Rosetta fly by of Asteroid Steins
on 5 September 2008

Image Credit: ESA, image by C.Carreau

Space scientists will be on the edge of their seats this Saturday (10 July 2010) as they wait for the first images to be received back from comet-chasing spacecraft Rosetta as it makes its rendezvous with her second asteroid, 21-Lutetia. Lutetia is a large main belt asteroid. Follow the event live at ESA, beginning at 9:00 AM Phoenix time (16:00 UTC).

Launched aboard an Ariane 5G rocket from Europe’s Spaceport in French Guiana in March of 2004, Rosetta is on a ten year mission to accompany comet 67P/Churyumov-Gerasimanko (or “C-G”) on its orbit around the Sun.

The first objective of the three bodies to be studied by Rosetta was asteroid 2867 Šteins (image at right).

2867 Šteins is an E-type asteroid with a diameter of approximately 4.6 km. Its surface is thought to be largely magnesium silicate (MgSiO3), and similar to terrestrial basalts or plutonic rocks that have been differentiated and reprocessed by melting and recrystallization.

Following its encounter with Šteins, Rosetta headed for its 10 July 2010 encounter with Lutetia.

When Rosetta reaches Lutetia, it will fly by at a separation of 3,200 kilometres, at a relative speed of 54,000 km/hr. They will be some 454 million km from Earth. Approximately two hours of high quality imaging will be recorded, which will be immediately piped back to Earth. The time of closest approach is currently estimated (8 July) at 9:10 AM Phoenix time (16:10 UTC), and the spacecraft’s accompanying lander, Philae, will be switched on earlier that day in order to collect data throughout the flyby.

The Rosetta probe was built by EADS Astrium. Rosetta consists of a 3,065-kg spacecraft (1,578-kg dry mass) and a 100-kg lander, Philae. Rosetta will enter orbit around the nucleus of comet Churyumov-Gerasimenko in August 2014, following three gravity assists from Earth and one from Mars.

Philae (excellent interactive graphic of the orbits and Rosetta accompanying C-G) was created by a European consortium under the leadership of the German Aerospace Research Institute (DLR). Other members of the consortium are ESA and institutes from Austria, Finland, France, Hungary, Ireland, Italy and the UK.

After Rosetta‘s rendezvous with Lutetia, she will be off to Churyumov-Gerasimenko, a comet with a current orbital period of 6.6 years, and discovered accidentally in 1969. Based on the orbital parameters, it appears that in 1959 C-G was nudged by an encounter with Jupiter into its present orbit, with a perihelion of 1.28 AU This is sufficiently close to create a comet tail. Prior to this, C-G had a perihelion of 3.0 AU. This orbit was established by an encounter with Jupiter around 1840. Prior to that, the perihelion was 4.0 AU.

Rosetta Observing Lutetia
Image Credit: ESA/ AOES Medialab.

Lander Philae
The Rosetta Lander – Philae
Image Credit: ESA

Here are the landmarks for Rosetta:

  • Rosetta will be the first spacecraft to orbit a comet’s nucleus.
  • It will be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System.
  • Rosetta will be the first spacecraft to examine from close proximity how a frozen comet is transformed by the warmth of the Sun.
  • Shortly after its arrival at Comet 67P/Churyumov-Gerasimenko, the Rosetta orbiter will despatch a robotic lander for the first controlled touchdown on a comet nucleus.
  • The Rosetta lander’s instruments will obtain the first images from a comet’s surface and make the first in situ analysis to find out what it is made of.
  • On its way to Comet 67P/Churyumov-Gerasimenko, Rosetta will pass through the main asteroid belt, with the option to be the first European close encounter with one or more of these primitive objects.
  • Rosetta will be the first spacecraft ever to fly close to Jupiter’s orbit using solar cells as its main power source.

An extensive description of Philae can be found here (pdf).

The Rosetta orbiter has eleven scientific instruments:

  • ALICE Ultraviolet Imaging Spectrometer
  • CONSERT Comet Nucleus Sounding
  • COSIMA Cometary Secondary Ion Mass Analyser
  • GIADA Grain Impact Analyser and Dust Accumulator
  • MIDAS Micro-Imaging Analysis System
  • MIRO Microwave Instrument for the Rosetta Orbiter
  • OSIRIS Rosetta Orbiter Imaging System
  • ROSINA Rosetta Orbiter Spectrometer for Ion and Neutral Analysis
  • RPC Rosetta Plasma Consortium (one of the five instruments is IES)
  • RSI Radio Science Investigation
  • VIRTIS Visible and Infrared Mapping Spectrometer

Image Credit: ESA, image by AOES Medialab

The Lander Philae has 10 instruments.

  • APXS – Alpha Proton X-ray Spectrometer – analyzes the chemical element composition of the surface below the lander. The instrument is an improved version of the APXS of the Mars Pathfinder.
  • COSAC – The COmetary SAmpling and Composition – The combined gas chromatograph and time of flight mass spectrometry will perform analysis of soil samples and determine the content of volatile components.
  • Ptolemy – an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus.
  • ÇIVA – Comet Nucleus Infrared and Visible Analyzer.
  • ROLIS – Rosetta Lander Imaging System.
  • CONSERT – COmet Nucleus Sounding Experiment by Radiowave Transmission -The Consert radar will perform the tomography of the nucleus by measuring electromagnetic wave propagation from Philae and the Rosetta probe throughout the comet nucleus in order to determine its internal structures and to deduce information on its composition.
  • MUPUS – MUlti-PUrpose Sensors for Surface and Sub-Surface Science.
  • ROMAP (Rosetta Lander Magnetometer and Plasma Monitor.
  • SESAME – Surface Electric Sounding and Acoustic Monitoring Experiment.
  • SD2 – The sampling, drilling and distribution subsystem.

Timeline (from NASA):

  • On March 2, 2004, Rosetta was launched into an orbit that enabled it to chase Earth around the Sun for about a year.
  • On March 4, 2005, Rosetta caught up with Earth and executed the first of its four gravity assists (three from Earth and one from Mars). This first gravity assist hurled Rosetta toward Mars for its meeting in 2007.
  • En route to Mars, Rosetta’s instruments analyzed the collision between Deep Impact’s impactor and comet Tempel-1 on July 4, 2005.
  • In February 2007, Rosetta executed a close flyby of Mars, which provided the gravity assist it needed to loop back toward Earth for a second flyby in November 2007.
  • In November 2007, Rosetta will execute its second Earth flyby, gaining the gravity assist it needs to pass Mars’ orbit and reach the asteroid belt.
  • On September 5, 2008, Rosetta will pass within 1700 km of asteroid Steins, enabling its instruments to closely observe the flying rock.
  • In November, 2009, Rosetta will swing back for a final boost from Earth’s gravity to return again to the asteroid belt.
  • On July 10, 2010, Rosetta will fly within 3000 km of asteroid Lutetia, and again use its instruments to observe at close range this asteroid, ten times larger than Steins.
  • By May, 2011, Rosetta will be coasting through areas in the outer solar system where the sun is almost a billion km away. At that distance, Rosetta’s solar panels will not be able to gather much energy from the Sun, so the spacecraft will shut down most electrical activities and hibernate until comet C-G returns from its long transit in the outer solar system.
  • In January 2014, Rosetta will fire its engine to position itself next to comet C-G in May 2014 as it comes hurtling by. Rosetta will release the Philae for a controlled soft landing on the comet. The Philae will then transmit critical data from the comet’s surface for relay back to Earth. Philae will use harpoons to anchor itself to the comet.
  • After escorting comet C-G past its perihelion (closest point to the Sun), Rosetta will terminate its mission.

3 thoughts on “Rosetta

  1. Pingback: Images of Lutetia « The National Space Society of Phoenix

  2. Pingback: Rosetta Encounters Lutetia « The National Space Society of Phoenix

  3. Pingback: July 2010 « NSS Phoenix Space News

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