Heavily instrumented probe parachutes through atmosphere,
begins sending data and images
Friday morning, after its seven-year journey through the Solar
System on board the Cassini spacecraft, ESA’s Huygens probe
successfully descended through the atmosphere of Titan,
Saturn’s largest moon, and safely landed on its surface.
(photo, below, on the surface)
The first scientific data arrived at the European Space
Operations Centre (ESOC) in Darmstadt, Germany, this afternoon at
1719 CET. Huygens is mankind’s first successful attempt to
land a probe on another world in the outer Solar System.
“This is a great achievement for Europe and its US partners
in this ambitious international endeavour to explore the Saturnian
system,” said Jean-Jacques Dordain, ESA’s Director
General.
Following its release from the Cassini mothership on December 25,
Huygens reached Titan’s outer atmosphere after 20 days and a
four million kilometer (about 2.5 milion miles) cruise. The probe
started its descent through Titan’s hazy cloud layers from an
altitude of about 1,270 km (790 miles) at 1113 CET. During the
following three minutes, Huygens had to decelerate from 18,000
km/hour (just over 11,000 mph) to 1,400 km/hour (about 870
mph).
A sequence of parachutes then slowed it down to less than 300
km/hour (about 185 mph). At a height of about 160 km (100 miles)
the probe’s scientific instruments were exposed to
Titan’s atmosphere. At about 120 km (75 miles), the main
parachute was replaced by a smaller one to complete the descent,
with an expected touchdown at 1334 CET. Preliminary data indicate
that the probe landed safely, likely on a solid surface.
The probe began transmitting data to Cassini four minutes into
its descent and continued to transmit data after landing at least
as long as Cassini was above Titan’s horizon. The certainty
that Huygens was alive came at 1125 CET, when the Green Bank radio
telescope in West Virginia picked up a faint but unmistakable radio
signal from the probe. Radio telescopes on Earth continued to
receive this signal well past the expected lifetime of Huygens.
Huygens data, relayed by Cassini, were picked up by NASA’s
Deep Space Network and delivered immediately to ESA’s
European Space Operation Centre in Darmstadt, Germany, where the
scientific analysis is currently taking place.
“Titan was always the target in the Saturn system where
the need for ‘ground truth’ from a probe was critical.
It is a fascinating world and we are now eagerly awaiting the
scientific results,” says Professor David Southwood, Director
of ESA’s scientific programmme.
“The Huygens scientists are all delighted. This was worth
the long wait,” says Dr Jean-Pierre Lebreton, ESA Huygens
Mission Manager. Huygens is expected to provide the first direct
and detailed sampling of Titan’s atmospheric chemistry and
the first photographs of its hidden surface, and will supply a
detailed ‘weather report’.
One of the main reasons for sending Huygens to Titan is that its
nitrogen atmosphere, rich in methane, and its surface may contain
many chemicals of the kind that existed on the young Earth.
Combined with the Cassini observations, Huygens will afford an
unprecedented view of Saturn’s mysterious moon.
“Descending through Titan was a once-in-a-lifetime
opportunity and today’s achievement proves that our
partnership with ESA was an excellent one,” says Alphonso
Diaz, NASA Associate Administrator of Science.
The Cassini-Huygens mission is a cooperation between NASA, the
European Space Agency and ASI, the Italian space agency. The Jet
Propulsion Laboratory (JPL), a division of the California Institute
of Technology in Pasadena, is managing the mission for NASA’s
Office of Space Science, Washington. JPL designed, developed and
assembled the Cassini orbiter.
“The teamwork in Europe and the USA, between scientists,
industry and agencies has been extraordinary and has set the
foundation for today’s enormous success,” concludes
Jean-Jacques Dordain.
(All photos courtesy of ESA/NASA/University of
Arizona)
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