MODIS

Moderate-resolution Imaging Spectroradiometer

MODIS Web Site (Goddard Space Flight Center)

Animation of MODIS science (3.0MB Quicktime .mov)

Animation of MODIS' scanning path (3.3MB Quicktime .mpg)

With its sweeping 2,330-km-wide viewing swath, MODIS sees every point on our world every 1-2 days in 36 discrete spectral bands. Consequently, MODIS greatly improves upon the heritage of the NOAA Advanced Very High Resolution Radiometer (AVHRR) and tracks a wider array of the earth's vital signs than any other Terra sensor. For instance, the sensor measures the percent of the planet's surface that is covered by clouds almost every day. This wide spatial coverage will enable MODIS, together with MISR and CERES, to determine the impact of clouds and aerosols on the Earth's energy budget. The sensor has an unprecedented channel (centered at 1.375 microns) for detection of wispy cirrus clouds—believed to contribute to global warming by trapping heat emitted from the surface. Conversely, cumulus clouds and aerosols are thought to have a cooling effect on the Earth's surface by reflecting and absorbing incoming sunlight. Which effect on climate will prove greater in the long run? MODIS, together with MISR and CERES, will help us answer that question.

MODIS is ideal for monitoring large-scale changes in the biosphere that will yield new insights into the workings of the global carbon cycle. While no current satellite sensor can directly measure carbon dioxide concentrations in the atmosphere, MODIS can measure the photosynthetic activity of land and marine plants (phytoplankton) to yield better estimates of how much of the greenhouse gas is being absorbed and used in plant productivity. Coupled with the sensor's surface temperature measurements, MODIS' measurements of the biosphere are helping scientists track the sources and sinks of carbon dioxide in response to climate changes.

Almost every day over the entire globe, the sensor monitors changes on the land surface, thereby building upon and extending the heritage begun by Landsat. MODIS maps the areal extent of snow and ice brought by winter storms and frigid temperatures. The sensor observes the "green wave" that sweeps across continents as winter gives way to spring and vegetation blooms in response. It sees where and when disasters strike—such as volcanic eruptions, floods, severe storms, droughts, and wildfires—and will hopefully help people get out of harm's way. MODIS' bands are particularly sensitive to fires; they can distinguish flaming from smoldering burns and provide better estimates of the amounts of aerosols and gases fires release into the atmosphere.

MODIS sees changes in the Pacific phytoplankton populations that may signal the onset of the famous El Niño/La Niña climatic siblings well ahead of their arrival. In turn, by coupling its sea surface temperature and ocean color measurements, MODIS will observe the impacts El Niño and La Niña have on the microscopic marine plant. While these measurements extend and build upon the heritage of the Coastal Zone Color Scanner and , MODIS also has a unique new channel for measuring chlorophyll fluorescence. All plants bombarded with light begin to glow, or fluoresce, but in wavelengths that our eyes cannot see. The more plants fluoresce, the less energy they are using for photosynthesis. Thus, MODIS not only maps the distribution of phytoplankton, it also helps us gauge its health.

Another MODIS instrument will launch later this year aboard Terra's sister ship—Aqua.

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