As skiers across the world pay close attention to the state of the snow on the slopes, there are a different group of scientific snow-watchers looking closely at a South Pole snowfield this January.
Scientists from around the world coordinated by the UK's National Physical Laboratory (NPL) are examining an Antarctic snowfield this January as part of the world's largest inter-comparison between satellite sensors.
The results will allow scientists to fully quantify differences between the measurements made by the satellite instruments in orbit. This will lead to improvements in their calibration and ensure that the data collected is all quality assured. This will ultimately result in more confidence in the data used for climate change, weather systems and monitoring disaster areas. Some of these measurements require the detection of changes of a few tenths of a percent per decade, yet current sensors exhibit biases between themselves of many percent, often more than 20 times this level.
Over 30 sensors from space agencies across the globe, including several from the UK, ranging in spatial resolution from a metre to several hundred metres will measure the reflectance of the sun by the Antarctic snow. All of the data will be cross-compared to each other supported by ground measurements of the site.
The measurements will be taken over a snowfield in Antarctica known as 'DOME C'. These can only be performed in December and January when the Sun is relatively high in the sky during the southern hemisphere summer.
Nigel Fox, head of Earth Observation in NPL's Optical Technologies software and computing team said:
"This is the most comprehensive comparison of its kind ever organised and is a direct result of efforts led by NPL to establish improved quality assurance of Earth observation data. As the data from many of the sensors involved in this comparison is used in studies of climate change, it is essential that we can reliably combine it together and start to use it as a truly global resource and reference for the future. This comparison will provide the information and evidence to allow this to happen"
This comparison is the first of a series led by NPL, supported by the Department for Innovation, Universities and Skills, the European Space Agency and the British National Space Centre, to address key issues in Earth Observation on behalf of the worlds Earth Observation community. Future ones include measurements of the temperature of the ocean and reflectance of a salt lake in Turkey.
Looking to the future, it is hoped that the UK can continue to take a lead in this niche but crucial role to underpin the calibration and validation of Earth Observation satellites. One example is the development of a "calibration satellite" in space to ensure the accuracy of satellites in orbit.
Notes to Editors
This comparison will be the first to follow the guidelines of a new international quality assurance framework for earth observation - QA4EO. This provides guidance on what needs to be done to ensure that all Earth Observation data can be assigned a "quality indicator". It also makes possible the linkage of data derived from different sensors to provide continuous operational data and enable long-time base studies, such as those needed by climate to be made. This is now being implemented throughout the world's space agencies ensuring that its next generation of satellites, the Sentinels, are fully compliant and able to deliver the key data needed by society. For more information go to: http://calvalportal.ceos.org/CalValPortal/showQA4EO.do?section=qa4eoIntro
This work is also in line with the aims of the intergovernmental body "the Group on Earth Observations" (GEO). This is looking to establish a "Global Earth Observation System of Systems" (GEOSS), to which the European "Global Monitoring of Environment and Security" (GMES) programme is a major contribution.
GEOSS must deliver comprehensive "knowledge/information products" worldwide and in a timely manner to meet the needs of its nine "societal themes" (one of which is climate). This will be achieved through the synergistic use and combination of data derived from a variety of sources (satellite, airborne and in situ) through the coordinated resources and efforts of the GEO members. This can only be achieved through the establishment of a Quality Assurance framework to facilitate interoperability and harmonisation.
For more information go to: www.earthobservations.org