After over 12 years Rosetta will be decommissioned by sending it down to impact with comet 67P/C-G. This fate was decided as the comet is moving away from the sun, beyond the orbit of Jupiter and the solar panels will not generate enough power to keep the spacecraft operational. Even “hibernation” is not a possibility as heaters are still required to keep the critical systems idling. Hence mission control will send commands in the next few days such that on September 29th a series of maneuvers will send it on a impact trajectory with the comet. As the comet’s gravity is rather weak (1/10,000 of Earth’s) it will most likely not be a fatal impact. However the Rosetta will be instructed to shutdown upon contact with the surface in order not to “pollute” the deep space communication network with spurious and uncommanded signals. This is expected to happen on September 30th 10:40 GMT.
So where is comet 67P/C-G? Travelling towards the orbit of Jupiter, in constellation Virgo, opposite to the sun from Earth’s perspective. Normally an event like this would be timed to be observable at night from Earth such that telescopes can gather scientific data. But at apparent magnitude 20 (to compare, Pluto has a mean apparent magnitude of 15) it will be very difficult to observe. And the impact is not expected to generate a large plume of dust. Therefore it will be up to Rosetta to record and beam back to Earth as much data during the descent before shutting down for good.
Rosetta and comet 67P/C-G position on September 30th
Exactly 25 years ago today, the Discovery space shuttle took off with the Hubble Space Telescope aboard. For all the mind-blowing images Hubble has been able to bring to us, the project started actually pretty badly…
Above all the funding challenges that such a large project faced, there were many issues on how and who should grind the primary mirror. In all three mirrors were built by three different companies should there be issues during production. The Challenger disaster in 1986 delayed the launch of the telescope, and when it was finally placed in orbit, a faulty mirror wasn’t able to correctly focus the image to the clear and crisp views everyone had expected. As the flaw was due to an error in the calibrating instrument during the final shaping of the mirror, it meant it was flawed to perfection, and could therefore be corrected by giving it “glasses”. It wasn’t until 1993 that corrective optics were incorporated and we could finally start exploring the potential of the telescope.
As the Hubble Space Telescope is in low earth orbit it is within easy reach to be serviced by astronauts, and five shuttle missions were dedicated to servicing Hubble, the last one being in 2009 to extend the operation until 2020. By then the James Webb Space Telescope (JWST) should be operational. Something to note here is that while Hubble could be serviced and maintained over time due to its proximity to Earth, JWST will be too far out, located at the L2 Lagrange point – 1.5 million km, beyond Moon’s orbit.
To celebrate these 25 years, NASA and ESA have released this wonderful galactic firework: Westerlund 2
First of all I want to congratulate the Rosetta team on their successful landing of Philae on the comet surface. When you consider that the spacecraft was launched 10 years ago, it was essentially designed and assembled with 15-year-old technology. Back then, digital cameras were just entering the market and the Palm III PDA was the mobile device everyone wanted. In fact, much of the code running on Rosetta and Philae was developed after the aircraft was launched.
Presently 67P is located between Jupiter and Mars, on its swing towards the sun. To give you an idea how far out it’s located in the solar system, it takes over 28 minutes for radio communications from Rosetta to reach Earth. Therefore if mission control sends a comment to Rosetta, the results are only known one hour later!
Location of comet 67P/Churyumov–Gerasimenko on November 13th, 2014 (Credit: ESA)
Starting in May 2015 67P will become visible to observers in the Northern Hemisphere, and will gradually brighten until achieving perihelion on August 13, 2015. Because it does not venture very close to the sun, past observations indicate that it will only reach magnitude 11 at best; a challenge to backyard telescopes.
Better slew your observation by 9 degrees north, that’s where comet 141P/Machholz will be in the same constellation (Gemini) and at magnitude 8; a slightly brighter target. And if you have no luck observing either comets or capturing them on photo, open cluster M35 is in the area.
Until then, you can follow Rosetta and Philae’s adventure on their blog: blogs.esa.int/rosetta/