Receiving and Decoding Weather Satellites

Have you ever though about predicting your own weather?

Weather forecasters today rely on a number of orbiting satellites, among many other things, to predict the weather. A number of times a day NOAA and meteor satellites pass over your head scanning the earth with varying different sensors.

These sensors allow clouds, rain & temperature to be recorded and transmitted back down to the ground.

The signals are transmitted in a number of different formats and on Number of different frequencies.

Hardware

Today we will be focusing on the APT (Automatic Picture Transmission) & LRPT (low-rate picture transmission) formats which are transmitted in the 137MHz region.

For receiving and decoding these signal you will need a few pieces of hardware:

  1. Windows PC (RPi versions are available but not covered here)
  2. SDR Dongle / Receiver. I use a RTL-SDR Blog Dongle V3.
  3. Antenna tuned for 137MHz. (144MHz / 2m Amateur radio antenna can be used but not as good)
  4. Low-Noise Amplifier (LNA) (Optional)
  5. Band Pass Filter for 137MHz (Optional)

Software

NOAA satellites can be decoded using software called WXtoIMG. The Meteor satellites can be decoded using a software package called MeteorGIS Suite. The Meteor GIS Suite comes complete with a version of SDR# which is required to connect with your SDR Receiver and receive the transmitted signals.

You will then require some software to feed the audio from SDR# into WXtoIMG. I use VB-Audio Cable but other options are available.

Finally you need some software to tell you when each satellite is passing over. To do this I use software called Orbitron. By loading the weather TLE’s and selecting the 4 satellites below it will show you there current location.

For starting out you can manually track the frequency as it passes overhead. Below are the transmit frequencies of each satellite.

SatelliteFrequency
NOAA-15137.62MHz (APT)
NOAA-18137.9125MHz (APT)
NOAA-19137.1MHz (APT)
MeteorM2137.1MHz (LRPT)
MeteorM2-1Lost on Launch
MeteorM2-2137MHz LRPT Disabled due to micrometeoroid impact
MeteorM2-3Scheduled launch in 2022 (LRPT)

As the satellite passes overhead the frequency will change slightly because the satellites are moving at such high speed. This is called doppler shift and is explained more on my page about working amateur radio satellites.

Optionally, you can also install MyDDE. This, in combination with Orbitron will control the frequency of SDR# automatically.

Once you get everything installed open SDR#. On the left hand side set the audio output to the VB-Audio cable input and click the play button to start receiving signals. Open up orbitron and find the next satellite to pass over your location and set SDR# to the correct frequency as in the table above.

METEOR

For the meteor satellites METEOR GIS should automatically launch when the satellite come above the horizon and the image should appear on the screen as it passes. The processed images should appear in the FinalImages folder in your MetoerGIS software.

Using MetworGIS_Configurator.exe you can configure additional settings such as the text overlay and country outlines ect… remember to save your changes and they will be applied the next time an image is processed.

NOAA

For NOAA satellites you will need to manually launch WXtoIMG. In Options->Recording Options you will need to set VB-Audio Cable Output as the sound card. Above you will need to also set it to record only when active APT satellites are overhead there are additional options here which can fine tune the timings to achieve better images.

Options->Active APT satellites tells the software which satellites you will be receiving.

Finally you will need to set your ground station location in Options->Ground station Location.

Now, so long as you set the correct frequency in SDR#, WXtoIMG should start decoding the received signal and the image should slowly appear on the screen. Once the pass has finished you should be able to experiment with the enhancements to view a variety of different images created from the RAW decoded image.

You can also experiment with the projections which reshape the images to match the view you would get on different maps.

Once you get proficient with working WXtoIMG you can set the Options->Auto Processing Options settings to automatically process and save a the decoded image in any number of enhancements and projections. You have a choice between single images, Movie’s, Composite images (combine mutiple passes of different satellites into a larger image) and adding the images to a webpage to display on a website. All these settings and many more are detailed in the manual available below.

You can see the images decoded by my setup here.