This animation features actual satellite images of the far side of the moon, illuminated by the Sun, as it crosses between the DSCOVR spacecraft’s Earth Polychromatic Imaging Camera (EPIC) and telescope, and the Earth – one million miles away. Credit: NASA

Moon seen crossing the face of the Earth

A NASA camera aboard the Deep Space Climate Observatory (DSCOVR) satellite captured a unique view of the moon as it moved in front of the Sunlit side of Earth last month. The series of test images shows the fully illuminated “dark side” of the moon that is never visible from Earth.

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.

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 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.

Still frame image from video shot by the Deep Impact spacecraft from 31 million miles away. Credit: NASA

Still frame image from video shot by the Deep Impact spacecraft from 31 million miles away. Credit: NASA

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 in September, 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.

Earth as seen on July 6, 2015 from a distance of one million miles by a NASA scientific camera aboard the Deep Space Climate Observatory spacecraft. Credit: NASA

Earth as seen on July 6, 2015 from a distance of one million miles by a NASA scientific camera aboard the Deep Space Climate Observatory spacecraft.
Credit: NASA

An EPIC view of the Earth

NASA recently released the first view of the entire sunlit side of the Earth as imaged by the DSCOVR satellite from one million miles away.

“This first DSCOVR image of our planet demonstrates the unique and important benefits of Earth observation from space,” said NASA Administrator Charlie Bolden. “As a former astronaut who’s been privileged to view the Earth from orbit, I want everyone to be able to see and appreciate our planet as an integrated, interacting system. DSCOVR’s observations of Earth, as well as its measurements and early warnings of space weather events caused by the Sun, will help every person to monitor the ever-changing Earth, and to understand how our planet fits into its neighborhood in the solar system.”

These initial Earth images show the effects of sunlight scattered by air molecules, giving the images a characteristic bluish tint. The EPIC team now is working on a rendering of these images that emphasizes land features and removes this atmospheric effect.

“The high quality of the EPIC images exceeded all of our expectations in resolution,” said Adam Szabo, DSCOVR project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The images clearly show desert sand structures, river systems and complex cloud patterns. There will be a huge wealth of new data for scientists to explore.”

The primary objective of DSCOVR, a partnership between NASA, the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force, is to maintain 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.

“These new views of the Earth, a result of the great partnership between NOAA, the U.S. Air Force, and NASA, give us an important perspective of the true global nature of our spaceship Earth,” said John Grunsfeld, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington.

The satellite was launched in February and recently reached its planned orbit at the first Lagrange point or L1, about one million miles from Earth toward the Sun. It’s from that unique vantage point that the EPIC instrument is acquiring science quality images of the entire sunlit face of Earth.  Data from EPIC will be used to measure ozone and aerosol levels in Earth’s atmosphere, cloud height, vegetation properties and the ultraviolet reflectivity of Earth. NASA will use this data for a number of Earth science applications, including dust and volcanic ash maps of the entire planet.

In addition to space weather instruments, DSCOVR carries a second NASA sensor — the National Institute of Science and Technology Advanced Radiometer (NISTAR). Data from the NASA science instruments will be processed at the agency’s DSCOVR Science Operations Center in Greenbelt, Maryland. This data will be archived and distributed by the Atmospheric Science Data Center at NASA’s Langley Research Center in Hampton, Virginia.

The Air Force provided the Space X Falcon 9 rocket for the mission. NOAA operates DSCOVR from its Satellite Operations Facility in Suitland, Maryland, and processes the space weather data at its Space Weather Prediction Center in Boulder, Colorado.

NASA will use this long-distance vantage point of space to increase understanding of our home planet. The data will be used to develop new ways to observe and study Earth’s interconnected natural systems with long-term data records.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth

For more information about DSCOVR, visit: http://www.nesdis.noaa.gov/DSCOVR/