L-band microwave radiometry for the monitoring of high latitude soil processes

Kimmo Rautiainen

Research output: ThesisDoctoral ThesisCollection of Articles


Remote sensing satellites provide vast possibilities for the observation of the Earth on both the regional (e.g. natural hazards, and various mapping and land use applications) and global scales (e.g. effects and indicators of climate change, weather phenomena). The increasingly rapid technological development of satellite payload instruments continues to make new innovations in Earth Observation possible. One such advancement was achieved with the successful launch of the SMOS (Soil Moisture and Ocean Salinity) satellite in late 2009. The SMOS payload instrument was the first two-dimensional aperture synthesis radiometer designed for the remote sensing of the Earth. A new imaging technique, using many receivers and passive aperture synthesis, was required to enable L-band observations at a spatial resolution and repetition time that were sufficient for SMOS mission requirements. With L-band observations, information on soil processes beneath the soil-atmosphere boundary layer can be gathered. Due to the characteristics of global L-band measurements, they are highly suitable for monitoring soil processes such as soil moisture and soil freezing and thawing. Global information on the annual soil cycle is important for understanding the Earth's climate. Soil freezing has an effect on the carbon and hydrological cycles as well as the energy balance between the soil surface and the atmosphere. Furthermore, soil freezing partially controls photosynthesis and the microbial activity within soils. This doctoral thesis combines the development work of the airborne L-band passive aperture synthesis radiometer (HUT-2D) and the development work of the soil freeze/thaw detection algorithm using L-band passive observations. HUT-2D was developed as an airborne demonstrator for the SMOS payload. The first successful 2D airborne images of Earth using aperture synthesis technique were acquired using HUT-2D. The HUT-2D project also provided many valuable insights for the SMOS payload development phase. The freeze/thaw detection algorithm developed within this thesis relates the L-band observations to the annual soil processes. The output product of the SMOS-based algorithm provides daily global soil freeze/thaw information with three distinct states; soil within a pixel cell is estimated to be either frozen, partially frozen, or thaw. Global information on soil states can be used for input parameterisation in various models such as weather prediction models, climate models and global circulation models.
Translated title of the contributionPohjoisten alueiden maaperäprosessien monitorointi L-alueen mikroaaltoradiometreillä
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Praks, Jaan, Supervising Professor
  • Pulliainen, Jouni, Thesis Advisor, External person
Print ISBNs978-952-60-7770-3
Electronic ISBNs978-952-60-7771-0
Publication statusPublished - 2017
MoE publication typeG5 Doctoral dissertation (article)


  • radiometry
  • soil processes
  • microwaves


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