The number of Earth Observation (EO) satellites is rapidly growing, whilst measurements from satellite sensors are used to answer increasingly urgent global issues, making it imperative that scientists and decision-makers be able to rely on the accuracy of EO data products.
Where long data records are required, to establish for example Climate Data Records (CDRs) such as Sea Surface Temperature (SST) and Land Surface Temperature (LST), it is essential for the data and associated measurement systems to be rigorously tied to international physical standards (Systeme International, SI) to enable:
- Confidence in the data
- The means to assign appropriate weights when making judgements
- Measurement consistent and independent of the time of measurement or those taking the measurements.
- Potential for data gaps in the observation record
- Measurements of the same measurand to be traceable to different base units without bias e.g. Thermal and Radiometric units
Fiducial Reference Measurements
“The suite of independent ground measurements that provide the maximum return on investment for a satellite mission by delivering, to users, the required confidence in data products, in the form of independent validation results and satellite measurement uncertainty estimation, over the entire end-to-end duration of a satellite mission”
(Sentinel-3 Validation Team)
An FRM must:
– Document evidence of its traceability to SI
– Be independent from the satellite geophysical retrieval process
– Detail an uncertainty budget for the instrumentation and measurement process for the range of conditions it is used over.
– Adhere to community agreed measurement protocols and management practises.