On September 15, 2017, it will be time to say goodbye to an astonishing piece of engineering, which has exceeded everybody’s hopes and expectations. After two decades in space, it is time for Cassini to be absorbed by the giant planet it has been studying for the past 13 years.
Cassini’s main mission has been to observe Saturn and its many moons, in particular Titan and Enceladus. On for the ride through space was the ESA lander,
Huygens, which successfully landed on Saturn’s largest moon, Titan, in January 2005.
During the 20 years that have passed since the start of the mission, Cassini will have traveled about 7.8 billion kilometers, including its 3.4 billion kilometer interplanetary trajectory from Earth to Saturn, and made 294 complete orbits of Saturn. 635 GB worth of science data will have been collected and over 453 000 pictures taken, showing us Saturn, Titan, Enceladus and its many smaller moons as we have never seen them before. Oceans on Titan and Enceladus have been found and 6 moons have been discovered, and these are just a few of the milestones of this once-in-a-lifetime-journey.
Figur 2: Instruments planned to be turned on during Cassini's final plunge.
Credit: NASA/JPL-Caltech - https://saturn.jpl.nasa.gov/resources/7754/
Cassini was the first spacecraft to carry a TiSurf® processed Langmuir probe from the Swedish IRFU into space as 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 and will be in operation until the very end.
Just as Cassini has had a lengthy timeline, so has TiSurf®. From its ‘discovery’ in 1990, it has been on many space adventures both near and far.
In 1992, it was approved to protect the Langmuir probe on Cassini and was launched into space in October 1997. In December 1998, the Earth-orbiting Swedish micro-satellite, Astrid-2, was sent into space with 2 TiSurf® processed Langmuir probes on board. Astrid-2’s objective was to perform detailed studies on the polar auroras/Northern Lights and how they are formed. Large quantities of data were received from the satellits until contact was lost in July 1999.
Five years passed until the next launch of space crafts with TiSurf® on board, but it was worth the wait, as one of them was the amazing comet-chasing Rosetta. Rosetta and the small lander, Philae, were sent on their way from Earth in March 2004, arriving 10 years later at Comet 67P/Churyumov-Gerasimenko and carrying 2 TiSurf® processed Langmuir probes. Rosetta studied the comet for 2 years and finally crashed down onto the comet in October 2016. In June 2004, 3 months after the launch of Rosetta, DEMETER was sent into orbit around Earth with 2 TiSurf® processed Langmuir probes. DEMETER observed electric and magnetic signals in Earth’s ionosphere and was operational until 2011.
On November 18, 2013, MAVEN started its journey heading for Mars and 4 days later, SWARM was launched into orbit around Earth. MAVEN has 2 TiSurf® processed Langmuir probes on board which, along with the other science instruments, have made some remarkable discoveries about Mars’ atmosphere and water loss. SWARM studies Earth's magnetic field and has 1 TiSurf® processed Langmuir probe on each of the mission’s 3 space crafts.
The Magnetospheric Multiscale Mission, MMS,is the latest mission with TiSurf® processed Langmuir probes. It launched in April 2015, and consists of 4 space crafts carrying a total of 16 TiSurf® processed Langmuir probes on the crafts. MMS is orbiting Earth, studying magnetic reconnection (how the Sun’s and Earth’s magnetic fields connect and disconnect, explosively transferring energy from one to the other).
Thus, after 20 years in space, TiSurf® is now present in the atmosphere of Saturn and on a comet, and is currently orbiting both Mars and Earth. On Earth, TiSurf® has evolved over the years, and researchers and developers have found many exciting new ways of using the technology on our own planet!
The Langmuir Probe on Cassini,
On September 8, 2017, Cassini made the last of its 22 Grand Finale dives through the gap between Saturn and its rings at an altitude of 1,680 kilometers above the cloud tops. Yesterday, September 11, the spacecraft gave Titan one last “kiss”, as Cassini made its last distant Titan flyby (aka, the "goodbye kiss") with an altitude of 119,049 kilometers above Titan's surface. Today, September 12, Cassini will be at its last apoapsis (the farthest point from Saturn in the orbit), 1.3 million kilometers from Saturn, before heading back to take its last pictures of the gigantic planet during September 14. On Friday, September 15, Cassini will dive into Saturn’s atmosphere, sending back data until the very end. Cassini will have been gone for about 83 minutes by the time its final signal reaches Earth. The current predicted time for the loss of signal on Earth is 4:55 a.m. PDT (7:55 a.m. EDT, which is 13:55 in Sweden) on September 15, 2017.
SentinaBay’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 with 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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