Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Huygens sets off with correct spin and speed

12.01.2005


On Christmas Day 2004, the Cassini spacecraft flawlessly released ESA’s Huygens probe, passing another challenging milestone for Cassini-Huygens mission. But, with no telemetry data from Huygens, how do we know the separation went well?



At 3:00 CET on 25 December, the critical sequence loaded into the software on board Cassini was executed and, within a few seconds, Huygens was sent on its 20-day trip towards Titan. As data from Cassini confirm, the pyrotechnic devices were fired to release a set of three loaded springs, which gently pushed Huygens away from the mother spacecraft. The probe was expected to be released at a relative velocity of about 0.35 metres per second with a spin rate of about 7.5 revolutions per minute. Telemetry data from Cassini confirming the separation were collected by NASA’s Deep Space Network stations in Madrid, Spain, and Goldstone, California, when the telemetry playback signal from Cassini eventually reached the Earth.

However, these data showed only that the Cassini systems had worked, and that the Cassini ‘attitude perturbation’ (how Cassini moved in reaction to the probe’s release) were as expected. Within hours, the preliminary analysis of this data confirmed that Huygens was on the expected trajectory and spinning within the expected range. The spin imparted to Huygens is vitally important to ensure that the probe remains in a stable attitude and on course when it enters Titan’s atmosphere. So how could we check the spin rate was correct?


When the Huygens probe was being designed more than 10 years ago, it was required that the probe had to be magnetically ‘clean’ when switched off, meaning that any residual permanent magnetic fields must not interfere with the sensitive Cassini magnetometers. Later, when the probe was built, it was found that there was still a weak magnetic field produced, but within acceptable limits for Cassini’s magnetometer sensors.

However, because magnetic fields have a ‘direction’ as well as a strength, and this weak field was slightly off-centre, it effectively gave the probe a ‘left’ and a ‘right’ side (it behaves like a small magnet with a north and south pole). With the implication being that if you can detect this magnetic field, then you can also detect how it is rotating.

Following an initial suggestion by Jean-Pierre Lebreton, the Huygens Project Scientist, scientists on the Cassini Dual Technique Magnetometer (MAG) team, from Imperial College, London, and Braunschweig, confirmed that their instrument should be able to detect this small rotating magnetic field and plans were put in place to measure this during the probe release period.

Magnetometers are direct-sensing instruments that detect and measure both the strength and direction of magnetic fields in the vicinity of the instrument. The Cassini MAG is measuring these fields while Cassini is in orbit around Saturn as well as during the close Titan encounters. But, just after separation on 25 December, the MAG scientists detected fluctuations in the magnetic field around Cassini that could only have come from Huygens rotating and moving away.

Professor Michele Dougherty, Principal Investigator for MAG, said, “What was observed by MAG just after the probe separation on 25 December 2004, were weak but clear fluctuations in both magnetic sensors which reside on the 11-metre magnetometer boom. These fluctuations were a clear indication of the Huygens probe moving away from the Cassini orbiter. This signature confirmed the spin rate of the probe at 7.5 revolutions per minute, the ideal rate which was predicted, and that Huygens is well on its way to Titan.”

Former MAG Principal Investigator David Southwood, who is now the Director of Science at ESA, said, “Detecting the spin was immensely reassuring - not only did it show Huygens was rotating correctly, but also because the spin is directly related to the departure velocity, that Huygens was headed off at the right speed. It was really great to do it with an instrument I knew so well.”

Franco Bonacina | alfa
Further information:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMY0HQ3K3E_0.html
http://www.esa.int

More articles from Physics and Astronomy:

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

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: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NASA's AIM observes early noctilucent ice clouds over Antarctica

05.12.2016 | Earth Sciences

Shape matters when light meets atom

05.12.2016 | Physics and Astronomy

Researchers uncover protein-based “cancer signature”

05.12.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>