Rosetta space probe has a close encounter with Comet 67P

THE Rosetta space probe has had a near-death experience after being ‘king hit’ on a close pass with a comet.

THE Rosetta space probe has had a near-death experience after being ‘king hit’ on a close pass with Comet 67P.

Rosetta “experienced significant difficulties in navigation” on a close pass last weekend, when the probe was sent skimming above the comet’s surface.

Status report: had some difficulties navigating close to #67P again & also had a safe mode, but I’m OK now! Details: http://t.co/WEilqXsKVS

— ESA Rosetta Mission (@ESA_Rosetta) April 1, 2015

Essentially, an eruption of gas from the comet struck the delicate robotic space craft — twisting its antenna array away from Earth.

Rosetta sent itself into “safe mode”, shutting down all but essential internal services and initiating a “reboot” cycle to re-establish contact with ground control.

Waking giant ... Gas and dust can be seen streaming away from Comet 67P. Rosetta passed through an unexpectedly thick patch. Source: ESA

It’s not the first time the space probe has made a close pass. Its closest fly-by was just 6km on February 14. The weekend’s pass was a seemingly safer 14km.

But a lot has changed since February.

The comet has begun to “wake”.

#Rosetta We have front-row seats as a comet begins to stir. The view is amazing. http://t.co/zdl41NleFk pic.twitter.com/f9id9Y24YX

— Jamie Seidel (@JamieSeidel) February 11, 2015

As its surface warms under the ever-closer sun’s rays, gases have begun bubbling out.

This means Rosetta has to pass through increasingly dense clouds of dust.

This increases drag which, in turn, can twist the spacecraft from its course.

But there is another effect: the dust “confuses” Rosetta’s eyesight.

The space probe had corrected being knocked out of alignment, but the blow had left it “seeing stars”.

Despite difficult flyby I still managed some good NAVCAM images about 20km from #67P! More: http://t.co/c3QwmvpXU9 pic.twitter.com/8G3778b4CS

— ESA Rosetta Mission (@ESA_Rosetta) April 1, 2015

It uses star trackers to navigate and maintain its orientation. But larger flecks of shiny debris from the comet are proving to be distractions.

Rosetta’s on-board brain mistook some of the dust for stars. This resulting confusion caused the probe to enter “safe mode”, the European Space Agency experts explained in a blog.

Up close and personal ... A montage of pictures showing Comet 67P during one of Rosetta’s surface-skimming passes. Source: ESA

“When the star trackers are not tracking, the attitude is propagated on gyro measurements,” they write. “But the attitude can drift, especially if the spacecraft is slewing a lot.”

It took almost 24 hours for Rosetta to eliminate the “noise” of the comet dust and start tracking the correct stars again.

Rosetta is already manoeuvring to go another round with Comet 67P next week.

Thanks for kind messages, I’m feeling much better & hoping to resume normal activities soon! http://t.co/WEilqXsKVS pic.twitter.com/bWagFyQRIg

— ESA Rosetta Mission (@ESA_Rosetta) April 2, 2015

@JamieSeidel