Some of the best views of Sunday's partial solar eclipse didn't come from Earth.
It’s an eclipse most of the world missed this past weekend: on Sunday, September 13th, the outer edge of the Moon’s shadow grazed the southern tip of Earth. And while residents of South Africa managed to catch sight of the partially eclipsed Sun, a few solar observing satellites also witnessed some unique perspectives from space.
The eclipse occurred just 28 hours before to the most distant lunar apogee of the year, so the Moon’s disk wouldn’t have fully covered the Sun even if its inner shadow had crossed paths with Earth. It would have produced an annular eclipse, a bright "ring of fire" that surrounds the silhouette of the apparently shrunken Moon.
Yesterday, you would have had to jump 230 miles above the surface of Antarctica to witness such an event. Sound impossible? Well, the European Space Agency’s Sun-observing PROBA 2 spacecraft managed to "thread the needle" and spy several partial eclipses from orbit, including a brief annular.
The odd looping path of the Moon seen in the video is due to PROBA 2’s motion around the Earth.
NASA’s Solar Dynamics Observatory (SDO) also got in on the eclipse action Sunday, catching a stunning view of the Sun, Moon, and the hazy limb of Earth from its enviable vantage point in space. Launched in 2010, SDO observes the Sun from geosynchronous orbit, and typically undergoes a series of eclipses every year during the spring and fall seasons, when Earth eclipses the Sun from SDO’s point of view.
Unfortunately, the joint NASA/JAXA Hinode solar observatory was performing a routine "CCD bakeout" maneuver during the eclipse and missed the event. NASA’s Deep Space Climate ObseRvatory (DSCOVR) also has the potential to provide interesting images of solar eclipses from its vantage point interior to Earth's orbit, though this time around it was a near miss. Orbiting in a halo or Lissajous orbit around the L1 Lagrangian point (the point between the Sun and Earth where the bodies' gravity cancels out), DSCOVR often has a slightly offset view of the Earth-Moon system.
Though no human in space caught this last eclipse, astronauts have briefly witnessed eclipses before during the Gemini 12 and Apollo 12 missions. “The Gemini mission executed a course correction to place them in the right location, but due to their high orbital speed they caught just the briefest glimpse of totality,” says Michael Zeiler, eclipse historian and creator of GreatAmericanEclipse.com. “The Apollo  mission also saw a total eclipse on the return of their mission from the Moon, but this solar eclipse was not caused by the Moon, but by Earth occulting the Sun.”
Coronagraphs: DIY Eclipses
Observing eclipses from space has more of an aesthetic appeal than scientific value because these events are so swift, mostly due to the speed of the orbiting spacecraft. A better way to study the Sun’s ghostly corona is to equip a spacecraft with a coronagraph to block the dazzling disk of our star, as the joint NASA/ESA Solar Heliospheric Observatory (SOHO) does.
Entering 20 years of service later this year, SOHO is currently the only coronagraph-equipped mission in space, but PROBA 2’s successor, PROBA 3, is will feature the first free-flying occulting disk based in orbit 150 meters in front of the spacecraft. Set to launch in 2018, PROBA-3 and its coronagraph will provide a view of the solar corona closer to the solar limb than ever before; the satellite duo will also test precise positioning systems.
Eclipses from Mars
Rovers on the Red Planet have also turned into eclipse chasers on occasion, catching transits of the lumpy twin Martian moons of Deimos and Phobos. Of course, the moons are too tiny to fully cover the disk of the Sun as seen from the Martian surface. Instead, they present a misshapen annular eclipse. These events still yield scientific value, as Curiosity’s observations of the solar transits of Deimos and Phobos help researchers better understand and refine the exact positions and orbits of the Martian moons.
Currently funded through the end of 2016, PROBA-2 may still be in service for the August 21, 2017, total solar eclipse, whose track of totality will span the United States. The PROBA 3 coronagraph team plans to journey to the U.S. that summer to test a version of the spacecraft camera gear to image the eclipse.
Whether from Earth or space, the wondrous celestial spectacles that eclipses provide continue to inspire.