[meteorite-list] Rosetta Arrives at Comet Destination

[Ron Baalke]

Presse Release 
N23-2014 

Paris, 6 August 2014

Rosetta arrives at comet destination

After a decade-long journey chasing its target, ESA's Rosetta has today 
become the first spacecraft to rendezvous with a comet, opening a new 
chapter in Solar System exploration. 

Comet 67P/Churyumov-Gerasimenko and Rosetta now lie 405 million kilometres 
from Earth, about half way between the orbits of Jupiter and Mars, rushing 
towards the inner Solar System at nearly 55 000 kilometres per hour. 

The comet is in an elliptical 6.5-year orbit that takes it from beyond 
Jupiter at its furthest point, to between the orbits of Mars and Earth 
at its closest to the Sun. Rosetta will accompany it for over a year as 
they swing around the Sun and back out towards Jupiter again.

Comets are considered to be primitive building blocks of the Solar System 
and may have helped to 'seed' Earth with water, perhaps even the ingredients 
for life. But many fundamental questions about these enigmatic objects 
remain, and through a comprehensive, in situ study of the comet, Rosetta 
aims to unlock the secrets within.

The journey to the comet was not straightforward. Since its launch in 
2004, Rosetta had to make three gravity-assist flybys of Earth and one 
of Mars to help it on course to its rendezvous with the comet. This complex 
course also allowed Rosetta to pass by asteroids ?teins and Lutetia, obtaining 
unprecedented views and scientific data on these two objects. 

"After ten years, five months and four days travelling towards our destination, 
looping around the Sun five times and clocking up 6.4 billion kilometres, 
we are delighted to announce finally 'we are here'," says Jean-Jacques 
Dordain, ESA's Director General.

"Europe's Rosetta is now the first spacecraft in history to rendezvous 
with a comet, a major highlight in exploring our origins. The discoveries 
can begin." 

Today saw the last of a series of ten rendezvous manoeuvres that began 
in May to adjust Rosetta's speed and trajectory gradually to match those 
of the comet. If any of these manoeuvres had failed, the mission would 
have been lost, and the spacecraft would simply have flown by the comet. 


"Today's achievement is a result of a huge international endeavour spanning 
several decades," says Alvaro Giménez, ESA's Director of Science and Robotic 
Exploration.

"We have come an extraordinarily long way since the mission concept was 
first discussed in the late 1970s and approved in 1993, and now we are 
ready to open a treasure chest of scientific discovery that is destined 
to rewrite the textbooks on comets for even more decades to come." 

The comet began to reveal its personality while Rosetta was on its approach. 
Images taken by the OSIRIS camera between late April and early June showed 
that its activity was variable. The comet's 'coma' - an extended envelope 
of gas and dust - became rapidly brighter and then died down again over 
the course of those six weeks.

In the same period, first measurements from the Microwave Instrument for 
the Rosetta Orbiter, MIRO, suggested that the comet was emitting water 
vapour into space at about 300 millilitres per second. 

Meanwhile, the Visible and Infrared Thermal Imaging Spectrometer, VIRTIS, 
measured the comet's average temperature to be about -70ºC, indicating 
that the surface is predominantly dark and dusty rather than clean and 
icy. 

Then, stunning images taken from a distance of about 12 000 km began to 
reveal that the nucleus comprises two distinct segments joined by a 'neck', 
giving it a duck-like appearance. Subsequent images showed more and more 
detail - the most recent, highest-resolution image was downloaded from 
the spacecraft earlier today and will be available this afternoon.

"Our first clear views of the comet have given us plenty to think about," 
says Matt Taylor, ESA's Rosetta project scientist. 

"Is this double-lobed structure built from two separate comets that came 
together in the Solar System's history, or is it one comet that has eroded 
dramatically and asymmetrically over time? Rosetta, by design, is in the 
best place to study one of these unique objects."

Today, Rosetta is just 100 km from the comet's surface, but it will edge 
closer still. Over the next six weeks, it will describe two triangular-shaped 
trajectories in front of the comet, first at a distance of 100 km and 
then at 50 km. 

At the same time, more of the suite of instruments will provide a detailed 
scientific study of the comet, scrutinising the surface for a target site 
for the Philae lander.

Eventually, Rosetta will attempt a close, near-circular orbit at 30 km 
and, depending on the activity of the comet, perhaps come even closer. 


"Arriving at the comet is really only just the beginning of an even bigger 
adventure, with greater challenges still to come as we learn how to operate 
in this unchartered environment, start to orbit and, eventually, land," 
says Sylvain Lodiot, ESA's Rosetta spacecraft operations manager.

As many as five possible landing sites will be identified by late August, 
before the primary site is identified in mid-September. The final timeline 
for the sequence of events for deploying Philae - currently expected for 
11 November - will be confirmed by the middle of October.

"Over the next few months, in addition to characterising the comet nucleus 
and setting the bar for the rest of the mission, we will begin final preparations 
for another space history first: landing on a comet," says Matt.

"After landing, Rosetta will continue to accompany the comet until its 
closest approach to the Sun in August 2015 and beyond, watching its behaviour 
from close quarters to give us a unique insight and realtime experience 
of how a comet works as it hurtles around the Sun."

Notes for Editors:

Rosetta woke up from deep space hibernation at 18:18 GMT on 20 January 
2014, nine million kilometres from comet 67P/Churyumov-Gerasimenko. Following 
wake-up, the orbiter's 11 science instruments and 10 lander instruments 
were reactivated and readied for science observations. Ten orbital correction 
manoeuvres were carried out between 7 May and 6 August, reducing the spacecraft's 
velocity with respect to the comet from 775 m/s to 1 m/s, equivalent to 
walking pace. Each of these manoeuvres was critical: if any had failed, 
no rendezvous would have been possible. More information about these manoeuvres 
can be found on the Rosetta blog: http://blogs.esa.int/rosetta/

The latest 'arrival' image will be presented in the science session of 
today's 'Rosetta comet rendezvous' event at ESA's Space Operations Centre, 
ESOC, in Darmstadt, Germany, and in parallel will be published online 
on the ESA Portal. 

About the European Space Agency

The European Space Agency (ESA) is Europe's gateway to space. It is an 
intergovernmental organisation, created in 1975, with the mission to shape 
the development of Europe's space capability and ensure that investment 
in space delivers benefits to the citizens of Europe and the world. 

ESA has 20 Member States: Austria, Belgium, the Czech Republic, Denmark, 
Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, 
Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland and the 
United Kingdom, of whom 18 are Member States of the EU. 

ESA has Cooperation Agreements with eight other Member States of the EU. 
Canada takes part in some ESA programmes under a Cooperation Agreement. 


ESA is also working with the EU on implementing the Galileo and Copernicus 
programmes. 

By coordinating the financial and intellectual resources of its members, 
ESA can undertake programmes and activities far beyond the scope of any 
single European country.

ESA develops the launchers, spacecraft and ground facilities needed to 
keep Europe at the forefront of global space activities. Today, it launches 
satellites for Earth observation, navigation, telecommunications and astronomy, 
sends probes to the far reaches of the Solar System and cooperates in 
the human exploration of space. 

For further information, please contact:

ESA Media Relations Office
Tel: + 33 1 53 69 72 99
Email: media at esa.int

Markus Bauer
ESA Science and Robotic Exploration Communications Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer at esa.int