IOCCG
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Background A recommendation to establish a permanent Task Force for satellite sensor calibration comes from the White Paper of the International Network for Sensor Inter-comparison and Uncertainty Assessment for Ocean Color Radiometry (INSITU-OCR) initiative. INSITU-OCR has been created under the framework of the Committee on Earth Observation Satellites (CEOS) Ocean Colour Radiometry-Virtual Constellation (OCR-VC). OCR-VC aims to "provide long time series of calibrated ocean colour radiance at key wavelength bands from measurements obtained from multiple satellites" and its activities include calibration. Successively, the INSITU-OCR white paper recognizes the need for the Space Agencies to facilitate collaboration among sensor characterization and calibration experts with particular expertise in ocean colour instruments for the goal of maximizing the accuracy and temporal and spatial stability of OCR records from individual missions. OCR necessitates special sensor calibration considerations because ocean colour mission requirements are particularly demanding: 0.5% uncertainty in sensor measured Top-of-the-Atmosphere (TOA) radiances as well as a significantly lower uncertainty on sensor characterization and relative radiometric calibration, spatial and temporal (IOCCG, 2012; IOCCG, 2013). A global group of ocean colour instrument calibration experts is small and these challenging requirements are most effectively addressed by their collective effort and sharing of multi-mission experience. Rationale The establishment of the sensor calibration Task Force answers to the needs of all ocean colour missions because accurately calibrated and characterized satellite sensors are a prerequisite for most of the OCR applications, from climate, Earth system science and marine ecosystem monitoring, to operational services including water quality, fisheries and algal blooms. The total 0.5% uncertainty goal dictates that each individual component contributing to this uncertainty has to be characterized to the order of 0.2% or less (IOCCG, 2012) in both pre-launch and on-orbit characterizations. Continuous monitoring of on-orbit temporal degradation needs to assure time-series stability. Although post-launch vicarious calibration removes a global bias from the measurements, any uncorrected instrument effects impact TOA radiance quality, vicarious gain stability, and reduce the accuracy of ocean-colour products. The ocean-colour needs impose specific mission and instrument requirements as well as calibration and characterization processes which are largely shared among different ocean colour missions. However, the knowledge of those is largely confined to a small group of experts worldwide. This proposal recommends the establishment of the Task Force to unite this expertise and to facilitate cross-pollination, further development and inter-Agency support. The Task Force is proposed to be composed of Space Agency calibration and characterization experts. The experts will meet and interact on specific technical problems, will work hands-on with data, prototype, deliver solutions and transfer the solutions to operations. Terms of Reference The Task Force provides a framework under which the ocean colour instrument calibration experts meet and exchange ideas, information and data, as well as conduct hands-on research and implementation. The exchanges as well as the resources are sanctioned by the Agencies contributing to the OCR-VC initiative. The scope of the Task Force responsibilities includes ocean colour satellite sensor calibration and characterization, pre-launch and on-orbit. System vicarious calibration is not in the scope of this Task Force. The Task Force is a joint IOCCG and CEOS OCR-VC activity in response to the INSITU-OCR White Paper. The Task Force is recognized by CEOS WGCV IVOS, with direct linkages and adoption of IVOS guidelines relevant to ocean colour. The Task Force reports to IOCCG and CEOS OCR-VC, i.e. INSITU-OCR project office, as well as to CEOS WGCV IVOS. Findings and recommendations are also communicated back to individual Agencies and their groups associated with ocean colour mission performance and cal/val. The aim of the Task Force is thus not to meet and write a report but to create a permanent inter-Agency platform for joint space instrument calibration and characterization work that is specifically focused on issues related to ocean colour sensors. The Task Force performs the following functions:
Mission Statement The goal of the Satellite Sensor Calibration Task Force is to create a framework for active and hands-on collaboration among instrument calibration and characterization experts from Agencies engaged in the OCR-VC initiative. The collaboration focuses on calibration needs specific to ocean-colour measurements and has the objective to maximize the accuracy and temporal and spatial stability of OCR records from individual missions for the purpose of climate, research and operational applications. Membership The chairmanship of the Task Force shall be initially established by the inter-Agency executive committee and will be expected to last for a 3-year term. Future rotations of the Chair shall be decided by the Task Force members. The Task Force members will be proposed by the Agencies in agreement with the Chair, initially 1 or 2 members per Agency. The members shall represent expertise in a broad range of satellite ocean colour instrument designs and have hands-on calibration and characterization competences. The membership of the group will not be time limited and the tenure will depend on the member's availability, the patron Agency, and the Chair. Member rotation or a new member can be proposed at any time. Additional outside experts may be consulted and invited to attend meetings and provide support. The following are suggested membership criteria:
Functioning of the IOCCG Task Force
References
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Calibration Task Force Documents |