EOS Validation Program

Dear EOS Team Leader/Principal Investigator:

We would like to respond to two important questions that have been asked regarding the EOS Validation Plans during recent meetings.

First, with regard to the time period to be covered in the plans, the validation plans need to cover planned pre-launch activities and to describe post-launch activities out to at least two years after launch. While general guidelines about the team's expectations beyond that time period are desired, detailed planning would become more speculative and less meaningful. As things begin to settle down after launch, probably about a year, we expect the teams will revise and extend their plans.

Second, several instrument teams, particularly the MODIS team, have requested clarification of activities that involve analysis and refinement of data products to improve data product quality and accuracy after launch and initial release of the data to the public.

Such refinements might result from improvements in the theoretical basis of the algorithms, improvements in the implementation of calibration data, results of validation studies, or improvements in the data processing procedure to address unforeseen problems. Problems with the data products might be identified through objective or subjective quality analysis, comparison with conventional or other data sources, or through problems encountered while using the products in various science applications. Efforts to identify potential data product problems and to develop corresponding corrections or improvements will most likely be led by the scientists of the Instrument Science Team (IST) and performed using their scientific computing facilities (SCFs). Other elements of EOS may also make strong contributions here, e.g., other ISTs and the IDS teams.

While the definition for the partition between calibration, validation and quality assurance activities, that has been adopted by the Panel on Data Quality of the IWG and the Project Science Office, surely does not correspond to that which would appear correct to each IST member, this does not leave this important class of IST activity without a home. The IST Data Quality Plan, the aggregate of the required IST Calibration, Validation, and Quality Assurance Plans, needs to address if and how the IST associated with a specific product generally intends to conduct analyses leading to refined and improved products (as opposed to estimates of the uncertainties associated with a product). The criteria, approaches, and procedures are likely to be instrument and even product specific. If not provided in other documentation, we encourage the ISTs to include a description of these activities in section 5.0 of your Science Data Validation Plan following the outline transmitted as Enclosure 3 with our letter of October 18, 1995 and also attached here. At the least, please indicate where the information is given.

We also point out that the IST validation plan should include, in section 5, a description of the expected interactions among calibration, vicarious calibration, validation, and quality assurance activities and with the data processing and EOSDIS. To this point, each of these activities has been considered somewhat separately with plans at various stages of maturity. An integrated view of the expected realization is sorely needed and would be quite useful to the Project Science Office, National Research Council, Earth System Science and Applications Advisory Committee (ESSAAC), and others. How do results of each of these related activities affect each other? How do they affect data processing? What are the mechanisms by which the interactions are to take place? In what time frame? What are the Instrument Team's expectations for large-scale data reprocessing? How is EOSDIS involved in the process? The modus operandi may be quite different for some data products, especially for the higher order geophysical data products, even within a specific instrument team. What is desired is a fairly succinct and down-to-earth description of the team's concept of how the system and the science will work to produce validated high quality data products over the life of the mission. You and the Project Science Office, as well as EOSDIS, must have a clear understanding of how you expect things to work.

I hope this helps to clarify questions you may have regarding information to be included in the EOS Validation Plans.

Sincerely,

David O'C Starr
EOS Validation Scientist

Michael D. King
EOS Senior Project Scientist