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Infrared technologies expert, Lynred, has provided its Neptune infrared (IR) detector as one of the payload on India’s recently launched Chandrayaan-2 orbiter. This is the second time that the Indian Space Research Organization (ISRO) has deployed a Lynred IR detector in a space mission. The first was the hyperspectral imaging satellite HYSIS, launched in November last year. Chandrayaan-2, launched on the 22nd of July 2019 from the Satish Dhawan Space Centre in India, is viewed as the ISRO’s most complex mission to date, as it will be the first to explore the Moon’s south-polar region, the territory farthest from the Moon’s equator, famously known as the dark side.
Weighing 3,877 kg, the Chandrayaan-2 payload includes 11 instruments, one of which is an imaging IR spectrometer (IIRS) designed with Lynred’s IR detector, called Neptune. It will conduct a more in-depth onsite chemical analysis of the Moon and detection of minerals, water molecules and hydroxyl (containing oxygen and hydrogen atoms, also called hydroxyl radical, OH). Since water is essential for life to function on Earth, the composition of the water-ice on the surface and subsurface and its origin are important objects of study for future space exploration and travel. The orbiter is expected to be in orbit of the Moon for one year.
There are five of the eleven instruments on the orbiter:
- An X-ray spectrometer to map the main features of the moon’s surface
- A synthetic aperture radar (SAR) operating in the L and S bands to analyze the top layers of the moon’s surface (to a thickness in the tens of meters), to confirm the presence of water in areas that are always in shadowed regions
- An IIRS imaging IR spectrometer built on Lynred’s IR detector to map the moon over a large spectrum in order to detect minerals, water molecules and hydroxyl (containing oxygen and hydrogen atoms, also called hydroxyl radical, OH)
- A mass spectrometer to perform a detailed study of the moon’s exosphere
- A TMC2 (Terrain Mapping Camera 2) to generate three-dimensional maps for the study of the moon’s mineralogy and geology
The presence of water on the Moon was confirmed during the previous Chandrayaan-1 mission, which did not include a Lynred IR detector. For Chandrayaan-2, the Lynred IR detector was chosen for its capacity to increase the upper spectral limit to 5.3 µm, up from 3µm on Chandrayaan-1, in order to improve observation capabilities.
Lynred developed the IR detector for the IR imaging spectrometer, a 500 x 256 pixel SWIR-MWIR detector with a pitch of 30µm and a spectral range of 0.9µm to 5.3µm. It operates at 90 Kelvin and is equipped with a special cold filter with four bands. Based on the well-established and space-proven Neptune / Saturn IR space detectors, the IR detector is designed for hyperspectral applications in which the image of the ground is distributed spectrally on the detector.
