After a few days of delay, the Deep Space Climate Observatory or DSCOVR was finally launched at 23:03 UTC on Wednesday, February 11, 2015.
DSCOVR was launched on a SpaceX Falcon 9 rocket from the Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida and is now on its way to the L1 point (Lagrangian point), the neutral gravity point between the Earth and Sun approximately 1.6 million km (1 million miles) from Earth. It will take about 110 days for DSCOVR to reach this point.
L1 orbit diagram. Credit: NOAA/NESDIS
L1 is a good position from which to monitor the Sun, because the constant stream of solar wind reaches L1 about an hour before reaching Earth. This provides us with the early warnings of CMEs and other solar storms bearing down on Earth.
Following successful activation of the satellite and check-out approximately 150 days after launch, DSCOVR will succeed aging NASA's Advanced Composition Explorer's (ACE) role in supporting solar wind alerts and warnings and at the same time it will look back at Earth with its Earth Polychromatic Imaging Camera (EPIC).
Solar wind activity will be measured by the Plasma-Magnetometer (PlasMag) instrument.
This instrument suite is a comprehensive science and space weather package that includes a fluxgate vector magnetometer, a Faraday Cup solar wind positive ion detector and a top-hat electron electrostatic analyzer. PlasMag instrument cluster provides high time resolution measurements in real time and represents the next generation of solar wind monitors.
EPIC is able to view the entire sunlit Earth from sunrise to sunset at an almost constant scattering angle between 165–178°. This scattering angle has minimal overlap with other satellites’ scattering angles. EPIC’s observations from the L1 position will provide a unique angular perspective and can be combined with other measurements to obtain particle shape, phase selection, optical depth, 3-D effects and stereo heights.
Imagery from EPIC will be used in science applications to measure ozone amounts, aerosol amounts, cloud height and phase, vegetation properties, hotspot land properties (a view of the land from angles where shadows are a minimum) and UV radiation estimates at Earth's surface.
Expected data products include: total ozone column, aerosol index, aerosol optical thickness, aerosol height, cloud fraction, cloud height, surface albedo, vegetation index, Leaf Area Index and RGB colored image of the Earth’s sunlit surface. These data products are of interest to climate science, as well as hydrology, biogeochemistry and ecology. Data collected by EPIC will also provide insight into Earth’s energy balance.
Its 1024×1024 px images will be publicly available approximately 24 hours after they are taken and the first images are expected to be posted approximately six months after launch.
Another important instrument aboard DSCOVR is NISTAR, a cavity radiometer designed to measure the absolute, spectrally integrated irradiance reflected and emitted from the entire sunlit face of the Earth. Having NISTAR at the L1 observing position offers a unique continuous view of the “Earth at noon.”
Solar irradiance is the power of electromagnetic radiation (radiative flux, measured in Watts) from the Sun per unit area incident on the Earth’s surface.
Because Earth is not an isotropically reflecting object, the uneven distribution of land, ocean and ice on the surface and the continually changing cloud cover, vegetation, ice and snow make modeling the radiant energy emitted and reflected by Earth difficult.
Nevertheless, we can accurately measure radiances over a critical angle range important for understanding Earth’s total radiant flux.
NISTAR will be the first instrument capable of providing continual measurements over this angle range for the entire Earth.
DSCOVR was formerly known as Triana, and unofficially as GoreSat. It was originally developed as a NASA satellite proposed in 1998 by then-Vice President Al Gore.
Featured image: DSCOVR launch on February 11, 2015. Credit: SpaceX
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