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| Satellite ground reception (Image for representation only) |
ISRO is all set to launch advanced earth observation satellite Hyperspectral Imaging Satellite (HySIS) abroad PSLV-CA (C-43 flight) from the spaceport of Sriharikota, Andhra Pradesh. According to ISRO, the primary mission of HySIS it to study earth surface in visible, near-infrared (NIR) and shortwave infrared (SWIR) bands of electromagnetic spectrum. The satellite is dual use in nature- it has both civilian and military application. Contrary to several media reports, HySIS is not the first Indian satellite equipped with hyperspectral imaging (HSI) payload. HSI technology was first used in a mini-satellite IMS-1.
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| Render of Hyperspectral Imaging Satellite ( HySIS): Deployed and stowed config. ( Image : ISRO) |
HySIS satellite has a hyperspectral imaging payload operating in the visible and near infrared regions of the electromagnetic spectrum. The imaging sensor of HySIS was developed by ISRO. Imaging payload of HySIS will operate in the 0.4 to 0.95µm spectral range, will have 55 spectral bands with 10-nanometre spectral sampling and 30-meter spatial sampling (resolution).
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| CCD sensor developed by ISRO for hyperspectral applications (Image: ISRO) |
What is hyperspectral imaging?
Traditionally, EO/IR imaging has been used by most platforms (satellite, manned/unnamed aerial vehicles). Hyperspectral Imaging is a new trend in earth observation satellite niche. HSI uses a greater number of spectral bands (range of wavelengths) than conventional imaging sensors. The human eye sees light in three bands (red, green, and blue) while hyperspectral sensors are designed to detect a much greater number of wavelengths.
So, how does the capability to detect a greater number of wavelength helps?
It makes it easier to distinguish between objects and their background by determining how they interact (spectral properties/characteristics) with various wavelengths. Basically, HSI creates spectral signature of different elements, which can be utilized to gather a greater level of detail from an image. It allows an operator to see what normally cannot be seen by the human eye or IR sensor. A hyperspectral image has a large number of spectral signatures. Each spectra is processed individually to get information that can be interpreted.
The real potential of HSI is unlocked by advanced algorithms. HSI generates a large amount of data and high-performance computers are required to process it. Lack of processing power and algorithms had been a bottleneck in the proliferation of HSI tech on small civilian and military platforms, however, with advancement in technology, HSI is now being fully utilized.
Application of hyperspectral imaging
Hyperspectral Imaging is a dual-use technology i.e. it has both civilian and military application.
Some Civilian application of hyperspectral imaging are:
- In Remote sensing Satellites (HySIS)
- Crop health monitoring and disease detection
- Oil spillage detection
- Soil mapping, classification, and analysis
- Forensics
- Detection of stains (bodily fluids)
- Self-driving cars
Military application
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| leftmost image - Visual image extracted from a hyperspectral image, middle image- processed hyperspectral image, rightmost image- highlighted detected target pixels (Image: CEPA JP 8.10) |
- Intelligence, surveillance, and reconnaissance
- Detection and identification of low-signature or hidden targets
- Even if the resolution of an optical device is low, targets can be detected and classified if their spectral signature is known, for example, man-made objects on the sea surface, tanks in the desert, camouflaged missile launcher etc.
- Advanced target detection and missile cueing system for UAVs and manned combat aircraft.
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