Summary of the
Since its formation in November 1996, the AG has focused on the 6 prototype projects initiated by the Strategic Implementation Team (SIT). The task of the AG is to supply CEOS Participants and the SIT with an analysis of the extent to which existing and planned missions are meeting the current set of defined user requirements. The AG's work has been integrated with Affiliates' plans for similar analyses. The AG has also provided a useful forum for the projects to take forward their discussions.
The AG has adopted an analysis technique that is based upon the content and structure of the CEOS database. In order to "interrogate" the database in an objective manner, the AG has further developed an existing software tool, already adopted by a number of CEOS Affiliates. The tool, which is intended to highlight critical areas for more detailed analysis, takes users' requirements and statements of provision from the database and carries out a comparative, quantitative analysis of the degree to which users' needs for space-based information are met.
The AG's report is intended to assist the SIT in developing further and implementing the space component of an overall IGOS - as well as investigating, with relevant partners, the practical, political, and programmatic mechanisms to act upon recommendations regarding correction of gaps/overlaps in observing programmes.
The AG's activities to date have shown that a truly integrated strategy in any area of Earth Observation is much more than simply identifying gaps and overlaps. First the participants must agree on the "state of the observations/science" in the focused area. This leads to the identification of many more gaps than overlaps. It appears that each of the 6 prototype projects is currently at this stage of development, and as such, will require additional time and effort to contribute to the development of an integrated global observing strategy and to demonstrate its value.
The long-term outlook for space-based total ozone measurements (NPOESS, METOP) is very encouraging, but there are concerns about the early part of the next century. In spite of the relatively large number of current and planned space-based instruments for measurement of the vertical profiles of ozone and associated species, it is clear that a more integrated and better defined strategy (involving ground- and balloon-based measurements as well as space-based ones) is necessary.
Observations of ozone alone are not adequate to interpret ozone changes. Much more serious consideration must be given to validation and calibration of space-based chemistry measurements, as these are essential to ensure the establishment and long-term maintenance of data quality across multiple platforms and instruments.
The loss of radiosonde observations (raobs) will have a negative impact on global numerical weather prediction forecasts which could be considerably mitigated if appropriate and immediate action is taken to use satellite sounding and wind data over land where the raobs are being removed.
Full capability of current satellite remote sensing measurements is not being realised. More resources must be focused towards better usage of the data.
The present suite of satellite observations does not meet median or optimum NWP requirements, with wind profiles needing the most improvement. Additionally, a global geostationary sounding capability is required.
System simulation experiments are required in order to study the impact of future observing systems as well as to synthesise the best composite observing system (satellite, ground, and other) and strategies such as adaptive observations.
Space agencies must work with NWP centres to enhance use of satellite observations over land in the near-term to help mitigate the decrease in radiosonde observations.
Overall, in terms of spatial resolution, frequency and timeliness most of the data will be close to optimum for all the periods and requirements.
In terms of accuracy (RMS), the requirements are fulfilled at better than the threshold level with the exception of salinity and wind vectors. However, wind speed data are available at better than threshold requirement and would cover a gap in vector data, particularly if other data can provide direction. It is recommended that the proponents of GODAE should, in collaboration with the suppliers, revisit the accuracy definition for speed and direction of the instruments providing wind vector data.
In the case of both winds and ocean topography there appears to be a problem of long term continuity. Concerning wind vectors, beyond 2004 there will only be the one double sided scatterometer flying on METOP/EPS (programme still in the approval process in Europe). An early confirmation of SeaWinds 2 as a payload on ADEOS III is needed. In addition, once ENVISAT is launched, the scatterometer on ERS1/2 is planned to be closed down. It is recommended that SIT address these problems.
For ocean topography there are no firm plans for data beyond 2004. It is also recommended that the relevant agencies consider how continuity of Jason and RA-2 can be ensured.
Of the variables required, only salinity is unobservable during the GODAE period and it is recommended that the space agencies consider how they can respond to this technical challenge.
For sea surface temperature and sea ice cover, there should be no problem with long term availability of adequate data. Any improvement should focus on the accuracy of SST measurements. However, this is seen as a low priority compared to those set out above.
Initial analyses have shown that existing sensors and those under development will provide data of useful precision. Noting that the objectives of this project are presently being carried out very effectively by the International Ocean Colour Coordinating Group (IOCCG), it is the appropriate body to develop future recommendations concerning IGOS to the SIT.
Present and future missions of CEOS agencies should provide ample coarse and fine resolution optical data and C-band SAR data for GOFC.
SIT should be aware of a serious gap in L-band data which is likely to occur between the end of the JERS-1 mission (likely 1998-2000) and the beginning of the ALOS mission (planned for 2003).
A well designed acquisition strategy is important to ensure sufficient usable fine resolution optical data.
Adequate land cover change information
requires long time series of data and blended high and low resolution
products. The SIT should consider ways of improving the accuracy
of these data by having high and low resolution sensors on the same
platform or flying in tandem.
Strong support and enthusiasm for this project have been demonstrated by a number of CEOS agencies and organisations involved with various aspects of disaster management, including civil preparedness. Noting this promising start, the SIT should continue to support the project through active participation of agency representatives in:
- development of information servers including links to agency systems and, where possible, to relevant data and information;
- hazard task teams which will address requirements for specific hazards (eg flooding, fires);
- project planning and oversight.
The SIT should encourage the participation of space agencies not yet directly involved.
The SIT should assist the project in developing outreach initiatives, especially for developing countries.
The main lesson is that the analysis of satellite requirements and performances is a very complex matter that cannot be accomplished without significant effort and time. Furthermore, unless sufficient resources are devoted to the problem then the results of the analysis will be misleading and dangerously counter-productive.
In this context the AG reviewed the scope of the analysis process, the suitability of the available databases and the analysis methodology. As regards scope, the AG recognised that user groups were already studying the theoretical capabilities of satellite systems, so that the AG could concentrate on the current and probable product plans of the space agencies.
A comparison of the two sets of results could then in due course serve to identify short-term improvements to the existing systems. The AG should not concern itself with matters such as data policy and data costs, although this would be of concern of the projects.
Concerning the databases, the AG recognised that considerable efforts had been made, notably in June 97, to populate them, but that there were still very significant errors and omissions. As a consequence of this experience the AG makes a number of recommendations:
- that the quality control of the databases must be drastically improved;
- that a single entity should become the focal point for all queries and suggestions regarding the structure and content of the database, with CEOS Members and Affiliates still "owning" the data;
- that further efforts must be made to populate and correct the database.
Significant effort is required from CEOS participants to realise the potential of the database. Without a reliable database, the work of the AG is undermined and no robust decision regarding the implementation of an IGOS can be made. The AG recommends, with the highest priority, that CEOS participants provide sufficient resources to correct factual errors in the database immediately.
As regards the analysis tool, the AG noted that this had been created initially to deal with upper air data for NWP. It had been optimised for that purpose and its use for other applications revealed some problems which were corrected after the Tokyo workshop. However, the tool itself revealed that there was a number of underlying problems with some of the definitions, including those of resolution and accuracy, which need to be addressed in further developments of the database.
Example summary charts (for the Upper Air project) are attached to this Executive Summary, while the corresponding parameter data sheets are attached to the main report. These example summary charts were constructed after making local corrections to the information extracted from the database.
Each project should report to the SIT, including its progress in defining a long-term strategy, a schedule of milestones, and specific recommendations or requests, where appropriate, for CEOS agency action.
Once the initial deficiencies of the CEOS database are addressed and an effective oversight process put into place, in the longer-term the CEOS database should be expanded to address wider project needs such as integrated data products. IGOS should have access to other sources of data such as in-situ sources of observations.
The SIT should address data policy issues to encourage, rather than inhibit, the use of CEOS agencies' data for the IGOS pilot projects.
Timely availability of baseline datasets, such as gravity and digital terrain models, must be included in the overall IGOS consideration, even if not specifically associated with a pilot project.
The AG concluded that considerable progress had been made with the analysis process and with the understanding of the factors which are important for further development of the database. It believes that the six SIT projects have made considerable progress in their planning in conjunction with the AG process.
This was a very intensive activity, with three large meetings within the space of six months. Such a high level of activity is not justified for the future and the AG believes its work can be continued more efficiently through much smaller groups.
The continued evolution of the database and analysis tools should be monitored through a small (2 -3 persons) "Common Dataset Validation Team" that has been set up by the CEOS Secretariat. This team should encourage all participants to check and correct their entries in the database as soon as possible. Only when the database problems have been addressed can future meaningful analyses be conducted.
It is clear that some group which sits outside each of the projects, but which has direct access to the results of their work, is needed. It is therefore proposed that a recommendation to CEOS Plenary is made that these activities take place within the framework of the SIT, possibly by establishing an SIT subgroup. The roles should be to:
i) synthesise the recommendations of the six existing projects and any new projects that may be defined;
ii) draw general inferences from the output of the projects and any new future projects;
iii) remain informed on the scientific integrity of the common dataset as implemented by the Validation Team;
iv) assist in the development of analysis tools in response to projects' needs;
v) maintain oversight of those requirements of Affiliates which are not addressed within the six projects and ensure that these are taken into account in the future development of an IGOS.
The AG considers that its initial task has been achieved. Given the establishment of the group referred to above, a recommendation to dissolve the AG should be made to the 1997 CEOS Plenary.