Sun, Moon and Earth line up for Proba-2
ESA鈥檚 Proba-2 microsatellite experienced a conjunction of the spheres on Tuesday, as the Sun, Moon and Earth all lined up in front of it.
As people on the ground observed the 4 January partial solar eclipse, Proba-2 provided a privileged top-of-atmosphere view 鈥� at least briefly.
Shortly after the Moon partially blocked Proba-2鈥檚 view of the Sun, the Sun-watching satellite flew into Earth鈥檚 shadow. At that point 鈥� when the video seen here goes dark 鈥� the Sun, Moon, Earth and Proba-2 were all on the same line in space.
鈥淭his is a notable event,鈥� said Bogdan Nicula of the Royal Observatory of Belgium (ROB), who calculated where and when this double-eclipse would happen. 鈥淚t is a nice exercise to model the orbit and relative positions of all three celestial bodies.鈥�
The images making up this video were observed by Proba-2 with its SWAP imager 鈥� designed and operated by ROB 鈥� which operates at extreme-ultraviolet (EUV) wavelengths to monitor the swirling layer of the solar corona just above the Sun鈥檚 surface.
During the eclipse event, SWAP鈥檚 view of the Sun and Moon faded as EUV was progressively blocked by Earth鈥檚 atmosphere 鈥� an EUV-sunset. After passing through Earth鈥檚 shadow, Proba-2 saw a brightening Sun 鈥� an EUV-sunrise. At that point of the orbit the Moon was no longer eclipsing the Sun.
鈥淲e had to work very hard to get this high-resolution pointing needed for these images,鈥� explained David Berghmans, SWAP鈥檚 principal investigator, adding that with the whole of Proba-2 less than a cubic metre in volume, SWAP is only the size of a large shoe box.
鈥淎nd, as far as I am aware, the Mayans did not predict this alignment should cause concerns!鈥�
The event proved scientifically useful for LYRA, Proba-2鈥檚 other Sun-monitoring instrument normally used to track solar radiation intensity, explained LYRA principal investigator Marie Dominique: 鈥淲hile the EUV sunset鈥搒unrise season blinds SWAP, it allows LYRA to track the amount of solar EUV light passing through Earth鈥檚 atmosphere, which helps determine its particle content.鈥�
Proba-2鈥檚 eclipse season
Proba-2鈥檚 orbit is optimised for solar observation, but for part of the winter season it experiences sunsets and sunrises, with Earth starting to obstruct Proba-2鈥檚 view of the Sun for a few minutes per orbit.
Because both SWAP and LYRA are observing in particular areas of the EUV spectrum, these instruments experience gradually progressing EUV sunsets (and sunrises), as the light in question is absorbed by lower layers of the terrestrial atmosphere.
The satellite continues to operate well during this eclipse season, and in some cases scientifically-useful data can be gathered 鈥� by tracking how much EUV light is blocked, LYRA gains insight into atmosheric composition, for example.
Proba-3: blotting out the Sun
Another mission in ESA鈥檚 technology-testing Proba series will manufacture its own artificial solar eclipses.
Scheduled for 2015-16, Proba-3 will comprise two formation flying satellites, with one casting the other into shadow to allow ongoing observation of the faint outer layers of the still-mysterious solar corona.
Provided by European Space Agency
