DSCOVR is the first Earth observing mission to the Lagrange-1 (L1) point. From L1, DSCOVR will have a continuous, synoptic, high time resolution view of the Sun-lit side of the Earth. DSCOVR will be an important addition to the current fleet of satellites, while at the same time exploring the potential of the new approach to Earth science observations made possible by the L1 vantage location.

DSCOVR will have the ability to view scenes in a synoptic context simultaneously with LEO and GEO satellites, affording the opportunity for synergism, calibration comparisons and production of unique data utilizing inputs from more than one satellite. For example, data requiring multi-angle, simultaneous views of the same scene can be produced using DSCOVR and other Earth-viewing satellites.

DSCOVR will be making both new and traditional types of measurements from its advanced absolute radiometers (Scripps-National Institute of Standards and Technology Advanced Radiometer (NISTAR)), the 10-channel imaging spectroradiometer (Scripps-Earth Polychromatic Imaging Camera (EPIC)), and the Plasma-Mag instruments. They should lead the way to future, more advanced missions at L1 and other deep space points around the Earth. The science areas to be addressed by DSCOVR, are summarized in the following paragraphs.

Radiation and Climate - Solar radiant energy is the major driver of the Earth's climate. The reflection, absorption, and re-emission (as infrared radiation) of that energy via a system of clouds, aerosols, atmospheric constituents, oceans, ice, and land surfaces determine the response of the Earth system to the incoming energy. The advanced radiometers will measure the reflected and emitted radiances over a critical angle range with unprecedented accuracy. Such accurate measurements will help refine and test our understanding of climate, climate change, and the Earth's radiative processes. In particular, the measurement of the near-infrared and visible parts of the reflected radiation may shed light on the issue of excess cloud absorption observed by Nimbus 7.

Upper Atmosphere Dynamics - The synoptic, high temporal and spatial resolution ozone maps retrieved from the Scripps EPIC instrument will be useful forstudying the upper atmosphere and aid our understanding of its circulation and climate.

Clouds and Their Microphysical Properties - The climate forcing by clouds is an order of magnitude larger than aerosols and ozone combined. DSCOVR will provide daytime synoptic pictures of diurnal global cloudiness. Knowledge of the cloud cover and microphysical properties is critical for converting the reflected and emitted radiances to Earth-disk albedo and outgoing longwave radiation, the quantities used to constrain the climate models. Cloud coverage, optical depth, and altitude are basic properties used in this process. The Scripps EPIC instrument visible and near-infrared channels will be used to derive these quantities for each image. Additional new information about the microphysics of ice clouds will be derived by routinely combining DSCOVR EPIC data with reflectances measured with Earth Observing System (EOS), geostationary, or other satellites at corresponding wavelengths. These synergistic, path-finding results will be valuable for further constraining climate models in their critical calculations of cloud interactions with solar radiation.

Aerosols -Aerosols impact climate directly by absorbing and scattering radiation. They also modify the microphysical structure and radiative properties of clouds (indirect effects). The magnitude of aerosol effects on climate depends on aerosol concentration, microphysics and chemistry, characteristics that exhibit substantial temporal and spatial variabilities from regional to global scales. Data from the combined visible and ultra violet (UV) spectral channels on the Scripps-EPIC instrument will be used to derive indices of aerosol particle size distributions and aerosol optical depths with greater resolution than possible with the Total Ozone Mapping Spectrometer (TOMS) (8 km vs. 80 km). EPIC data may also be used for tracking aerosol plumes from fires, desert-dust sources, and volcanoes.

Surface Reflectance and Vegetation Index - Surface reflectance cannot be observed directly from spacecraft because of atmospheric effects. EPIC's aerosol, precipitable water, and cloud products provide the information necessary to convert at-satellite EPIC radiances to surface reflectances, thus allowing direct comparison with surface reflectances made from other instruments and platforms. The normalized difference vegetation index (NDVI) is a measurement of contrast between red and near-infrared spectral bands. Because plant leaves strongly absorb red light and strongly reflect near-infrared light, the contrast in these two bands is a measure of the density of the vegetation cover. Mapping the vegetation index derived from surface reflectances provides a global picture of vegetation condition and abundance. DSCOVR's ability to acquire hourly views of every Sun-lit Earth location provides a unique opportunity to acquire vegetation index data for the whole globe in a short period of time.

Vegetation Canopy Measurements - Due to its location near the Sun-Earth L-1 point, DSCOVR will acquire images of the Earth in and near the solar retro-reflection direction, also known as the hotspot direction. From this direction, the shadows of objects, such as leaves or tree crowns, are hidden behind the objects. Thus, hotspot reflectances have little or no shadow component, a circumstance that enhances the spectral separation of vegetation and ground layers. Moreover, the daily change in the angle of the view path from sunrise to noon to sunset through the vegetation canopy produces changes in surface reflectance that can be related to the height of vegetation crowns and the size of canopy gaps. In this way, the unique L1 viewing position of DSCOVR can reveal vegetation canopy structure.

Ultraviolet Radiation - The UV radiation reaching the Earth's surface will be monitored with data from the EPIC instrument. Furthermore, DSCOVR's sunrise-to-sunset view of the full Earth disk will enable hourly estimates of surface UV over the entire globe. Cloud cover is a key factor affecting UV exposure at the ground. DSCOVR will observe clouds throughout the day at a given location, giving a picture of the UV reduction by clouds and therefore, of the UV reaching the surface. Measurements of cloud reflectivity at 380 nm will be used to determine cloud UV transmittance.

Solar Wind and Space Weather - Another useful product from DSCOVR will be rapid warning for solar flares and other extreme solar events. Such warnings could allow utility companies and satellite operators to execute timely procedures to protect their assets. The plasmas magnetometer instruments on the Advanced Composition Explorer (ACE), a space science satellite currently operating at L1, but which is nearing the end of its design lifetime, have already demonstrated such capability. DSCOVR's Plasma-Mag instrument suite is an advanced, smaller version of the ACE instrumentation. National Oceanic and Atmospheric Administration (NOAA), the agency with responsibility for space weather forecasting, is already preparing to receive this data, as they do now with ACE data.

Educational Outreach - A most exciting and significant element of the DSCOVR mission is in the area of education. Under the sponsorship of NASA, a separate educational enhancement follow-on project will involve professional educators in developing high quality educational products. These efforts will start with the inspirational views of the full sunlit Earth, and will lead to up-to-date educational materials that can be shared over the Internet. We see this enabling students to work on and experience science issues such as global changes in ozone, cloud cover, weather patterns, tracking of pollution plumes and seasonal changes. We will support new and innovative inquiry based learning that involves multiple disciplines, such as mathematics, geography, computer technology, and physical sciences.