Huygens probe
A scale replica of the probe, 1.3 metres across.
Organization:	ESA
Mission type:	Lander
Satellite of:	Saturn
Launch Date:	December 25, 2004
Launch Vehicle:	Cassini orbiter
NSSDC ID:	1997-061C
Webpage:	Huygens Homepage
Mass:	319 kg
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The Huygens probe, supplied by the European Space Agency (ESA) and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry probe carried to Saturn's moon Titan as part of the Cassini-Huygens mission. The combined Cassini-Huygens spacecraft was launched from Earth on October 15, 1997. Huygens separated from the Cassini orbiter on December 25, 2004, and landed on Titan on January 14, 2005 near the Xanadu region. It touched down on land (the possibility that it would touch down in an ocean was also taken into account in the design). The probe continued to send data for about 90 minutes after reaching the surface. Image File history File links Download high resolution version (2592x1273, 1310 KB) en: The Hugyens probe; scale 1 facsimile fr: La sonde Hugyens ; maquette échelle 1 présentée au Salon Européen de la Recherche, Paris, 3-5 juin 2005 Copyright © 2005 David Monniaux File links The following pages... ESA redirects here. ... Adjective Saturnian Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... December 25 is the 359th day of the year (360th in leap years) in the Gregorian Calendar, with 6 days remaining for the year. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... NASA logo The National Space Science Data Center (NSSDC) is a department in NASAs Solar System Exploration Division. ... ESA redirects here. ... Christiaan Huygens Christiaan Huygens (pronounced in English (IPA): ; in Dutch: )(April 14, 1629–July 8, 1695), was a Dutch mathematician, astronomer and physicist; born in The Hague as the son of Constantijn Huygens. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Atmospheric characteristics Pressure 146. ... Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... October 15 is the 288th day of the year (289th in leap years). ... 1997 (MCMXCVII) was a common year starting on Wednesday of the Gregorian calendar. ... December 25 is the 359th day of the year (360th in leap years) in the Gregorian Calendar, with 6 days remaining for the year. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... January 14 is the 14th day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Xanadu is the bright area at the centre-right of this image Xanadu (often called Xanadu Regio, though this is not its official name) is a highly reflective area of Saturns moon Titan. ...

Overview

Huygens was designed to enter and brake in Titan's atmosphere and parachute a fully instrumented robotic laboratory down to the surface. When the mission was planned, it was not yet certain whether the landing site would be a mountain range, a flat plain, an ocean, or something else, and it was hoped that analysis of data from Cassini would help to answer these questions. Alborz Mountains, Iran A mountain is a landform that extends above the surrounding terrain in a limited area. ... In geography, a plain is a large area of land with relatively low relief. ... Oceans (from Okeanos in Greek) are saline waters that cover almost three quarters (71%) of the surface of the Earth. ...

The first image released, taken from an altitude of 16 km, showing what are speculated to be drainage channels flowing to a possible shoreline. The darker areas are flat plains, while the lighter areas represent high ground.

Based on pictures taken by Cassini at 1200 km away from Titan, the landing site appeared to be, for lack of a better word, shoreline. Assuming the landing site could be non-solid, the Huygens probe was designed to survive the impact and splash-down with Titan's liquid surface for several minutes and send back data on the conditions there. If that occurred it was expected to be the first time a human-made probe would land in an extraterrestrial (i.e. non-Earth) ocean. The spacecraft had no more than three hours of battery life, most of which was planned to be taken up by the descent. Engineers only expected to get at best 30 minutes of data from the surface. Image File history File links This is one of the first raw images returned by the European Space Agencys Huygens probe during its successful descent to Titan. ... Image File history File links This is one of the first raw images returned by the European Space Agencys Huygens probe during its successful descent to Titan. ...

The Huygens probe system consists of the 318 kg probe itself, which descended to Titan, and the probe support equipment (PSE), which remained attached to the orbiting spacecraft. Huygens' heat shield was 2.7 m in diameter; after ejecting the shield, the probe was 1.3 m in diameter. The PSE included the electronics necessary to track the probe, to recover the data gathered during its descent, and to process and deliver the data to the orbiter, from which it will be transmitted or "downlinked" to the ground.

The probe remained dormant throughout the 6.7-year interplanetary cruise, except for bi-annual health checks. These checkouts followed preprogrammed descent scenario sequences as closely as possible, and the results were relayed to Earth for examination by system and payload experts.

Prior to the probe's separation from the orbiter on December 25, 2004, a final health check was performed. The "coast" timer was loaded with the precise time necessary to turn on the probe systems (15 minutes before its encounter with Titan's atmosphere), then the probe detached from the orbiter and coasted in free space to Titan in 22 days with no systems active except for its wake-up timer. December 25 is the 359th day of the year (360th in leap years) in the Gregorian Calendar, with 6 days remaining for the year. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

The main mission phase was a parachute descent through Titan's atmosphere. The batteries and all other resources were sized for a Huygens mission duration of 153 minutes, corresponding to a maximum descent time of 2.5 hours plus at least 3 additional minutes (and possibly a half hour or more) on Titan's surface. The probe's radio link was activated early in the descent phase, and the orbiter "listened" to the probe for the next 3 hours, including the descent phase, and the first thirty minutes after touchdown. Not long after the end of this three-hour communication window, Cassini's high-gain antenna (HGA) was turned away from Titan and toward Earth.

Very large radio telescopes on Earth were also listening to Huygens's 10-watt transmission using the technique of very long baseline interferometry and aperture synthesis mode. At 11:25 CET on January 14, the Robert C. Byrd Green Bank Telescope (GBT) in West Virginia detected the carrier signal from the Huygens probe. The GBT continued to detect the carrier signal well after Cassini stopped listening to the incoming data stream. In addition to the GBT, eight of the ten telescopes of the continent-wide VLBA in North America, located at Pie Town and Los Alamos, NM; Fort Davis, TX; North Liberty, IA; Kitt Peak, AZ; Brewster, WA; Owens Valley, CA; and Mauna Kea, HI, also listened for the Huygens signal. Very Long Baseline Interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy, in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk. ... Green Bank Telescope: the largest fully steerable single dish in the world, 100 x 110 m. ... VLBA locations. ... Los Alamos is an unincorporated townsite in Los Alamos County, New Mexico. ... Fort Davis is a census-designated place (CDP) in Jeff Davis County, Texas, United States. ... North Liberty is a city located in Johnson County, Iowa. ... The Kitt Peak National Observatory (KPNO) is a United States astronomical observatory located on a 2,096 m (6,880 ft) peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oodham Nation, 88 kilometres (55 miles) southwest of Tucson. ... Brewster is a city located in Okanogan County, Washington. ... Owens Valley is the arid ranching valley of the Owens River in southeastern California in the United States. ... Mauna Kea is a dormant volcano in the Hawaiian Islands, one of five volcanic peaks that together form the island of Hawaii. ...

The signal strength received at Earth from Huygens was comparable to that from the Galileo probe (the Jupiter atmospheric descent probe) as received by the VLA, and was therefore too weak to detect in real time because of the signal modulation by the (then) unknown telemetry. Instead, wide-band recordings of the probe signal were made throughout the three-hour descent. After the probe telemetry is finished being relayed from Cassini to Earth, the recorded signal is processed against a telemetry template, enabling signal integration over several seconds for determining the probe frequency. It is expected that through analysis of the Doppler shifting of Huygens' signal as it descends through the atmosphere of Titan, wind speed and direction will be able to be determined with some degree of accuracy. Through interferometry, it is also expected that the radio telescopes will allow determination of Huygens's landing site on Titan with exquisite precision, measuring its position to within 1 km at a distance from Earth of about 1200 million kilometres). This represents an angular resolution of approximately 170 microarcseconds. A similar technique was used to determine the landing site of the Mars exploration rovers by listening to their telemetry alone. Galileo being deployed after being launched by the Space Shuttle Atlantis on the STS-34 mission Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. ... VLA can be used, as an acronym, for Very Large Array - a telescope configuration in astronomy. ... Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... A terametre (American spelling: terameter) (symbol: Tm) is a unit of length equal to 1012 metres. ... Angular resolution describes the resolving power of any optical device such as a telescope, a microscope, a camera, or an eye. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... Artists Concept of Rover on Mars NASAs Mars Exploration Rover (MER) Mission (since 2003) is a unmanned Mars exploration mission that includes sending two Rovers (robots) to explore the Martian surface and geology. ...

Findings

Huygens landing site as determined by descent imagery

The preliminary findings confirm that the targeted region is indeed near the shoreline of a liquid ocean. The photos indicate the existence of drainage channels near the mainland and what appears to be a methane sea complete with islands and a mist-shrouded coastline. There are indications of chunks of water ice scattered over an orange surface, the majority of which is covered by a thin haze of methane. The instruments revealed "a dense cloud or thick haze approximately 18-20 kilometers from the surface" which is likely the reservoir of methane on the surface. The surface itself appears to be clay-like "material which might have a thin crust followed by a region of relative uniform consistency." One ESA scientist compared the texture and color of Titan's surface to a Crème brûlée, but admitted this term probably would not appear in the published papers. Image File history File links Estimated landing site of the Huygens probe on Titan (white circle) (credit ESA/NASA/JPL/University of Arizona) From ESA so probably: But also from NASA so it could be: Source: ESA web site File history Legend: (cur) = this is the current file, (del) = delete... Image File history File links Estimated landing site of the Huygens probe on Titan (white circle) (credit ESA/NASA/JPL/University of Arizona) From ESA so probably: But also from NASA so it could be: Source: ESA web site File history Legend: (cur) = this is the current file, (del) = delete... Methane is a significant and plentiful fuel which is the principal component of natural gas. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ... Crème brûlée (French, burnt cream, pronounced (IPA) in English; in French) is a dessert consisting of a custard-like base whose sugar topping has been burnt into a delicate, glass-like caramelized layer. ...

On January 18 it was reported that Huygens landed in "Titanian mud", and the landing site was estimated to lie within the white circle on the picture to the right. Mission scientists also reported a first "descent profile", which describes the trajectory the probe took during its descent. January 18 is the 18th day of the year in the Gregorian calendar. ...

Detailed Huygens activity timeline

Ellipse shows approximate landing site on this image taken earlier by Cassini. The bright region to the right is Xanadu Regio.

Colour image released from the landing site.

Contrast-enhanced version of surface image

• Huygens probe separated from Cassini orbiter at 02:00 UTC on December 25, 2004 in Spacecraft Event Time.
• Huygens probe entered Titan's atmosphere at 10:13 UTC on January 14, 2005 in SCET, according to ESA.
• The probe landed on the surface of the moon at ~163.1775 degrees east and ~10.2936 degrees south around 12:43 UTC in SCET (2 hours 30 minutes after atmospheric entry).(1.)

There was a transit of the Earth and Moon across the Sun as seen from Saturn/Titan just hours before the landing. The Huygens probe entered the upper layer of Titan's atmosphere 2.7 hours after the end of the transit of the Earth, or only one or two minutes after the end of the transit of the Moon. However, the transit did not interfere with Cassini orbiter or Huygens probe, for two reasons. First, although they could not receive any signal from Earth because it was in front of the Sun, Earth could still listen to them. Second, Huygens did not send any readable data to the Earth; it transmitted data to Cassini orbiter, which relayed the data received to the Earth later. For details about transits of the Earth as seen from Saturn, see also Transit of Earth from Saturn. Image File history File links Download high resolution version (1200x600, 271 KB)Approximate landing site of Huygens probe on Titan I added an ellipse to show the approximate landing site (~163. ... Image File history File links Download high resolution version (1200x600, 271 KB)Approximate landing site of Huygens probe on Titan I added an ellipse to show the approximate landing site (~163. ... Categories: Astronomy stubs | Saturns moons ... Download high resolution version (316x630, 38 KB)Image of Titans surface taken by the Huygens lander on January 14, 2005; the simulated colour is based on spectral measurements taken by the probe. ... Download high resolution version (316x630, 38 KB)Image of Titans surface taken by the Huygens lander on January 14, 2005; the simulated colour is based on spectral measurements taken by the probe. ... Image File history File links Contrast-stretched sum of JPEG sections selected from all images taken on surface of Titan -- sections selected according to data quality. ... Image File history File links Contrast-stretched sum of JPEG sections selected from all images taken on surface of Titan -- sections selected according to data quality. ... Coordinated Universal Time (UTC - see Abbreviation below for explanation) is a high-precision atomic time standard. ... December 25 is the 359th day of the year (360th in leap years) in the Gregorian Calendar, with 6 days remaining for the year. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Spacecraft Event Time is the time an event occurs at a spacecraft. ... January 14 is the 14th day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... A transit of Earth across the Sun as seen from Saturn takes place when the planet Earth passes directly between the Sun and Saturn, obscuring a small part of the Suns disc for an observer on Saturn. ...

See also Detailed timeline of Huygens mission. This page lists a chronology of events which have occurred or are expected to occur during the Cassini-Huygens mission to Saturn and Titan. ...

Instrumentation

The Huygens probe had six complex instruments aboard that took in a wide range of scientific data after the probe descended into Titan's atmosphere. The six instruments are:

Huygens Atmospheric Structure Instrument (HASI)

This instrument contains a suite of sensors that measured the physical and electrical properties of Titan's atmosphere. Accelerometers measured forces in all three axes as the probe descended through the atmosphere. With the aerodynamic properties of the probe already known, it was possible to determine the density of Titan's atmosphere and to detect wind gusts. The probe was designed so that in the event of a landing on a liquid surface, its motion due to waves would also have been measurable. Temperature and pressure sensors measured the thermal properties of the atmosphere. The Permittivity and Electromagnetic Wave Analyzer component measured the electron and ion (i.e., positively charged particle) conductivities of the atmosphere and searched for electromagnetic wave activity. On the surface of Titan, the conductivity and permittivity (i.e., the ratio of electric flux density produced to the strength of the electric field producing the flux) of the surface material was measured. The HASI subsystem also contains a microphone, which was used to record any acoustic events during probe's descent and landing; ^[1] this was only the second time in history that audible sounds from another planetary body had been recorded (a Venera-13 recording being the first). A depiction of an accelerometer designed at Sandia National Laboratories. ... The electron is a fundamental subatomic particle that carries an electric charge. ... Multivalent redirects here. ... In physics, the electric displacement field or electric flux density is a vector-valued field that appears in Maxwells equations and that generalizes the electric field. ... In physics, an electric field or E-field is an effect produced by an electric charge that exerts a force on charged objects in its vicinity. ... Venera 13 Soviet Venus lander Venera 13 and Venera 14 were a pair of identical probes in the Soviet Venera program for the exploration of Venus. ...

Doppler Wind Experiment (DWE)

This experiment used an ultra-stable oscillator to improve communication with the probe by giving it a very stable carrier frequency. This instrument was also used to measure the wind speed in Titan's atmosphere by measuring the Doppler shift in the carrier signal. The swinging motion of the probe beneath its parachute due to atmospheric properties may also have been detected. Although the failure of one of Huygens's data channels resulted in this data being lost to Cassini, enough was picked up by Earth-based radio telescopes to reconstruct it. Measurements started 150 kilometres above Titan's surface, where Huygens was blown eastwards at more than 400 kilometres per hour, agreeing with earlier measurements of the winds at 200 kilometres altitude, made over the past few years using telescopes. Between 60 and 80 kilometres, Huygens was buffeted by rapidly fluctuating winds, which are thought to be vertical wind shear. At ground level, the Earth-based doppler shift and VLBI measurements show gentle winds of a few metres per second, roughly in line with expectations. Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... In contrast to an ordinary telescope, which produces visible light images, a radio telescope sees radio waves emitted by radio sources, typically by means of a large parabolic (dish) antenna, or arrays of them. ... 50 cm refracting telescope at Nice Observatory. ... Very Long Baseline Interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy, in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk. ...

Descent Imager/Spectral Radiometer (DISR)

This instrument made a range of imaging and spectral observations using several sensors and fields of view. By measuring the upward and downward flow of radiation, the radiation balance (or imbalance) of the thick Titan atmosphere was measured. Solar sensors measured the light intensity around the Sun due to scattering by aerosols in the atmosphere. This permitted calculation of the size and number density of the suspended particles. Two imagers (one visible, one infrared) observed the surface during the latter stages of the descent and, as the probe slowly spun, they built up a mosaic of pictures around the landing site. In addition, a side-view visible imager obtained a horizontal view of the horizon and of the underside of the cloud deck. For spectral measurements of the surface, a lamp was switched on shortly before landing to augment the weak sunlight. The Sun is the star at the center of the Solar System. ... Aerosol pollution over Northern India and Bangladesh - Photo: NASA Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid (a smoke) or liquid (an aerosol) suspended in a gas. ...

Gas Chromatograph Mass Spectrometer (GC/MS)

A worker in the Payload Hazardous Servicing Facility (PHSF) stands behind the bottom side of the experiment platform for the Huygens probe.

This instrument is a versatile gas chemical analyzer that was designed to identify and measure chemicals in Titan's atmosphere.^[2] It was equipped with samplers that were filled at high altitude for analysis. The mass spectrometer built a model of the molecular masses of each gas, and a more powerful separation of molecular and isotopic species was accomplished by the gas chromatograph.^[3] During descent, the GC/MS also analyzed pyrolysis products (i.e., samples altered by heating) passed to it from the Aerosol Collector Pyrolyser. Finally, the GC/MS measured the composition of Titan's surface. This investigation was made possible by heating the GC/MS instrument just prior to impact in order to vaporize the surface material upon contact. This article has been listed as needing cleanup for over two months. ... Image File history File links Download high resolution version (2265x1523, 886 KB)Huygens probe experiment platform (bottom) during assembly. ... Image File history File links Download high resolution version (2265x1523, 886 KB)Huygens probe experiment platform (bottom) during assembly. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... This article has been listed as needing cleanup for over two months. ... This article has been listed as needing cleanup for over two months. ... This article has been listed as needing cleanup for over two months. ...

Aerosol Collector and Pyrolyser (ACP)

This experiment drew in aerosol particles from the atmosphere through filters, then heated the trapped samples in ovens (using the process of pyrolysis) to vaporize volatiles and decompose the complex organic materials. The products were flushed along a pipe to the GC/MS instrument for analysis. Two filters were provided to collect samples at different altitudes.^[4] Aerosol pollution over Northern India and Bangladesh - Photo: NASA Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid (a smoke) or liquid (an aerosol) suspended in a gas. ... Simple sketch of pyrolysis chemistry Pyrolysis usually means the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam. ... Volatile is the name of more than one concept: A financial instrument with high volatility is considered volatile in economics. ... This article has been listed as needing cleanup for over two months. ...

Surface-Science Package (SSP)

The SSP contained a number of sensors designed to determine the physical properties of Titan's surface at the point of impact, whether the surface was solid or liquid. An acoustic sounder, activated during the last 100 meters of the descent, continuously determined the distance to the surface, measuring the rate of descent and the surface roughness (e.g., due to waves). The instrument was designed so that if the surface were liquid, the sounder would measure the speed of sound in the "ocean" and possibly also the subsurface structure (depth). During descent, measurements of the speed of sound gave information on atmospheric composition and temperature, and an accelerometer recorded the deceleration profile at impact, indicating the hardness and structure of the surface. A tilt sensor measured pendulum motion during the descent and was also designed to indicate the probe's attitude after landing and show any motion due to waves. If the surface had been liquid, other sensors would also have measured its density, temperature and light reflecting properties, thermal conductivity, heat capacity, and electrical properties (permittivity and conductivity). A penetrometer instrument, that protruded 55mm past the bottom of the Huygens probe descent module, was used to create a penetrometer trace as Huygens landed on the surface by measuring the force exerted on the insturment by the surface as the instrument broke though the surface and was pushed down into the planet by the force of the probe landing itself. The trace shows this force as a function of time over a period of about 400ms. The trace has an initial spike which suggests that the instrument hit one of the icy pebbles on the surface photographed by the DISR camera. The F70 type frigates (here, La Motte-Picquet) are fitted with VDS (Variable Depth Sonar) type DUBV43 or DUBV43C towed sonars SONAR (SOund Navigation And Ranging) â€” or sonar â€” is a technique that uses sound propagation under water (primarily) to navigate, communicate or to detect other vessels. ... The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium. ... Simple gravity pendulum assumes no air resistance and no friction of/at the nail/screw. ... Density, or volumic mass (ISO 31), is a measure of mass per volume. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ...

The Huygens SSP was developed by the Planetary and Space Sciences Research Institute (PSSRI) of the UK Open University and the Rutherford Appleton Laboratory Space Science Department under the direction of Professor John Zarnecki. Affiliations EADTU, MSACS Website www. ...

Spacecraft design

Application of multi-layer insulation shimmers under bright lighting during final assembly. The gold color of the MLI is due to light reflecting off of the aluminium coating on the back of sheets of amber colored Kapton.

Huygens was built under the Prime Contractorship of Aérospatiale in Cannes, France now part of Alcatel Alenia Space. The heat shield system was built under the responsibility of Aérospatiale near Bordeaux, now part of EADS SPACE Transportation. Image File history File links Download high resolution version (2245x1518, 915 KB)Original caption:KENNEDY SPACE CENTER, FLA. -- An employee in the Payload Hazardous Servicing Facility (PHSF) sews thermal insulation material on the back cover and heat shield of the Huygens probe during prelaunch processing, testing and integration in that... Image File history File links Download high resolution version (2245x1518, 915 KB)Original caption:KENNEDY SPACE CENTER, FLA. -- An employee in the Payload Hazardous Servicing Facility (PHSF) sews thermal insulation material on the back cover and heat shield of the Huygens probe during prelaunch processing, testing and integration in that... Closeup of Multi-layer insulation from a satellite. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... Kapton is a polyimide film developed by DuPont which can remain stable in a wide range of temperatures, from -269°C to 400°C. Kapton is used in, among other things, flexible printed circuits and spacesuits. ... The Aérospatiale Corvette first flew in 1970 and went into service in 1974. ... For the annual festival, see Cannes Film Festival. ... Alcatel SA is a global company, headquartered in France that provides hardware, software and services to telecommunications service providers and enterprises. ... EADS SPACE Transportation (acronym: EADS-ST) was formed in June 2003 from the Space Infrastructure division of Astrium (whose core was originally ERNO) and the EADS Launch Vehicles division (formerly Aerospatiales Space division). ...

Parachute

Martin-Baker Space Systems was responsible for Huygens' parachute systems and the structural components, mechanisms and pyrotechnics that control the probe's descent onto Titan. IRVIN-GQ was responsible for the definition of the structure of each of Huygens' parachutes. Irvin worked on the probe's descent control sub-system under contract to Martin-Baker Space Systems. Martin-Baker Aircraft is a manufacturer of aircraft seats and is the oldest existing maker of ejector seats. ... The Apollo 15 capsule landed safely despite a parachute failure. ... IRVIN-GQ is a company that designs, manufactures and supplies a range of parachutes and emergency, rescue and survival equipment to the military, coastguard and civilian aerospace markets. ...

A critical design flaw resolved

Long after launch, a few persistent engineers discovered that the communication equipment on Cassini had a fatal design flaw, which would have caused the loss of all data transmitted by the Huygens probe.

As Huygens is too small to transmit directly to Earth, it is designed to transmit the telemetry data obtained while descending through Titan's atmosphere to Cassini by radio, which would in turn relay it to Earth using its large 4-meter diameter main antenna. Some engineers, most notably ESA Darmstadt employees Claudio Sollazzo and Boris Smeds, felt uneasy about the fact that, in their opinion, this feature had not been tested before launch under sufficiently realistic conditions. Smeds managed, with quite some difficulty, to convince superiors to perform additional tests while Cassini was in flight. In early 2000, he sent simulated telemetry data at varying power and Doppler shift levels from Earth to Cassini. It turned out that Cassini was unable to relay the data correctly. In telecommunications, transmission is the act of transmitting electrical messages (and the associated phenomena of radiant energy that passes through media). ... Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... Darmstadt is a city in the Bundesland (federal state) of Hessen in Germany. ... Boris Smeds (born 16 October 1944) is a Swedish radio engineer and European Space Agency employee, noted for detecting a critical flaw in Cassini-Huygens space mission. ... This article is about the year 2000. ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ...

The reason: When Huygens descends to Titan, it will accelerate relative to Cassini, causing its signal to be Doppler-shifted. Consequently, the hardware of Cassini's receiver was designed to be able to receive over a range of shifted frequencies. However, the firmware was not: The Doppler shift changes not only the carrier frequency but also the timing of the payload bits, coded by phase-shift keying at 8192 bits per second, and this, the programming of the module fails to take into account. A source of waves moving to the left. ... In computing, firmware is software that is embedded in a hardware device. ... A carrier wave, or carrier is a waveform (usually sinusoidal) that is modulated (modified) to represent the information to be transmitted. ... In cargo transport, the payload is the valuable contents of the vehicle. ... This article is about the unit of information. ... Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ...

Reprogramming the firmware was impossible, and as a solution the trajectory had to be changed. Huygens detached a month later (December 2004 instead of November) and approached Titan in such a way that its transmissions travelled perpendicularly to its direction of motion relative to Cassini, greatly reducing the Doppler shift.^[5]

The trajectory change overcame the design flaw and data transmission succeeded, though the information from one of the two radio channels was lost due to an unrelated error.

"Channel A" data lost

Huygens was programmed to transmit telemetry and scientific data to the Cassini orbiter for relay to Earth using two redundant S-band radio systems, referred to as Channel A and B, or Chain A and B. Channel A was the sole path for an experiment to measure wind speeds by studying tiny frequency changes caused by Huygens' motion. In one other deliberate departure from full redundancy, pictures from the descent imager were split up, with each channel carrying 350 pictures. Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... The S band ranges from 2. ...

As it turned out, Cassini never listened to channel A because of a software commanding error. The receiver on the orbiter was never commanded to turn on, according to officials with the European Space Agency. ESA announced that the program error was a mistake on their part, the missing command was part of a software program developed by ESA for the Huygens mission and that it was executed by Cassini as delivered.

The loss of Channel A means only 350 pictures were received instead of the 700 planned. Also all Doppler radio measurements between Cassini and Huygens were lost. Doppler radio measurements of Huygens from Earth were made, though not as accurate as expected measurement that Cassini would have made; when added to accelerometer sensors on Huygens and VLBI tracking of the position of the Huygens probe from Earth, reasonably accurate wind speed and direction measurements can still be derived. This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Very Long Baseline Interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy, in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk. ...

Amateur contributions

The Huygens mission benefited significantly from amateur contributions. This was enabled by the decision of the imaging science Principal Investigator Marty Tomasko to make the image raw data of the DISR instrument available to the public. The many small and low contrast images had to be assembled into mosaics and panoramas of the landing region in a time consuming process, and space science enthusiasts all around the world began to deal with this challenge. Only some hours later the first mosaics of the Huygens landing region were published,^[6] created by Daniel Crotty, Jakub Friedl and Ricardo Nunes.^[7] Christian Waldvogel published an improved and colorized Panorama. Another amateur, René Pascal, intensively engaged in the Huygens image processing. Pascal developed a method to remove camera artifacts from the images and created a comprehensive mosaic of the region now called Adiri.^[8] Christian Waldvogel - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Adiri as seen by Huygens Adiri is a bright albedo feature on Saturns moon Titan. ...

See also

• Cassini-Huygens
• Cassini-Huygens timeline
• Europlanet

Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... This page lists a chronology of events which have occurred or are expected to occur during the Cassini-Huygens mission to Saturn and Titan. ... There are very few or no other articles that link to this one. ...

References

1. ^ M. Fulchignoni, F. Ferri, F. Angrilli, A. Bar-Nun, M.A. Barucci, G. Bianchini, W. Borucki, M. Coradini, A. Coustenis, P. Falkner, E. Flamini, R. Grard, M. Hamelin, A.M. Harri, G.W. Leppelmeier, J.J. Lopez-Moreno, J.A.M. McDonnell, C.P. McKay, F.H. Neubauer, A. Pedersen, G. Picardi, V. Pirronello, R. Rodrigo, K. Schwingenschuh, A. Seiff, H. Svedhem, V. Vanzani and J. Zarnecki (2002). "The Characterisation of Titan's Atmospheric Physical Properties by the Huygens Atmospheric Structure Instrument (Hasi)". Space Science Review 104: 395 - 431. DOI:10.1023/A:1023688607077.
2. ^ Niemann HB, Atreya SK, Bauer SJ, Biemann K, Block, Carigan GR, Donahue TM, Frost RL Gautier D, Habermann JA, Harpold D, Hunten DM, Israel G, Lunine JI, Mauersberger K, Owen TC, Fraulin, Richards JE, Way, SH (2002). "The Gaschromatograph Mass Spectrometer for the Huygens Probe". Space Science Review 104: 533-591. DOI:10.1023/A:1023680305259.
3. ^ H. B. Niemann, S. K. Atreya, S. J. Bauer, G. R. Carignan, J. E. Demick, R. L. Frost, D. Gautier, J. A. Haberman, D. N. Harpold, D. M. Hunten, G. Israel, J. I. Lunine, W. T. Kasprzak, T. C. Owen, M. Paulkovich, F. Raulin, E. Raaen, S. H. Way (2005). "The abundances of constituents of Titan’s atmosphere from the GCMS instrument on the Huygens probe". Nature 438: 77-9-784. DOI:10.1038/nature04122.
4. ^ Israel G, Cabane M, Brun J-F, Niemann H, Way S, Riedler W, Steller M, Raulin F, Cosica D (2002). "Huygens Probe Aerosol Collector Pyrolyser Experiment". Space Science Review 104: 433-468. DOI:10.1023/A:1023640723915.
5. ^ Oberg, James. "Titan Calling", IEEE Spectrum, October 4, 2004. (offline as of 2006-10-14, see Internet Archive version)
6. ^ http://anthony.liekens.net/index.php/Main/Huygens
7. ^ http://en.wikipedia.org/wiki/User:Ricnun
8. ^ http://www.beugungsbild.de/huygens/huygens.html

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Galunggung in 1982, showing a combination of natural events. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... IEEE Spectrum is a magazine edited by the Institute of Electrical and Electronics Engineers. ...

External links

• Huygens probe lands on Titan: a scientific leap for mankind
• Amateur compositions of images, preceding NASA and ESA releases
• Animation of raw images on ground
• European Space Agency Cassini-Huygens website, including videos of the descent
• ESA Huygens scientific information
• Interactive Flash-Animation of Cassini orbits through 2008
• Latest News on the Huygens Probe
• NASA's Cassini-Huygens page
• New Scientist — Cassini-Huygens: Mission to Saturn
• Planetary Society's Saturn coverage
• Raw images from descent
• Surface Mosaics and extensive Image Processing by an Amateur
• The Huygens Probe: Science, Payload and Mission Overview
• Exploratorium webcasts about Saturn and Titan
• Yahoo group dedicated to the Cassini-Huygens mission