Chapter 7

Satellite Remote Sensing in Precision Agriculture

Hyperspectral Satellites

Compared with a large number of satellite-based multispectral sensors (e.g., Landsat, SPOT, WorldView, QuickBird, Sentinel-2), there are significantly fewer hyperspectral sensors. Hyperion, PROBA-CHRIS, PRISMA, HISUI, Pixxel, and HySIS are a few examples of satellite hyperspectral sensors. EO-1 Hyperion is the most widely used satellite-based hyperspectral sensor for agriculture. The primary advantage of hyperspectral remote sensing relative to multispectral sensing is that it involves narrower bandwidths (<10 nm). Reflectance spectra from hyperspectral imagery show excellent continuity from one band to another, typically starting at blue wavelengths and ending in the near-infrared (NIR) or short-wave infrared (SWIR) wavelengths. Continuous spectra are amenable to more sophisticated and wavelength-specific interpretations than multispectral imagery.

EO-1 Hyperion

EO-1 Hyperion imaging spectrometer was the first satellite to record hyperspectral reflectance data. The PO 1 Hyperion was launched in 2001 and decommissioned in 2016. The revisit frequency was 16 days, and spatial resolution was 30 m. Hyperion collects 220 unique spectral channels ranging from 0.357 to 2.576 micrometers with a 10-nm bandwidth. The instrument operates in a pushbroom fashion, with a spatial resolution of 30 meters for all bands. The standard scene width is 7.7 kilometers. The standard scene length is 42 kilometers, with an optional increased scene length of 185 kilometers.

PROBA-CHRIS

The Project for Onboard Autonomy-1 (PROBA-1) satellite carries a hyperspectral instrument called the Compact High Resolution Imaging Spectrometer (CHRIS). The main payload of the PROBA-1 satellite, CHRIS is a hyperspectral imager that can record scenes with a resolution of 17 to 34 meters across up to 63 spectral bands. CHRIS can be reconfigured to provide different spectral bands and spatial resolutions.

PRISMA

PRISMA carries two sensor instruments, the HYC (Hyperspectral Camera) module and the PAN (Panchromatic Camera) module. The HYC sensor is a prism spectrometer for two bands, VIS/NIR (Visible/Near Infrared) and NIR/SWIR (Near Infrared/Short-wave Infrared), with a total of 239 channels across both bands. Its primary mission objective is the high-resolution hyperspectral imaging of land, vegetation, inner waters, and coastal zones. The second sensor module, PAN, is a high-resolution optical imager with one channel and is co-registered with HYC data to allow testing of image fusion techniques.

HISUI

The Hyperspectral Imager Suite (HISUI) is a Japanese spaceborne hyperspectral and multispectral Earth observation system developed by the Ministry of Economy, Trade, and Industry (METI). HISUI is designed to capture detailed spectral information across a wide range of wavelengths, enabling precise analysis of Earth's surface materials. HISUI's high spectral resolution allows for detailed analysis of agricultural areas, including crop type identification, vegetation health monitoring, soil property assessment, and precision farming.

Pixxel

Pixxel is an India-based startup company developing a constellation of hyperspectral imaging satellites to create a range of applications for agriculture, government, environment, energy, and mining. The imager has capabilities in visible and near-infrared (VNIR) and short-wave Infrared (SWIR) spectral bands, where it can provide the perspective of planetary-scale ecosystems and biospheres. The hyperspectral imager onboard TD-1 and 2 carries 150 spectral bands with a spatial resolution of 10 m.

HySIS

Hyperspectral satellites like HySIS offer valuable data for agricultural applications by capturing detailed spectral information of crops, enabling precise crop monitoring, stress detection, and yield estimation. HySIS, an Indian satellite, provides hyperspectral imagery for various applications, including agriculture, forestry, and coastal assessments. Hyperspectral data can be used to identify crop types, assess nutrient deficiencies, detect disease and pest infestations, and monitor plant health.

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