Search results for: EMWIN

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.

Decoding EMWIN Weather Information VHF Rebroadcasts with an RTL-SDR

EMWIN is an acronym for Emergency Managers Weather Information Network, and is a service for emergency managers that provides weather forecasts, warnings, graphics and other information in real time. EMWIN is broadcast from geostationary NOAA GOES satellites, and if you have a GOES SDR receiver setup it is possible to receive and decode EMWIN data.

However, if you don't want to set up a GOES receiver, KD9IXX writes on his blog how he investigated EMWIN and found that 24/7 dedicated EMWIN VHF repeaters are common around the US. Having found an EMWIN repeater in his area at 163.37 MHz he used the TrueTTY decoder and was able to successfully decode the 1200 baud 8-bit ASCII encoded signal and receive weather text information. He notes that VHF EMWIN is an excellent source of non-internet based weather data that could be useful to anyone requiring weather data in emergency circumstances.

EMWIN VHF Repeater Decoded with TrueTTY
EMWIN VHF Repeater Decoded with TrueTTY

Receiving GOES LRIT Full Disk Images of the Earth and EMWIN Weather Data with an Airspy

Over on Reddit user devnulling has made a post showing how he was able to use his Airspy SDR to download full disk satellite images of the earth from the GOES satellite. In a separate imgur post he also shows that he was able to receive EMWIN weather data images from the same GOES satellite.

The Geostationary Operational Environmental Satellite (GOES) is a weather satellite placed in geosynchronous orbit (same position in the sky all the time) which is used for weather forecasting, severe storm tracking and meteorology research. It transmits full disk images of the earth on its Low Rate Information Transmission (LRIT) signal, and weather data images and text on its Emergency Managers Weather Information Network (EMWIN) signal. EMWIN is a service for emergency managers that provides weather forecasts, warnings, graphics and other information in real time.

In his post devnulling writes about receiving GOES:

GOES LRIT runs at 1691.0 MHz , EMWIN is at 1692.7 MHz and is broadcasted from GOES-13 and GOES-15. GOES-14 is currently in a backup position to take over in either fails.

FFT/Waterfall of LRIT + EMWIN – http://i.imgur.com/rgSIORv.jpg
http://www.n2yo.com/?s=36411|29155|35491

For the hardware side, it is recommended to use roughly a 1.2m or larger dish, depending upon how far north you are, you may need a 1.8m dish (larger the better). Repurposed FTA or C-band dishes are easy to come by and work well.

I made a 5 turn helical feed with some 12ga copper wire and a piece of copper plate, and used this calculator to design it – https://jcoppens.com/ant/helix/calc.en.php

Picture of my dish/feed setup: http://i.imgur.com/Q1ZBFrs.jpg

I have a short run of coax into the LNA/Filter box. The first LNA is a TriQuint TQP3M9037 which has a very low noise figure (0.3 dB NF and 22 dB gain at 1.7 GHz).

That is ran into a Lorch 1675 MHz filter (150 MHz pass band), then a LNA4ALL and another Lorch before going over a 30ft run of RG-6 to the SDR.

Picture of the LNA/Filter box – http://i.imgur.com/yt7SvFL.jpg

I am using @usa_satcom (twitter.com/usa_satcom, usa-satcom.com)’s LRIT Decoder and that feeds into XRIT2PIC to produce the images and other data streams. By default the decoder only works with the Airspy, but with a custom GNU Radio UDP block, it can be fed with other SDRs like the BladeRF/USRP/SDR Play. A regular R820T(2) RTL probably won’t work because of the higher frequency (rtls tend to not work above 1.5 GHz) and 8 bit ADC. I’m going to try and use the Outernet e4k to see if I can pickup the EMWIN signal in the near future.

EMWIN is broadcasted on 1692.7 MHz, along with being encoded in the LRIT stream at 1691 MHz. The 1692.7 MHz signal is stronger and narrower, so it is easier to pickup. For decoding EMWIN I used @usa_satcom’s EMWIN decoder that piped data into WxEmwin/MessageClient/Weather Message Server from http://weathermessage.com.

LRIT will contain the full disk images from GOES-15, and relayed images from GOES-13 and Himawari-8. It will also included zoomed in pictures of the USA, and northern/southern hemispheres. The images will be visible light, water vapor and infrared. The full disk images are transmitted every 3 hours, with the other images more often. EMWIN will contain other weather data, text, charts, and reports.

Full disk GOES-15 – http://i.imgur.com/tWlmNMW.jpg

Charts / images from EMWIN – http://imgur.com/a/tsn1K

Text data – http://pastebin.com/raw/ULJmSSTP

Zoomed in west coast USA LRIT – http://i.imgur.com/rzfB0SV.jpg

Northern Hemisphere LRIT – http://i.imgur.com/5tKtPmn.jpg

Himawari-8 LRIT – http://i.imgur.com/sVzikys.jpg

Himawari-8 LRIT – http://i.imgur.com/LBvpTD1.jpg

It seems as though it may be possible to receive LRIT and EMWIN signals with an RTL-SDR since the signals are at 1690 MHz, which should be covered by cooled R820T2 and E4000 dongles. The only hardware requirements would be a 1m+ dish, 1690 MHz L-band feed, and an LNA + filter.

In 2017 these satellites are due to be replaced by new ones that will use a HRIT signal, which will be about 1 MHz. New software to decode this signal will be required then, but we assume the same hardware could still be used as the frequency is not due to change significantly.

Please note that the decoding software is only available by directly contacting usa-satcom, and devnulling writes that you must have the proper equipment and be able to show that you can receive the signal first before attempting to contact him.

GOES Full Disk Image
GOES Full Disk Image
One of several received EMWIN images
One of several received EMWIN images

RTL-SDR.COM GOES 16/17 and GK-2A Weather Satellite Reception Comprehensive Tutorial

GOES 16/17 and GK-2A are geosynchronous weather satellites that transmit high resolution weather images and data. In particular they are far enough away from the earth to be able to take beautiful 'full disk' images which show the entirety of one side of the Earth. As these satellites are in a geosynchronous orbit, they can be counted on to be in the same position in the sky at all times, so no tracking hardware is required and images can be pulled down constantly throughout the day without having to wait for a polar orbiting satellite to pass over like you would with the NOAA APT or Russian Meteor satellites.

With a low cost WiFi grid dish antenna, LNA and RTL-SDR dongle, any home user within the footprint of one of these weather satellites can receive and decode live images directly from the sky. Setting up a station is overall not too difficult, but it can be a bit fiddly with a number of steps to complete. Below is our comprehensive guide. We'll show how to set up a self contained Raspberry Pi based system with goestools (free), as well as a guide for the Windows PC software XRIT decoder (US$125).

We've attempted to make the tutorial as newbie friendly as possible, but we do need to assume basic RF knowledge (know what antennas, SDRs, coaxial, adapters etc are), basic Linux competency for the goestools tutorial (using the terminal, using nano text editor), and basic Windows competency for the XRIT decoder tutorial (unzipping, editing text files, running programs).

Click for the full size image (14MB)
A full disk false color image received directly from the GOES-17 satellite with an RTL-SDR. Click for the full size image (14MB).

There are two fourth generation NOAA GOES satellites that are currently active, GOES-16 and GOES-17. These transmit HRIT signals, and also transmit shared data from the older third generation GOES 15, and Japanese Himiwari8 satellites. At the moment GOES-16 and GOES-17 are producing full disk images every 30 minutes, and close up "mesoscale" shots of the USA every ~15 minutes. GOES-16 (aka GOES-R) and GOES-17 (aka GOES-S) are also known as GOES-EAST and GOES-WEST respectively. At least one of these satellites can be received from North/South America, Canada, Alaska/Hawaii, New Zealand, Eastern Australia and some pacific islands.

There is also the older generation GOES-15 and GOES-14 which have been placed in standby orbits. These transmit LRIT signals which provide images at a slower rate. 

GOES 16/East and GOES 17/West Signal Footprint
GOES 16/East and GOES 17/West Signal Footprint

There is also the Korean GK-2A (GEO-KOMPSAT-2A) satellite which is very similar to the GOES satellites. GK-2A covers countries like India, Asia, Australia, New Zealand and parts of Russia. Note that you may have previously heard of the COMS-1 satellite which used to cover this area. Since July 2019 COMS-1 was replaced by GK-2A. Unlike GOES, GK-2A images are encrypted. However it has been found that "sample" encryption keys found online in demo code work just fine.

GK-2A contains both LRIT and HRIT channels, but at the moment only the LRIT channel can be decoded with the currently available software. The LRIT channel sends full disk IR images every 10 minutes in 2200 x 2200 resolution. Compared to the 5424 x 5424 resolution GOES full disk images, this is smaller, but still large enough to be interesting.

Note that even if HRIT decoding is added by the current software, you would require an Airspy or other wideband SDR as the GK-2A HRIT signal bandwidth is 5 MHz. Also since the HRIT bandwidth is so wide, the signal strength is reduced, meaning that you'll need a larger dish. People who have received the HRIT signal note that a 3M+ sized dish seems to be required.

GK-21 (GEO-KOMPSAT-2A) Foorprint
GK-21 (GEO-KOMPSAT-2A) Footprint

You might ask why bother receiving these satellite images directly, when you can get the exact same images from NOAA at https://www.star.nesdis.noaa.gov/GOES/index.php. Well, you might want to set up your own station to be independent from the internet, or you live in a remote location without internet, or maybe just for the fun and learning of it.

To set up a receiver for GOES 16/17 HRIT or GK-2A LRIT you'll need to purchase a dish antenna such as a cheap 2.4 GHz WiFi antenna, an RTL-SDR, GOES LNA, and a Raspberry Pi if using goestools, otherwise a Windows PC can be used. The total cost could be anywhere from $150 - $200 depending on what pieces you already have available.

Before we start the tutorial, you might want to use an augmented reality Android app like "Satellite-AR" to get a rough idea of where either GOES 16/17 or GK-2A (GEO-KOMPSAT-2A) is in your sky, and if receiving them is even feasible for your location. You'll need to find an area on your land where you can mount a small satellite dish with an unobstructed line of sight view to the satellite (no trees or buildings can be blocking the signal path). If the satellite is low on the horizon (below 25 deg elevation), then things get a little more difficult as you have more obstructions and a weaker signal. But it can still be done, and we're able to routinely get good results at 24.5 deg elevation.

Note that for Europe and Africa, unfortunately there are no satellites that can be received easily with an SDR and LNA. But you might instead be interested in the EUMETCAST service, which can be received from EUTELSAT 10A (Ku band), Eutelsat 5 WEST A (C Band) and SES-6 (C Band) . To receive this service you'll need a DVB-S2 receiver and a satellite dish with appropriate band LNB. You also need a license keys and software which all together cost €100. EUMETCAST reception is not covered in this tutorial, instead see this video.

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Receiving GOES Weather Satellite Images with a Small Grid Antenna and an Airspy Mini

GOES is an L-band geosynchronous weather satellite service that can be received typically with a satellite dish. It produces very nice full disk images of the earth. In the past we’ve posted about Lucas Teske’s work in building a GOES receiving system from scratch (including the software decoder for Airspy and RTL-SDR receivers), devnullings post about receiving GOES and also this talk by @usa_satcom on decoding GOES and similar satellites.

Over on Twitter @usa_satcom has been tweeting about his experiments where he has been successfully receiving GOES L-Band weather satellite images with a small grid antenna and an Airspy Mini. In a Tweet he writes that the antenna is an $85 USD Hyperlink 1.9 GHz 22 dBi Grid Antenna made by L-com. A grid antenna may be more suitable for outdoor mounting for many people as they are typically lighter, smaller and more suitable for windy and snowy conditions. As the GOES satellite is in geosynchronous orbit, no tracking motor or tracking mount is required.


Creating a GOES Weather Satellite Demodulator

Last week we posted about Lucas Teske’s (@lucasteske) experience with setting up an antenna system that can receive the geostationary GOES weather satellites. He set up a dish antenna, feed, LNA and filter and was able to successfully receive the GOES signal with an RTL-SDR and Airspy.

Now Lucas has uploaded his second post where he discusses how to demodulate the GOES signal. The GOES satellites transmit a Low-Rate Information Transmission (LRIT) signal which contains full disk images of the earth as well as other weather data from the secondary Emergency Managers Weather Information Network (EMWIN) signal.

In order to demodulate the signal Lucas wrote a BPSK demodulator in GNU Radio. His post goes into good technical detail and shows exactly how the demodulator is constructed. Basically the the BPSK signal is first decimated down to 2.5e6, normalized with an AGC, then cleaned up with a Root Raised Cosine Filter. From there the signal goes through a Costas Loop PLL to receover the carrier wave, then a Clock Recovery MM block to recover the symbol clock. The data is then output to a TCP pipe for the decoder.

In the upcoming third part of his article Lucas will show us how to actually turn the demodulated data into an image of the earth.

GOES LRIT Decoder
GOES LRIT Decoder