Tagged: NOAA

Receiving NOAA Global Area Cover (GAC) Images with LeanHRPT

A few weeks ago we posted about how @ZSztanga and @aang254 were able to record and decode Global Area Cover (GAC) images from polar orbiting NOAA weather satellites. GAC images are low resolution, but they provide an image of the entire orbit. The GAC signal is only transmitted over the USA.

A week earlier than @ZSztanga and @aang254 above decoded GAC, another software called LeanHRPT by @Xerbo also implemented a GAC decoder. LeanHRPT is available on Windows, Linux and MacOS, and ready to download binaries are available on the releases page. You'll need the LeanHRPT demodulator too, in order to initially demodulate the signal.

@Xerbo also notes that @dereksgc has also released a useful Python script for predicting NOAA GAC transmissions. It shows when a particular NOAA satellite will begin and end their GAC transmission, as well as the frequency, polarization and elevation of the satellite. 

GAC Transmission Prediction Tool

Global Area Coverage (GAC) Images Decoded from NOAA Satellites

Thank you to @ZSztanga and @aang254 for submitting news about their recent success at decoding the L-Band Global Area Coverage (GAC) signal from polar orbiting NOAA satellites. GAC images are low resolution, and described by NOAA as follows:

Global Area Coverage (GAC) data set is reduced resolution image data that is processed onboard the satellite taking only one line out of every three and averaging every four of five adjacent samples along the scan line.

While it's low resolution, the interesting thing about this data is that you get an image of the entire orbit, not just the data from your current location as you'd receive with the standard 137 MHz APT or L-Band HRPT signal. The catch is that the signal is usually only transmitted over the USA, and you'll need a motorized or hand tracked L-Band satellite dish setup to receive it.

We note that GAC data is not to be confused with the Direct Sounding Broadcast (DSB) signal decoding software we posted about in 2020. 

@ZSztanga has provided some more information about what images are available and who can receive it, and @aang254's tweet below provides some images and additional information:

With @aang254 we decoded GAC from NOAA satellites. It's basically a dump of reduced resolution data from the whole orbit. It includes all the instruments and is transmitted on L-band along with HRPT (mostly over USA, rarely above Europe and only NOAA-19 dumps outside the US). All the decoders are in SatDump.

There is also a schedule available (https://noaasis.noaa.gov/cemscs/polrschd.txt) that includes all the dumps in the upcoming week. It might be a bit hard to interpret, but basically there is a date and the ground station name (SVL stands for Svalbard and it is the only one receivable in Europe). Entries with "GAC" or "PBK" are referring to the GAC transmission.

We've also seen a tweet by @OK9UWU that shows a much longer image of a full orbit.

Demonstrating the New 3D Maps in SDRAngel

In December of last year we posted about a video demonstrating the many features that the SDRAngel software comes standard with. Recently they've added a new feature which are 3D maps that can be used to visualize signal data.

In the latest video demonstration they show these 3D maps projecting NOAA weather satellite images onto a 3D globe and at the same time tracking the NOAA satellites over the globe as it produces imagery. They also show the software visualizing a 3D model of aircraft on the globe, using live ADS-B data to show aircraft maneuvers when taking off, cruising and landing. With multiple SDRs they also show how the visualization can be combined with air traffic voice. Finally they also show marine vessels being visualized via live AIS data. There appear to be a wide range of vessel 3D models implemented.

SDRAngel Features Overview: ADS-B, APT, DVB-S, DAB+, AIS, VOR, APRS, and many more built-in apps

SDRAngel is a general purpose software defined radio program that is compatible with most SDRs including the RTL-SDR. We've posted about it several times before on the blog, however we did not realize how much progress has occurred with developing various built in plugins and decoders for it.

Thanks to Jon for writing in and sharing with us a demonstration video that the SDRAngel team have released on their YouTube channel. From the video we can see that SDRAngel now comes stock with a whole host of built in decoders and apps for various radio applications making it close to an all-in-one SDR platform. The built in applications include:

  • ADS-B Decoder: Decodes aircraft ADS-B data and plots aircraft positions on a map
  • NOAA APT Decoder: Decodes NOAA weather satellite images (in black and white only)
  • DVB-S: Decodes and plays Digital TV DVB-S and DVB-S2 video
  • AIS: Decodes marine AIS data and plots vessel positions on a map
  • VOR: Decodes VOR aircraft navigational beacons, and plots bearing lines on a map, allowing you to determine your receivers position.
  • DAB+: Decodes and plays DAB digital audio signals
  • Radio Astronomy Hydrogen Line: With an appropriate radio telescope connected to the SDR, integrates and displays the Hydrogen Line FFT with various settings, and a map of the galaxy showing where your dish is pointing. Can also control a dish rotator.
  • Radio Astronomy Solar Observations: Similar to the Hydrogen line app, allows you to make solar measurements.
  • Broadcast FM: Decoding and playback. Includes RDS decoding.
  • Noise Figure Measurements: Together with a noise source you can measure the noise figure of a SDR.
  • Airband Voice: Receive multiple Airband channels simultaneously
  • Graves Radar Tracker: For Europeans, track a satellite and watch for reflections in the spectrum from the French Graves space radar. 
  • Radio Clocks: Receive and decode accurate time from radio clocks such as MSF, DCF77, TDF and WWVB.
  • APRS: Decode APRS data, and plot APRS locations and moving APRS enabled vehicles on a map with speed plot.
  • Pagers: Decode POCSAG pagers
  • APRS/AX.25 Satellite: Decode APRS messages from the ISS and NO-84 satellites, via the built in decoder and satellite tracker.
  • Channel Analyzer: Analyze signals in the frequency and time domains
  • QSO Digital and Analog Voice: Decode digital and analog voice. Digital voice handled by the built in DSD demodulator, and includes DMR, dPMR and D-Star.
  • Beacons: Monitor propagation via amateur radio beacons, and plot them on a map.

We note that the video doesn't show the following additional features such as an analog TV decoder, the SDRAngel "ChirpChat" text mode, a FreeDV decoder and several other features.

LeanHRPT – A set of tools for the manipulation of HRPT data

Over on Reddit u/Xerbot has posted about the release of his new software called "LeanHRPT". When combined with a software defined radio, this software can be used to decode and view HRPT weather satellite images received from satellites such as NOAA, Meteor, MetOp and FengYun. We note that unlike APT and LRPT weather satellite signals which transmit in the VHF bands, HRPT signals are generally at ~1.70 GHz and require a motorized or hand tracked satellite dish to receive. u/Xerbot writes:

LeanHRPT is a flexible, easy to use and powerful set of tools for the manipulation of HRPT data (maybe I could be convinced to add LRPT support).

When used properly LeanHRPT Decode can generate (almost) L1B data usable in actual land/weather observation, or just pretty images :)

You can get it here: https://github.com/Xerbo/LeanHRPT-Decode

The LeanHRPT project also contains LeanHRPT Demod, as you probably guessed, a HRPT demodulator. It features an incredibly high sensitivity as well as being able to do both realtime (through SoapySDR) and offline demodulation (baseband).

You can get it here: https://github.com/Xerbo/LeanHRPT-Demod

LeanHRPT Applying a map overlay on FengYun

Decoding NOAA on an Debian Chrooted Android Smartphone

Over on Reddit Ian Grody (u/DutchOfBurdock) has posted about his success in using a modded Android smartphone to run an RTL-SDR Blog V3 and NOAA decoder software all within the phone itself.

In the past we posted about Ian's work in getting rtl_power scans to work in conjunction with the Tasker app, in order to generate automated frequency scans on his phone on the go. His more recent work from the past year includes showing us how it's possible to install Debian chroot on an Android phone, and run Linux software like GQRX, GNU Radio, DSD, rtl_433, multimon-ng and dump1090 directly on the phone with an RTL-SDR.

His latest Reddit post shows that the NOAA-APT decoder also runs well on the Debian chroot, leading to a truly portable NOAA decoding setup. He notes that he is now working on the possibility of Meteor M2 decoding on the phone.

Below is his video from last year demonstrating SDR GQRX and GNU Radio running on the Debain chrooted phone.

GQRX, GNU Radio, Rooted Android

Building an Automated NOAA and Meteor Weather Satellite Image Collector with RTL-SDR

Over on his YouTube channel saveitforparts has uploaded a video showing how he has built an automated weather satellite image collector for the NOAA APT and Meteor M2 LRPT satellites. The video shows a time lapse of him building a QFH antenna, and how he's mounted a Raspberry Pi and RTL-SDR inside a waterproof enclosure attached to the antenna mast. He goes on to show how he's automating the system with the Raspberry-NOAA V2 software

Automated Home Weather Station (Satellite Image Collector)

Raspberry-NOAA V2: Raspberry Pi Automated NOAA and Meteor Weather Satellite Capture

Raspberry-NOAA is open source code and a set of scripts that allows you to set up a Raspberry Pi as an automated NOAA and Meteor weather satellite station with an SDR like an RTL-SDR. The software makes use of the Raspberry Pi version of WXtoIMG and meteor_decoder for decoding the satellites, a program called predict for predicting satellite passes, and various automatically generated cron scripts to schedule recording and processing.

Recently V2 has been released by Justin Karimi who builds on the work of the original creators. It seems that the webpanel has been upgraded and made mobile friendly, as well as many more enhancements that can be seen on the Release page notes.

Raspberry-NOAA V2 Web Panel