These images were taken between 3:50 p.m. and 8:45 p.m. EDT on July 16,
showing the moon moving over the Pacific Ocean near North America. The North
Pole is in the upper left corner of the image, reflecting the orbital tilt of
Earth from the vantage point of the spacecraft.
The images were
captured by NASA's Earth Polychromatic Imaging Camera (EPIC), a four megapixel
CCD camera and telescope on the DSCOVR satellite orbiting 1 million miles from
Earth. From its position between the sun and Earth, DSCOVR conducts its primary
mission of real-time solar wind monitoring for the National Oceanic and
Atmospheric Administration (NOAA).
EPIC maintains a constant
view of the fully illuminated Earth as it rotates, providing scientific
observations of ozone, vegetation, cloud height and aerosols in the atmosphere.
Once EPIC begins regular observations next month, the camera will provide a
series of Earth images allowing study of daily variations over the entire
globe. About twice a year the camera will capture the moon and Earth together
as the orbit of DSCOVR crosses the orbital plane of the moon.
The far side of the
moon was not seen until 1959 when the Soviet Luna 3 spacecraft returned the
first images. Since then, several NASA missions have imaged the lunar far side
in great detail. The same side of the moon always faces an earthbound observer
because the moon is tidally locked to Earth. That means its orbital period is
the same as its rotation around its axis.
In May 2008 NASA's Deep
Impact spacecraft captured a similar view of Earth and the moon from a distance
of 31 million miles away. The series of images showed the moon passing in front
of our home planet when it was only partially illuminated by the sun.
EPIC's "natural
color" images of Earth are generated by combining three separate
monochrome exposures taken by the camera in quick succession. EPIC takes a
series of 10 images using different narrowband spectral filters -- from
ultraviolet to near infrared -- to produce a variety of science products. The
red, green and blue channel images are used in these color images.
Combining three images
taken about 30 seconds apart as the moon moves produces a slight but noticeable
camera artifact on the right side of the moon. Because the moon has moved in
relation to the Earth between the time the first (red) and last (green)
exposures were made, a thin green offset appears on the right side of the moon
when the three exposures are combined. This natural lunar movement also
produces a slight red and blue offset on the left side of the moon in these
unaltered images.
The lunar far side
lacks the large, dark, basaltic plains, or maria, that are so prominent on the
Earth-facing side. The largest far side features are Mare Moscoviense in the upper
left and Tsiolkovskiy crater in the lower left. A thin sliver of shadowed area
of moon is visible on its right side.
"It is surprising how
much brighter Earth is than the moon," said Adam Szabo, DSCOVR project
scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"Our planet is a truly brilliant object in dark space compared to the
lunar surface."
Once EPIC begins regular
observations next month, NASA will post daily color images of Earth to a
dedicated public website. These images, showing different views of the planet
as it rotates through the day, will be available 12 to 36 hours after they are
acquired.
DSCOVR is a partnership
between NASA, NOAA and the U.S. Air Force with the primary objective of
maintaining the nation's real-time solar wind monitoring capabilities, which
are critical to the accuracy and lead time of space weather alerts and
forecasts from NOAA.
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