Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First measurement of Titan’s winds from Huygens

09.02.2005


Using a global network of radio telescopes, scientists have measured the speed of the winds faced by Huygens during its descent through the atmosphere of Titan.


Huygens probe descending through Titan’s atmosphere



This measurement could not be done from space because of a configuration problem with one of Cassini’s receivers. The winds are weak near the surface and increase slowly with altitude up to about 60 km, becoming much rougher higher up where significant vertical wind shear may be present.

Preliminary estimates of the wind variations with altitude on Titan have been obtained from measurements of the frequency of radio signals from Huygens, recorded during the probe’s descent on 14 January 2005. These ‘Doppler’ measurements, obtained by a global network of radio telescopes, reflect the relative speed between the transmitter on Huygens and the receiver on the Earth.


Winds in the atmosphere affected the horizontal speed of the probe’s descent and produced a change in the frequency of the signal received on Earth. This phenomenon is similar to the commonly heard change in pitch of a siren on a speeding police car.

Leading the list of large radio antennas involved in the programme were the NRAO Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, USA, and the CSIRO Parkes Radio Telescope in Australia. Special instrumentation designed for detection of weak signals was used to measure the ‘carrier’ frequency of the Huygens radio signal during this unique opportunity.

The initial detection, made with the ‘Radio Science Receivers’ on loan from NASA’s Deep Space Network, provided the first unequivocal proof that Huygens had survived the entry phase and had begun its radio relay transmission to Cassini.

The very successful signal detection on Earth provided a surprising turnabout for the Cassini-Huygens Doppler Wind Experiment (DWE), whose data could not be recorded on the Cassini spacecraft due to a commanding error needed to properly configure the receiver. “Our team has now taken a significant first step to recovering the data needed to fulfil our original scientific goal, an accurate profile of Titan’s winds along the descent trajectory of Huygens,” said DWE’s Principal Investigator Dr Michael Bird (University of Bonn, Germany).

The ground-based Doppler measurements were carried out and processed jointly by scientists from the NASA Jet Propulsion Laboratory (JPL, USA) and the Joint Institute for VLBI in Europe (JIVE, The Netherlands) working within the DWE team.

Winds on Titan are found to be flowing in the direction of Titan’s rotation (from west to east) at nearly all altitudes. The maximum speed of roughly 120 metres per second (430 km/h) was measured about ten minutes after the start of the descent, at an altitude of about 120 km. The winds are weak near the surface and increase slowly with altitude up to about 60 km.

This pattern does not continue at altitudes above 60 km, where large variations in the Doppler measurements are observed. Scientists believe that these variations may arise from significant vertical wind shear. That Huygens had a rough ride in this region was already known from the science and engineering data recorded on board Huygens. “Major mission events, such as the parachute exchange about 15 minutes into the atmospheric flight and impact on Titan at 13:45 CET, produced Doppler signatures that we can clearly identify in the data,” Bird said.

At present, there exists an approximately 20-minute interval with no data between the measurements at GBT and Parkes. This gap in Doppler coverage will eventually be closed by data from other radio telescopes which are presently being analysed. In addition, the entire global set of radio telescopes performed Very Long Baseline Interferometry (VLBI) recordings of the Huygens signal to determine the probe’s precise position during the descent.

“This is a stupendous example of the effectiveness of truly global scientific co-operation,” said Jean-Pierre Lebreton, ESA Huygens Project Scientist. “By combining the Doppler and VLBI data we will eventually obtain an extremely accurate three-dimensional record of the motion of Huygens during its mission at Titan,” he concluded.

Guido de Marchi | EurekAlert!
Further information:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMA8SXEM4E_0.html
http://www.esa.int

More articles from Physics and Astronomy:

nachricht Electrocatalysis can advance green transition
23.01.2017 | Technical University of Denmark

nachricht Quantum optical sensor for the first time tested in space – with a laser system from Berlin
23.01.2017 | Ferdinand-Braun-Institut Leibniz-Institut für Höchstfrequenztechnik

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Tracking movement of immune cells identifies key first steps in inflammatory arthritis

23.01.2017 | Health and Medicine

Electrocatalysis can advance green transition

23.01.2017 | Physics and Astronomy

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>