Thursday, November 13, 2014

The petit Philae (Rosetta)

In case you have been living in a cave this week:

Little Philae at work

The European Space Agency lander module Philae successfully separated from parent satellite Rosetta, and was landed on comet 67P/Churyumov–Gerasimenko (after some bouncing) on 12 November 2014. This is the first controlled landing on a comet.

 In a more direct analogy to its namesake, the Rosetta spacecraft also carries a micro-etched nickel alloy Rosetta disc donated by the Long Now Foundation inscribed with 13,000 pages of text in 1200 different languages.

A video of the 12 year trajectory of Rosetta:


Interesting Facts:
  • 67P/Churyumov-Gerasimenko is a comet that orbits our Sun every 6.45 years, discovered in 1969
  • Rosetta launched on 2 March 2004 at 7:17 GMT from the Guiana Space Center in French Guiana
  • Rosetta used multiple gravity assists from Earth and Mars flybys to gain speed. This is needed because no launcher could propel the spacecraft into the required orbit to reach 67P
  • Electrical power for the spacecraft comes from two solar arrays totaling 64 square meters (690 sq ft). This charges a battery with a life of about 60 hours.
  • During its 10 year journey towards comet 67P, the spacecraft has passed by two asteroids: 2867 Steins (in 2008) and 21 Lutetia (in 2010)
  • Rosetta entered deep-space hibernation mode in June 2011 (for 31 months), and 'woke up' on 20 January 2014
  • Beginning in May 2014, Rosetta '​s velocity was reduced by 780 m/s (2,800 km/h; 1,700 mph) with a series of thruster firings. See Figure 1 below
  • Rosetta cumulatively traveled over 6.4 Billion km
  • The spacecraft rendezvoused with 67P on 6 August 2014, and began orbiting the comet on 10 September 2014
  • Philae separated from Rosetta, and landed on the comet nucleus on 12 November 2014

Figure 1. Rosetta's Trajectory upon approach of 67P

Over the next 2.5 days, the lander will conduct its primary science mission, assuming that its main battery remains in good health. An extended science phase using the rechargeable secondary battery may be possible, assuming Sun illumination conditions allow and dust settling on the solar panels does not prevent it. This extended phase could last until March 2015, after which conditions inside the lander are expected to be too hot for it to continue operating.
Science highlights from the primary phase will include a full panoramic view of the landing site, including a section in 3D, high-resolution images of the surface immediately underneath the lander, on-the-spot analysis of the composition of the comet's surface materials, and a drill that will take samples from a depth of 23 cm and feed them to an onboard laboratory for analysis.
The lander will also measure the electrical and mechanical characteristics of the surface. In addition, low-frequency radio signals will be beamed between Philae and the orbiter through the nucleus to probe the internal structure.
The detailed surface measurements that Philae makes at its landing site will complement and calibrate the extensive remote observations made by the orbiter covering the whole comet.

Comet 67P/Churyumov-Gerasimenko, taken by Rosetta on 14 September 2014

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