Tagged: NOAA

Open-Weather APT: Updates to the Web Based NOAA APT Image Decoder

Dr. Sasha Engelmann and Sophie Dyer, the team behind the Open-Weather project have recently announced the launch of their new version of open-weather apt, a web-based NOAA APT image decoder. The web-based program accepts a WAV file containing a NOAA satellite APT recording, demodulates and decodes it, and displays the resulting weather satellite image.

Sasha writes:

In our recent newsletter, we summarised the updates as follows:

Open-weather apt is the only public, maintained, browser-based decoder for Automatic Picture Transmissions (APT) from satellites NOAA-19, NOAA-18 and NOAA-15. It was developed to improve access to satellite signal decoding for all practitioners.

We are excited to share a new and improved version available here! The new version includes the following updates and additional features:

  • Improved accuracy in decoding and finding sync positions (locates more sync positions than other comparable decoders)
  • Upload a WAV file of any sample rate (no more re-sampling with Audacity!)
  • Option to see the ‘raw’ image without syncing, and to ‘Find the Syncs’
  • Option to Rotate 180 degrees, often useful for viewing images from nighttime passes
  • Go deeper in your analysis: explore Signal Value and Image Value Histograms
  • Upload directly from open-weather apt to the Public Archive

Open-weather apt is co-developed by open-weather with Rectangle (Lizzie Malcolm and Dan Powers), Bill Liles (NQ6Z) and Grayson Earle. We have had a lot of fun testing and experimenting. Please let us know if you have feedback!

Open-Weather APT Web Decoder
Open-Weather APT Web Decoder

Weather Satellite HRPT and LRPT Megaprojection Project Nov 30 – Dec 1

Over on the /r/amateursatellites subreddit, user elmarkodotorg is organizing a group megaprojection project. The Megaprojection Project seeks to create a composite of as much of the earth as possible from weather satellite images captured by hobbyists in a single day, via data from NOAA and Meteor polar-orbiting satellites. They will be accepting HRPT or LRPT data from either Nov 30 or Dec 1 (date yet to be confirmed).

Hobbyists can receive these satellites' LRPT and HRPT signals using an RTL-SDR and appropriate antenna setup.

If you want to contribute, you can join DerekSGC's Discord server, https://sgcderek.github.io, where coordination will be carried out. elmarkodotorg writes that currently, they have confirmed contributors with stations from the west coast of the US all the way over to the western edge of Asia. Currently, they are still hoping to find contributors from the Canary Islands, Turkey, Equatorial Africa, the general area of Indonesia, and Northern Australia. In a more recent Reddit thread, elmarkodotorg provides a link to a Google docs sheet, where you can also register interest.

Recently, on November 16 a test was carried out and they were able to successfully combine 24 images received across the world.

Megaprojection Nov 16 Test: 24 contributors from all over the world submitted HRPT and LRPT images received from their home satellite ground stations.
Megaprojection Nov 16 Test: 24 contributors from all over the world submitted HRPT and LRPT images received from their home satellite ground stations.

Discovery Dish April Manufacturing Update

This was posted over on our Discovery Dish Crowd Supply updates page and we are cross-posting here too.

It’s been over a month since our last update so we thought we’d share some of the recent progress. As mentioned in our last update, during the month of February all manufacturing was shut down due to the Chinese New Year holiday. In early March, staff returned to the factories and began making progress on finishing Discovery Dish.

We have a snazzy new logo, and we are working on obtaining some stickers to include with the feeds.

 

Dish Manufacturing Progress

The molds for the dish stamping machine were successfully created in March and the test stamps have come out great. The manufacturer is still tweaking the secondary mold that stamps the mounting and connecting holes, but we expect that to be completed shortly. Once that is done and tested, we can begin stamping the dish segments en masse.

The Dish mounting system was also finalized and we added 45-degree markers to it, which can help with aligning skew.

We are still awaiting the results of the anodizing tests, but they should be completed by the end of this month. Anodizing the dish is important as the dish must be a dark non-reflective matte color, so that it does not focus hot sunlight onto the feed point plastic head.

Feed Manufacturing Progress

PCB Upgrades

While waiting for the manufacturers to finish up with the molds, we’ve been further refining the PCB feed. Our final version of the PCB has now moved to a PTFE substrate with significantly lower loss at higher frequencies. This has yielded an over 1 dB increase in SNR at the GOES 1.69 MHz frequency.

The change to PTFE was not without problems. An interesting RF engineering problem occurred with the move to PTFE that we wanted to share. When moving to PTFE the only changes to the board layout are PCB trace width changes to keep the impedances matched. Other than that, the boards and layout are essentially identical. However, we discovered that the dual LNA design started oscillating when we moved the PTFE substrate. Oscillations can occur with LNAs when RF essentially bounces back and forth between the two LNAs, which causes undefined behavior in the LNA, such as poor gain, multiple spikes in the spectrum, and unexpected current draw values.

We found this quite odd because oscillations were not occurring in the original FR4 PCB, and the QPL9547 LNA is advertised as ‘unconditionally stable’ which means that it should never oscillate. However, we found that unconditionally stable guarantees may not apply to two-stage designs. In the end, the fix was simple, we just needed to add a damping resistor to one of the inductors on the circuit which reduces its Q-value. It seems that the change from FR4 to PTFE effectively increased the Q-value of this inductor so much, which in turn induced an oscillation in the circuit.

Discovery Dish Feed Head Enclosure

We’ve also refined the entire feed assembly. The feed arm pipe now has a ruler laser etched onto it so that mounting it at the correct distance is easy. A skew angle guide has also been added around the neck. A thumbscrew locking mechanism has been added to the feed head neck too, so that skew can easily be adjusted without the need for a screw driver or Allen wrench to loosen the set screw.

The PCB enclosure has been slightly refined and the injection molding die is currently in production and due to be completed in mid-May. While waiting for the die to be made, we’ve been testing different plastic mixes for the head enclosure to make sure that they are UV stable. The plastic mix has certain strict requirements and choosing the correct mix is crucial. It has to be RF-transparent with a low relative permittivity value, it has to endure direct sun, UV damage, and freezing weather, as well as be water-proof too.

S-Band Feed

Previously as noted in prior updates we were testing an S-band feed with the FR4 substrate. But we found that there was too much loss and the SNR values we got were not great. The move to PTFE substrate means that our experimental S-band feed is now working very well. We will be releasing this in the near future as an additional feed product that can be used with Discovery Dish. This feed will have a frequency range of 2.2 GHz - 2.3 GHz. This covers the main S-band weather satellites, other satellites like Coriolios and JASON as well as the many dump-only S-band satellites that transmit signals only over certain regions.

As requested by most people interested in an S-band feed, the S-band feed will not include a downconverter, so to use it you will either need an SDR like the HackRF which is capable of tuning to the S-band, or a third-party downconverter product.

Discovery Dish Outdoor Metal Enclosure Progress

Our enclosure set is now complete, and the final packing has almost been completed. The user manual can be found here Discovery Dish Outdoor Enclosure User Manual.pdf.

The final set consists of:

  • 1x Metal Enclosure
  • 3x Custom metal cable glands
  • 1x Vent
  • 1x Electronics mounting board
  • 1x Pole mounting set (with hose clamps)
  • 1x Wall/DIN mounting set
  • 1x 10 mm x 10 mm x 8 mm thermal pad (to be placed under the electronics mounting board)
  • 1x 10 mm x 10 mm x 3 mm thermal pad (to be placed under electronics on top of the mounting board)
  • 1x Set of various screws and washers

(Note that there will be some minor changes from this image in sets going out of customers - the hose clamp will be shorter, and the mounting rails will be longer)

Meteor M2-4 Launch

We mentioned in our last update that a new weather satellite Meteor M2-4 was due to launch. The launch was successful and the satellite is now in orbit. The satellite was briefly turned on after launch, and we were able to receive HRPT images from it in the L-band. However, now it is currently in a testing phase so the transmitters are often turned off. We don’t know how much longer it will be in testing, but we assume it won’t be more than a few more months.

GOES-U / GOES-19 Launch Updates

We’ve been keeping an eye on the expected launch date for the next GOES satellite. Currently, it has been delayed from April 30, 2024, to the new date of June 25, 2024, when it will be launched on a Falcon Heavy from Kennedy Space Center, Florida.

Elektro-L4 Updates

In the last update, we mentioned that we were having some problems getting SatDump to receive Elektro L4 properly on computing devices that used ARM processors. After some investigation, we determined that this was a problem with buffer size settings in SatDump and we were able to suggest a fix in https://github.com/SatDump/SatDump/pull/616 which was implemented. New versions of SatDump have this problem fixed.

Driver Tweaks

We have been looking at the RTL-SDR drivers and have found a few tweaks that can improve performance at L-band frequencies. We’ve put a modified version of the librtlsdr/librtlsdr fork up our the rtlsdrblog GitHub at https://github.com/rtlsdrblog/librtlsdr. With this fork and the PTFE feed upgrades, we now get around 5-6 dB of SNR on GOES-18.

Antenna Rotator

The low-cost antenna rotator is finishing up with prototype testing, and we are now working on improving the design’s manufacturability.

Timeline

The ramping of progress from the Chinese New Year holidays to now has been a little slower than expected, but if everything goes perfectly to plan, we will be on time for shipping by the end of June. However, this is currently a best-case scenario. There are still a few manufacturing stages to get through like the final mass production, CE testing and sea freight shipping. Unfortunately, from prior manufacturing experience, there are always setbacks along the way that slow progress, so we are conservatively pushing our advertised timeline back by about 1-2 months. We apologize for any potential delays, but we are working hard to get the product out to you ASAP!

Customer Questions

We have had a few more customer questions over email which we’d like the answer publicly below:

Would it be practical to use this kit indoors to do hydrogen-line astronomy? I ask because I live in a flat in a block of retirement flats, and wouldn’t be able to place an aerial or dish outside, but could find space for a Discovery dish + rotation gear inside.

Unfortunately, indoor Hydrogen line astronomy is out of the question. The hydrogen line signal is just too weak to be seen indoors, and there would most likely be too much interference indoors as well.

What all do i need to purchase and get for the Discovery Dish for Radio Astronomy?

You’ll need these two components from the Discovery Dish Crowd Supply store:

  • Discovery Dish (Dish & Mount Only)
  • Hydrogen Line Discovery Feed

You will also need a software defined radio, such as an RTL-SDR Blog V3/V4 which can be purchased separately, a computer and somewhere to mount your dish (e.g. a mast/tripod etc).

Have you tested this for C-Band / Aero downlink reception?

Currently, we do not have a C-band feed, so we have not tested it for this purpose. Generally, a larger 1.2 m+ dish is required for C-band AERO, so the 70 cm Discovery Dish may not be suitable. We may test this with Discovery Dish in the near future just in case however.

I want to purchase a hydrogen antenna. Where should I buy it? Also, please tell me what is needed to observe seti radio waves.

The Discovery Dish (Dish & Mount) and Hydrogen Line Discovery Feed can be pre-ordered from the Discovery Dish Crowd Supply store. I’m not sure exactly what you are referring to with SETI radio waves. An alien signal could in theory be on any frequency, but the 1.42 GHz Hydrogen line frequency could be a good bet as it’s a universal frequency of interest that any technological civilization would be observing. Realistically the Discovery Dish would be too small to detect potential alien signals unless they were very strong.

I’ve seen a small home made 3D-printed dish called a ‘heliocone dish’ being used for HRPT. How is Discovery Dish different?

The heliocone 3D printer design going around is a great DIY solution for L-Band polar orbiting HRPT satellites. But it has some limitations as it cannot receive the weaker geostationary satellites due to its smaller size and use of a circular polarized feed. It also cannot receive satellites using the opposite circular polarization. It also cannot receive satellites on different frequencies or the Hydrogen Line without designing a new helical feed and using a different LNA+filter combo. Discovery Dish is a more of a general purpose ‘does-it-all’ and ‘ready to use’ out-of-the-box dish. With our dish and feeds you can receive the L-Band polar orbiting HRPT satellites as well as the geostationary satellites. You can quickly swap out the feed for a different feed that covers a different band as well.

 

IndiaRocketGirl Receives NOAA-19 Weather Satellite Images with a Tape Measure Yagi Antenna

Over on her YouTube channel IndiaRocketGirl (@VU3BIZ) has posted a video showing how she was able to receive weather satellite images from the polar orbiting NOAA-19 weather satellite at 137 MHz.

She uses a home made four element Yagi antenna with elements made from a tape measure. This allows the elements to be easily folded down for transportation. A phone running the Heaven's above app is used to help track the satellite in the sky as it passes over, and then SatDump and an RTL-SDR Blog V3 running on a laptop is used to decode the signal into an image.

IndiaRocketGirl notes that in her next video she will show how to make the Yagi antenna that she was using. In a previous post IndiaRocketGirl also showed how she was able to receive geostationary FengYun-2H S-VISSR signals.

How to Receive Real Time Images from Low Earth Orbit Satellites | India Rocket Girl | NOAA-19

WXCorrector: Updating Keplers for Linux users of WXtoIMG

Thank you to Hamdy Abou El Anein for submitting news about the release of his software called "WXCorrector".  

WXCorrector is a dedicated solution designed specifically for Linux users who face challenges with the handling of Kepler elements in Wxtoimg. This tool addresses a critical issue where incorrect or outdated Keplerian elements can cause disruptions in tracking software, leading to inaccurate predictions and potential data loss.

It work on Linux, it needs sudo rights and Python3 installed.

https://github.com/hamdyaea/wxcorrector-for-linux

WXtoIMG is a commonly used piece of software for decoding images from NOAA APT weather satellites. However,  WXtoIMG is now considered abandonware as the original website has gone, and the main author has not updated the program in many years. The latest versions from 2017 can be downloaded from Archive.org. An alternative download site is https://www.wraase.de/wxtoimg, where they also provide a way to update Keplers for Windows machines.

Due to it's abandonment, certain features like Kepler updates from the internet appear to have broken over time with changes to the way Kepler files are served. Up to date Kepler files are required for the software to know exactly where satellites are in the sky for tracking and scheduling.

A modern alternative to WXtoIMG is SatDump, which now supports NOAA APT satellites.

WXtoIMG

Downloading Stored Images and Data from the NOAA Weather Satellite GAC Broadcast

With polar orbiting weather satellite reception we as amateur ground station operators with SDR receivers typically download images via "Direct Broadcast", which provides imagery of what the satellite is currently seeing live. However, the main way satellites such as the NOAA POES (NOAA 15, 18 & 19) satellites downlink is via "Global Area Coverage" (GAC) broadcast which provides the full stored imagery data of the entire global pass. However, GAC is only broadcast in locations where the satellite operator operates ground stations.

Over on YouTube dereksgc has uploaded a video showing how to receive GAC data from the NOAA POES satellites. He notes that GAC is now broadcast at 2247.5 MHz in the S-band, and the ground station it now downlinks to is likely in Svalbard, rather than in the USA. This means that amateur satellite stations close to the North Pole can receive the GAC signal, including dereksgc's station which (we believe) is in the Czech Republic.

Dereksgc uses a large 250cm offset dish with S-band feed connecting to a HackRF. In the video he demonstrates him receiving the signal, and then decoding it using SatDump. Finally he shows all the images from various locations around the earth that he was able to receive from one satellite pass.

Downloading stored data from NOAA weather satellites (GAC revisited) || Satellite reception pt.12B

Saveitforparts: Building an L-Band Satellite Antenna out of an Umbrella

Over on his YouTube channel "saveitforparts" has uploaded a video where he uses an umbrella, pin tin and tin foil tape to create a simple dish antenna for receiving GOES, NOAA and METEOR HRPT satellites.

The full build consists of an umbrella covered in tin foil tape, a helical wire feed on a pie tin, a filtered LNA, an RTL-SDR and an Android phone running SDR++. While he did have initial success at receiving, he soon decided to swap out the helical wire feed for a PCB linear feed instead which worked much better as helical feeds can be very difficult to get right.

Through the video saveitforparts goes over the failures he had, in the end noting that it's not a great antenna, but it's something that can be used in a pinch.

We've also seen the umbrella satellite dish used a few times in the past, where here it was used for NOAA APT reception, and here for Hydrogen Line radio astronomy.

We also want to remind readers that we are currently Crowd Funding for our Discovery Dish, which will be a low cost way to get into L-band satellite reception.

Can I Get Satellite Data With An Umbrella?

SatDump Version 1.1.0 Released – Feature Overview

SatDump is a popular program that can be used with RTL-SDRs and other software defined radios for decoding images from a wide array of weather imaging (and other) satellites including GOES, GK-2A, NOAA APT, NOAA HRPT, FengYun, Electro-L and Meteor M2 LRPT + HRPT, and many many others. It is multiplatform, running on Windows, MacOS, Linux and even Android. Because of it's good decoding performance, wide satellite and OS compatibility, it is the most recommended software for satellite decoding.

Recently SatDump was updated to version 1.1.0 and the new version brings many enhancements and new features. In summary, Lua scripting support has been added, calibrated products are now possible, composites can be made via Lua scripting, nightly builds are now available on GitHub, Mac .dmg builds are now available, decimation has been added, an SDR Server is available, and a Windows installer was added.

Support for various satellites and their instruments have also been added for NOAA APT, CCSDS LDPC decoding for Orion, LandSat-9, TUBIN X-Band, FengYun-3G/3F, Meteor M2-3, Geonetcast (soon), GOES RAW X-Band,  STEREO-A, DSCOVR EPIC, ELEKTRO-L N°4, Inmarsat STD-C, UmKA-1 (soon), PROBA-V GPS .

SatDump also now includes rotor tracking control which works together with it's satellite pass predictor and scheduler. There is no more need to use programs like Orbitron or Gpredict as everything can be handled by SatDump.

An insane amount of work has gone into SatDump, so if you like the software please remember to support the developer @aang23 by donating on Ko-Fi.

SatDump Rotator controller, Tracker and Scheduler