Calibration & Validation
A dedicated framework for performing a detailed analysis of the instrument products, assessing their quality and supporting the instrument calibration.
The analysis of the spacecraft payload behaviour is a complex activity that requires dedicated tools. Quick detection of problems or anomalies is essential in order to prevent data loss and ensure the proper correction measures are taken. Calibration activities are also fundamental to keep the instruments operating under the best conditions.
DEIMOS Space has supported ESA in the design, development and operations of several facilities devoted to the monitoring and validation of instrument data of several Earth Observation missions. Depending on the mission approach, this task has been performed together with the Performance Monitoring or independently.
As a result of the experience gained in these projects, starting with ENVISAT and followed by CryoSat, GOCE or SMOS, a generic framework has been implemented to support these activities. The basic components of the system are specific toolboxes that analyse the instrument products or HK telemetry in order to detect potential deviations from the nominal behaviour or to propose calibration activities. These toolboxes shall be run automatically, and the system must collect all required input data and make it available to the toolboxes. In most of the cases the toolboxes have an important scientific component and are coded in high-level languages like IDL or Matlab. The framework supports the translation of input products (usually XML formatted) into IDL / Matlab variables. Once the toolbox has been executed, the results are stored locally, published in dedicated web servers (HTML reports) or disseminated via e-mail to the relevant experts.
In many cases the analysis to be performed requires keeping track of instrument or HK TM data from long periods of time. The most efficient way for doing this, instead of opening all the input products each time, is to have them stored in a local database. For this, QUARC infrastructure (Quality Analysis and Reporting Computer), originally developed by DEIMOS for ENVISAT but designed as an independent system able to support any mission, is used. At the core of QUARC lies a Database, which keeps the monitoring parameters into a common data model. This generic, but highly flexible and adaptable, representation provides very powerful capabilities to the system, with a dedicated high-level language to manipulate it.
Another important characteristic of the system is the interactive manipulation of data. In many cases, the automatic toolboxes can detect a problem, but it will be the expert user that will have to go deeper into the data, applying ad-hoc checks or algorithms to further analyse it. The framework provides these interactive capabilities, either in IDL or in Matlab, handling transparently to the user the data retrieval and transformation into easily manageable variables.
The framework implemented by DEIMOS is nearly mission-independent, and can be applied with minor customisation as the basis for calibration and validation activities in space missions.
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