Before this update, to automate the reception and decoding of APT and LRPT satellites a Windows PC, and a huge stack of various decoding and tracking programs and SDR# plugins are required, some of which are now even abandonware.
For APT a typical chain was SDR# -> DDETracker -> Orbitron -> WXtoIMG and for LRPT a typical chain is SDR# -> DDETracker -> Orbitron -> LRPT Demodulator -> LRPT Decoder -> SmoothMeteor -> MeteorGIS. Setting this chain of programs up can obviously be a lot of hard work.
The latest version of SatDump adds automation features which means these two entire chains can be replaced with just one program - SatDump. SatDump is available for Windows, Linux and Mac, so it can even run on something like a Raspberry Pi 5 or Orange Pi 5.
Thank you to Carl Reinemann for writing in and sharing with us that the Meteor M2 LRPT decoder by Oleg (Robonuka) was recently updated. The Russian Meteor M2-3 weather satellite was launched in June of this year and is currently the only operational Meteor M2 satellite in the sky. It transmits images at 137 MHz in the digital LRPT format.
To receive it a simple V-Dipole antenna and RTL-SDR is usually sufficient. And to decode it software like SatDump or M2_LRPT_DECODER combined with the Meteor Demodulation Plugin for SDR# can be used. Instructions for the latter are available on HappySats instructional page.
Regarding the update Carl writes:
Thanks to Oleg (Robonuka), Happysat and Usradioguy have been testing the new decoder for about 6 weeks now, and it is ready to go!
The stability of the processing has been improved: The decoder is now more likely to produce stable results, even when there are errors in the input data.
The procedure for generating RGB and calculating GEO in the error-handling block has been improved. Now, the decoder's processing is considered unfinished until the GEO calculation is completed.: This means that the decoder will now wait until the GEO calculation is finished before generating the RGB values. This helps to prevent errors and produce more accurate results.
Exception errors fixed: Some errors that were previously causing the decoder to crash have been fixed.
AutoClose=yes by default: This means that the decoder will now automatically close when it is finished decoding. This can be helpful for saving resources and preventing memory leaks.
80K is much more stable: The decoder is now more stable than before. This means that it is less likely to crash or produce unexpected results.
Overall, these changes make the decoder more reliable and easier to use.
Over on his YouTube channel dereksgc has uploaded the next video in his series on satellite reception. In this video he shows how to build a Yagi antenna tuned for 137 MHz, which is great for receiving NOAA APT and Meteor M2-3 LRPT. Note that a Yagi antenna will give you stronger reception compared to a turnstile, QFH or V-Dipole, but as it is a directional antenna you will need to manually point it towards the satellite as it passes over your location.
For Meteor M2-3 LRPT, a Yagi antenna may be beneficial, as it appears this satellite is having some issues with signal strength, due to a possibly defective antenna that did not fully unfold on the satellite.
The Yagi antenna design is a four element design, with one reflector, two directors and one driven dipole element. The physical construction consists of a piece of wood for the boom, brass welding rods for the elements, and a terminal block for the active dipole element. 3D printed handles are added for easy holding and the RTL-SDR and LNA sit directly on top of the boom.
On his Medium.com blog, Mohsen Tahmasebi has posted an article about his journey into listening to satellites which started with his acquisition of an RTL-SDR Blog V3 dongle. The article begins by explaining his motivations for receiving satellites and how difficult hobbies like this are to get into in his home country of Iran. Despite the challenges he tasted success when he was able to receive NOAA APT signals on his second attempt using the included portable dipole antenna in a V-dipole configuration. Shortly after Mohsen was also able to receive Meteor-M2 LRPT.
Mohsen then built a more permanent V-dipole out of copper rods and optimized his antenna using NEC simulation software, finding that adding a reflector significantly improved reception. He then moved on to building a slightly more complex Turnstile antenna, which yielded even better results and allowed him to explore CubeSats at 435 MHz and contribute to SatNOGS. Finally, Mohsen ordered a Bullseye LNB and using a homemade bias tee, he received the QO-100 amateur radio transponder.
Overall, Mohsen's journey demonstrates that there is a lot of fun and learning available from internationally available satellites even in a country where equipment is hard to come by.
Over on his blog Derek (OK9SGC) has recently uploaded a very comprehensive beginners guide to receiving HRPT weather satellite images. HRPT reception can be a little daunting as it requires a good L-Band dish setup which involves choosing and building a feed, and importantly, a way to track the satellite with the dish as it moves across the sky. Tracking can be achieved manually by hand, but that can be very difficult and so a motorized tracking mount is recommended.
This is unlike the much easier to receive NOAA APT or Meteor LRPT satellite signals in the VHF band which can be received by a V-dipole antenna, or the geostationary GOES HRIT satellites that can be received with a WiFi grid dish and LNA. Both of which do not require tracking.
The advantage of HRPT however, is that you end up with high resolution, close-up, and uncompressed images of the earth. For example Derek notes that NOAA APT gives 4km/px resolution, and Meteor LRPT gives much better 1km/px resolution but it is heavily compressed. Whereas HRPT gives peak resolutions of 1km/px uncompressed. There are also nine satellites in operation sending HRPT, so there are more opportunities to receive.
Derek has created a very comprehensive beginners guide that covers almost everything from purchasing and building the hardware, to finding and tracking the satellites, to setting up the software and decoding images. He notes that an RTL-SDR can be used as the receiver, and that a WiFi dish with GOES SAWBird LNA can work, although the difficult tracking requirements are still there so a smaller offset dish with custom helix feed might be preferred. Derek also provides useful tips, like the fact that the NOAA15 HRPT signal is quite a lot weaker than others.
Thanks to a tweet by @rf_hacking we recently came across an interesting project called "r2cloud". This is an open source program provided on a ready to use image for the Raspberry Pi that can be used to set up an automated satellite recording station for NOAA APT and Meteor LRPT signals, as well as for CubeSats.
The software presents a web based user interface that is easy to setup and view decoded images on. It appears that the software also communicates with a public server that can aggregate and log your data, and also provide it to SatNOGS and provide FunCube satellite telemetry to FunCube Warehouse.
Russian weather satellite Meteor M2 is a popular reception target for RTL-SDR radio enthusiasts, as it allows you to receive high resolution images of the Earth. However, currently it appears to be exhibiting orientation issues, causing off center and skewed images and sometimes poor/no reception. Russian blog "aboutspacejornal", writes that the orientation of the satellite can sometimes be restored presumably by a reset command from Earth, but shortly after goes back into uncontrolled rotation.
These sorts of off-axis images were commonly received from the older decommissioned Meteor-M1 satellite, which woke up from the dead in 2015. The resurrection was speculated to be from the batteries shorting out, allowing power to directly flow from the solar panels while in full sunlight. These days Meteor-M1 is no longer transmitting.
Hopefully Meteor-M2 can be fixed, but if not, Meteor M2-2 is due to be launched on July 5 which should also have an LRPT signal that can be received easily with an RTL-SDR. Hopefully the launch is more successful than the November 2017 launch of Meteor M2-1 which unfortunately was a complete loss as it failed to separate from the rocket.
Over on GitHub dbdexter-dev has released a new lightweight and open source Meteor M2 demodulator. Meteor M2 is a Russian weather satellite that transmits images down in the digital LRPT format. This provides much higher resolution images compared to the NOAA APT signals. With an RTL-SDR, appropriate satellite antenna and decoding software it is possible to receive these images.
This new lightweight demodulator may be especially useful for single board PCs like the Raspberry Pi. Previously, on Linux GNU Radio based demodulators have been used, and GNU Radio isn't exactly a light weight piece of software. To use the software you first need to record an IQ file of the Meteor M2 LRPT signal, downsample the IQ file to 140 kHz (if required), then pass it into the demodulator. This will spit out an 8-bit soft-QPSK file which can be used with LRPTofflinedecoder (now known as M2_LRPT_Decoder) on Windows or meteor_decoder on Linux to generate an image.