Tag: Saturn

End of the Cassini Mission to Saturn

Two days from now, on Friday the 15th of September 2017 the Cassini Spacecraft will make it’s final orbit around Saturn. After exploring Saturn and its moons for the past 13 years Cassini is now nearly out of fuel and NASA has decided to plunge the probe into the atmosphere of the ringed planet. The reason for ending the probe’s mission in this fiery fashion is to make certain that Cassini does not crash onto one of Saturn’s moons and possibly contaminate it with micro-organisms from Earth.

The Cassini-Huygens mission began almost 20 years ago on the 15th of October 1997 when the spacecraft was launched from Kennedy Space Center aboard a Titan IV-Centaur rocket. The probe’s long seven year journey to Saturn required gravity boosting flybys from Venus (twice), Earth and Jupiter in order to gain enough energy to reach the outer Solar System. The image below shows the Cassini-Huygens spacecraft prior to its launch.

Cassini-Huygens Spacecraft (Credit: NASA)

Entering orbit around Saturn on the first of July 2004 Cassini released the Huygens landing module on the 25th of December 2004 and Huygens successfully landed on the Moon Titan on January the 14th, 2005. The lander, which was built by the European Space Agency, operated for 90 minutes sending back images and instrument measurements from the surface of the second largest moon in the Solar System. The first image below is a picture of the Huygens lander and the second is an image from the surface of Titan.

Huygens Lander (Credit: David Monniaux)
The Surface of Titan (Credit: ESA-NASA-JPL)

During it’s short operating life the Huygens lander found that the atmosphere of Titan was denser than Earth’s by about 45% with a composition of 95% nitrogen and 5% methane at a temperature of 98.3 degrees Kelvin (-179.3 Celsius). The rocks in the surface image above are actually water ice at a temperature so cold they are as hard as rocks!

The discoveries on Titan by Huygens were augmented by those of the Cassini orbiter which found both large lakes of liquid methane along with signs of channels other indications of erosion caused by flowing liquid methane. Between them Cassini and Huygens portray Titan as a world very similar to our own except it is so cold that methane has replaced water.

Since then the Cassini orbiter has continued its mission, making several major discoveries. One of the most important has been the eruptions of water ‘volcanoes’ spewing out of the moon Enceladus. The energy causing these eruptions is thought to be generated by the tidal forces of Saturn and its other moons and is similar to the process that heats Jupiter’s moons Io and Europa. After discovering the ‘volcanos’ the Cassini spacecraft was even sent into them in an attempt to analyze their composition. The plumes are indeed water but with a small amount of complex hydro-carbons mixed in. Are these complex molecules a sign of the beginning of life on Enceladus? Only time, and a lander to the moon will tell. The picture below is an artists idea of the hydro-thermal activity on Enceladus.

Hydro-Thermal Activity on Enceladus (Credit: NASA-JPL-Caltech)

As far as I’m concerned however the best part of any mission to Saturn is simply the images of the planet and its system of rings. So without further ado I’ll just add a few below.

Saturn by Cassini (Credit: NASA-JPL)
Saturn’s North Pole (Credit: NASA-JPL)
Saturn’s Rings (Credit: NASA-JPL)

NASA has actually set up live internet coverage of Cassini’s final moments, although we can’t be quite certain exactly when that will happen. The show will start at 7AM Eastern Daylight Time on Friday the 15th and if you’d like to tune in, I will be, click on the link below to be taken to NASA’s Cassini End of Mission Activities website.

https://www.nasa.gov/press-release/nasa-announces-cassini-end-of-mission-media-activities

This Week in Space

Several news stories dealing with space exploration came out this week but didn’t receive much attention so I decided to take a moment to highlight them.

The first item on my list is the beginning of the final, and perhaps most exciting phase of the Cassini spacecraft’s mission to the planet Saturn. The Cassini mission is expected to end in September of next year with Cassini plunging into Saturn’s atmosphere but starting this week the spacecraft has begun a series of ring grazing orbits that will be followed by orbits closer to the giant planet than anything ever attempted.

In the picture below the gray lines indicate the ring grazing orbits while the blue lines are the planet grazing orbits. These orbits are dangerous, a collision with debris from the rings could easily destroy the spacecraft which is why NASA has waited till the end of the mission to attempt them. The possibility of close up observations of the ring system is too great a chance to miss however.

Cassini Spacecraft Ring grazing Orbits

Hopefully in the next several weeks NASA will be able to release spectacular images of Saturn’s Rings. If you’d like to know more about the Cassini mission here’s a link to the official NASA website.

https://www.nasa.gov/mission_pages/cassini/main/index.html

Another interesting NASA story is the awarding of a contact to the California based company Space Systems/LORAL. I used to work for them back in the 1980s designing antennas for geostationary communications satellites. The contact is for the development of a satellite refueling spacecraft called the Restore-L spacecraft bus.

Refueling satellites in space is an idea that’s been talked about since the 80’s and I’m glad to see they are finally getting around to doing it. You see, all the satellites we put into space to sent you your direct TV signal or complete your overseas telephone call or keep an eye on the hurricane brewing in the Atlantic have only a limited amount of fuel to keep them in the proper orbit and, just as importantly pointing in the right direction. Once their fuel is gone these technological miracles costing hundreds of millions of dollars are just trash.

Having an unmanned spacecraft that could go to these satellites and refuel them is another step on the road to building the infrastructure of space, turning low Earth orbit (LEO) into a work environment of benefit to everyone here on Earth. If you’d like to read more about Restore-L here’s a link to the story.

http://perfscience.com/content/2145143-refueling-mission-spacecraft-project-wins-nasa-approval-127-million-payment

A closely related story is the selection by INTELLSAT, the international consortium managing most of the world’s communications satellites, of Orbital ATK as the provider for a Mission Extension Vehicle-1, MEV-1. The objective of the MEV-1 will be very similar to NASA’s Restore-L spacecraft in that the MEV-1 will go to satellites already in orbit and either refuel or repair them, thereby extending their useful life.

These twin spacecraft, are scheduled to be developed over the next three to four years and together they will provide a new capability for mankind in space. To read the original story from Spacecraft Insider click on the link below.

http://www.spaceflightinsider.com/organizations/orbital-sciences-corp/intelsat-taps-orbital-atks-mev-1-extend-life-orbiting-satellites/