A few weeks ago the second TUDelft satellite (Delfi-n3Xt) was successfully launched into an orbit around Earth. In space, yes! This satellite was designed and built by students of my university. However, their other 5-year-old satellite (Delfi-C3) is still flying and communicating its data towards Earth. A student, a colleague and I are using this old satellite to test our idea for a new satellite-orbit determination-project. I always like to call it: "Listening to the sound of satellites" (see previous posts).
During the launch event I was thinking that it would be cool to capture both satellites' transmission in one observation using the VHF antennas. So I ask the ground station operator (the student), if this was possible. After a few days he send me this figure:
He found a day that both satellites were visible from the TUDelft ground station. The red line is the orbit track of the Delfi-n3Xt (new one). The green cross is the location of the TUDelft ground station and its visibility area shown with the dotted yellow line. Delfi-C3 (old one) can be seen in between the red lines, shown here as green dots. Both satellites were in view of the ground station that day, which meant that they both could be recorded at the same time.
There is, however, a small theoretical problem. Both satellites use a transmitting frequency of 145.870 MHz, so they would be plotted on top of each other in a frequency plot. Still, I asked to record both satellite's signal and this is what it looked like in frequency domain:
(Click on the figure to get an even better view.) Here both TUDelft-built satellites are observed by recording their transmitting signal and performing a Fourier transformation. Both satellites shown the characteristic S-shape due to the Doppler effect (see previous posts). The left and slightly smaller signal is the Delfi-C3, which was less powerful than the newly launched Delfi-n3Xt, shown here on the right. It can also be seen that the carrier frequency of both satellites is not the designed 145.870 MHz, because they do not overlap each other (and the vertical green line in the middle represents 145.870 MHz).
I can't stop watching this figure, because it shows student engineering at its best. Two TUDelft tandem-flying satellites in space. Next time, think again, when you want to say that students aren't capable!