Tagged: meteor scatter

Meteor Logger: A Tool for Counting Meteor Detections with an RTL-SDR

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).

Everything else you may find on my website http://www.ars-electromagnetica.de/robs/download.html

Meteor Logger
Meteor Logger

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.

Using National Weather Service Stations for Forward Scatter Meteor Detection

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#.
A possible meteor detection in SDR#.
Aircraft detection doppler
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.

A Screenshot based Meteor Scatter Detector for HDSDR

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.

Andy's screenshot based meteor detection software
Andy’s screenshot based meteor detection software

Helping to Raise Funds for the Canadian Centre for Experimental Radio Astronomy (CCERA)

Patchvonbraun (aka Marcus Leech) is one of the pioneers in using low cost SDR dongles for amateur radio astronomy experiments. In the past he’s shown us how to receive things like the hydrogen line,  detect meteors and observe solar transits using an RTL-SDR. He’s also given a good overview and introduction to amateur radio astronomy in this slide show.

Now Marcus and others are starting up a new project called the “Canadian Centre for Experimental Radio Astronomy (CCERA)”. They write that this will be an amateur radio astronomy research facility that will produce open source software and hardware designs for small scale amateur radio astronomers. Currently they also already have a hydrogen line telescope set up, which is producing live graphs and data. From their recent posts it also looks like they’re working on building antennas for pulsar detection. They also have a GitHub available for any software they produce at https://github.com/ccera-astro.

Currently CCERA is looking for donations over at gofundme, and they are hoping to eventually raise $25k. They write:

About CCERA:

Radio astronomy is one of the most important ways to observe the cosmos. It is how we learned about the existence of the afterglow of the big bang (the cosmic microwave background), it is how we observe huge swaths of the universe that are otherwise obscured by dust. Most of what’s going on out there can’t be seen with visible light.

Astronomy has traditionally been one of the areas in science where dedicated non-professionals have continued to make an enormous contribution to the field. Optical astronomy requires little more than a telescope and knowledge.

Radio astronomy has, up until recently, required a lot more skill and resources. However, technology has advanced enough that small groups could be making serious contributions to radio astronomy. With the right sorts of software and information, many dedicated non-professionals could be doing good work in the area, and CCERA intends to help make that a reality.

CCERA will be producing open source software and hardware designs to help non-professional and professional radio astronomers alike, documenting them, and helping people get up to speed so that they can use these powerful tools themselves. Our GitHub repository is: https://github.com/ccera-astro

CCERA will also be operating its own radio astronomy facilities, initially in Ontario, Canada. These will serve as a test-bed for our own designs, as a place for us to train interested people in the operation of low cost radio astronomy equipment, and will also be used for real radio astronomy work. All our data will be publically-available.

About us:

Roughly 10 years ago, I and a number of others started a project to restore a large, historic, satellite earth station antenna at Shirleys Bay in Ottawa. Our goal was to bring the dish back on-line for use in amateur radio astronomy, research, and importantly, educational outreach about science, and radio astronomy.

The project came to a sudden end back in 2013/14 when the owner of the dish (The Canadian Space Agency) needed to dismantle it to make way for other occupants of the site.

However, during that period, we became fascinated with the possibilities that opening up radio astronomy to skilled non-professionals could bring.

Since then, our group has been working on another far lower cost project to build our own a specialized radio telescope somewhere in the Rideau Valley area. Many of our group live in the area, and Marcus lives in Smiths Falls. With good attention to the usability of our designs and open publication of our tools under appropriate open source licenses, our work should be replicable by others. We thus hope to kick off a new era in non-professional radio astronomy.

What we need the money for:

We’ve secured a small office in the Gallipeau Center outside of Smiths Falls, and will be able to erect our specialized antenna arrays over the coming year.

While we have a lot of the equipment we’ll need, we’ll have more equipment to buy, and on-going expenses to cover, including rent, insurance, miscellaneous mechanical construction materials (lumber, metal, etc). We also need to cover expenses relating to incorporation as a not-for-profit.

Our goal is to provide a test facility for small-scale radio astronomy research, and to develop techniques that allow small organizations and educational institutions to run their own small-scale radio astronomy observing programs.

If we are successful, in addition to making our designs and software available under open source licenses, we’ll be holding regular public lectures, host training seminars, host school groups, etc. We will also produce videos of our work for those who cannot visit us directly in Ottawa. We want to make some of the techniques of “big science” accessible and understandable.

We can’t do it without the help of the public, who, we hope, will become our students, collaborators, and ongoing supporters.

We will also make all of our data available to the public without fee or restrictions. We believe in openness in scientific endeavours, even small ones such as ours.

Marcus Leech
(tentative) Director
Canadian Centre for Experimental Radio Astronomy

If you have even a passing interest in radio astronomy please consider donating, as CCERA’s work may open up exciting new possibilities for amateur radio astronomers with low cost SDR dongles.

The pulsar antenna being built at CCERA.
The pulsar antenna being built at CCERA.

Live: Perseids Meteor Shower with RTL-SDR

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.

But for now if you just want to observe others then currently there is this temporary live stream (now offline) shown below from Poland on YouTube and this always running live stream from the USA.

Equpment used by Reddit user Maxworm to detect Perseids meteors using the Graves radar: Dipole, LNA, Bias-Tee RTL-SDR.
Equipment used by Reddit user Maxworm to detect Perseids meteors using the Graves radar: Dipole, LNA, Bias-Tee and RTL-SDR.
Meteor detected by MaxWorm.
Meteor detected by MaxWorm

Detecting meteor radio echoes using the RTL-SDR USB dongle

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.

Live meteor detection stream from livemeteors.com
Live meteor detection stream from livemeteors.com

Determining the Radiant of Meteors using the Graves Radar

With an RTL-SDR or other radio it is possible to record the echoes of the 143.050 MHz Graves radar bouncing off the ionized trails of meteors. This is called meteor scatter and it is usually used to count the number of meteors entering the atmosphere. Amateur radio astronomers EA4EOZ and EB3FRN decided to take this idea further and synchronised their separate receivers and recordings with a PPS GPS signal in order to determine the radiant of the meteors they detected. They write:

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.

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 the Geminids meteor shower.
Possible solutions for the radiant of several meteors detected during the Geminids meteor shower.

Techniques for using the RTL Dongle for Detecting Meteors

Back in 2013 we posted about a Dr. David Morgan who had written a tutorial paper discussing how he used the Funcube Dongle Pro+ for radio astronomy. Recently Dr Morgan has also written another paper showing how to use the RTL-SDR together with the Spectrum Lab software to detect meteors.

A software defined radio can be used to detect and count meteors entering the earth’s atmosphere by detecting strong radio waves reflected by ionized trails left by the meteor. If you are unfamiliar with how to detect meteors using radio waves, you should consult Dr Morgans older papers called Detection of Meteors by RADARMeteor Radar SDR Receiver (Funcube Dongle), and Antennas for Meteor Scatter. The tutorial shows how to set up SDR# and Spectrum Lab to work together to detect meteors using the Graves Radar in France at 143.050 MHz.

Meteor Scatter Detection in Spectrum Lab
Meteor Scatter Detection in Spectrum Lab