cassini huygens mission

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Countdown to Cassini’s Grand Finale


After nearly 13 years in orbit around Saturn, the international Cassini–Huygens mission is about to begin its final chapter: the spacecraft will perform a series of daring dives between the planet and its rings, leading to a dramatic final plunge into Saturn’s atmosphere on 15 September.

On 22 April, Cassini successfully executed its 127th and final close flyby of Saturn’s largest moon, Titan.

The manoeuvre put the spacecraft onto its ’grand finale’ trajectory: a series of 22 orbits, each lasting about a week, drawing closer to Saturn and passing between the planet’s innermost rings and its outer atmosphere. The first crossing of the ring plane will occur on 26 April.

With the repeated dives in this yet unvisited region, the mission will conclude its journey of exploration by collecting unprecedented data to address fundamental questions about the origin of Saturn and its ring system.

Launched in 1997, the Cassini-Huygens spacecraft embarked on a seven-year voyage across the Solar System, eventually reaching Saturn in July 2004. Several months later, the Cassini orbiter released ESA’s Huygens probe, which landed on Titan on 14 January 2005 – the first landing in the outer Solar System.

The mission has greatly contributed to our understanding of the Saturnian environment, including the giant planet’s system of rings and moons.
Combining the data collected in situ by Huygens and the observations performed by Cassini during flybys of Titan, the mission revealed the atmospheric processes of this moon and their seasonal evolution, as well as the surface morphology and interior structure, which may include a liquid water ocean.

Enshrouded by a thick nitrogen-dominated atmosphere and partly covered by lakes and rivers, Titan has a weather and hydrological cycle that bears some interesting similarities to Earth. However, there are important differences: the key component there is not water, like on our planet, but methane, and the temperature is very low, around –180°C at the surface.

Over its 13-year mission, Cassini will have covered about half of Saturn’s orbit, in which the planet takes 29 years to circle the Sun. This means that the spacecraft has monitored two seasons on Titan, an object that can teach us much on the past and the future of Earth.

Another of Cassini’s breakthroughs was the detection of a towering plume of water vapour and organic material spraying into space from warm fractures near the south pole of Saturn’s icy moon, Enceladus. These salt-rich jets indicate that an underground sea of liquid water is lurking only a few kilometres below the moon’s icy surface, as confirmed by gravity and rotation measurements.

A recent analysis of data collected during flybys of Enceladus with the Cassini Ion Neutral Mass Spectrometer also revealed hydrogen gas in the plume, suggesting that rock might be reacting with warm water on the seafloor of the moon’s subsurface ocean. This hydrothermal activity could provide a chemical energy source for life, enabling non-photosynthetic biological processes similar to the ones found near the hydrothermal vents on the Earth’s ocean floor and pointing to the potential habitability of Enceladus’ underground ocean.

Following over a decade of ground-breaking discoveries, Cassini is now approaching its end. With little fuel left to correct the spacecraft trajectory, it has been decided to end the mission by plunging it into Saturn’s atmosphere on 15 September 2017. In the process, Cassini will burn up, satisfying planetary protection requirements to avoid possible contamination of any moons of Saturn that could have conditions suitable for life.

The grand finale is not only a spectacular way to complete this extraordinary mission, but will also return a bounty of unique scientific data that was not possible to collect during the previous phases of the mission.

Cassini has never ventured into the area between Saturn and its rings before, so the new set of orbits is almost like a whole new mission.
These close orbits will be inclined 63 degrees with respect to Saturn’s equator and will provide the highest resolution observations ever achieved of the inner rings and the planet’s clouds. The orbits will also give the chance to examine in situ the material in the rings and plasma environment of Saturn.

With its radio science investigation, Cassini will measure Saturn’s gravitational field as close as 3000 km from Saturn’s upper cloud layers, greatly improving the current models of the planet’s internal structure and winds in its atmosphere. Scientists expect the new data will also allow them to disentangle the gravity of the planet from the tiny pull exerted on the spacecraft by the rings, estimating the total mass of the rings to unprecedented accuracy. ESA ground stations in Argentina and Australia will help receive Cassini’s radio science data, providing a series of 22 tracking passes during the grand finale.

The grand finale orbits will also probe the planet’s magnetic field at similarly close distances. Previous observations have shown that the magnetic field is weaker than expected, with the magnetic axis surprisingly well aligned with the planet’s rotation. New data to be collected by the Cassini magnetometer will provide insights to understand why this is so and where the sources of magnetic field are located, or whether something in Saturn’s atmosphere has been obscuring the true magnetic field from Cassini until now.

While crossing the ring plane, Cassini’s Cosmic Dust Analyzer will directly sample the composition of dust particles from different parts of the ring system, whereas the Ion Neutral Mass Spectrometer will sniff the upper atmosphere layers of Saturn to analyse molecules escaping from the atmosphere as well as water-based molecules that originate from the rings.
“At last, we have now reached the final and most audacious phase of this pioneering mission, pushing the spacecraft once again into unexplored territory,” says Nicolas Altobelli, ESA Cassini project scientist.
“We are looking forward to the flow of exciting new data that Cassini will send back in the coming months.”

Christiaan Huygens

On this day but in 1629 was born the astronomer and mathematician Christiaan Huygens.

Huygens was a leading scientist of his time. His work included early telescopic studies of the rings of Saturn and the discovery of its moon Titan, the invention of the pendulum clock and other investigations in timekeeping. He published major studies of mechanics and optics, and pioneered work on games of chance.

Huygens (spacecraft)

Huygens was an atmospheric entry probe that landed successfully on Saturn’s moon Titan in 2005. Built and operated by the European Space Agency (ESA), it was part of the Cassini–Huygens mission and became the first spacecraft ever to land on Titan and the furthest landing from Earth a spacecraft has ever made. The probe was named after the Dutch 17th-century astronomer Christiaan Huygens, who discovered Titan in 1655.

Read more: Wikipedia

Image Credit: NASA / JPL / ESA & Caspar Netscher

This false-color view from NASA’s Cassini spacecraft shows clouds in Saturn’s northern hemisphere. The view was produced by space imaging enthusiast Kevin M. Gill, who also happens to be an engineer at NASA’s Jet Propulsion Laboratory.

The view was made using images taken by Cassini’s wide-angle camera on July 20, 2016, using a combination of spectral filters sensitive to infrared light at 750, 727 and 619 nanometers.

Filters like these, which are sensitive to absorption and scattering of sunlight by methane in Saturn’s atmosphere, have been useful throughout Cassini’s mission for determining the structure and depth of cloud features in the atmosphere.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

Object Names:Infrared Saturn Clouds

Image Type:  Astronomical

Credit: NASA/JPL-Caltech/Space Science Institute/Kevin M. Gill/Cassini

Time And Space

Jet Propulsion Laboratory (JPL) workers examine the Huygens probe after removal from the Cassini spacecraft in the Payload Hazardous Servicing Facility (PHSF) at KSC. The spacecraft was returned to the PHSF after damage to the thermal insulation was discovered inside Huygens from an abnormally high flow of conditioned air. The damage required technicians to inspect the inside of the probe, repair the insulation, and clean the instruments.

After returning from the PHSF to Launch Pad 40 at Cape Canaveral Air Station, Cassini/Huygens launched successfully in October 1997, and reached Saturn in July of 2004. Scientific instruments carried aboard the Cassini orbiter studied Saturn’s atmosphere, magnetic field, rings, and several moons, while the Huygens probe separated and landed on the surface of Titan, Saturn’s largest moon.

The Cassini-Huygens mission owes its name to the Dutch astronomer Christiaan Huygens and Italian astronomer Giovanni Domenico Cassini. Both had spectacular careers as observers of the heavens, which included important discoveries about Saturn and its satellites. Huygens (1629-1695) discovered Saturn’s largest moon, Titan, in 1655 and in 1656 described the shape and phase changes of Saturn’s rings. Cassini (1625-1712) was the first to observe four of Saturn’s moons, Iapetus, Rhea, Tethys, and Dione, in the 1670s and 1680s. He also, in 1675, discovered the gap in Saturn’s rings, now called the Cassini Division, and proposed that the rings were formed from many tiny particles.

Cassini-Huygens is a joint mission of NASA, the European Space Agency (ESA), and the Italian Space Agency, Agenzia Spaziale Italiana (ASI).

Exciting NASA news

… as if there’s not been some of that already this week.

(Image credit: NASA/JPL)

It seems that NASA’s slated to select two proposals for their Discovery program missions.

A “Discovery” mission at NASA is generally a smaller mission that happens very quickly. Something like the Curiosity rover or the Cassini-Huygens mission aren’t Discovery program missions, those are called “Flagship” missions.

NASA’s incredible Dawn mission is a Discovery mission.

Right now the five missions under consideration are:

VERITAS (Venus Emissivity, Radio Science, InSAR Topography and Spectroscopy): Basically a mission that would orbit Venus (a planet deserving to be visited again) and map its surface with high resolution radar.

- Psyche: This mission would explore a huge, metal-rich asteroid in the asteroid belt. Important and potentially influential mission (there are lots of entrepreneurs looking for metal-rich asteroids to mine in the near future).

- Lucy: This mission would explore a series of “Trojan” asteroids, basically asteroids that trail behind Jupiter.

- NEOCam: This would search for dangerous near-Earth asteroids.

DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging): As you might guess from its name, this spacecraft would descend through the Venusian atmosphere, studying it as it goes down.

If the rumors I’ve heard are true, it’s possible NASA might be able to select two missions from this excellent pile.

What are your picks?

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Titan’s Atmosphere

Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found

Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan’s polar regions.

The atmosphere is largely nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. Titan’s lower gravity means that its atmosphere is far more extended than Earth’s and about 1.19 times as massive. It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan’s surface features obscure.Atmospheric methane creates a greenhouse effect on Titan’s surface, without which Titan would be far colder. Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.

Titan’s clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.The findings of the Huygens probe indicate that Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface. Clouds typically cover 1% of Titan’s disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the southern summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only after the southern summer solstice but also during mid-spring.

Image Credit: NASA/JPL/Space Science Institute

Radio Occultation: Unraveling Saturn’s Rings
Specially designed Cassini orbits place Earth and Cassini on opposite sides of Saturn’s rings, a geometry known as occultation. Cassini conducted the first radio occultation observation of Saturn’s rings on May 3, 2005.
Three simultaneous radio signals of 0.94, 3.6, and 13 centimeter wavelength (Ka-, X-, and S-bands) were sent from Cassini through the rings to Earth. The observed change of each signal as Cassini moved behind the rings provided a profile of the distribution of ring material as a function of distance from Saturn, or an optical depth profile.
This simulated image was constructed from the measured optical depth profiles. It depicts the observed ring structure at about 10 kilometers (6 miles) in resolution. Color is used to represent information about ring particle sizes in different regions based on the measured effects of the three radio signals.
Purple color indicates regions where there is a lack of particles of size less than 5 centimeters (about 2 inches). Green and blue shades indicate regions where there are particles smaller than 5 centimeters (2 inches) and 1 centimeter (less than one third of one inch). The saturated broad white band near the middle of ring B is the densest region of ring B, over which two of the three radio signals were blocked at 10-kilometer (6-mile) resolution, preventing accurate color representation over this band. From other evidence in the radio observations, all ring regions appear to be populated by a broad range particle size distribution that extends to boulder sizes (several to many meters across).
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The radio science team is based at JPL.

Saturn’s shadows

It may seem odd to think of planets casting shadows out in the inky blackness of space, but it is a common phenomenon. Earth’s shadow obscures the Moon during a lunar eclipse, and Jupiter’s moons cast small shadows onto their parent planet.

One of the best places in our Solar System to spot intriguing and beautiful celestial shadows is at Saturn. On 1 July, the international Cassini mission celebrates 10 years of exploring Saturn, its rings and its moons, an endeavour that has produced invaluable science but also stunning images like this.

Drifting along in the foreground, small and serene, is Saturn’s icy moon Mimas. The blue backdrop may at first appear to be the gas giant’s famous and impressive set of rings, with pale and dark regions separated by long inky black slashes, but it is actually the northern hemisphere of Saturn itself. The dark lines slicing across the frame are shadows cast by the rings onto the planet.

Although we may not associate the colour blue with Saturn, when Cassini arrived at the planet the northernmost regions displayed the delicate blue palette shown in this image. As this region of Saturn is generally quite free of cloud, scattering by molecules in the atmosphere causes sunlight to take a longer path through the atmosphere. The light is scattered predominantly at shorter – bluer – wavelengths. This is similar to why the sky on Earth appears blue to our eyes.

Seasonal changes over the years since this photo was taken have turned the blue into Saturn’s more familiar golden hue. The reverse is occurring in the south, which is slowly becoming bluer.

This image is composed of infrared, optical and ultraviolet observations from Cassini’s narrow-angle camera on 18 January 2005. The colours closely match what the scene would look like in true colour.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and Italy’s ASI space agency.

Copyright NASA/JPL/Space Science Institute

Mimas Stares Back

The great eye of Saturn’s moon Mimas, a 130-kilometer-wide (80-mile) impact crater called Herschel, stares out from the battered moon. Several individual ringlets within the F ring are resolved here, and the small moon Atlas is also seen faintly outside the main rings.

Mimas is 397 kilometers (247 miles across); the view shows principally the moon’s anti-Saturn hemisphere. Atlas is 32 kilometers (20 miles) across.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 5, 2005, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 72 degrees. The image scale is 13 kilometers (8 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Image Credit: NASA/JPL/Space Science Institute

A focus on Titan.

Titan (or Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.

Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter 50% larger than the Moon and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter’s moon Ganymede, and is larger by volume than the smallest planet, Mercury, although only 40% as massive. 

Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan’s polar regions. The geologically young surface is generally smooth, with few known impact craters, although mountains and several possible cryovolcanoes have been found.

The atmosphere of Titan is largely composed of nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan’s methane cycle is viewed as an analogy to Earth’s water cycle, although at a much lower temperature.

Titan’s surface temperature is about 94 K (−179.2 °C). At this temperature water ice has an extremely low vapor pressure, so the little water vapor present appears limited to the stratosphere. Titan receives about 1% of the amount of sunlight that Earth gets.

Atmospheric methane creates a greenhouse effect on Titan’s surface, without which Titan would be far colder. Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.

Titan’s clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze. The findings of the Huygens probe indicate that Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface.

 It was summer in Titan’s southern hemisphere until 2010, when Saturn’s orbit, which governs Titan’s motion, moved Titan’s northern hemisphere into the sunlight. When the seasons switch, it is expected that ethane will begin to condense over the south pole.

Titan’s surface is marked by broad regions of bright and dark terrain. These include Xanadu, a large, reflective equatorial area about the size of Australia. It was first identified in infrared images from the Hubble Space Telescope in 1994, and later viewed by the Cassini spacecraft. The convoluted region is filled with hills and cut by valleys and chasms. It is criss-crossed in places by dark lineaments—sinuous topographical features resembling ridges or crevices. These may represent tectonic activity, which would indicate that Xanadu is geologically young. Alternatively, the lineaments may be liquid-formed channels, suggesting old terrain that has been cut through by stream systems. 

After years of searching, planetary scientists think they may finally have spotted waves rippling on the seas of Titan.

NASA’s Cassini spacecraft spied several unusual glints of sunlight off the surface of Punga Mare, one of Titan’s hydrocarbon seas, in 2012 and 2013. Those reflections may come from tiny ripples, no more than 2 centimetres high, that are disturbing the otherwise flat ocean.

Picture : This image shows Titan in ultraviolet and infrared wavelengths, with Xanadu in the bright region at the center-right. It was taken by Cassini’s imaging science subsystem on Oct. 26, 2004. Red and green colors represent infrared wavelengths and show areas where atmospheric methane absorbs light. These colors reveal a brighter (redder) northern hemisphere. Blue represents ultraviolet wavelengths and shows the high atmosphere and detached hazes.

Credit : NASA/JPL/Space Science Institute

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Some great news

We’ve just gotten word from NASA that they won’t be cancelling the seven missions that were up for review this year. Thank goodness.

Amongst the seven missions in danger were the Mars Curiosity Rover and the Cassini-Huygens mission to Saturn and Titan.

It’s looking like the Curiosity rover will get to continue blasting rocks apart with lasers and searching for signs of life and useful materials in preparation for human astronauts in twenty or so years.

The Cassini probe will get to continue zipping around Saturn and Titan doing science on the ringed planet.

( dcfcloverforever, you’re absofruitly right! Thanks, I changed it :D )

Crescent Saturn

Saturn appears to Cassini’s cameras as a thin, sunlit crescent in this unearthly view. Citizens of Earth, being so much closer to the Sun than Saturn, never get to enjoy a view of Saturn like this without the aid of our robot envoys. Parts of the night side of Saturn show faint illumination due to light reflected off the rings back onto the planet, an effect dubbed “ringshine.” This view looks toward the unilluminated side of the rings from about 43 degrees below the ringplane. The image was taken in green light with the Cassini spacecraft wide-angle camera on Aug. 4, 2013.

The view was obtained at a distance of approximately 1.2 million miles (2 million kilometers) from Saturn. Image scale is 75 miles (120 kilometers) per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

Image Credit: NASA/JPL-Caltech/Space Science Institute

Environmental Health Specialist Jamie A. Keeley of EG&G Florida Inc., KSC’s base operations contractor, uses an ion chamber dose rate meter to measure radiation levels in one of the three radioisotope thermoelectric generators (RTGs) that will provide electrical power to the Cassini spacecraft. Technicians tested and monitored four RTGs, including one spare, in the Radioisotope Thermoelectric Generator Storage building in KSC’s Industrial Area. The RTGs use heat from the natural decay of plutonium to generate electric power. This nuclear powered system enables the spacecraft to operate far from the Sun, where solar power systems are not feasible. Similar RTGs powered the Galileo and Ulysses spacecraft.

A close-up study of Saturn and its moons, the Cassini/Huygens mission launched from Cape Canaveral Air Station in October 1997 and reached the Saturnian system in July 2004 for four years of observation. Scientific instruments carried aboard the Cassini orbiter will study Saturn’s atmosphere, magnetic field, rings, and several moons, while the Huygens probe will separate and land on the surface of Titan, Saturn’s largest moon.

The Cassini-Huygens mission owes its name to the Dutch astronomer Christiaan Huygens and Italian astronomer Giovanni Domenico Cassini. Both had spectacular careers as observers of the heavens, which included important discoveries about Saturn and its satellites. Huygens (1629-1695) discovered Saturn’s largest moon, Titan, in 1655 and in 1656 described the shape and phase changes of Saturn’s rings. Cassini (1625-1712) was the first to observe four of Saturn’s moons, Iapetus, Rhea, Tethys, and Dione, in the 1670s and 1680s. He also, in 1675, discovered the gap in Saturn’s rings, now called the Cassini Division, and proposed that the rings were formed from many tiny particles.

Cassini-Huygens is a joint mission of NASA, the European Space Agency (ESA), and the Italian Space Agency, Agenzia Spaziale Italiana (ASI). JPL is managing the Cassini project for NASA. The mission was proposed in November 1982 by a group of European and American scientists from the European Science Foundation and the National Academy of Sciences. The Solar System Exploration Committee of the NASA Advisory Council endorsed the idea in April 1983, and NASA and ESA began a joint assessment study in 1984. ESA officially adopted the project in November 1988, and Congress approved funding for NASA’s portion of the mission in FY 89.