BTS: Building a Comet as Rosetta Nears Historic Landing

The ESA Rosetta Mission

The Rosetta spacecraft was launched on 2 March 2004; its target was a small 10-km wide comet called 67P/Churyumov-Gerasimenko (67P/GC) roughly 500 million kilometers distant (between the orbit of Mars and Jupiter). It used four gravity assists (one by Mars, three by Earth) to sling shot it out to the distance of its target. Rosetta entered a hibernation phase in June 2011, which is designed to conserve power at such great distances from the Sun. Earlier this year, with great fanfare, on 20 January 2014 Rosetta awoke from its 3 year hibernation and began stretching its legs. On 6 August 2014, Rosetta reached its target and successfully entered into orbit around it, a first for human kind. Rosetta wants to learn a lot about comets during this mission: the origin of comets, the relationship of cometary and interstellar material, how the solar system formed. Further, it will be learning about what the comet is made of, the dynamics of the system, how outgassing happens, etc.
Rosetta actually comes in two pieces: the orbiter and the lander. The orbiter is outfitted with 12 science instruments and will continue to orbit the small comet for the duration of the mission. The lander, named Philae, carries with it 10 science instruments that will help it understand, amongst other things, the internal composition and density of the comet. This lander will be released on 12 November 2014 at 3:03am EST, with touchdown occurring around 11am EST. Philae will be released approximately 22 km from the centre of the comet. This is an unpowered decent, done only by the gravity of 67P/GC. Upon touching down, the 3 feet of Philae will deploy screws to lock it down, and two harpoons will be jettisoned for further support. The landing site, ‘site J,’ is located on the ‘head’ lobe of the double lobed comet, and is relatively inactive. This is the first soft landing ever on a cometary body. (there is an approximately 30 min time delay for messages).
Suggested Reading: ESA Rosetta Mission HomepageScience @ NASA, Rosetta Wiki.

ALMA spots a Planetary Disk

ALMA pointed its (currently) 66 7-m dishes towards the young star HL Tauri and observed something groundbreaking: a solar system in the midst of formation. Models, simulations, and earlier observations have shown that planets probably form inside a dusty disk of material that forms around a newly formed star. Since the disk will likely be slightly inhomogenous, it’s likely that gravity will begin to collect matter in various places throughout the disk. As this happens, and the globules become bigger, their gravity will begin to sweep up material in their orbit as the travel around their parent star. This SHOULD leave behind massive gaps in the dusty disk, a prediction that has now been proven to be true by observation. Gaps can also form due to gravitational resonances (like Saturn’s rings for instance), so an analysis will be needed to decide just how many planets are forming in this dusk of material. Nevertheless, this is exciting science.
Suggested Reading: ESO Press Release, ALMA Press Release, Bad Astronomy article,

Update on Antares and SpaceShipTwo

Orbital Sciences: latest press release here. Early investigations show that it was likely a turbopump related failure in the main Aero Rocketdyne AJ26 propulsion system. As a result, this system will be discontinued from use. It appears this is not a one off disaster, but a flaw in the design of the AJ26, making it’s further use dangerous.
Virgin Galactic: ‘Based on information they have released about their investigation to date, the NTSB has recovered the intact engine and rocket propulsion fuel tanks with no signs of burn through or mid-air explosion. This definitively dismisses the premature and inaccurate speculation that the problem was related to the engine or the fuel.
The NTSB also evaluated the vehicle’s feathering mechanism, which is the unique technology that turns the wing booms into position for re-entry. The NTSB indicated that the lock/unlock lever was pulled prematurely based on recorded speed at the time, and they have suggested that subsequent aerodynamic forces then deployed the feathering mechanism, which resulted in the in-flight separation of the wings and vehicle. At this time, the NTSB investigation is still ongoing and no cause has yet been determined – these are purely facts based on initial findings. We are all determined to understand the cause of the accident and to learn all we can.’

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