Tagged: weather satellite

More Information about the NOAA-15 AVHRR Failure

Thank you to Carl Reinmann (aka usradioguy) for submitting his blog post which goes into deeper detail about the NOAA-15 weather satellite imaging failure that we posted about last week. 

In his post Carl discusses in detail the technical aspects of the AVHRR Scan Motor failure, shows plots of the AVHRR motor current increasing, provides multiple examples of corrupt images being recently received and notes the history of previous failures which were eventually resolved.

He also notes that even with the AVHRR failure the other sensors on the satellite will remain functional, however a failure of this instrument would mean the end of the easy to receive APT images at 137 MHz from NOAA-15. We note that there is still the opportunity to receive NOAA-18 and NOAA-19 which are the remaining operational satellites that transmit APT at 137 MHz.

NOAA have now also released an official notice about the failure which reads:

Product Outage/Anomaly: NOAA-15 AVHRR degraded image data issued by NESDIS NSOF
Date/Time Issued: Oct 22, 2022 1947Z

The NOAA-15 AVHRR Scan Motor current began showing signs of instability on Oct 18 at approximately 1800Z, when the current began to gradually rise from about 205 mA to about 250 mA, where it remained until Oct 24. At about 0000Z on Oct 24, the current began rising again throughout the day, peaking at about 302mA on Oct 25. Scan motor temperature began rising about the same time and is currently steady at ~29°C. The instrument is still producing data, but it is highly degraded. This behavior may be a sign of an impending scan motor stall but requires further investigation. Options for recovery are limited.

NOAA-15 Scan Motor Failure

The NOAA-15 Weather Satellite may be Failing (Again)

The NOAA APT weather satellites are popular because they fly over most places on earth frequently, and they are easy to receive images directly from with modest hardware such as an RTL-SDR and v-dipole antenna.

Three NOAA APT satellites currently operational include NOAA-15, NOAA-18 and NOAA-19. The satellites are however long past their rated mission age, with NOAA-15 being almost 25 years old now.

Unfortunately NOAA-15 appears to be having trouble with it's image scanning motor at the moment, and it is producing corrupted images. This problem has occurred in the past in 2018 and 2019, before fixing itself, so the hope is that it will fix itself again this time.

NOAA does not appear to have released any information about the outage yet on their General Satellite Messages page.

We also wanted to note the recent news that NOAA will be transitioning NOAA-15, 18 and 19 to a private company for on-orbit operations.

Tracking and Decoding Guide for NOAA Weather Satellites

Thank you to Samual Yanz (N7FNV) for submitting a guide that he's created about tracking and decoding NOAA weather satellites. The guide can be downloaded from this link as a PDF. 

Currently there are three operational polar orbiting NOAA weather satellites that transmit image data in the APT format at 137 MHz. When one of these satellites pass overhead, it is possible to use an RTL-SDR with appropriate satellite antenna and software to receive the satellite weather images they transmit.

Samual's guide focuses on the software and shows how to setup Virtual Audio Cable for piping audio between programs, SDR# for receiving the signal, Orbitron for tracking the satellite and WXtoIMG for decoding the image.

SDR#, Orbitron and WXtoIMG

SelfieStick: Combining noisy signals from multiple NOAA APT satellites for clean imagery

Researchers from Carnegie Mellon University have recently presented a paper detailing how they combined noisy signals from multiple passes of low earth orbit (LEO) satellites NOAA 15, NOAA 18 and NOAA 19 in order to create a higher quality image. For a receiver they used a low cost RTL-SDR Blog V3 mounted indoors with a whip antenna.

In a normal setup, weather satellite images from NOAA LEO weather satellites can be received with an RTL-SDR, computing device and an appropriate outdoor mounted antenna that has a good view of the sky. If the antenna is not suited for satellite reception, and/or is mounted indoors, at best only poor quality very noisy images can be received.  

The researchers demonstrate that it is possible to combine noisy images received over time, and from different satellites in order to generate a higher quality image. The challenge is that the different satellites and different receiving times will all produce different images, because the satellites will be at a different location in the sky each pass. They note that simply transforming the images in the image domain would not work very well for highly noisy images, so instead they have devised a method to transform the images in the RF domain. The RF signals are then coherently combined before being demodulated into an image.

The results show that 10 noisy satellite images from the indoor system are comparable to one from a comparison outdoor system. However, they note some limitations in that the system assumes unchanging cloud cover during passes. In the future they hope to extend the system to cover other modulation schemes used by other low earth orbit satellites in order to increase the number of usable satellites.

Selfiestick: Combining noisy images from multiple NOAA satellites received by an indoor RTL-SDR system.

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.

Receiving X-Band Images from the Arktika-M1 Arctic Monitoring Satellite

Recently on Twitter @arvedviehweger (Arved) has tweeted that he has successfully received images from the Russian Arctic monitoring satellite known as ARKTIKA-M1, via it's X-band downlink at 7865 MHz. We've reached out to Arved and he's provided the following information on his setup and how he's receiving and decoding the images.

 

The Arktika-M1 satellite is a Russian weather satellite which operates in a HEO orbit. It was launched in February 2021 and has downlinks on multiple bands. The main payload downlink for the imagery is on 7865 MHz (which is also known as the lower X-Band). The satellite only transmits imagery on the X-Band at the moment, it is currently unknown whether it will ever transmit any image data on L-Band.

For Amateur reception that means having access to X-Band RF gear. It usually consists of a low noise pre-amplifier and a downconverter to convert 7865 MHz down to a lower frequency for easier reception with a high bandwidth SDR such as the LimeSDR, a USRP etc.

In my personal setup I use a surplus pre-amplifier made by MITEQ (around 36dB of gain, 1dB NF), my own self-made DK5AV compact X-Band downconverter and a LimeSDR-USB.

The L-Band gear is mounted on top (helix and the pre-amp behind it) and the X-Band gear is right below. From left to right you can see the feed, the downconverter (silver box) and the LNA (mounted to a heatsink and a fan). Recording is done with a LimeSDR-USB running at a sample rate of 50 MSPS. The satellite transmits every 15 minutes once it reaches its apogee, each transmission including the idle period lasts for about 10 minutes. Some pictures of the idle transmission and the actual data transmission can be found in this Tweet, [noting that Idle = more spikes, actual data looks weaker]:

Depending on the geographical location a rather large satellite dish is also required for Arktika-M1. Reception reports all over Europe clearly show that the satellite has a beamed antenna (similar to ELEKTRO-L2).

In my setup I can get away with a 2.4m prime focus dish (made by Channel Master) in North Eastern Germany. It produces around 9 - 10 dB of SNR in the demod of @aang254’s excellent SatDump software. Anything above 5dB will usually result in a decode but since the satellite does not have any FEC you will need more than that for a clean picture. (Image of SNR in Satdump)