Forty-five years after the first Earthrise photo was taken by NASA astronaut William Anders, a new version of Earthrise was sent back from the moon by the Lunar Orbiter (LRO). Like the first Earthrise image, the new photo shows the Earth as a blue and white sphere rising up into the dark and bleak lunar skies.
While the Lunar Orbiter isn't a stranger to bearing witnesses to numerous Earthrises, the main mission of the orbiter is to take photos of the lunar surface. This means that it rarely points its cameras up into the lunar sky. On average, the LRO goes through 12 Earthrises on a daily basis.
"LRO experiences twelve earthrises every day, however LROC is almost always busy imaging the lunar surface so only rarely does an opportunity arise such that LROC can capture a view of the Earth," says the Arizona State University. "On the first of February of this year LRO pitched forward while approaching the north pole allowing the LROC WAC to capture the Earth rising above Rozhdestvenskiy crater (180-km diameter)."
To capture the recent Earthrise, the LRO used its onboard LROC Wide Angel Camera or WAC for short. Compared to most modern cameras, the WAC captures images at much lower resolutions. In fact, a modern smart phone snapper will blast the LRO's WAC out of the water in terms of pixel count alone. Even a low end smart phone can capture images at 5 megapixels (5 million pixels). In comparison, an image taken by the WAC will only have 9856 pixels.
While the WAC has a relatively low pixel count, it was actually designed with something else in mind. The WAC can take very large images. It does this by taking a number of smaller images while the LRO continues on its orbit around the moon. The type of technique is referred to as "push-frame." By taking a series of smaller images, the LRO is able to capture the entire area of the moon as it goes around it. The resulting images can even be put together into animation clips that show an LRO-eye view of the moon.
While the LRO was sent to the moon specifically for making observations of the lunar surface, scientists sometimes point the orbiters camera up into the lunar skies. This is done to calibrate the orbiter's sensitive instrumentation. Aside from calibration purposes, pointing the WAC up into the sky also allows the LRO to take measurements regarding the moon's exosphere. The data gathered by the LRO is then beamed back to Earth.
