How many scenes are there for ASTER per year ? From what I understand is that the temporal is every 16 days. So, some month it will have 2 and some months it will have one.
The ground track repeat cycle for ASTER is 16 days, which means every 16 days the pattern of orbit is repeated. So, each year a ground track is repeated (365/16) approximately 23 times. Therefore, you can acquire images of the same area 23 times per year.
The orbit period is approx. 98 minutes. Therefore, each year there are (365*25*60 = 547500/98), give or take, 5587 orbits per year.
The circumference of the earth is approx. 40,075km. For a scene size of 150km, that means (40,075/150) 267 150km scenes per orbit.
267*5587 = 1,491,729 scenes per year or 124,310 per month.
There are many assumptions built in here (e.g. the satellite is always capturing data, scene size is approximated), but that's a literal approach to the question you asked - is this actually what you were looking for or did you just want the repeat cycle?