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Leti IR technology provided key information throughout Cassini mission, including a surprise about Saturn’s rings


When the history-making Cassini spacecraft descended into Saturn's atmosphere for a fiery finale in September, two decades and two mission extensions after its launch, scientists at Leti could proudly say "mission accomplished".

Published on 7 November 2017
Leti and the Astrophysics Laboratory at CEA Saclay had designed, tested and fabricated infrared detectors for Cassini's Composite Infrared Spectrometer (CIRS). Spectrometers split light into different colors, like a glass prism, and CIRS was special because it was sensitive to invisible heat rays, or infrared light emitted by the planet, its rings and its moons.

This information helped scientists study the thermal structure and composition of all those objects.

Thinner than we ever imagined!'

"Leti detectors onboard Cassini functioned perfectly from the beginning till the very end of the mission," said Olivier Gravrand, research director of IR devices.  "They provided information about the temperature of a variety of objects in Saturn's atmosphere, including an extremely useful measurement of temperature gradients in Saturn's rings. This provided vital information for estimating ring thickness. It was less than 10 meters, thinner than we ever imagined!"

When NASA, the European Space Agency (ESS) and the Italian Space Agency (ASI) were equipping Cassini and its temporary companion, Huygens, Leti was the only reliable source that could provide focal plane arrays for the IR detectors for the long wavelength range.

Leti's highflying knowhow

Leti The Cassini-Huygens mission is the most ambitious effort in planetary space exploration ever undertaken, but Leti has helped equip several missions over the years:

  • SWARM, 2012 launch – Next-generation Absolute Scalar Magnetometer for ESA mission, which will put three satellites in different polar orbits to take high-precision and high-resolution measurements of the magnetic field and improve our understanding of Earth's interior and climate.
  • Herschel Space Observatory, launched in 2009 – Leti and CEA/SAp, the astrophysics division of CEA, developed the bolometer arrays for the PACS photometer of the Herschel telescope that is studying the universe by the light of the far-infrared and sub-millimeter portions of the spectrum.
  • Ohmic Switch – With funding from CNES and the ESA, Leti developed this RF switch for space applications. The major advantage of this design over previous ones is that it is insensitive to charging effects, a major fault that had to be overcome to improve the switch's reliability.
  • Champ Mission, launched in 2000 – Leti developed a Nuclear Magnetic Resonance magnetometer for this German mission to measure Earth's magnetic field.
  • Oersted Project, launched in 1999 – Leti developed the Nuclear Magnetic Resonance magnetometer. Originally planned to last 14 months, the mission is still transmitting data on Earth's magnetic field to scientists!


Working with its long-term partners CNES and ESA, Leti developed instruments or subsystems, such as the bolometers, for the Herschel Space Observatory (2009-13) and absolute scalar magnetometers for the SWARM mission (2013).

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