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1. Monitor the total and spectral solar irradiance from an uninterrupted,overlapping series of spacecraft radiometers employing in-flightsensitivity tracking.

There is an urgent need to rapidly implement the necessary long term commitment for this monitoring because of the danger that the present monitoring sequence will be interrupted and the long term record invalidated as a result of lack of instrumental cross-calibration. This primary recommendation is particularly challenging and probably will not be achieved because of the dearth of ready access to space.

A series of small spacecraft dedicated to solar monitoring could provide the necessary data. Overlapping observations are required to cross-calibrate measurements by different instruments whose inaccuracies typically exceed the true solar variability. Simultaneous observations from different instruments provide important validation that real variability, rather than instrumental degradation, is being measured and provide the redundancy needed to preserve the long term data base in the case of instrument failure. Improved radiometric long term precision and calibration accuracies would contribute to a more reliable solar forcing record.

In lieu of a spacecraft series dedicated to solar monitoring, it may be possible to use the NOAA or DMSP operational satellites, for which overlapping is a feature of their design.

Additional Recommendations

To augment the prime monitoring task, a suite of efforts from diverse geophysical research fields is needed to achieve the USGCRP objectives of monitoring, understanding, and predicting solar influences on global change. Pursuit of recommendations 2 to 6 is essential to the crossdisciplinary effort needed to reduce uncertainties in knowledge of solar forcing of global change in order to provide a sound scientific basis for policy-making on global change issues. The actions of recommendations 7 to 12 are essential to ensure that complete understanding is achieved of all potential coupling mechanisms.