Metop-A ASCAT NRT SSM orbit geometry 12.5 km sampling

The Level 2 surface soil moisture product is derived from the radar backscattering coefficients measured by the Advanced Scatterometer (ASCAT) on-board the series of Metop satellites using a change detection method, developed at the Research Group Remote Sensing, Department for Geodesy and Geoinformation (GEO), Vienna University of Technology (TU Wien). In the TU Wien soil moisture retrieval algorithm, long-term Scatterometer data are used to model the incidence angle dependency of the radar backscattering signal. Knowing the incidence angle dependency, the backscattering coefficients are normalized to a reference incidence angle. Finally, the relative soil moisture data ranging between 0% and 100% are derived by scaling the normalized backscattering coefficients between the lowest/highest values corresponding to the driest/wettest soil conditions (more information can be found on the Product User manual PUM). More information on the soil moisture retrieval algorithm can be found in the Algorithm Theoretical Baseline Document (ATBD)

• Spatial Coverage: Global
• Cycle: On completion of each orbit. Each orbit lasts 101 minutes (orbital period), resulting in ca. 14 orbits/day. Observing cycle over Europe: 36 h (full geographical coverage).
• Resolution (H101-H16): Spatial sampling on a regular 12.5 km grid in orbit geometry with a spatial resolution of 25-34 km × 25-34 km.
• Resolution (H102-H103): Spatial sampling on a regular 25 km grid in orbit geometry with a spatial resolution of 50 km × 50 km.
• Accuracy: Correlation coefficient (CC) - 0.50 (Threshold), 0.65 (Taget), 0.80 (Optimal)
• Timeliness: 2hr
• Dissemination: By dedicated FTP Server for the H-SAF users - By EUMETCast to most other users, especially scientific
• Formats: BUFR

In the figure below is described the relationship between H07 and the related global product H16 and H101. H07 has been obtained by means of a cutting of the global product H101 over the H-SAF area and, since Metop-B became operational, by means of a cutting of H16

The ASCAT soil moisture orbit NRT products have been provided as EUMETSAT Secretariat products, which also took care of the processing of the NRT products. A trial dissemination of the ASCAT soil moisture orbit NRT products based on Metop-A has started in May 2008 and became fully operational in December 2008 at EUMETSAT. After the launch of Metop-B in September 2012, a trial dissemination of Metop-B NRT soil moisture products started in November 2012. The ASCAT soil moisture orbit NRT products based on Metop-B became fully operational in January 2013.

Since November 2015 the ASCAT soil moisture orbit NRT products are formally handed over to H-SAF and part of the H-SAF soil moisture product portfolio. The soil moisture products have not been changed, only their programmatic context has been shifted. The EUMETSAT Secretariat is still in charge of processing and distributing the data sets in NRT.

Archived H101, H102, H16 and H103 are available at EUMETSAT's data portal (and can be ordered for a given lon/lat boundary box and time period, this way the users can get exactly the same area also covered by H07) and NRT data from EUMETCast