How to select specific row in a matrix

i have data like

doy  time   aod
22  09  0.70800
22  09  0.72300
22  10  0.68500
24  04  0.51200
24  04  0.50200
24  05  0.49700
24  05  0.52200
24  06  0.52300
24  07  0.51100
24  08  0.52300
24  08  0.57800
24  09  0.56600
24  09  0.55700
24  09  0.55800
25  04  0.80100
25  05  0.95500
25  05  1.06800
25  06  1.05500
25  07  1.09200
25  08  0.93800
25  08  0.89200

i want output like

doy    time      aod
22  09  0.70800
22  10  0.68500
24  04  0.50200
24  05  0.49700
24  06  0.52300
24  07  0.51100
24  08  0.52300
24  09  0.55700
25  04  0.80100
25  05  0.95500
25  06  1.05500
25  07  1.09200
25  08  0.89200

here doy represent day of year and i have taken data of aod(aerosol optical depth) at different times if observation is repeated at the same time then i want minimum aod, if not repeated then i want same aod as recorded.