ETM+ provides Landsat data continuity and improved land remote-sensing capabilities.
ETM+ is a passive sensor aboard Landsat-7 that measures the solar radiation emitted and reflected by the Earth. Enhancing its predecessor (Landsat 5/TM), ETM+ has added capabilities that include a 15-meter resolution panchromatic band, a Long Wave Infrared (LWIR) 60-meter resolution band, and six 30-meter resolution multispectral bands. Because of Landsat's importance in providing accurate measurements in support of NASA's "Mission to Planet Earth," increased emphasis has been placed on ETM+'s calibration accuracy: three independent onboard calibration systems calibrate the panchromatic visible and near infrared (VNIR) and short wave infrared (SWIR) bands. The radiometric accuracy achieved is 5% absolute (2% relative).
The Landsat-7 spacecraft was launched on April 15, 1999, with an ETM+ dedicated payload. It operates in a 705-km, sun-synchronous orbit with a 9:45 a.m. (descending) equatorial crossing time.