The hydrosphere state (hydros) satellite mission: An earth system pathfinder for global mapping of soil moisture and land freeze/thaw

Dara Entekhabi, Eni G. Njoku, Paul Houser, Michael Spencer, Terence Doiron, Yunjin Kim, Joel Smith, Ralph Girard, Stephane Belair, Wade Crow, Thomas J. Jackson, Yann H. Kerr, John S. Kimball, Randy Koster, Kyle C. McDonald, Peggy E. O'Neill, Terry Pultz, Steve W. Running, Jiancheng Shi, Eric F. WoodJakob Van Zyl

Research output: Contribution to journalArticlepeer-review

195 Scopus citations

Abstract

The Hydrosphere State Mission (Hydros) is a pathfinder mission in the National Aeronautics and Space Administration (NASA) Earth System Science Pathfinder Program (ESSP). The objective of the mission is to provide exploratory global measurements of the earth's soil moisture at 10-km resolution with two- to three-days revisit and land-surface freeze/thaw conditions at 3-km resolution with one- to two-days revisit. The mission builds on the heritage of ground-based and airborne passive and active low-frequency microwave measurements that have demonstrated and validated the effectiveness of the measurements and associated algorithms for estimating the amount and phase (frozen or thawed) of surface soil moisture. The mission data will enable advances in weather and climate prediction and in mapping processes that link the water, energy, and carbon cycles. The Hydros instrument is a combined radar and radiometer system operating at 1.26 GHz (with VV, HH, and HV polarizations) and 1.41 GHz (with H, V, and U polarizations), respectively. The radar and the radiometer share the aperture of a 6-m antenna with a look-angle of 39° with respect to nadir. The lightweight deployable mesh antenna is rotated at 14.6 rpm to provide a constant look-angle scan across a swath width of 1000 km. The wide swath provides global coverage that meet the revisit requirements. The radiometer measurements allow retrieval of soil moisture in diverse (nonforested) landscapes with a resolution of 40 km. The radar measurements allow the retrieval of soil moisture at relatively high resolution (3 km). The mission includes combined radar/radiometer data products that will use the synergy of the two sensors to deliver enhanced-quality 10-km resolution soil moisture estimates. In this paper, the science requirements and their traceability to the instrument design are outlined. A review of the underlying measurement physics and key instrument performance parameters are also presented.

Original languageEnglish (US)
Pages (from-to)2184-2195
Number of pages12
JournalIEEE Transactions on Geoscience and Remote Sensing
Volume42
Issue number10
DOIs
StatePublished - Oct 2004

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering
  • Earth and Planetary Sciences(all)

Keywords

  • Land freeze/thaw
  • Microwave remote sensing
  • Satellites
  • Soil moisture

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