April 25, 2017
On the 26th of April, 2017, Cassini will make its first daring dive between Saturn and its innermost rings. After completing the 22 orbits of “The Grand Finale”, it will ultimately plunge down into Saturn’s atmosphere, where it will be vaporized within minutes and forever become a part of Saturn.
Cassini was the first mission to carry a TiSurf® treated Langmuir probe, and was launched during the summer of 1997. The Langmuir probe from the Swedish IRFU is part of the Radio and Plasma Wave Science (RPWS) instrument suite. The probe has been measuring the density and temperature of the local plasma since its arrival at Saturn during the summer of 2004, after 7 years of travelling through space.
The Langmuir Probe on Cassini, source: http://cassini.physics.uiowa.edu/cassini/gifs/CAS-RPWSLangmuirProbe.jpg Cassini’s main mission has been to observe Saturn and its many moons, particularly Titan and Enceladus. On for the ride through space was also the ESA lander, Huygens, which successfully landed on Saturn’s largest moon, Titan, in January 2005.
The ageing spacecraft is running low on fuel, but most of the instruments on board are still operational, some with reduced power. Some of the systems have become cranky, which the operational team has learned to handle with care, but the Cassini spacecraft is one of a kind. The radioisotope generators which produced 875 watts at launch, now only deliver 615 watts of power. The whole spacecraft is powered with about half the power that a hairdryer uses. The computers on Cassini have 512kB of RAM memory storage and its highest-resolution imager is a 1 megapixel black and white camera (it uses rotating filters when taking pictures, which are combined on earth to recreate the colors). In comparison, a modern mobile phone commonly has 16GB of storage or more, and 12 megapixel cameras. Cassini reaped the experience of engineers who had already spent their entire careers dedicated to spaceflight and learned from earlier missions such as Voyager, Galileo and Magellan. Cassini carries redundant systems; it has 2 radios, 2 computers, 2 thruster systems and 2 main engines. Cassini is still on its main engine, but has switched to the back-up thrusters. The spacecraft’s computers have only been reset twice since leaving Earth back in 1997.
“It’s a once-in-a-life-time spacecraft” - Julie Webster, Chief Engineer.
The final commands to change its course have already been sent to the spacecraft, sending it into the 22 final orbits between the planet and its innermost rings. The first orbit began April 23rd and the last will end on September 15, when Cassini does one finally dive into Saturn’s atmosphere. After 20 years in space. Cassini is expected to last about 3 minutes before it will be vaporized by Saturn’s atmosphere. This will prevent the spacecraft from possibly contaminating the moons Titan and Enceladus with Earth microbes and ensuring that those environments, where extraterrestrial life is a possibility, are untouched and intact. Below are two interesting public talks about Cassini’s final months and the science and discoveries the mission has revealed:
At this moment in time, the following active space missions carry TiSurf® coated instruments:
SentinaBays’s TiSurf process® for titanium has been tested for space projects by NASA and the University of Uppsala/Ångströms laboratory. Tests show that titanium nitride is by far the best surface for photoelectric properties, resistance to particle impact and erosion resistance. TiSurf is today the standard for surface materials for probes in space and is part of a number of ESA and NASA projects, including the Cassini satellite and MMS. The creator of the TiSurf process®, Erik Johansson, is currently part of the NewSoTech technical team that is further developing TiSurf technology in order to industrially produce eco-efficient components for demanding applications which strive for low friction, low weight and high resistance to corrosion, e.g. next-generation vehicles, offshore, the energy sector, chemical industries, etc. An upcoming area is replacing components made of hard chrome, which will be produced restrictively due to negative environmental impact. TiSurf® is 2-3 times harder than hard chrome and is a ”green choice”.
*TiSurf® is based on the thesis “Surface modification in tribology” by Erik Johansson, PhD, TiSurf International AB/patents EP-B1-0449793 / US 5, 530, 686 / US 5,427, 631 (TiSurf Process®).
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