The 33 years old 10 m radiotélescope located in Parc de la Villette in Paris has delivered its very first radio image from spectral analysis of signals recorded during 24 hours from july 30 to 31, 2019.
The following spectrogram represents minute by minute the radio signals power density received in hydrogen frequency band between 1419,50 and 1421,50 MHz. Every image pixel represents the energy of signal integrated over 60 seconds on a 3906 Hz bandwidth. Time is on vertical axis and frequencies are on horizontal axis. The frequency spectra are computed using a mathematical function called a Fourier transform. While the antenna is immobilized at 90° toward zenith direction due to an elevation motor breakage, the Earth rotation creates a sweep along the sky by an angle of 0.25 degrees per minute. Thus image vertical axis also represents 360 degrees and each pixel 1 degree (angular aperture of the antenna at 3dB).
Read the technical aspects for building the above image from radio signals.
Jean-Jacques Maintoux (radioamateur F1EHN) has computed this calibrated image from the first 24 hours sky survey signals. It shows from 12:00 to 21:00 UTC the transit of galaxy plane over la Villette radiotelescope (galactic coordinates refered to time UTC 1 point per hour). Velocity of galactic parts are converted from frequency according to Doppler effect.
F1EHN provided the following map of the Galaxy composed of spectra from Galactic hydrogen radio signals at different longitudes.
Recently replacing the SDR receiver by a more accurate one helped us to perform more precise capture and analysis of galactic radio signals.