The transmitter power of ICE is 5 watts. To put this into context, a GSM mobile phone transmits with 2 watts maximum. The problem now is the incredible distance these 5 watts need to travel, which currently (as of March 2014) is about 40 million km. This is a bit less than a third of the distance of the Earth to the Sun. Even at the speed of light, any radio signal from ICE takes 3 minutes to reach us.

Such a low transmitter power coupled with these distances require large antennas in order to concentrate the signal into the receiver. Think about a magnifying glass concentrating sunlight until it is powerful enough to light a matchstick. Our "magnifying glass" is such a concentrator, and it is a Junkyard treasure. The Bochum Observatory was built in the early 1960s and used for barely more than a decade. It was an industrial monument for close to 30 years until it was brought back into service by radio amateurs some 10 years ago. With its diameter of 20 meters, it is one of the largest radio telescopes worldwide that is under full-time control by radio amateurs. The surface for collection of radio waves is still fine today. The actual receivers were replaced with 21st-century cutting-edge hardware, which is performing very close to the limits of physics.

The mighty collection power of such a large telescope comes at a price: a very narrow field of view. Think about a spotting scope, which is very good at watching things at a distance, but searching an area with it is a very time-consuming task. Our telescope has a field of view that is about the apparent size of the moon. Finding ICE without prior knowledge of its approximate position in the sky would be hopeless. Fortunately, Jeremy Bauman from KinetX Aerospace was kind enough to provide us with a trajectory estimation based on the last tracking data from NASA, which dated back to 2008. We then knew where to look in the sky and thanks to documents on the internet, we also knew which frequency we had to tune in (similar to finding a particular radio station in your car).

March 1, 2014: Once all the hardware was wired together and the telescope repositioned to the estimated position, the data recording took place and modern digital signal processing could work its magic. This sounds very sophisticated but essentially is very similar to a PC soundcard and an algorithm called Fast Fourier Transformation (FFT). A particular way of presenting a long duration FFT analysis is the waterfall display, where the signal value of an FFT graph is coded with a color and displayed as a single line. If your setup now is producing one FFT analysis per second and your software is stacking these lines on top of each other as they are generated, the appearance of such a display is similar to a (very slow) waterfall, hence the name: waterfall display. The horizontal axis represents the frequency of a signal, and the vertical axis the received time (higher up is later).

So this is what we got out of 15 minutes of data: