BY SPACEFLIGHT NOW
Follow the Huygens probe's descent to the surface of Saturn's moon Titan! Reload this page for the latest on the mission.
SATURDAY, JANUARY 15, 2005
Read our full story.
Also, you can see our montage of Huygens pictures showing the landing area here.
2015 GMT (3:15 p.m. EST)
"After over seven years in space, the European Space Agency's (ESA) Huygens probe has descended through the atmosphere of Titan, the largest of Saturn's multitude of moons.
"Pictures of Titan's exotic environment were provided by the Descent Imager/ Spectral Radiometer (DISR), a complex instrument designed and built by Lockheed Martin for the University of Arizona and the NASA Jet Propulsion Laboratory (JPL). NASA's Cassini spacecraft, with the Huygens probe in tow, was inserted into orbit around Saturn on June 30, 2004, initiating four years of orbital science investigations of the giant ringed planet and its many mysterious moons.
"We couldn't be more pleased for our colleagues at the University of Arizona, NASA and ESA as Huygens has allowed us unprecedented access to one of the most mysterious moons in the solar system,' said James Crocker, vice president, Civil Space, at Lockheed Martin Space Systems Company. 'The superb performance of the DISR hardware and the many years of hard work by the DISR team are equally gratifying, and we're proud to play a role in this exciting international voyage of exploration.'
"As Huygens descended by parachute through Titan's thick atmosphere, DISR made a range of imaging and spectral observations using several sensors and fields of view. The radiation balance of the atmosphere was measured by monitoring the upward and downward flow of radiation. A calculation of the size, number and density of suspended particles in the atmosphere was made possible by measuring the light intensity around the Sun. Two imagers (one visible, one infrared) observed the surface during the latter stages of the descent, and built up a mosaic of pictures around the touch down site. A side-view visible imager captured a horizontal view of the horizon and the underside of the cloud deck. The spectral measurements of the surface were enabled by a lamp that switched on shortly before touch down to augment the weak sunlight.
"The study of Titan, Saturn's largest moon, is one of the major goals of the Cassini/Huygens mission. Although it is believed to be too cold to support life, haze-covered Titan may preserve, in deep-freeze, many of the same chemical compounds that preceded life on Earth. The Huygens descent and touch down is the most distant descent by a robotic probe ever attempted on another object in the solar system. Over the course of the orbital mission, Cassini will have executed 45 flybys of Titan, coming as close as approximately 590 miles (950 km) above the surface.
"This will permit high-resolution mapping of the moon's surface with an imaging radar instrument, which can see through the opaque haze of Titan's upper atmosphere.
"The second largest planet in our solar system, after Jupiter, Saturn serves as a natural laboratory to better understand the formation of our Solar System five billion years ago, as the planet and its rings are a close analog to the disc of gas and dust surrounding the nascent Sun that formed the planets. Detailed knowledge of the dynamics of interactions among Saturn's elaborate rings and numerous moons will provide valuable data for understanding how each of the solar system's planets evolved.
"The Cassini spacecraft was launched on a Lockheed Martin-built Air Force Titan IV/Centaur rocket Oct. 15, 1997. The Cassini propulsion module - also built by Lockheed Martin - is the largest U.S. planetary spacecraft propulsion system ever built, and was fired 17 times en route to Saturn, and will be ignited approximately 150 more times before the end of the mission. In addition to DISR, the Titan IV/Centaur and the propulsion system, Lockheed Martin Space Systems Company designed and built the three radioisotope thermoelectric generators (RTGs) that power spacecraft systems.
"JPL designed, developed and assembled the Cassini orbiter. ESA managed the development of Huygens and is in charge of operations of the probe from its control center in Darmstadt, Germany. The Italian Space Agency provided the high-gain antenna, much of the radio system and elements of several of Cassini's science instruments. JPL manages the overall program for NASA's Office of Space Science, Washington, D.C."
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With two data paths, scientists had their choice of either relaying the same set of pictures to Cassini twice for redundancy or taking two sets of pictures to maximize the potential number of images. They opted to acquire two sets of pictures, and the lack of Channel A caused half of the expected number of pictures from Huygens to be lost.
The Channel A problem also resulted in the loss of data for the Doppler wind experiment between Huygens and Cassini. But ESA's chief scientist says data from radio telescopes on Earth that were listening to the tones from Huygens should allow researchers to complete the winds experiment.
FRIDAY, JANUARY 14, 2005
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"This is a great achievement for Europe and its U.S. partners in this ambitious international endeavour to explore the Saturnian system," said Jean-Jacques Dordain, ESA's director general.
"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 program.
"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 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.
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"The Huygens space probe has arrived on Titan. The probe was built by prime contractor Alcatel Space, a subsidiary of Alcatel, leading a consortium of 40 companies and laboratories. Alcatel Space is the first European company to have met the challenge of constructing a spacecraft designed to resist such draconian conditions. This is the first time that a man-made object has landed on the moon of a planet so far away in our solar system. This is also the first time that an European probe has successfully landed on another part of the solar system.
"The interplanetary voyage of Cassini/Huygens took seven years, and made use of successive gravity boosts from Venus (twice), the Earth and Jupiter. Huygens had to stand up to temperatures of 212 deg F near Venus, and made a blind crossing of the asteroid belt between Mars and Jupiter, then the rings of Saturn. However, the technical challenge reached its zenith during the descent towards Titan, which lasted nearly three weeks after the separation from the Cassini mother-craft on December 25. Following aerodynamic braking in the upper atmosphere, then deployment of three parachutes to control the descent, the probe landed on the surface of Titan. Huygens is a veritable flying lab, featuring six advanced instruments to carry out all measurements expected by the scientific community.
"Meanwhile, Cassini is in orbit around Saturn for its own observation mission, while relaying data from Huygens back to Earth.
"The Cassini/Huygens programs was an unprecedented technical challenge, tackling aspects that had never before been studied:
"We are especially proud of this huge success by our customer ESA, in partnership with NASA and ASI," said Pascale Sourisse, Chairman and CEO of Alcatel Space. "Not only is it a world first in exploration of the universe, it also marks a major step forward in better understanding the origins of life. With the Huygens mission now accomplished, we want to reaffirm our unyielding commitment to carrying out the most demanding programs for interplanetary exploration and observation of the universe, alongside European scientists and space agencies. We hope that this mission will pave the way to other adventures that prove to be just as exciting, both scientifically and technologically."
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"We have a scientific success," ESA director general Jean-Jacques Dordain reports. "We are the first visitors of Titan."
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"But at this moment we cannot say more. I mean, we have not seen the data. What we have seen is a tone, a signal, which was indicating that the probe was transmitting but we have not seen any real data yet. So I would like to wait a bit more to say whether we have a successful mission or not."
The first Huygens data via the Cassini telemetry playback is expected in about an hour.
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"The Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, USA, a part of the global network of radio telescopes involved in tracking the Huygens Titan probe, has detected the probe's 'carrier' (tone) signal.
"The detection occurred between 11:20 and 11:25 CET (5:20-5:25 a.m. EST), shortly after the probe began its parachute descent through Titan's atmosphere. The extremely feeble signal was first picked up by the Radio Science Receiver supplied by the NASA Jet Propulsion Laboratory. This signal is an important indication that the Huygens probe is 'alive'. However, it does not contain yet any substance; the latter is expected to come a few hours later via the Cassini spacecraft.
"What the Green Bank radio telescope has detected is only a 'carrier' signal. It indicates that the back cover of Huygens must have been ejected, the main parachute must have been deployed and that the probe has begun to transmit, in other words, the probe is 'alive'. This, however, still does not mean that any data have been acquired, nor that they have been received by Cassini. The carrier signal is sent continuously throughout the descent and as such does not contain any scientific data. It is similar to the tone signal heard in a telephone handset once the latter is picked up.
"Only after having received the data packets at ESOC will it be possible to say with certainty whether data were properly acquired. The first data set from Cassini will reach ESOC in the afternoon. Additional downlinks will follow throughout the evening and night for redundancy.
"Further analysis of the signals will be conducted using other three independent data acquisition systems at the Green Bank Telescope. In addition to the GBT, sixteen other radio telescopes in Australia, China, Japan and the USA are involved in tracking the Huygens probe.
"The ultimate goal of the tracking experiment is to reconstruct the probe's descent trajectory with an unprecedented accuracy of the order of one kilometre. The measurements will be conducted using Very Long Baseline Interferometry (VLBI) and Doppler tracking techniques. This would enable studies of the dynamics of Titan's atmosphere, which is considered to be a 'frozen' copy of that of the early Earth.
"The VLBI component of the tracking experiment is coordinated by the Joint Institute for VLBI in Europe (JIVE) and ESA; the Doppler measurements are conducted by the Jet Propulsion Laboratory."
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The first science information is expected on Earth about two hours from now.
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A second radio telescope now has picked up the signal as well and Europoean Space Agency project scientist Jean-Pierre Lebreton said engineers were even able to confirm at least one of the probe's six on-board instruments had activated as planned.
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1115 GMT (6:15 a.m. EST)
Earlier, controllers heard a simple tone emitted from Huygens that did announce the craft was at least alive.
A news conference is coming up at 1230 GMT (7:30 a.m. EST). Cassini will resume communications with Earth about three hours later, and the data playback will continue for several hours.
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This is just a signal with no actual data included. The data is being relayed to the Cassini orbit and will be played to Earth later today.
Nonetheless, the fact that a signal has been received to verify that Huygens is functioning prompted screams and cheers in mission control.
THURSDAY, JANUARY 13, 2005
Released from NASA's Cassini Saturn orbiter on Christmas Eve, the flying saucer-shaped probe is targeted to slam into Titan's atmosphere at a velocity of 12,400 mph at 5:13 a.m. EST (1013 GMT).
Over the next three to four minutes, the 705-pound probe is expected to endure peak heating of nearly 3,500 degrees and a braking force of some 16 Gs, slowing the craft to a more sedate 895 mph. At that point - 5:17 a.m. - the probe should release a small 8.5-foot pilot chute that will pull away a protective rear cover.
Just 2.5 seconds later, the craft's 27.2-foot-wide main parachute will unfurl. For the first time since pre-release tests, an on-board radio will begin transmitting data to Cassini around 5:18 a.m. as the NASA spacecraft streaks past Titan some 37,000 miles away.
Huygens is expected to reach the surface of Titan around 7:31 a.m. But with its main antenna pointed toward the landing zone, Cassini will be out of contact with Earth, leaving anxious engineers and scientists in the dark until the NASA craft turns back toward Earth and begins transmitting recorded data around 10:17 a.m. That's nearly three hours after Huygens touches down.
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WEDNESDAY, JANUARY 12, 2005
Beaming pictures and a torrent of data to NASA's Cassini Saturn orbiter, the flying saucer-shaped Huygens probe will give scientists their first close-up look at one of the largest expanses of unexplored territory in the solar system.
Researchers are hopeful Huygens will answer their most pressing questions: whether hydrocarbons fall like rain and form pools of liquid ethane and similar compounds on the moon's frigid surface; and what erosional or depositional processes are responsible for covering up impact craters and producing a relatively flat, mountain-free surface.
No matter what Huygens actually sees on the surface, scientists expect to gain insights into the workings of a thick, complex atmosphere that in some respects mirrors Earth's shortly after the planet's birth.
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Read our earlier status center coverage.
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