Tagged: APT

Using 50 Lines of Python Code to Decode NOAA APT Weather Satellite Images

There are already many image decoders for the NOAA APT weather satellites available, with the most common and feature rich program being the abandoned freeware "WXtoIMG".

However many people may not know how simple the APT digital signal processing code is. Over on his blog post Dmitrii Eliuseev explains how only 50 lines of Python code are required to decode an image from received APT audio. Dmitrii's post shows how a Hilbert transform is used on the APT audio which is essentially the entire decoding step. This is then followed by a for loop that calculates the pixel luminosity from the decoded data, and plots it onto an image file. 

Of course the image is only grayscale (or in Dmitrii's case he decided to use greenscale), but adding false color and various other image enhancements found in advanced software like WXtoIMG are just standard image processing techniques.

Dmitrii concludes with the following:

Interesting to mention, that there are not so many operational radio communication systems in the world, the signal of which can be decoded using 20 lines of code. The NOAA satellites are about 20 years old, and when they finally will retire, the new ones will most likely be digital and format will be much more complex (the new Russian Meteor-M2 satellite is already transmitting digital data at 137 MHz). So those who want to try something simple to decode can be advised to hurry up.

[Also mentioned on Hackaday]

Simple decoding of NOAA APT satellites in Python

FAASGS: A Setup to Build a Fully Automatic Amateur and APT Weather Satellite Ground Station

Over on GitHub stdevPavelmc has released his software called FAASGS (Fully Automatic Amateur Satellite Ground Station). FAASGS is an open source program that allows RTL-SDR users to set up a satellite ground station that tunes, record and generate images for NOAA APT weather satellites, as well as records FM amateur radio satellites. The software runs on a single board computer such as a Raspberry Pi, however in the authors own setup he uses an Orange Pi Prime board. The features include:

  • Web interface to see the next passes, the recorded ones, and details for it.
  • Receive any satellite in FM mode (SSB is possible but no there is doppler control yet, so no SSB by now)
  • Record the satellite pass and keep the audio for later.
    • APT WX audio is preserved in wav format and 22050 hz of sampling (the format wximage needs to work with)
    • FM audio satellites is preserved in .mp3 mode but with high quality settings, and other tricks.
      • The spectrogram of the audio is embedded as album art (see below).
      • The pass data and receiving station are stored in the mp3 tags.
  • Automatic decode APT images from WX sats (NOAA 15, 18 and 19)
  • For the voice FM sats we craft a spectrogram and embedd the metadata of the pass on the image
FAASGS main screen showing recordings
FAASGS screen showing an FM amateur radio satellite pass

Explaining the 9A4QV V-Dipole Design for Receiving 137 MHz Weather Satellites

Back in 2017 we posted about Adam 9A4QV's simple V-Dipole antenna design which works very well for receiving NOAA and Meteor weather satellites at 137 MHz. This type of antenna is a lot easier to build compared to a QFH or turnstile, and it results in good performance if built and set up correctly. Over the years he notes that he's received a number of questions asking to clarify the design and so he's uploaded a YouTube video which explains the built and dimensions of the antenna clearly.

137 MHz WX-SAT original 9A4QV V-dipole antenna

Open Weather: An Artistic Performance Involving Live NOAA APT Signal Decoding for Sound Arts Festival

Just after our post a few days ago about an art project involving weather satellite reception with SDRs, we received a story submission about an artistic performance with similar weather satellite and SDR themes. The submission from Sasha Engelmann reads:

Open Work, Second Body is a live-streamed performance by designer Sophie Dyer (@sophiecdyer) [M6NYX] and geographer Sasha Engelmann (@sashacakes) [M6IOR] in collaboration with the author Daisy Hildyard. The work was performed twice during Reveil 2020, a global sound arts festival streaming sounds from listening points around the planet on the day of the International Dawn Chorus.

Open Work, Second Body asks: From the climate crisis to coronavirus: what are the tools we need to make sense of events unfolding on vastly disparate scales? Through spoken word, field recordings and live radio reception of two NOAA satellite images, the work probes the porous boundaries between our bodies, local atmospheres and weather systems.

Still image capture from livestream of Open Work, Second Body, AM performance, May 2nd 2020

Due to lockdown constraints in London, Sophie and Sasha were not able to be in the same place or to leave their apartments, so they performed the work via simultaneous streams from their respective balconies in South East and North West London. Using RTL-SDRs, Turnstile antennas, Open Broadcast Software and collaborating with two NOAA satellite passes, Sophie and Sasha shared the process of decoding NOAA satellite images with hundreds of viewers around the world, employing spoken word poetry and field recordings to complicate relationships of local and global, weather and climate, the individual and the collective. 

Recordings of the performances can be found at the links below. 

☀️Morning: https://youtu.be/-5JrxwNpJqI [performance starts at 05:25]
?️ Afternoon: https://youtu.be/h88zaCtX8cw [performance starts at 05:00]

Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020
Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020

Open Work, Second Body is part of Sophie and Sasha's larger artistic research and design project Open Weather, which employs ham radio, open data and feminist theories and approaches to build new and diverse communities around satellite image decoding and weather sensing. The Open Weather web platform will be launched in Summer 2020 and will host an archive of SDR-generated weather images, visually rich how-to guides for those with no radio and engineering experience, and material about Sophie and Sasha's collaborative artistic practice. 

For Open Work, Second Body, Sophie and Sasha would like to thank the Soundcamp Team: Grant Smith, Dawn Scarfe, Christine Bramwell, Maria Papadomanolaki and Ciara Drew. They are grateful to Daisy Hildyard for her willingness to be in conversation with them, Bill Liles NQ6Zfor technical advice, Jol Thoms for sound design, Rachel Dedman, Laure Selys and Arjuna Neuman (Radio Earth Hold) for early curatorial input, Akademie Schloss Solitude for the support of a residency, the satellites NOAA 18 and NOAA 19 and the RTL-SDR and wider ham radio community. 



It's very cool to see technical hobbies like ours starting to make an impact in art and reaching a wider audience. More content and images available on Sophie's Open Weather webpage, and Sasha's Open Weather webpage

Open Weather Live Stream

A Few GOES Reception Tips and Info on Receiving EMWIN Data

Thank you to Carl Reinemann for writing in and sharing his website that contains a few tips that he's learned when setting up an RTL-SDR based receiver for GOES 16/17 weather satellite image reception.  As well as the tips, he's uploaded a nice set of images that show his setup, and several of the images he has received.

In addition, he's also noted how the default config files provided by goestools do not download EMWIN (Emergency Managers Weather Information Network) images. EMWIN images are not photos, but rather weather forecast and data visualizations that may be useful for people needing to predict or respond to weather. Over on his Github he's uploaded a modified version of goestools which has config files for EMWIN and other image products that might be of interest to some.

If you're interested, Carl Reinemann also has various bits of information about building APT/Meteor satellite RTL-SDR receivers on his main site too. Of interest in particular is his notes on creating wide area composites of NOAA APT images with WXtoIMG which we have posted about in the past.

Some EMWIN Images Received by Carl Reinmann's GOES receiver.
Examples of some EMWIN Images Received by Carl Reinemann's GOES receiver.

YouTube Tutorial on Receiving Weather Images from NOAA Satellites

Over on YouTube the "Ham Radio Crash Course" channel has uploaded a new video showing how to receive APT images from NOAA weather satellites. There are many tutorials (such as ours here) and videos on this topic already, but more cannot hurt, and this one makes specific reference to how to download the WXtoIMG software now that the official website has been abandoned.

In the tutorial he uses an SDRplay with SDRuno as the receiver software, VBCable as the audio piping software, and WXtoIMG as the decoding software.

How To Receive Images Directly From NOAA Satellites

Creating An Automated Raspberry Pi and RTL-SDR Based NOAA Weather Satellite Station

The nootropicdesign blog has recently uploaded a comprehensive tutorial showing how to create an automated NOAA Weather Satellite ground station using an RTL-SDR V3 and an Raspberry Pi 3. The project also makes use of an Amazon S3 bucket, which is a cheap web storage platform that allows you to store and access the downloaded images.

The tutorial starts by showing you how to set up your Amazon AWS credentials and bucket on the Raspberry Pi, and how to host a simple webpage that can be accessed publicly. The second stage shows how to set up the RTL-SDR drivers and wxtoimg which is used to decode the images. Finally, the third stage shows how to create the automation scripts that automatically schedule a decode, and upload images to the AWS bucket.

Flowgraph for an automated NOAA satellite weather image station.
Flowgraph for an automated NOAA satellite weather image station.

r2Cloud: Software for Automatically Decoding APT/LRPT Weather Satellites and Cubesats on a Raspberry Pi with RTL-SDR

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.

Block Diagram for the r2cloud software.
Block Diagram for the r2cloud software.