20 year old germanium lens still going strong!

Precision Solutions is delighted at the continuing, stunning success of NASA’s Cassini-Huygens mission to explore Saturn, its rings and its moons and is proud that the spacecraft’s Composite Infrared Spectrometer (CIRS) features a germanium lens, manufactured in 1994 by Precision Solution’s forerunner, Precision-Optical Engineering (P-OE). While incredible images transmitted from Cassini, such as the first where Saturn, its moons and rings, and also Earth, Venus and Mars, are visible in a single image, tend to capture the headlines, the 12 scientific instruments carried on-board continue to carry out sophisticated scientific studies of Saturn. They collect data in multiple regions of the electromagnetic spectrum, study dust particles, and characterise Saturn’s plasma environment and magnetosphere.

The CIRS is used to measure infrared emissions from atmospheres, rings and surface in the huge Saturn system to determine their composition, temperatures and thermal properties. It consists of two combined interferometers operating in the far-infrared (10-600 cm-1) and the mid-infrared (600 – 1400 cm-1). The two interferometers share a common telescope and scanner. A germanium lens is used on the mid-infrared interferometer to focus the interferometer output onto the instrument’s focal planes.

Head of Precision Solutions, Robin Addison, explains: “A series of germanium lenses were diamond machined by P-OE back in 1994 in order to obtain the best optical match for the instrument. These lenses were part of a subsystem contributed by Oxford University. P-OE’s diamond machined optics had been used previously in space on board the Upper Atmosphere Research Satellite.”

The Cassini-Huygens mission is a co-operative project of NASA, the European Space Agency and the Italian Space Agency. Cassini launched in October 1997 with the European Space Agency’s Huygens probe. The probe, equipped with six instruments to study Titan, Saturn’s largest moon, landed on Titan’s surface on Jan. 14, 2005. Meanwhile, Cassini’s 12 instruments have returned a daily stream of data from Saturn’s system since arriving at Saturn in 2004. The composite infrared spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md, while The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the overall mission for NASA’s Science Mission Directorate, Washington, D.C.

Addison continued: “The original Cassini mission was planned to last from 2004 to 2008, but two major extensions, firstly to 2010 and now to 2017, are testament to the extraordinary performance and reliability of the instruments and their components. NASA suggests that CIRS’ most exciting results so far have the discovery of ‘hot cracks’ on the south pole of Saturn’s moon Enceladus. The cracks were seen by the Cassini cameras (ISS), but CIRS was able to tell that they are much hotter than the surroundings.”

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