[@aang254] made a custom HRPT decoder and ported HRPT blocks for NOAA, METEOR and MetOp to work with gnuradio 3.8 on Linux. Right now it is the only free and open source decoder for MetOp (that works), and he also thinks about implementing FengYun support. I tested the decoder and it works great.
He's also working on extracting the full data from HRPT, not just the AVHRR/MSU-GS imagery but also all the telemetry and other instrument data.
HRPT is a high resolution weather satellite image signal that is broadcast from the same NOAA satellites that provide the more commonly received low resolution APT images at 137 MHz. HRPT is also broadcast by the FengYun-3, Metop and Meteor satellites. However, HRPT transmits at 1.7 GHz, so a high gain dish antenna with motorized tracking mount (or hand guided tracking), LNA and a high bandwidth SDR like an Airspy is required to receive it.
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.
Back in March we posted about The Thought Emporium’s YouTube video that explained weather satellites and demonstrated that images could be downloaded from them using an SDR like a HackRF or RTL-SDR. Now The Thought Emporium have uploaded part two of the video series, which is a tutorial that shows exactly how to use the free software to receive, demodulate and decode NOAA and Meteor satellites.
The first part of the video shows how to use SDR#, Audacity and WXtoIMG to receive NOAA APT weather images. The second part of the video shows how to use SDR#, Audacity, LRPTrx, LRPTofflinedecoder, SmoothMeteor and LRPT processor to receive Meteor M2 LRPT images.
Receiving Images From Satellites Part 2: Decoding and Demodulating NOAA and METEOR Transmissions
Over on YouTube Adam 9A4QV has uploaded a video showing how to build a DIY bandpass filter for 137 MHz. This can help improve the reception of NOAA and Meteor M weather satellites, by blocking strong out of band signals. Adams design is a 132 MHz – 142 MHz Butterworth bandpass filter which gives about 35 dB attenuation outside of the pass band. He’s also posted a write up documenting the filter design on his website.
Lucas Teske recently went ahead and built the 137 MHz filter suggested by Adam. Lucas didn’t have the correct capacitor values so he ended up cascading several in series. His results showed that the filter did improve his reception significantly.
Over on Reddit user merg_flerg has uploaded an imgur post that carefully details a step by step guide for building a double cross antenna. A double cross antenna is great for reception of satellites like NOAA and Meteor since it has a sky oriented radiation pattern with very few nulls. This means that it can receive satellite signals coming from the sky well. Alternative antennas for NOAA/Meteor include turnstiles and QFH antennas, although the double cross antenna seems to have the least nulls, meaning that the signal is less likely to fade in and out as the satellite moves across the sky.
merg_flerg’s design is also modified from the standard design slightly, allowing it to become easily disassembled and carried within a backpack. At the end of his tutorial he writes that he gets much better reception with his double cross antenna than he does with his QFH.
In the post he demonstrates the final constructed antenna decoding a NOAA APT weather satellite image with an RTL-SDR and the WXtoIMG software. See our tutorial for information on decoding NOAA weather satellite images.
According to various reports the Russian Meteor M-N2 satellite appears to be active again once more. The Meteor M N-2 is a polar orbiting Russian weather satellite that was launched in July 2014. It transmits with the LRPT protocol which allows us to receive weather satellite images with an RTL-SDR that are of a much higher resolution than the NOAA APT satellites.
Unfortunately late last year Meteor M N-2 had some problems and LRPT transmissions were turned off for the time being. During this downtime the Russian space agency switched the LRPT transmitter on the older Meteor M N-1 satellite back on, even though the satellite was tumbling in orbit. Currently people are not reporting any signal from Meteor M N-1, so this may have been turned off, perhaps temporarily.
Now however, it seems that Meteor M N-2 has been switched back on again and various people have already successfully received its signal. If you want to receive these Meteor M N-2 weather images with an RTL-SDR dongle or other SDR then you can view the tutorial written by Happysat here.
The Meteor M N-2 is a polar orbiting Russian weather satellite that was launched in July 2014. It transmits with the LRPT protocol which allows us to receive weather satellite images that are of a much higher resolution than the NOAA APT satellites. For a while since the launch RTL-SDR users had a good time receiving beautiful images from Meteor M-N2, but unfortunately since late last year the N2 LRPT transmitter has been turned off, due to technical problems with the IR sensors as cited by Russian meteorologists.
Fortunately for Meteor N2 enthusiasts the old Meteor M N1 satellite which was thought to be dead sprung back into life around November 2015. Recently Matthew A., a reader of our blog wrote in to let us know that while N2 is still not transmitting, N1 is still transmitting, albeit with somewhat distorted images. Matthew also mentions this link: http://homepage.ntlworld.com/phqfh1/status.htm, which contains up to date info on the status of all weather satellites. He also writes:
While transmissions are readily detectable and decodable at night, it seems that M N-1’s infrared sensors are not functioning. Yielding only black, with the typical noise bars of Red, Green, or Blue
As has been previously mentioned, Meteor MN-1’s stabilization system has obviously failed, and the horizon is clearly visible. Perhaps not of scientific value, but certainly beautiful.