ALTHOUGH this image is published on a 1st of April, it is NOT a joke at all! ;-)

What you see here is a RADAR echo from a French RADAR facility named GRAVES caused by a fat meteorite entering earth's atmosphere and creating a huge plasma trail, scattering back the signal we see here.

GRAVES is a groundbased RADAR station sending RF-pulses into the sky at a frequency of 143.050 MHz. Using an antenna pointing towards an area where we would expect the RADAR signals hitting something passing over it (e.g. satellites - StarLink is often seen and disturbing observation, meteorites, atmospheric ionizing, planes, etc...). My own receiver is offline for a new setup but I had the WebSDR running which is available on the internet. It is a multi-band amateur radio-astronomy facility in the Netherlands which has a receiver running for GRAVES and is streaming its signal to the web.

This type of view is called "waterfall diagram". The flow direction is from bottom to top, though.

The Y-axis displays the elapsing time while the X-axis is showing the frequency. Thus, a stationary object (e.g. spaceship Enterprise parking above the radar) will cause a vertical line on the display. The same as the ionosphere of our own atmosphere. So, not any vertical line is an alien spaceship ;-)

As soon as the object moves relative to the radar sender, the received frequency scattered back off the object will differ from the emitted frequency. We all know this as Doppler-effect. So, as soon as the object moves it will cause the reflexion to shift, which is known as Doppler-shift.

This signal shown here is the scattered-back radar signal caused by the meteorite's trail which consists of ionized particles ablated from the meteorite. It is widely spread because the material is moving. With a little practice it is possible to destinguish satellites from airplanes from atmospheric effects from meteorites and - least not least - from the "Enterprise". This signal is strong enough to have eventually originated from a serious meteorite which might have been visible by naked eye during day time.

Maybe you'll find this interesting ;-)