We extend the theory of quality-adjusted expenditure indices to estimate benefits from public investment. In particular, we model the selection of new instruments (in the form of remote-sensing devices) to enhance the longest-operating U.S. satellite-based land-observing program, Landsat. We then apply the model to the use of Landsat in measuring global forest carbon sequestration. Improving measurement of the role of forests in storing carbon has become a prominent concern in climate policy. By characterizing the value of Landsat data in forest measurement, the expenditure function allows us tohelp inform public investment decisions in the satellite system. The expenditure function also makes explicit the sensitivity of the selection of instruments for the satellites to the value of Landsat information, thus linking instrument choice explicitly to policy design.