Albedo in an albedo range of 0.1 to 0.4. The average albedo of Earth is about 0.3. This is far higher than for the ocean primarily because of the contribution of clouds. Earth's surface albedo is regularly estimated via Earth observation satellite sensors such as NASA's MODIS instruments on board the Terra and Aqua satellites, and the CERES instrument on the Suomi NPP and JPSS. As the amount of reflected radiation is only measured for a single direction by satellite, not all directions, a mathematical model is used to translate a sample set of satellite reflectance measurements into estimates of directional-hemispherical
Incompressible surface compressing "S" along "D". A non-negative complexity measure on compact surfaces without 2-sphere components is "b"("S") − "χ"("S"), where "b"("S") is the zeroth Betti number (the number of connected components) and "χ"("S") is the Euler characteristic. When compressing a compressible surface, the Euler characteristic increases by two, while "b" might remain the same or increase by 1. Thus, every properly embedded compact surface without 2-sphere components is related to an incompressible surface through a sequence of compressions. Sometimes we drop the conditions that "S" be compressible or that "D" be anything more than a disk that intersects "S" only along