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

P Panciera, J Walker, T Jackson, Douglas Gray, M Tanase, Dongryeol Ryu, Alessandra Monerris, Heath Yardley, Christoph Rudiger, Xiaoling Wu, Ying Gao, Jorg Hacker

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    139 Citations (Scopus)


    NASA's 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.

    Original languageEnglish
    Article number6479292
    Pages (from-to)490-507
    Number of pages18
    JournalIEEE Transactions on Geoscience and Remote Sensing
    Issue number1
    Publication statusPublished - Jan 2014


    • L-band
    • Microwave
    • Polarimetric L-band imaging synthetic aperture radar (PLIS)
    • Polarimetric L-band multibeam radiometer (PLMR)
    • Remote sensing
    • remote sensing
    • Soil moisture
    • soil moisture
    • Soil moisture active passive (SMAP)
    • soil moisture active passive (SMAP)
    • Synthetic aperture radar (SAR)L-band multibeam radiometer (PLMR)


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