I am in need of 8-day NDVI composites at a finer resolution (250 m). For this, I have used MODIS/006/MOD09GQ in GEE but the outputs have masked values. Can someone please suggest to me how to solve this? I tried to go for daily surface reflectance images to obtain the same with the Maximum Value composite method but I would like to know that how appropriate is it against 8-day surface reflectance products.