Advanced understanding of the global carbon budget requires large-scale and long-term information on forest carbon pools and fluxes. In situ and remote sensing measurements have greatly enhanced monitoring of forest carbon dynamics, but incomplete data coverage in space and time results in significant uncertainties in carbon accounting. Although theoretical and mechanistic models have enabled continental-scale and global mapping, robust predictions of forest carbon dynamics are difficult without initialization, adjustment, and parameterization using observations. Therefore, this dissertation is focused on a synergistic combination of lidar measurements and modeling that incorporates biophysical principles underlying forest growth. First, spaceborne lidar data from the Geoscience Laser Altimeter System (GLAS) were analyzed for monitoring and modeling of forest heights over the U.S. Mainland. Results showed the best GLAS metric representing the within-footprint heights to be dependent on topography. Insufficient data sampling by the GLAS sensor was problematic for spatially-complete carbon quantification. A modeling approach, called Allometric Scaling and Resource Limitations (ASRL), successfully alleviated this problem. The metabolic scaling theory and water-energy balance equations embedded within the model also provided a generalized mechanistic understanding of valid relationships between forest structure and geo-predictors including topographic and climatic variables. Second, the ASRL model was refined and applied to predict large-scale patterns of forest structure. This research successfully expanded model applicability by including eco-regional and forest-type variations, and disturbance history. Baseline maps (circa 2005; 1-km2 grids) of forest heights and aboveground biomass were generated over the U.S. Mainland. The Pacific Northwest/California forests were simulated as the most favorable region for hosting large trees, consistent with observations. Through sensitivity and uncertainty analyses, this research found that the refined ASRL model showed promise for prognostic applications, in contrast to conventional black-box approaches. The model predicted temporal evolution of forest carbon stocks during the 21st century. The results demonstrate the effects of CO2 fertilization and climate feedbacks across water- and energy-limited environments. This dissertation documents the complex mechanisms determining forest structure, given availability of local resources. These mechanisms can be used to monitor and forecast forest carbon pools in combination with satellite observations to advance our understanding of the global carbon cycle.

In-orbit calibrations of space instruments are often necessary to ensure the accuracy of the measurements. The Moon provides a target with very predictable characteristics. In this report, the opportunities to perform in-orbit lunar calibrations of the MicroCarb instrument are evaluated and a procedure for conducting the Mission Planning for these calibrations is developed. Through modeling the spacecraft in its orbit, simulations show that continuous observation sequences of up to 48 minutes can be expected each lunation. The variability of the optical properties of the Moon during an opportunity is related to the orientation of the plane of the orbit of the spacecraft with respect to the cone with axis the Moon-Sun direction and apex the center of the Moon that contains the spacecraft. Choosing a value of the phase angle (Sun-Moon-Spacecraft angle) around −20 degrees to plan the lunar calibrations allows to minimize the variations of apparent radiance of the Moon during the observation. The results make it possible to refine the choice of the best moments to plan the lunar calibrations. This also allows the satellite operations team to anticipate the planning of lunar calibrations on the scale of several months. / Kalibreringar i omloppsbana för rymdinstrument är ofta nödvändiga för att säkerställa mätningarnas noggrannhet. Månen utgör ett kalibreringsmål med mycket förutsägbara egenskaper. I denna rapport utvärderas möjligheterna att utföra månkalibreringar i omloppsbana för MicroCarb-instrumentet och ett förfarande för genomförande av uppdragsplanering för dessa kalibreringar har utvecklats. Genom att modellera rymdfarkosten i sin bana visar simuleringar att kontinuerliga observationssekvenser på upp till 48 minuter kan förväntas varje månvarv. Variationen hos de optiska egenskaperna för månen under ett tillfälle är relaterad till orienteringen av rymdfarkostens plan i förhållande till konen med axeln för månen-solens riktning. Att välja ett värde för fasvinkeln (Sun-Moon-Spacecraft-vinkel) på runt −20 grader vid planering av månkalibreringarna gör det möjligt att minimera variationerna i månens strålning under observationen. Resultaten gör det möjligt att förfina valet av de bästa tidpunkterna för månkalibreringarna. Detta gör det också möjligt för satellitoperationsteamet att förutse planeringen av månkalibreringar flera månader framåt.