FINCH (Field Imaging Nanosatellite for Crop residue Hyperspectral mapping) is a 3U+ CubeSat mission designed to conduct crop residue mapping over Canada from Low-Earth Orbit.
Crop residue mapping involves the use of hyperspectral remote sensing technology to collect data on the waste materials generated by agriculture. This information is crucial for understanding soil health, managing agricultural waste, and optimising sustainable farming practices [src].
Crop residue mapping
But what is hyperspectral remote sensing? Let’s break this down.
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with it, such as via satellites or drones. It can be done actively or passively, the latter of which is applicable to us, where one measures the radiation reflected off of the object, typically sunlight.
Remote sensing with a satellite
To learn more about remote sensing, check out Fundamentals of Remote Sensing: A Canada Centre for Remote Sensing Remote Sensing Tutorial.
Hyperspectral imaging is a technique that collects and processes information across the electromagnetic spectrum to obtain a spectrum for each pixel in an image, instead of just assigning them primary colors (red, green, blue).
It involves using an imaging spectrometer, also known as a hyperspectral imager, to collect spectral information. The data collected by a hyperspectral imager is arranged to form a data structure known as a data cube where there are three dimensions: two spatial dimensions (x and y) - as with any other image - and an additional, third, spectral dimension (λ). This is shown below:
A data cube
The result is a hyperspectral image where each pixel represents a unique spectrum. Since every material and compound reacts with light differently, their spectral signatures are also different. Just like fingerprints can be used to identify a person, the spectra can be used to identify and quantify the materials in the image - crop residue mapping.
Transmission spectrum showing presence of carbon dioxide and methane
Okay, this is all fine and dandy, but how do we bring together the “hyperspectral” and the “remote sensing” with a satellite in space?
A pushbroom scanner, also known as an along-track scanner, images one scan line at a time, as shown below, where the dark purple squares represent the subset of the area seen by the scanner at any given time and the lighter purple squares show previously scanned lines.
Pushbroom scanning GIF
Pushbroom (along-track) scanning