likely ensure overlap with SORCE. A 1.5 year collection of data on orbit however leaves a gap of more than a year between the stated end of TCTE and beginning of the TSIS on JPSS FF-1. Based on data furnished by the spacecraft provider and LASP, the Committee found the likelihood of achieving overlap with the JPSS/TSIS is 0.56, or slightly better than 50 percent. If the launch of the JPSS FF-1 is delayed, the probability of overlap will decrease. Although the TCTE mission will not ensure continuity of the TIM-era data record, it is more likely to ensure continuity of the full, lower quality data record. The Committee does note that NOAA would be wise to utilize all available data resources (e.g., TCTE, other instruments, proxy models) to fill the gap.

Taken together, the NOAA Plan and the Kopp and Lean studies provided a balanced discussion of strengths and weakness of the proposed method to fill the TSI gap and recognized fully the limitations of TCTE. The Committee was not initially convinced that the CDR requirements as posed represent requirements that were derived from those relevant to understanding climate change. The Committee’s research on the source of the requirements given suggests they derive from empirical knowledge of solar variability and instrumental capability and are less related to the energetics of the Earth system. To determine the implications of these requirements on the understanding of the Earth’s climate system, the Committee considered two different pathways for setting these requirements based on climate sensitivity, rather than on solar variability or instrumental capability. Coincidentally, the outcome of the calculations made by the Committee agrees with the pre-defined CDR requirements. Hence, given that the recommendations were based on these requirements, the Committee considers that the plan, to an appreciable extent, explored the implications of loss of, or changes in, TSI measurements on the understanding of Earth’s climate system and processes.

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