient to soil moisture variations during the campaign, considering a full set of ground measurements characterizing the forest environment. Index Terms— SMAPEx, soil moisture, forests. 1. INTRODUCTION To address the requirement for higher resolution soil moisture data, the National Aeronautics and Space Administration (NASA) has proposed the Soil Moisture Active Passive (SMAP) mission, with an expected launch date in 2014. This mission will provide global maps of soil moisture at ~9 km spatial resolution with a 2-3 days repeat through the combined use of radiometer data at 36 km and radar data at 3 km spatial resolution [1]. The Soil Moisture Active and Passive Experiment (SMAPEx) consisted of three airborne campaigns held in the Murrumbidgee Catchment (New South Wales, Australia) between 2010 and 2011, in order to encompass seasonal variations of soil moisture and vegetation [2]. The SMAPEx airborne facility consists of the Polarimetric L-band Multibeam Radiometer (PLMR; 1.41 GHz) and the Polarimetric L-band Imaging Synthetic aperture radar (PLIS; 1.26 GHz) which, when used together on the same aircraft at a flight altitude of 3 km, allows acquiring SMAP-like data with passive microwave footprints at 1km and active microwave footprints at better than 10m resolution [3, 4]. The present study focuses on the analysis of passive data collected over the Gillenbah and Boona State Forests during the third SMAPEx campaign (SMAPEx-3), which took place during the austral spring in September 2011. A sensitivity analysis to soil moisture content and tree biophysical parameters, provided by the ground sampling in the growing season, has been performed. The SMAPEx-3 data have been interpreted using the theoretical model developed at Tor Vergata University, and will be used to test and verify earlier theoretical findings [5]. The model is based on a discrete approach and is able to simulate both active and passive microwave signature of forests [6, 7]. 2. DATASET A total of eight PLIS/PLMR flights were conducted over Gillenbah (7 km x 8 km) and Boona State Forests during the austral spring (5 th to 23 rd September 2011) in the Yanco Region (NSW, Australia), together with a detailed forest inventory accounting for vegetation structure (Fig.1). This area presents semiarid characteristics and has been monitored since 2001 for remote sensing purposes [8]. The main trees species in the forests are Murray Pine (Calitris Glucophylla) and mixed Murray Pine and Grey Box (Eucalyptus microcarpa). Ground sampling and inventory was performed at 20 locations. In the Gillenbah Forest, 12 different sites consisting of 5 plots each, were sampled to characterize an area of about 1ha around the site center. Inside each plot, all trees with diameter at breast height (DBH) > 5 cm were recorded and the total and crown height [m] were measured. The smaller trees (DBH < 5 cm) were counted and their average height visually estimated. The total biomass for each tree was calculated using allometric equations [9, 10] and aggregated at plot level [t ha -1 ]. For representative trees, the crown (CWC [m 3 /m 3 ]) and trunk water content (TWC [m 3 /m 3 ]) were measured for each tree species. Soil moisture (SM [m 3 /m 3 ]) and soil surface temperature (Ts [K]) were measured using Hydraprobe instruments. 987 978-1-4799-1114-1/13/$31.00 ©2013 IEEE IGARSS 2013