Comet 67P slipped right between the spacecraft and the Sun, and the Rosetta team was ready to snap the image.
Rosetta was positioned a comfortable 329 kilometers from the center of the comet when it captured the stunning image. What was it doing that far back? When the image was captured (March 27) the spacecraft was moving even further away to get a better look at Comet 67P’s coma and tail.
An ESA blog post explains how the image was taken.
Thanks to the combination of a long, four-second exposure, no attenuation filter and a low-gain setting on the analogue signal processor of NAVCAM (a setting that is used to image bright targets), the image reveals the bright environment of the comet, displaying beautiful outflows of activity streaming away from the nucleus in various directions.
Today, Rosetta is maneuvering back closer to Comet 67P. It’s less than 600 kilometers away right now, but will be even closer soon. On April 9, the spacecraft will soar past at an altitude of just 30 kilometers. Not the 12 kilometers seen in the March 19th image below, but still close.
Rosetta’s grand finale
Rosetta can’t stay powered around Comet 67P forever. A combination of reduced solar power and its positioning near the Sun will make communications difficult. Comet 67P already completed its closest approach to the Sun. And as every day passes, the precious sunlight needed to power Rosetta becomes dimmer. Ultimately, that means there won’t be enough power to operate every scientific instrument at the same time.
The position of Comet 67P and the sun (as seen from Earth) isn’t helping either. On October 1, the comet (and Rosetta) will slip behind the sun. In the month prior, communications and data streaming will be “extremely challenging” according to the ESA.
So what’s the plan?
Remember Philae, the little lander that couldn’t quite stick its landing on the comet’s surface? Rosetta will meet a similar fate. The plan is for a controlled impact on the surface of Comet 67P sometime in September. Details are still being worked out, but the Rosetta team expects to gather scientific data all the way until impact.
The Rosetta team doesn’t expect the spacecraft to survive impact. And even if it does, communication will be nearly impossible. Rosetta’s antenna needs to be pointed at Earth for communications to be established. If it’s off by even half a degree, ground stations on Earth won’t be able to communicate with it.