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Main Characteristics of The Smallest СubeSat Cameras

by Staff Writer
19 Apr 2021 at 10:40hrs | Views
CubeSat cameras are an essential part of small-sized satellites today. Let's discuss some of their characteristics. We delve right into details to help you understand everything you need to know!

There is a wide range of CubeSat cameras available for use in geographic information systems (GISs). While these products tend to have basic graphics, they are still different when it comes to uses within the GIS. Satellite imagery provides better contextual information for a GIS and is often used to conduct heads-up digitizing; here, the images' features are converted into vector data.

CubeSat Cameras Imagery
Satellite imagery has become increasingly popular as CubeSat cameras are set up with technologically advanced sensors and then sent out into space. These particular satellites are often used for research, weather, navigation, communication, earth observation, and military purposes. Currently, there are more than 3,000 satellites in space, out of which the US and Russia have launched 2,500. All these satellites maintain different orbital centers, synchronies, eccentricities, inclinations, and altitudes so that they can image a wide range of processes and surface features.

There are two types of CubeSat nanosatellite - active and passive. Active satellites utilize remote sensors to detect responses reflected from objects irradiated from energy sources; most of these energy sources are artificially generated. Some examples of active sensors include sonar sensors (emit sound waves), laser sensors (emit light waves), radars (emit radio waves). In all these cases, the sensor will send a signal and calculate the time it takes for the signal to bounce back. The distance of the feature and the emitted signal's speed is calculated via the time it takes for the reflected signal to return.

Alternatively, passive CubeSat optical camera satellites also use sensors that detect emitted or reflected electromagnetic radiation from natural sources. Typically, the sun's energy is this natural source; however, there can be other sources like geothermal activity and magnetism. Imagine that you are trying to click a photo. If you use the in-built flash, it would be active remote sensing; if you use the camera without a flash, it would be passive remote sensing.

Types Of Image Resolution
One of the most basic CubeSat requirements of satellite imagery is the resolution. For characterizing any particular remote sensor, there are four types of resolution. They are:

1. Spatial Resolution
A CubeSat hyperspectral imager's spatial resolution is a direct representation of the ground coverage based on the pixels on the image. If the imagery has a 10-m resolution, each pixel will have a ground coverage of 10-m X 10-m or 100 square meters. Spatial resolution will be determined by the IFOV (Instantaneous field of view) or the sensors. The IFOV is basically the ground area via which the sensor will receive the electromagnetic radiation signal. It is determined by the angle and height of the imaging platform.

2. Spectral Resolution
The spectral resolution measures the sensor's ability to resolve intervals between the wavelengths within the electromagnetic spectrum. This resolution is determined by the number of intervals that are being scanned and the size of the wavelengths. For example, hyperspectral and multispectral sensors can measure a multitude of intervals between each wavelength.

3. Temporal Resolution
Temporal resolution is the measure of time between the collection periods of each image. This resolution is measured by the repeat cycle of the orbit of the satellite. Temporal resolution is often thought of as true-nadir and off-nadir. Areas located directly under the sensor are considered true-nadir, while imaged obliquely areas are considered off-nadir. In most cases, true-nadir imaging can take up to 3-4 months, while off-nadir imagery can be done within a week.

4. Radiometric Resolution
The radiometric resolution, as the name suggests, measures the sensor's sensitivity based on brightness variations. This resolution is depicted on grayscale levels that the sensor can image. Mostly, the sensor will have a radiometric value of 8-bit (for values between 0-255). However, there are also others like 11-bit (for values between 0-2,047), 12-bit (for values between 0-4,095), and 16-bit (for values between 0-63,535).

When it comes to CubeSat dimensions (in terms of imagery), there is often a trade-off between the types of resolution. If you improve one kind of resolution, you will have to reduce a different kind of resolution. For instance, if you want to increase the spatial resolution, you will have to decrease the spectral resolution.

According to several expert CubeSat manufacturers, one great example would be geostationary satellites; these satellites circle the Earth's equator once a day. Geostationary satellites yield a high temporal resolution, while the spatial resolution is relatively low. While technological advancements have improved the resolutions on an image, you need to ensure that your chosen imagery is sufficient to model or represent the geospatial features you are looking for.

Final Thoughts
CubeSat Cameras are not like standard cameras optimized to click photos that represent what your eyes see as close as possible. A typical CubeSat camera will use a color filter, the Bayer filter mosaic; the matrix of pixels or photo sensors will have the Red, Green, and Blue (RGB) filters. Some of these cameras used commercially will be fitted with a demosaicing algorithm to interpolate the RGB values and recreate the spectral content of the image.

What are your ideas on CubeSat cameras? Please share them in the comments section!

Source - Byo24News