Satellite ground station system uses tiny low-cost receiver module
Transmission signals from satellites hundreds of miles into space are very weak, making it imperative that receivers have sufficient power and a clear enough line of sight to capture them effectively. To put this into perspective, say the researchers, it is comparable to a cell phone trying to receive communication from towers at distances 10 to 100 times further than what’s currently in place.
As a result, real-time access to images from LEO satellites overhead is challenging to obtain. LEO satellite ground receivers are bulky, expensive and sparsely deployed in the world. Despite the exponential increase in LEO small satellites orbiting the planet today – there is a significant time gap between an image capture on such a satellite and users who need it the most in remote and ecologically-sensitive regions.
To address this, the researchers began looking for ways to boost these signals using cheap (under $30), compact, and portable satellite receiver systems.
“Imagine you take a massive antenna and shrink it,” says Carnegie Mellon Electrical and Computer Engineering Associate Professor, Swarun Kumar. “The signal you receive becomes much weaker and noisier, making it difficult to capture anything useful.”
“However,” says Kumar, “using many satellites, we’ve found a way to reinforce those signals, stitching them together to improve the data we receive. Think about your smartphone’s camera in low light or night mode; it takes a lot of pictures, then puts them together to make a brighter, sharper image.”
Using that same idea, the researchers developed a novel handheld antenna device, dubbed the “SelfieStick,” along with back-end software and algorithms to combine a number of very weak transmission signals into something more substantial. To demonstrate the capabilities of this new method, the researchers captured satellite images of planet Earth.
While the data from one satellite produces a noisy and unimpressive result, stitching ten or more photos together creates an image comparable to that of a bulky, expensive weather antenna.
“Under the hood, there is a lot of machine learning and signal processing going on to line the images up correctly,” says Kumar. “The images aren’t canceling one another out, but rather improving each other by eliminating the noise.”
While large “clunky” stationary receivers are still the quickest way to receive crystal clear satellite signals and images, say the researchers, using several smaller receivers can provide a similar result. These more cost-effective receivers also allow operators to use them in various locations, providing a different type of utility.
“One thing that inspired us to pursue this research is the lack of accessibility to infrastructure on the ground,” says Kumar. “There is a lot of commodification and reusability of the satellite infrastructure, but antennas and receivers are heavily monopolized by whoever owns and runs them. “More than anything else, the cost of large receivers is bottlenecked by finding someone to install these extensive setups. We envision the ability to place and use these small receivers anywhere, rather than finding a single location to build a bulky, expensive structure.”
While the earth imaging aspect of the research is a proof of concept of sorts, say the researchers, they believe this method could lead to a better way of harnessing internet and television satellite signals without having large dish receivers installed on the roof of homes. The method, they say, could also result in a better way to transmit cellular signals.
For more, see “SelfieStick: Towards Earth Imaging from a Low-Cost Ground Module Using LEO Satellites.”
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