A land remote sensing satellite system consists of five major components, each of which is critical to producing useful data: 1. Sensors: Optical systems gather light in various spectral (color) bands from Earth's surface and focus it on photosensitive surfaces that convert the light to digital electrical impulses that can be transmitted to Earth electronically. Landsats 4 and 5 collect light in seven spectral bands, ranging from the blue to the infrared. The thematic mapper sensor is capable of distinguishing objects as small as 30 meters across. Landsat 6 carries a higher resolution sensor, able to distinguish objects only 15 meters across. 2. Spacecraft and Transmitters: The spacecraft provides a stabilized platform and power for the sensors and their optics, the receiving and transmi