Hayabusa2 views Earth and the Moon on approach to December 3 flyby
Posted By Emily Lakdawalla
01-12-2015 19:26 CST
I just love photos of Earth from planetary missions -- especially if they manage to get Earth and Moon in the same shot, as Hayabusa2 did on November 26. Hayabusa2 is on the way in to a flyby of Earth on December 3 at 10:07 UT. You can watch a realtime simulation here.
I did a little bit of processing on this image; like most spacecraft cameras, Hayabusa2's Optical Navigation Camera gets color information by rotating a filter wheel in front of a monochrome detector, and we back on Earth must assemble those component images into a color photo. When the targets are moving, there are often color fringes around the edges of the objects, so I worked on the image a bit in order to reduce those color fringes and make the photo a little more visually pleasing. Pleasing to me, anyway. Perhaps not everyone is bothered by these tiny details!
Anyway, whenever I see an image of Earth, I always want to know which face of Earth I'm looking at. Since it was taken at 12:46 Japan time, you know that Japan is near the middle of the sunlit part of the disk. I was thrown off a bit by how gibbous it looks -- but it's important to remember that we're getting pretty close to the winter solstice in the northern hemisphere. Happily, I have a cool new tool available for seeing what portion of Earth is sunlit at any given (recent) time and date: the DSCOVR spacecraft, which is parked at the Earth-Sun L1 point and regularly sending us fully-lit global images of Earth using its EPIC instrument. Here is the photo from DISCOVR EPIC that was taken closest to the time of the Hayabusa2 image:
Compare the DSCOVR image to the Hayabusa2 photo and you'll see that the Hayabusa2 photo has north to the left, and Japan nearly at the center of the disk. Which shouldn't be a surprise, I guess!
There's a great summary of the Hayabusa2 mission and the train of smaller spacecraft accompanying it in its Earth flyby at Spaceflight101. This flyby has the distinction of being the largest grouping of vehicles making a solar-orbit Earth flyby at the same time -- a total of five, of which two are active and three not -- according to Jonathan McDowell. The other active spacecraft, PROCYON, is also taking frequent images of Earth on approach; you can find PROCYON's Earth images on the mission's Facebook page, including this photo of Earth and the Moon from November 29.
If, like me, you just can't get enough images of Earth from planetary missions, check out my huge archive of them in the Bruce Murray Space Image Library.