## 3 Results
### Measurements of Vegetation Canopy  
Both hemi-con and bi-hemi configurations for SI, SII and SIII were conducted to measure vegetation canopy during the days, while only SIV of hemi-con configuration was setup as a reference. The upwelling hemispherical sensors of the three systems and the conical sensor of SIV were mounted at different height but had almost the same FOV. Similar to measuring soil ground, diurnal variations of IT of the four systems with conical sensors (9 th May) and with hemispherical sensors for the upwelling channel (12 th May) are shown in Figure 9. On 9 th May, when the downward pointing sensors of all systems measured with conical sensors, ITS of SI and SII were much lower than the other two, and the IT of SII was about half of that of SI, which was same as measuring the bare soil ground. On May 12 th, when the downward sensors of SI, SII, and SIII were equipped with cosine correctors, all ITS became longer. And IT of SII was closer to but still much lower than that of SIV compared to the results on May 9 th. Similar patterns have been found when the upwelling hemispherical sensors of the three  
Figure 7: Diurnal variations of integration time (**A,B**) irradiance and (**C,D**) radiance of different systems with hemi-con configuration while the downward bare fiber pointing toward bare soil background. The right volume is the magnification of integration times (ITs) of systems I and II (SI and SII). systems and the conical sensor of SIV were mounted at the same height but had different fields of view, as shown in Figure A5. Whether the upwelling sensor equipped with cosine corrector or not, SII always has the shortest IT, i.e., the greatest efficiency. Figure 10 showed the irradiance, radiance and reflectance of SI and SII when downward pointing sensors (Figure 10A,B) were conical sensors and (Figure 10C,D) were hemispherical sensors measuring vegetation canopy. The irradiance and radiance measured by the two systems were very close. Hence, the reflectance calculated from these two systems was also quite similar. The small fluorescence peak of reflectance at 687 nm could be observed from both SI and SII. In contrast, the fluorescence peak of reflectance at 760 nm was clear from SII while that from SI had an abnormal vibration, which was possibly due to spectral shifting caused by the impalpable difference between the two paths of the splitter fiber. Whether it was downward pointing conical sensors or hemispherical sensors, the shapes of reflectance had no difference. SII shows its advantage of avoiding spectral shifting and being able to measure \"perfect\" shape of vegetation reflectance. Reflectance measured by the four systems of hemi-con and bi-hemi configurations at different (Figure 11A,C) and the same heights (Figure 11B,D) were displayed in Figure 11. All reflectances were measured under similar illumination condition. Figure 11A,B shows differences among reflectance from four systems, which were similar to those shown in Figure 6, probably owing to the different IT of the four systems and asynchronous measurements of incident irradiance and reflected radiance. Either at different or the same heights, reflectance measured with hemispherical sensors (Figure 11C,D) exhibited obvious differences to those measured with conical sensors (Figure 11A,B), with relatively higher reflectance in red region and lower reflectance in far-red region. Even though the FOV of the hemispherical sensor was theoretically covered by vegetation, it seems the reflectance measured by hemispherical sensor contains the signal of background. To test the usefulness of cosine corrector in measuring reflected radiance of vegetation, we conducted another experiment to clarify the \"real\" FOV of it. Figure 8: Reflectance of different systems with (**A**) hemi-con and (**B**) bi-hemi configurations while the upwelling sensors pointing toward bare soil background. As described in Section 2.3 for the test of CC-3 FOV (Figure 6), two pots of _E.