“It pays to keep an open mind, but not so open your brains fall out.”
― Carl Sagan
Receiving NOAA and Meteor M2 APT (Automatic Picture Transmission) Satellite Imagery.
Table of contents
- What Is APT Reception
- How to build a QFH Antenna
- Recommended Guides and groups
- WxtoImg Documentation
- SDR# and WxtoImg Settings
- Building Wide Area Composites with WXtoImg
- Decoding Meteor Satellites
- Other Software options
Automatic Picture Transmission
The Automatic Picture Transmission (APT) system is an analog image transmission system developed for use on weather satellites. It was introduced in the 1960s and over five decades has provided image data to relatively low-cost user stations at locations in most countries of the world. A user station anywhere in the world can receive local data at least twice a day from each satellite as it passes nearly overhead. Currently, I receive from these Polar-Orbiting Satellites, US NOAA 15,18, and 19, and Russian Meteor M-2 and M2-2 (NOTE M2-2 is currently experiencing an anomaly, and is not transmitting on APT frequencies (a possible micrometeorite strike).
I have my system up and running 24/7, and have both Meteor captures and NOAA captures all set to run automatically with the hardware and software listed below. It only takes minimal effort to check the system from time to time. In fact, I control the whole computer system remotely from either my main desktop computer or my smartphone utilizing Google Remote Desktop
For Hardware I am running an older desktop computer, running Windows 10 64bit with a 3.20 GHz processor and 4GB ram with a UPS battery backup, and the following USB RTL-SDR dongles and accessories:
For APT Imagery hardware, I use a Nooelec SmarteeXTR dongle and/or a RTL-SDR Blog V3 dongle. (Note the RTL-SDR Blog site is overflowing with useful information). I also use a Nooelec Sawbird+ LNA for NOAA APT (LNA Low Noise Amplifier, in this case, tuned to 137 Mhz). See my system diagram here.
For an antenna, I have found that this antenna, which is called a QFH (Quadrifilar Helix Antenna) antenna, which you can build yourself with plumbing parts, is suitable and works great. Why such a bizarre-looking construct? Here is a simple explanation- Antennas perform best when they are properly polarized, or the antennas are pointed in the same direction in three-dimensional space. When you have a satellite orbiting the earth, even if the antenna is pointed straight down, its polarization to you on earth will change as it goes from horizon to horizon. The solution is to build an antenna that is properly polarized in all directions, hence the QFH antenna. Since the QFH antenna is stationary, Oribtron sends commands to SDR# and adjusts the frequency of the receiver to adjust for the doppler shift, as the selected satellite whizzes past at about 17,000 MPH (27358 KPH).
How to build a QFH Antenna
I have a build sheet PDF here It originally came from Tinhat Ranch site, and I have modified it with the original author’s permission. I use commonly available RG6 Quad shield cable for the antenna to RTL-SDR.
My QFH Antenna built from the plans above.
I use the Following FREE Software: (all links open in a new tab)
- Orbitron – For tracking satellites as they orbit the earth, and controlling SDR# during the pass. Orbitron software available here: Orbitron
- WxtoImg – For decoding and generating imagery from NOAA APT satellites (All NOAA APT pic start out as B/W, WxtoImg generates the false colors. It is available here: WxtoImg
- MeteorGIS – MeteorGIS is an outstanding free program for georeferencing images transmitted by the Russian weather satellite Meteor MN-2 & MN-2.2 It is available here: MeteorGIS
- Low Rate Picture Decoder for decoding Meteor Imagery It is available here (this is a direct zip download) LRPT Decoder
- SDR# – SDR Sharp, the de facto standard free SDR# software for signal acquisition, analysis, and demodulation. It is available here: SDR# (Note: there are many SDR software out there.)
I also utilize the following plugins necessary to track and demodulate the signals received by SDR#
- Meteor Demodulator Plugin v2.3
- DDE Tracking Client v1.2
- VBCable is a virtual audio device working as a virtual audio cable. All audio signals coming in the CABLE input is transported to the CABLE output. It pipes the audio from SDR# to WxtoImg. It can be downloaded here: VBCable
- Smooth Meteor – for color correcting and rectifying (correcting shape) of Meteor Imagery. It is available here: Smooth Meteor
- LRPT Image Processor – another Meteor image processor It is available here: LRPT Image Processor
- MeteorGIS 2.24 MeteorGIS is a free program for referencing images send by the Russian weather satellite Meteor MN-2 & MN-2.2 More info at bottom of this page as well. MeteorGIS official page
- I also use an image processor to help colorize and add my particular label to generated images, I use Photoshop Elements, but others will work if needed.
So what do these programs do?
Orbitron tracks the satellites, and when the one that is in your parameters appears, it sends a signal to DDE Tracker to start SDR# and runs the commands that you configure within SDR#. If it is a NOAA bird the audio received in the signal is piped via VBcable to WXtoImg where it is converted into an image(s).
If the satellite is Meteor, then the Meteor Demodulator takes the QSPK signal from the Meteor Satellite signal and demodulates it from the signal stream, this is then sent via TCP within your computer to MeteorGIS, which, when there is data to decode, opens up the LRPT (Low Rate Picture Transmission) Decoder which takes the data streamed to it over TCP and line by line builds a picture out of whatever channels the Meteor is sending (and yes it does change from time to time). This Picture is then transferred to MeteorGIS where it combines the channels into several formats depending on your configuration. The GIS part then overlays the ‘picture’ onto a ‘map’ with different data like precipitation, false color, etc. One thing it should generate is a “treated” image which you can then manipulate separately with a program like Smoothmeteor.GUIDES
There are many, many, many helpful guides out there, here are two really great ones. you can find others for Linux, Pi, Mac, and more
- Guide for setting up Weather Decoding Rev 2020 Written by Graham of the Facebook page Weather Satellite Image Group, I HIGHLY recommend following this guide!! WINDOWS/RTL based APT POLAR Weather Satellite station
- NOAA APT Decoding Here is a basic guide to getting started with NOAA APT imagery. Receiving NOAA Satellite Images
- Meteor M2 and M2-2 Decoding Heres is my goto site: Courtesy of HappySat – Guide to Setup Meteor M-N2/N2-2 with LRPT-Decoder and MeteorGis
- MeteorGIS 2.24 Command-Line Options A list of the options within MeteorGIS that can be run from a command line or Batch file. MeteorGIS 2.24 Command Line options.
You may feel slightly or totally OVERWHELMED when trying to set up and dial in your system. Don’t fret, there are some great online groups I would definitely encourage you to join.
- Weather Satellite Imagery Facebook Group – A must join group, it’s the group that helped me get started and they have a mentoring program.
- APT Group on Facebook
- The Amateur Satellite subreddit over on Reddit
Some useful documents and tools for using the WXtoImg Software (compiled from the original WXtoImg site and re-edited).
- Comparison of enhancements
- WXtoImg reference manual in PDF format (includes GUI Interface manual, FAQ, and Required Calibration) (39 pages, 141k)
- WXtoImg command line interface manual in PDF format (32 pages, 217k)
- Example of a RAW audio file from NOAA 15 that WxtoImg can decode. It was taken 1/1/2020 over North America. You can click to listen, or save as to experiment with.
Here are some helpful hints that I have found useful.
- Backup your config and bat files, ESPECIALLY when upgrading software packages to a new or beta version.
I added my WxtoImg, Orbitron, and SDR# to my Windows Startup directory, that way if the system crashes, or reboots, the software will load and continue to run automatically.Synch your PC time frequently, or get some software that will do it automatically.If you look elsewhere on my other sites, such as my Radio Restoration Page you’ll see my radio room is pretty cramped. It’s also on the second floor of my house. I have all my RTL-SDR radios and computers up there. BUT I rarely even go up there. I have found that for me, using Google Remote Desktop is just the ticket. I can run all my computers on the second floor, remotely from my comfortable office and computer on the first floor. I can also run any of them from my Note 9 Smartphone with the Google Remote app!
Sometimes the satellites break or fight each other…
Yes, not everything works all the time, and satellites break, and die. Some times part of the satellite breaks and the other parts keep chugging away (Meteor Mn2-2 Got hit with a micrometeorite knocking APT out completely, and causing major issues with the rest of the systems) Here is a link to check the status of Polar Operational Environmental Satellites (POES) spacecraft status POES Operational Status – POES Status – OSPO.
As for fighting, it kind of is true. Space is big, but not that big, and satellites very frequently overlap each other. Just when you think you’re going to get a nice pass of NOAA 19, Meteor M2 (on the same frequency) can be overhead as well and hijack your signal! Or all four sats might be over your location at the same time (within a few thousand miles of each other). Watch your passes in Orbitron and at least once a month you’ll see some issue of timing and overlap.
My SDR# and WxtoImg Settings
NOTE: These work for me on my system, to capture both NOAA satellites and Meteor Satellites, You may have need of different settings.
|SDR# Settings||WXtoImg Settings|
Sampling Mode – Quadrature Sampling
Device Sampling Rate – 0.90001 MSPS
Decimation – noneRadio – WFM
Bandwidth – 41,000
Order – 500
Correct IQ is checked ✔
I do not use any filters or Noise reduction plugins
Example of Tracking DDE Client plugin Settings for NOAA_18
radio_frequency_Hz<137912500> You would, of course, need to change this for the respective satellite
Example of Tracking DDE Client plugin Settings for Meteor-M_2
start_programm_Path<C:\Meteor\MeteorGIS.bat> NOTE I use a batch file to run MeteorGIS2.24
|There are many options- this is what I have checked:Under Options:|
I have these checked ✔
✔ Disable auto-decode
✔ Crop Telemetry
✔ ResynchSensor Illumination – VIS
Noise Filter – 5×5 Gausian Medium
Despeckle – 2.0
Contrast – Hist Eq
Illumination Compensation – None
Gamma – 1.4
Sharpen – 0.6Under Projection:
✔ NormalUnder Satellite:
✔Autodetect APTUnder Direction:
Building Wide Area Composites with WXtoImg
Thanks to Jeff Kelly (New Jersey, US), Mike Kimzey (Philadelphia, US), David Kunz (San Francisco, US), Cornelius Danielsen (Norway), Alan Hinton (UK), Michael Sørensen (Denmark), and Hans-Juergen Luethje (Germany) who provided the pristine images on their websites to create this wide-area Multi-Spectral Analysis image.WXtoImg has the ability to combine images from multiple ground stations into very wide-area composite images. With images from enough ground stations, it would be possible to produce an image that covered the globe. Pristine images, available on many websites, and raw images can be downloaded and processed by WXtoImg almost identically to locally recorded images. By obtaining pristine or raw images from other WXtoImg sites, it is possible to create composite images that cover a much wider area than a single ground station could cover.
- You’ll need a registered version of WXtoImg, and version 2.10.6 or later to perform this task.
- NOTE: Be sure your TLE’s are current, and your computer time is synched!
- Firstly, in Options -> Projection Options you’ll need to set the following:
- Reference Latitude: in general, should be set to a latitude that is within the north and south boundaries below
- Reference Longitude: this must be set to a longitude within the west and east boundaries below (use something near the middle if in doubt)
- North Boundary (latitude): The northern latitude limit of the projection (use negative numbers for degrees south)
- South Boundary (latitude): The southern latitude limit of the projection (use negative numbers for degrees south)
- West Boundary (longitude): The western longitude limit of the projection (use negative numbers for degrees west)
- East Boundary (longitude): The eastern longitude limit of the projection (use negative numbers for degrees west)
- Scale: Images can get very large, using a scale of about 1.0 will preserve most of the detail, but using a scale of 0.8 or 0.5 or even 0.25 is not unreasonable, alternatively you can set the width of the desired image in pixels (e.g. 1024)
- Select Options -> Save Options. Note that these projection boundaries won’t affect WXtoImg’s production of composite images during autoprocessing.
- Set Projection to Eckert IV or Eckert VI or Mercator. Some projections like Orthographic produce very curved and distorted images when the composite image gets very wide.
- It is a good idea to set Contrast to none or Linear (constant) and Illumination Compensation to Full so that the images will blend together nicely.
- Set Enhancement to whatever you like (except Pristine).
- Now build the wide-area composite image by opening pristine (or raw images) using File -> Open Raw Image. (You can also open your own audio files for this step.) A large image will be created, mostly black.
- Choose File -> Composite image to… and save this. It is preferable to use a PNG extension if you plan to put together more than about 8 images. Using a ..JPG extension is less desirable because JPEG images are lossy and the loss increases each time you add an image.
- Repeat steps 6 and 7, compositing the image to the same file you chose the first time you performed step 7. Note that you will be prompted if you want to replace the image, choose OK, it won’t replace your composite image, just merge the new image into it.
- To view your composite image, select File -> View Image and select the file you created (or look in the Composites tab).
- You can increase the contrast in the final image (you’ll likely want to do this if you selected none for Contrast in step 4), by selecting Histogram to equalize Image from the Image menu (and saving the resulting image.) Alternatively, you could select Increase Contrast from the Image menu several times.
Sites with Pristine images If you are interested in sharing your WXtoImg website, send me the link and I will post it here – email to firstname.lastname@example.org
Pristine images may be downloaded and processed by WXtoImg nearly identically to locally made recordings. Using multiple sites, they can be used to generate wide-area composite images as shown above. To process a pristine image, simply download the full-size image and open using (File -> Open Raw Image) in WXtoImg.
SITES WITH PRISTINE IMAGES
Updated 5-18-2020 (Please note that these sites are operated by individuals and may running be or down, or offline for repairs or upgrades.)
Contact me to have your site included.
Additional Worldwide Satellite Image links updated 5-18-2020
Other Satellite Capture Pages: These currently do not show “Pristine” Images needed for a wide area capture, but are great sites as well.
Sites that have not had ANY updated images within the past year, or have since been deactivated have been removed.
The Meteor-M N2 (Launched on July 8, 2014)and the newly launched Meteor M N2-2 (Launched on July 5, 2019 -Unfortunately Meteor M2-2 suffered a possible collision in orbit on 12/18/2019, and as of this writing looks to be permanently offline for APT ) are polar-orbiting Russian weather satellites. Their main missions are weather forecasting, climate change monitoring, seawater monitoring/forecasting, and space weather analysis/prediction.
Meteor-M N2 and M N2-2 transmit images using the digital LRPT protocol at 137.1 MHz or 137.9MHz (That Frequency can Change!!) and can be received with an RTL-SDR and proper antenna.
Excellent site with instructions for setting up your own Meteor Capture Station http://happysat.nl/Setup_Meteor/Setup.html
Example of one of my Meteor Captures:
Meteor Links of use.
- MeteorGIS.space MeteorGIS is a free program for referencing images sent by the Russian weather satellite Meteor MN-2.
- RadioFouine.net – Downloads
- Setup Meteor M-N2/N2-2 with LRPTDecoder and MeteorGIS
- Meteor M-N2 and N-2-2 Satellite Operational Status
Other Software options
If you made it this far down my page, I am guessing your kind of interested in this…so Here is one more cool thing to try, even if you don’t use any SDR’s or receivers.
I tried some new (to me) open-source software to try out from the Space Science and Engineering Center a the University of Wisconsin-Madison. It’s called McIDAS-V (Man Computer Interactive Data Access System). It has some high-level capabilities, I’ve been using it for a few weeks now, trying out the hundreds of options and modeling of weather you can do.
The software is VERY CPU intensive and graphics card intensive, so DO NOT try and run it if you are running other software like WxtoImg or LRPT or MeteorGIS.
You can do 3D modeling of winds, weather, etc. I have some screen captures of this below, It also allows for animated loops of just about everything you see posted, I just did not copy my loops. Ther is a new version coming out called McIDAS-X -DO NOT download this version, it is not Open Source as of yet, and requires big $$$. My friend at SSEC says that the X version will be available in a year or so. There are three OS versions Windows, Mac and Linux. Read the system requirements to see if your computer can run it. (the 32 bit Java Runtime Environments (JRE) utilize a maximum of 1536 MB RAM, while 64 bit JREs can utilize ALL of the RAM available to the operating system (64 bit OS required).
I was able to import a NOAA 15 and A GOES image into it, but only as an image, there is a way to load up GOES raw data, but I haven’t done that as of yet. For those of you out there that can receive GOES GRB data, there is a slick GOES-R Series Ingestor package as well. I am still experimenting with it, but feel free to try it for yourself.
NOTE: while a lot of data can be had Globally. most if not all of the radar and ground information is U.S.A related. Ther are plenty of open-source software pieces available out there, for Europe and other areas as well.
I am NOT an expert on this. Please read the system requirement and the list of firewall port assignments for data as well! It seemed daunting, but great for experimenting!
The following ports are used to access remote data, and must be open through any firewalls or proxies at your location:
21 – FTP
80 – WWW
112 – ADDE servers (imagery, radar, point, upper air and profiler data)
8080 – THREDDS data servers
Here are some samples of what I did with this software.