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

• Published in: IEEE transactions on geoscience and remote sensing Vol. 52; no. 1; pp. 490 - 507
• Main Authors: Panciera, Rocco, Walker, Jeffrey P, Jackson, Thomas J, Gray, Douglas A, Tanase, Mihai A, Ryu, Dongryeol, Monerris, Alessandra, Yardley, Heath, Rudiger, Christoph, Wu, Xiaoling, Gao, Ying, Hacker, Jorg M
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 2014; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: agricultural soils; Algorithms; Applied geophysics; biomass; Earth sciences; Earth, ocean, space; environmental monitoring; Exact sciences and technology; Experiments; field experimentation; grazing; grazing lands; Internal geophysics; L-band; latitude; Meteorology; microwave; Microwave radiometry; Monitoring; polarimetric L-band imaging synthetic aperture radar (PLIS); polarimetric L-band multibeam radiometer (PLMR); Radiometers; remote sensing; seasonal variation; semiarid soils; Soil moisture; soil moisture active passive (SMAP); soil surveys; soil temperature; soil water; spatial data; surface roughness; Synthetic aperture radar; synthetic aperture radar (SAR); vegetation; Vegetation mapping; vegetation structure; Australia; experimental studies; microwaves; algorithms; Australasia; latitude; vegetation; cycles; L-band; soil moisture active passive (SMAP); roughness; polarimetric L-band multibeam radiometer (PLMR); soils; Synthetic aperture radar; microwave; high resolution; biomass; soil moisture; NASA; sampling; testing; polarimetric L-band imaging synthetic aperture radar (PLIS); remote sensing; brightness temperature; synthetic aperture radar (SAR); growth; strategy; radar methods
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/tgrs.2013.2241774

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.