ESA's Rosetta Spacecraft Spies Comet Beginning To Form Its Tail

Brett Smith for redOrbit.com – Your Universe Online

The comet targeted for research by the European Space Agency’s Rosetta probe has begun to develop its tail as it zooms closer and closer to the Sun. The probe is maneuvering to align with the comet’s orbit this month and is slated to rendezvous with it in August.

On Thursday, the ESA released a series of images showing comet 67P/Churyumov–Gerasimenko developing its tail, or coma. Taken between March 27 and May 4, the pictures show the coma gradually extending to a length of over 800 miles.

While the comet is still nearly 400 million miles from the Sun, its surface is slowly being warmed – causing surface ice to sublimate and break off. Solar radiation is also causing gas to be released from the comet’s nucleus and carry off the bits of ice and dust that form the coma. The coma will grow longer and longer until the comet reaches its closest point to the Sun in August 2015.

ESA scientists said the emergence of the coma provides the chance to analyze dust generation and structures inside the tail ahead of the comet drawing much closer to Earth and the Rosetta probe.

“It’s beginning to look like a real comet,” said Holger Sierks, principal investigator for the Rosetta’s Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) at the Max Planck Institute for Solar System Research, Germany. “It’s hard to believe that only a few months from now, Rosetta will be deep inside this cloud of dust and en route to the origin of the comet’s activity.”

The probe will also be monitoring the periodic transformations in brightness that show the nucleus is spinning every 12.4 hours – around 20 minutes shorter than previously thought.

“These early observations are helping us to develop models of the comet that will be essential to help us navigate around it once we get closer,” said Sylvain Lodiot, ESA Rosetta spacecraft operations manager.

OSIRIS and Rosetta’s navigation cameras have been routinely capturing images to ascertain the probe’s exact trajectory in relation to the comet. Applying this data, the spacecraft has recently started a series of maneuvers that will gradually carry it in line with the comet prior to making its rendezvous in early August.

Launched in March 2004, Rosetta has used four gravity assist maneuvers, three from Earth and one from Mars, to approach its target. The probe went into deep space hibernation from June 2011 to January 2014.

The mission will be the first-ever to orbit a comet’s nucleus and land a probe on its surface. It will also end up being the first spacecraft to travel alongside a comet while it heads to the inner Solar System.

Rosetta is also the very first space mission to journey past the primary asteroid belt and rely exclusively on solar cells for power, as opposed to the conventional radio-isotope thermal generators. The new solar-cell technology utilized on the orbiter’s two massive solar panels allows it to function over 500 million miles from the Sun, where sunlight amounts are only 4 percent of those on Earth.