Algorithm Theoretical Based Document (ATBD) - CESBIO

SO-TN-ESL-SM-GS-0001
Issue 1.a
Date: 31/08/2006
SMOS level 2 processor
Soil moisture ATBD
The outputs of the calibration operations described above are incorporated in level 1 processing.
It is foreseen that additional calibration constraints, mainly on antenna properties, will be obtained from comparing
redundant visibilities.
• It is estimated that the ultimate calibration can only be obtained using vicarious methods. The most likely
candidates for this include one surface point at Dome C in the Antarctic, and mainly a network of drifting
floaters over the ocean.
• In addition, statistical vicarious methods assuming stability of major features of the brightness temperature
global distribution are considered.
• The geo-location accuracy will be tested through an analysis of SMOS data maps in the vicinity of well known
features such as isolated islands.
• The knowledge of many features of the auxiliary data (static maps of soil structure, thickness of forest cover)
will be improved by analyzing particular subsets of L2 data.
3.4.1.2 Validation
Algorithm validation plan will be based on using made targets, realistic synthetic scenes and eventually Reall data
collected during campaigns. Validation is described in [AD11] and will imply:
The core of the validation plan consists of three parts, which differ mainly by the data used as input.
• The first part (part 1) is mainly devoted at assessing the retrieval validity domain on conditions similar to those of
previous sensitivity studies, i.e. use fully simulated academic data 7 in view of carrying out a systematic exploration
of observing conditions for homogeneous scenes.
In a second step (part 2) the SMOS performance as assessed through performing the retrieval on a large sample as
provided by actual, realistic auxiliary data. The assessment will be carried out through statistical analysis of the
results.
Optimization of various operating parameters is foreseen in both parts 1 & 2. The assessment of retrieval efficiency is
foreseen in part 2.
• Finally the third part addresses the specific test sites which will be selected for product verification and prepares
this verification.
Parts 2 & 3 are meant as rehearsals for the product verification phase. Inasmuch as they are properly designed, they
should simply be repeated using actual SMOS data.
On top ofthese activities, specific retrival algorithm subsets such as updating the current maps will be verified. This
task should cover pending validation issues.
3.4.2 Quality Control and Diagnostics
For easier reading of the ATBD, these topics, which are closely linked both the theoretical algorithmic approach and to
the analysis likely to trigger a second retrieval attempt, are addressed in section 3.2.5.1.
3.4.3 Exception Handling
Identified exception cases are twofold:
3.4.3.1 Mandatory data are not available
In the general sense many data are expected to be present and usable in the present document. If for some reasons it is
not true then it may result in a process failure.
However, when processing a DGG node, some events can be handled by an exception mechanism that tries to maintain
the health for vital parts of the process.
In these cases, the L2 DAP output has to be defined in order to flags these events as well as to record the appropriate
informations to provide feeback, and ultimately the reasons to explain why the retrieval was not carried out.
The following is a starting point
7 i.e., very schematic, simplified, not necessarily bearing a relation with real life data but elaborated to assess a given point
.
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