|A DSCOVR image of the Earth and the far side of the Moon taken on July 16. 2015. Note Mexico and the United States on the Earth. NASA Image|
Simply because this was the season where we finally saw close-up photos of Pluto and its moons, the summer of 2015 has been a memorable one for space exploration. And that’s even before considering Dawn’s close-up shots from the largest body in the asteroid belt, Ceres, and more photos from Rosetta as Comet 67P/Churyumov–Gerasimenko made its closest approach to the Sun.
But those images have been upstaged in my mind by images from a spacecraft that was launched on February 11 to little fanfare. Today the Deep Space Climate Observatory or DSCOVR is parked in space a million miles away from Earth at the L1 Lagrangian point where the gravity of the Earth and Sun balance the centrifugal forces of the satellite. A number of spacecraft at L1 are gathering data on the Sun, but DSCOVR is taking advantage of the fact that from this point, spacecraft always see the sunlit side of the Earth.
On July 16, DSCOVR shot a sequence of photos of the Moon passing in front of the Earth. The side of the Moon visible in these photos is the far side, often erroneously called the dark side. The Moon’s rotation rate means that we always see one side of the Moon from Earth, but the other side can only be seen from space. While earlier space probes have shot images of the Earth and the Moon together, none have matched the quality or the perspective of DSCOVR’s photo sequence.
That photo sequence, which was released on August 5, is only the second photo release from DSCOVR. The first colour image of the whole Earth taken from DSCOVR was released on July 20 to great fanfare, in part because it reminded many people of the famous “Blue Marble” photo of Earth taken from Apollo 17 in 1972.
Once the Earth Polychromatic Imaging Camera (EPIC) on DSCOVR is in full operation in September, images of Earth will be posted daily on a dedicated web page. As well, EPIC and other instruments will provide information on changes in Earth’s atmosphere, including the levels of ozone and aerosols.
The concept of regular photos of Earth from this vantage point did not originate with a scientist, but from Al Gore, who was vice president of the United States in 1998 when he first came up with the idea that was soon turned into a spacecraft called Triana. The idea faced withering political ridicule from Gore’s Republican opponents, and the administration of George Bush, the man who defeated Gore in highly controversial fashion in the 2000 presidential election, put Triana into storage in 2001 instead of launching it.
In 2012, incidently when the Democrats were back in office under Barack Obama, Triana was taken out of storage, taken apart, reassembled, renamed DSCOVR and prepared for its launch earlier this year. Not surprisingly, Al Gore was amongst those who watched the launch from Cape Canaveral.
DSCOVR is a joint project of NASA and the National Oceanic and Atmospheric Administration, and it is being controlled from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
As it was always designed to do, DSCOVR will be also keeping close watch on the Sun, and providing advance warning of particles emitted from the Sun that could affect communications and electrical infrastructure on Earth. We know that solar storms can affect life on Earth - as a resident of Montreal in 1989, I lived through a major power failure that originated with a solar storm - so DSCOVR will be an important part of our space infrastructure.
DSCOVR is four times as far away from the Earth as the Moon, so the Earth and Moon are very close to real scale in its images. And seeing the Moon pass in front of the Earth from that altitude drives home how close the Moon is to our home planet, at least compared to other celestial bodies.
Other observers have noted that the Moon is quite dark compared to Earth. Although the Moon looks very bright in our night sky, it actually reflects only about eight percent of the sunlight that falls on it. It is a celestial lump of coal.
When the EPIC camera begins full operations in September, I expect that its web page will become a very popular place. We may even see its images become a regular part of television weather forecasts, and I expect to see more photo sequences from DSCOVR showing the rotation of our Earth and changing weather patterns. Thanks, Al Gore!