After the 140th day of seeding, the reflectance and NDVI at 11:00 were symmetrical, and NDVI changed in M-shape, being able to be simulated by a quartic polynomial.

• 整个冬小麦生长季11:00反射率及NDVI以播种后第140天为中心对称，NDVI的季节变化表现为M型，可用四次多项式拟合；