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A new three year work programme for the CEOS Working Group on Calibration and Validation

The 10th CEOS Plenary Meeting endorsement of the concept of an Integrated Global Observing Strategy (IGOS) and the modification of the CEOS Terms of Reference to authorise broader participation by CEOS Affiliates and Observers, have great significance for the CEOS Working Group on Calibration and Validation (WGCV).

WGCV was also encouraged by Plenary to address Cal/Val recommendations from the IGOS related In Situ Observations meeting on September 1996 in Geneva. These were that the Global Observing Systems Space Panel should develop a scheme for identifying priorities in validation issues, and that on the basis of these priorities WGCV should consider developing pilot project(s) to address issues such as measurement protocols, test regimes and data management.
These Plenary decisions formed the focus for the working group's latest meeting. WGCV12, kindly hosted by DARA and DLR-DFD at Oberpfaffenhofen, Germany 4th to 6th December, 1996. The meeting saw the development of a new three year work plan. This follow the actions, guiding principles and recommendations of the WGCV's Strategic Vision Document. The preliminary elements of the new work plan are described below.

A new WGCV web site
The WGCV secretariat hosts and maintains a new world wide web(WWW) site at:
http://www.eos.co.uk/ceos-calval
This contains background material, contact details for members and links to non-CEOS sites dealing with calibration and validation issues. The goal is for the WGCV web site to become a first port of call for anyone seeking Cal/Val information.
The site is being expanded to list conferences. New introductory material is being prepared, and a slide set providing generic Cal/Val examples is being prepared; slide sets related to specific Cal/Val topics will follow. The web site will also contain key references and reference sites as compiled by the four WGCV sub-groups. Copies of WGCV newsletters will be available. Finally minutes of the latest WGCV meetings, including WGCV12, are available.

2.The WGCV Dossier
This dossier provides information on calibration laboratories, on test sites and instruments in a uniform way. The dossier development, led by NASA, will continue over the nest three years. The Dossier can be found at:
http://spso.gsc.nasa.gov/calval/homepage.html

3.Linkages to non-CEOS Groups
To improve liaison with organizations lacking CEOS representation. WGCV will invite individuals to meetings as technical experts. The WGCV's Infrared and Visible Optical Sensors(IVOS) sub group, which met the two days prior to WGCV12, set precedent with an excellent presentation from the UK National Physics Laboratory on new advances in instrument calibration.
Representation from developing countries is particularly important for validation, where local expertise is needed world-wide. The WGCV recognizes that funding for participation may be a problem. However, it was felt that if invitations were made in the context of special sessions, funding may be easier to find. WGCV will invite experts from developing countries in this context, and CEOS Affiliates will be asked to identify relevant individuals. Most WGCV subgroup meetings already feature one specialist session, and all subgroup chairs agreed that this will continue.

4.Co-ordination and implementation of validation activities.
WGCV12 debate concerting validation began with the Geneva meeting recommendations. These are largely paralleled by recommendations made in the WGCV's Strategic Vision Document. Firstly, that WGCV should from ad hoc groups with common interests in the validation of specific parameters and encourage inter-comparison of parameters derived from different instruments. Secondly that WGCV should compile a list of validation data sets and activities which should receive priority.
WGCV12 concluded that validation will from a focus for our work over the next three years, and at least in the near-term, work will continue within the four subgroups.
Priority parameters must be identified. This list must consider existing activities as the costs of international validation exercises is high. The Geneva recommendation that the Space Panel provide such a list should be expanded to include all CEOS Members, Affiliates and Observers. However Affiliates should strengthen their involvement in the WGCV activities. The priority list should recognize that not all parameters are at the same level of maturity. In this light WGCV12 participants identified seven pilot projects which will be used to analyse issues such as accuracy requirements, measurement and sampling protocols, test site(s), data management requirements and implications for all CEOS participating organizations. Parameters include Visible/Near-Infrared Top-of Atmosphere reflectance (these are a critical first step to creation of derived parameters such as Leaf Area Index); Sea Surface Temperature validation; intercomparison of Digital Terrain Model generation from optical and microwave data; Wind Speed; Significant Wave Height; Wave Frequency and Wave Direction.

conclusions:
The new work plan represents a significant expansion of activity concerning validation. However, the pilot projects build on previous WGCV actions and on proposals for project work by CEOS agencies represented in WGCV. The three year work plan will build on the results of these projects, will certainly adapt to the evolving IGOS and will evolve to best serve the needs of the international community. My thanks go to all those who participated in WGCV12.

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