Thank you to Florent for submitting his website which contains a live log of his meteor scatter observations. Meteor scatter occurs when radio signals reflect off the ionized trail left behind by meteors when they enter the atmosphere. This trail is highly RF reflective, so it can allow distant radio stations to be briefly received.
His set up consists of an RTL-SDR dongle running on a Raspberry Pi 3. His antenna is a homemade 6 element Yagi. Florent is based in France and listens for reflections from the Graves radar at 143.05 MHz. His software captures 768 Hz worth of bandwidth every 0.5s, and then uploads and displays the spectrum plot on his website. When the Graves radar signal is visible on the spectrum, it is an indication of a meteor having entered the atmosphere (or possibly an aircraft).
If you are interested in other peoples live meteor scatter streams, then there is another site at livemeteors.com which displays a live video of an SDR# screen looking for meteor echoes.
Some Meteor Scatter Logs displayed on Florents website
Thanks to "gmbertani" for letting us know about his recently released RTL-SDR compatible software called "Echoes". Echoes is a Windows, Linux and Raspberry Pi/Arch compatible tool that can be used together with an RTL-SDR and appropriate antenna to monitor for meteor scatter detections.
Meteor scatter works by receiving a distant but powerful transmitter via signal reflections off the trails of ionized air that meteors leave behind when they enter the atmosphere. Normally the transmitter would be too far away to receive, but if its able to bounce off the ionized trail in the sky it can reach far over the horizon to your receiver. Typically powerful broadcast FM radio stations, analog TV, and radar signals at around 140 MHz are used. By listening to these signal blips it can be possible to estimate the number of meteors falling.
Below we paste the official description and feature list of Echoes, and at the end is a video demonstrating Echoes in action:
Echoes it's a radio spectral analysis software for RTL-SDR devices, designed for meteor scattering purposes.
Echoes doesn't demodulate neither decode any human-made signal. Its main goal is to analyze and record the total power of natural signals and generate screenshots and tabular data (CSV, GNUplot) output in presence of particular peaks in a selected narrow range of frequencies. Since there is no demodulation, there is no provision for audio listening, except for a notify sound when an event has been recorded.
Features
Captures waterfall spectra as PNG screenshots and statistics data files.
Optionally generates GNUplot data files
Multiple instances can manage separate dongles plugged in the same computer
Three operating modes: continuos (records data only), periodic (captures data and screenshot every X seconds) and automatic (record data and screeshot each time a customizable (S-N) treshold is exceeded)
HTML report production
Installers ready for Windows7++ and RPMs / SRPMs for Linux
xz binary package for Raspberry PI / Arch distro
It can run headless, recording GNUplot and statistic data only
Over on our forums Andy (M0CYP) has posted about his new meteor scatter detection program which works with HDSDR and any supported SDR like an RTL-SDR. It works in an interesting way, as instead of analyzing sound files for blips of meteor scatter activity it analyzes screenshots of the HDSDR waterfall. The software automatically grabs the screenshots and determines if a signal is present on any given frequency. You can set a preconfigured detection frequency for a far away transmitter, and if the waterfall shows a reflection it will record that as a meteor.
Meteor scatter works by receiving a distant but powerful transmitter via reflections off the trails of ionized air that meteors leave behind when they enter the atmosphere. Normally the transmitter would be too far away to receive, but if its able to bounce off the ionized trail in the sky it can reach far over the horizon to your receiver. Typically powerful broadcast FM radio stations, analog TV, and radar signals at around 140 MHz are used. Some amateur radio enthusiasts also use this phenomena as a long range VHF communications tool with their own transmitted signals. See the website www.livemeteors.com for a livestream of a permanently set up RTL-SDR meteor detector (although that site does not use Andy’s software).
Andy writes that his meteor scatter detection software is still in beta so there might be some bugs. You can write feedback on the forum post, in the comments here, or contact Andy directly via the link on his website.
Over on his blog Dave Venne has been documenting his attempts at using National Weather Service (NWS) broadcasts for forward scatter meteor detection with an RTL-SDR. Forward scatter meteor detection is a passive method for detecting meteors as they enter the atmosphere. When a meteor enters the atmosphere it leaves behind a trail of highly RF reflective ionized air. This ionized air can reflect far away signals from strong transmitters directly into your receiving antenna, thus detecting a meteor.
Typically signals from analog TV and broadcast FM stations are preferred as they are near the optimal frequency for reflection of the ionized trails. However, Dave lives in an area where the broadcast FM spectrum is completely saturated with signals, leaving no empty frequencies to detect meteors. Instead Dave decided to try and use NWS signals at 160 MHz. In the USA there are seven frequencies for NWS and they are physically spaced out so that normally only one transmitter can be heard. Thus tuning to a far away station should produce nothing but static unless a meteor is reflecting its signal. Dave however does note that the 160 MHz frequency is less than optimal for detection and you can expect about 14 dB less reflected signal from meteors.
So far Dave has been able to detect several ‘blips’ with his cross-dipole antenna, RTL-SDR and SDR#. He also uses the Chronolapse freeware software to perform timelapse screenshots of the SDR# waterfall, so that the waterfall can be reviewed later. Unfortunately, most of the blips appear to have been aircraft as they seem to coincide with local air activity, and exhibit a Doppler shift characteristic that is typical of aircraft. He notes that the idea may still work for others who do not live near an airport.
A possible meteor detection in SDR#.Aircraft detection doppler
We note that if you are interested in detecting aircraft via passive forward scatter and their Doppler patterns, then this previous post on just that may interest you.
Thanks to Wolfgang Kaufmann for submitting news about his new software called ‘Meteor Logger’. This tool can be used to count the number of meteors entering the atmosphere which have been detected by a meteor scatter setup using an RTL-SDR or similar SDR.
Wolfgang writes about his software:
I have developed a new piece of software “Meteor Logger” to detect and log radio meteors from the digital audio stream of a PC-soundcard. It is based on Python 3. It is addressed to those meteor enthusiasts who want get the most information out of forward scattering of radio waves off meteor trails. “Meteor Logger” do not display spectrograms, it delivers an instantaneous and continuous numerical output of the detected signal with a high time resolution of about 11 ms. Thereby a radio meteor signal is not detected on the basis of an amplitude threshold but on its signature in the frequency domain. “Meteor Logger” has a built in auto notch function that may be helpful in case of a persistent strong interference line. From these data not only hourly count rates can be derived but it is also possible to easily study power profiles of meteors as well as Doppler shifts of head echoes.
As receiving front end a RTL-SDR is fine, if you strive after a very high signal resolution you may use a Funcube Dongle Pro. I employed SDR# to run the RTL-SDR. GRAVES-radar is used as transmitter. The added screenshot shows this setup together with “Meteor Logger”.
Additionally I wrote an also Python 3 based post processing software “Process Data” that allows for clearing the raw data, viewing and analysing them and exporting them in different ways (e.g. as RMOB-file for opening with “Cologramme Lab” of Pierre Terrier, see added screenshot).
Meteor scatter works by receiving a distant but powerful transmitter via reflections off the trails of ionized air that meteors leave behind when they enter the atmosphere. Normally the transmitter would be too far away to receive, but if its able to bounce off the ionized trail in the sky it can reach far over the horizon to your receiver. Typically powerful broadcast FM radio stations, analog TV, and radar signals at around 140 MHz are used. Some amateur radio enthusiasts also use this phenomena as a long range VHF communications tool with their own transmitted signals. See the website www.livemeteors.com for a livestream of a permanently set up RTL-SDR meteor detector.
The annual Perseids meteor shower is peaking right now (this Wednesday and Thursday), and with the right equipment (and location) you can detect these meteors with an RTL-SDR dongle and appropriate antenna. When a meteor enters the atmosphere it leaves behind a brief trail of ionized air which is highly reflective to RF signals. These trails can reflect carrier waves from distant transmitters towards your antenna, allowing you to detect a meteor entering the atmosphere. This is called meteor scatter.
If you live in Europe, you can use the powerful Graves radar at 143.050 MHz as the transmitter. In other locations and the USA you can also use analogue TV broadcasts like in this post where the observer uses a TV tower in Canada. For Graves all you’ll need is a dipole antenna and perhaps LNA, but for TV transmissions you may need a directional Yagi antenna. More information can be found in our previous posts about meteor scatter and is this document.
At the recent 2015 Society of Amateur Radio Astronomers (SARA) Conference Ciprian Sufitchi (N2YO) presented a paper titled “Detecting meteor radio echoes using the RTL/SDR USB dongle” (pdf). His paper introduces the RTL-SDR, the theory behind forward scatter meteor detection as well as the practical application of the RTL-SDR to meteor detection. Ciprian summarizes meteor scatter as the following:
When a meteor enters the Earth’s upper atmosphere it excites the air molecules, producing a streak of light and leaving a trail of ionization (an elongated paraboloid) behind it tens of kilometers long. This ionized trail may persist for less than 1 second up to several minutes, occasionally. Occurring at heights of about 85 to 105 km (50-65 miles), this trail is capable of reflecting radio waves from transmitters located on the ground, similar to light reflecting from a mirrored surface. Meteor radio wave reflections are also called meteor echoes, or pings.
In the paper he explains how analog TV transmissions are the best for meteor scatter, but unfortunately these been discontinued within the USA. Instead he has been able to use analog TV transmitters from Canada, who still transmit this type of signal. He shows that about half of the USA could use the transmitter he is using for meteor scatter, which is based in Ontario, Canada.
Ciprian is also running a very cool live meteor detection stream on his website at livemeteors.com. His setup is located in the DC Metropolitan area and uses a directional Yagi antenna pointed at the Canadian analog TV tower which is broadcasting at 55.237 MHz. The receiver is an RTL-SDR dongle coupled with SDR# and the ARGO software.
The idea was to analyze the Doppler from the head echoes and and see if something useful can be extracted from them.
We detected a meteor from two distant locations and measured Doppler and Doppler slope at those locations. The we tried to find solutions to the meteor equation by brute force until we obtain a big number of them. Then we plotted those solutions in the sky and we see some of them pass near a known active radiant at the time of observation. Then, we checked the velocity of those solutions near the known radiant and found they are quite similar to the velocity of the known radiant, so we concluded probably they come from that radiant.
But they can come from everywhere else in the sky along the solution lines! There is not guarantee these meteors to be Geminids, although probabilities are high. Once all the possible radiants of a meteor are plotted into the sky, there is no way to know who of all them was the real one. Doppler only measurement from two different places is not enough to determine a meteor radiant. But don’t forget with some meteors, suspect to come from a known shower, the possible results includes the right radiant at the known meteor velocity for that radiant, so there seems to be some solid base fundamentals in this experiment.
Initially they ran into a little trouble with their sound cards, as it turns out that sound cards don’t exactly sample at their exact specified sample rate. After properly resampling their sound files they were able to create a stereo wav file (one receiver on the left channel, one receiver on the right channel) which showed that the doppler signature was different in each location. The video below shows this wav file.
Double station meteor head echoes
Using the information from their two separate recordings, they were able to do some doppler math, and determine a set of possible locations for the radiant of the meteors (it was not possible to pinpoint the exact location due to there being no inverse to the doppler equation). The radiant of a meteor shower is the point in the sky at which the meteors appear to be originating from. Although their solution couldn’t exactly pinpoint the location, some of the possible solutions from most meteors passed through the known radiant of the Geminids meteor shower. With more measurement locations the exact location could be pinpointed more accurately.
Possible solutions for the radiant of several meteors detected during the Geminids meteor shower.
