| Since 2001, the Valencia Anchor Station is currently being prepared for the validation of
SMOS land products. The site has recently been selected by the Mission as a core
validation site, mainly due to the reasonable homogeneous characteristics of the
area which make it appropriate to undertake the validation of SMOS Level 2 land
products during the Mission Commissioning Phase, before attempting more complex
areas.
Close to SMOS launch, ESA defined and designed the SMOS Validation Rehearsal
Campaign Plan with the purpose of repeating the Commissioning Phase execution with all
centers, all tools, all participants, all structures, all data available, assuming that all tools and
structures are ready and trying to produce as close as possible the post-launch conditions. The
aim was to test the readiness, the ensemble coordination and the speed of operations to be
able to avoid as far as possible any unexpected deficiencies of the plan and procedure during
the real Commissioning Phase campaigns.
For the rehearsal activity which successfully took place in April 2008, a control
area of 10 x 10 km2 was chosen at the Valencia Anchor Station study area where a
network of ground soil moisture measuring stations is being set up based on the
definition of homogeneous physio-hydrological units, attending to climatic, soil type,
lithology, geology, elevation, slope and vegetation cover conditions. These stations
are linked via a wireless communication system to a master post accessible via
internet.
Complementary to the ground measurements, flight operations were performed over the
control area using the Helsinki University of Technology TKK Short Skyvan research aircraft.
The payload for the campaign consisted of the following instruments: (i) L-band radiometer
EMIRAD (Technical University of Denmark, TUD), (ii) HUT-2D L-band imaging
interferometric radiometer (TKK), (iii) PARIS GPS reflectrometry system (Institute for Space
Studies of Catalonia, IEEC), (iv) IR sensor (Finnish Institute of Maritime Research,
FIMR).
Together with the ground soil moisture measurements, other ground and meteorological
measurements from the Valencia Anchor Station area, kindly provided by other institutions,
are currently been used to simulate passive microwave brightness temperature to have
satellite “match ups” for validation purposes and to test the retrieval algorithms. The
spatialization of the ground measurements up to a SMOS pixel is carried out by using a
Soil-Vegetation-Atmosphere-Transfer (SVAT) model (SURFEX, SURFace EXternalisée) from
Météo France. Output data, particularly soil moisture, will then be used to simulate the
L-band surface emission through the use of the L-MEB (L-band Microwave Emission of the
Biosphere) model. For that purpose, the microwave model uses specific ground information
regarding the soil and vegetation properties provided by the validation teams. The
aggregation of the brightness temperatures at the SMOS pixel scale is then carried out in an
operational way taking into account the SMOS viewing configuration and antenna
properties.
This paper presents an overview of the ESA SMOS Validation Rehearsal Campaign at the
Valencia Anchor Station area making more emphasis on the development of the ground
activities which are significant for the performance of the different validation components and
giving an outline of the methodology to be used for the whole SMOS Reference Pixel. |