SANTA BARBARA, Calif., May 7 -- Raytheon Co.'s second Moderate Resolution Imaging Spectroradiometer (MODIS) entered Earth's orbit on May 4 on board the Aqua, a satellite in NASA's Earth Observing System (EOS). Raytheon also provided a MODIS sensor for Aqua's companion satellite Terra, launched in December 1999. The Aqua MODIS instrument will work in conjunction with Terra MODIS to gather information at different equatorial crossing times. The primary role of the Aqua spacecraft is to gather information about water in the Earth's system. During the five-year mission, Aqua will gather information on changes in ocean circulation and how clouds and surface water processes affect our climate. Raytheon's MODIS instruments will collect detailed information about cloud cover, sea-surface temperature, chlorophyll levels, land-cover changes, land-surface temperature, and vegetation properties. The MODIS sensor uses a sophisticated imaging-spectroradiometer, consisting of a cross-track scan mirror and collecting optics, and a set of linear detector arrays with spectral filters that will provide imagery in 36 discrete bands selected by the science community for diagnostic significance in earth science. MODIS will provide daylight reflection and day/night emission spectral imaging of any point on the Earth at least every two days. MODIS was built by Raytheon's Santa Barbara Remote Sensing, under contract with NASA's Goddard Space Flight Center.