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. 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 0.25 degrees. The 10 m antenna aperture angle is close to 1 degree at 1420 MHz. Consequently four successive vertical pixels translate globaly signals from the same sky direction during four minutes.
Read the technical aspects for building the above image from radio signals.
Jean-Jacques Maintoux (radioamateur F1EHN) has computed this better 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 figures in order to explain our observations.
Galactic plane corresponds to galactic Latitude = 0°
Thus for a galactic longitude close to 90° around 00:30 and 155° around 08:00 UTC
Those values are reported on galactic plane computed in Orsay (dotted ellipses)