Besides the detection of fire focus, the orbital remote sensing allows the use of a series of spectral indexes for the identification of burn scars. The objectives of this work were to avaliate the performance of indexes in the determination of the burned area and to validate the detections of the Burn Monitoring Portal. There were calculated nine indexes with spectral information of the sensors Thematic Mapper and Enhanced Thematic Mapper Plus (30m) of the Landsat series. There were raised heat focus between june of 1988 and december of 2015 of all the available orbital sensors in the Burn Monitoring Portal. The indexes Normalized Burn Ratio and Char Soil Indexs had the best performance in the identification of the burned areas. These indexes differ from others because the consider spectral information of the near and medium infrared regions. The more critical period was from september to november. Of the total of burns identified by data from the series Landsat, 37% also were detected by the Burn Monitoring Portal. This low percentage of success is due to the low spatial resolution of the sensors used by this portal. Many fire focus weren''''t detected because they were in the opposite face of the sensor''''s passing, or due to the cloud cover, or yet by the ocurrence of fire between the period of the sensor''''s passing. Besides this limitation, these data are very useful to determine the time of fire focus concentration.