At this years FOSDEM 2020 conference Apostolos Spanakis-Misirlis has presented a talk on his PICTOR open source radio telescope project. We have posted about PICTOR in the past [1, 2] as it makes use of an RTL-SDR dongle for the radio observations. The PICTOR website and GitHub page provide all the information you need to build your own Hydrogen line radio telescope, and you can also access their free to use observation platform, where you can make an observation using Apostolos' own 3.2m dish radio telescope in Greece.
The PICTOR radio telescope allows a user to measure hydrogen line emissions from our galaxy. Neutral Hydrogen atoms randomly emit photons at a wavelength of 21cm (1420.4058 MHz). The emissions themselves are very rare, but since our galaxy is full of hydrogen atoms the aggregate effect is that a radio telescope can detect a power spike at 21cm. If the telescope points to within the plane of our galaxy (the milky way), the spike becomes significantly more powerful since our galaxy contains more hydrogen than the space between galaxies. Radio astronomers are able to use this information to determine the shape and rotational speed of our own galaxy.
This feature allows SDR users to open multiple instances of SDR#, each able to tune to a seperate signal within the currently tuned frequency range of the SDR. This is somewhat similar to the old multi-VFO plugin from rtl-sdr.ru, however the advantage of Slicer is that you can have seperate spectrum and waterfall graphs for each signal.
Other recent changes include 'true dBFS' automatic scaling, where 0 dBFS now indicates that the ADC is likely saturated.
Passive Radar works by using already existing powerful transmitters such as those for TV/FM. A receiver listens for these signals being reflected off of objects like aircraft and vehicles, and compares the reflection with a signal received directly from the transmitter. From this information a doppler (speed) vs range graph of detected objects can be calculated and displayed.
By measuring the path an object travels across the range-doppler display some interesting information about the objects movement can be obtained. However, the display can be noisy, with the reflected object often coming in and out of view on the display. In order to track an object across the range-doppler display in the face of these uncertainties Max uses a Kalman filter to obtain smoothed results. A Kalman filter is an algorithm which combines actual data with predicted data, with the weighting depending on measurement confidence. The result is shown in the video below. A smooth and accurate track of an aircraft can be seen.
Max notes that in the future he'll be working on tracking multiple aircraft detected by the passive radar, and also incorporating direction finding data in his results in order to get cartesian coordinates which could be plotted on a map.
We note that Max's GNU Radio code should be compatible with our KerberosSDR unit, which already has the clock sharing hack built in to the hardware.
On September 15 we began our 33% off stock reduction sale for the Bullseye LNB. The Bullseye is an ultra stable LNB for receiving QO-100 and other Ku-Band satellites/applications. We'll be ending this sale on Wednesday, so if you'd like to purchase a unit please order soon to avoid missing out on the sale price. The current sale price is US$19.97 including free worldwide shipping to most countries.
To order the product, please go to our store, and scroll down until you see the QO-100 Bullseye TCXO LNB heading. Alternatively we also have stock via our Aliexpress storeor on eBay.
For more information about the Bullseye and some reviews please see the original sale post.
Back in June we posted about the release of Zbigniew Sztanga's NOAA-HIRS-Decoder which can decode HIRS instrument data which measures the vertical temperature profile of the Earth's surface. This HIRS signal is broadcast by NOAA satellites at the same time as their APT images and the HIRS frequency is close by at 137.350 MHz.
Recently Zbigniew has released a new decoder for the Microwave Humidity Sounder (MHS) instrument which is available on NOAA-19 only. This MHS instrument observes the Earth in the 89-190 GHz microwave band, which can be useful for measuring humidity levels. However, unlike the APT and HIRS signals which downlink data at around 137 MHz, the MHS data is broadcast in the L-band within the HRPT signal, so a motorized or tracked satellite dish will be required to receive it. Zbigniew writes:
The MHS (Microwave humidity sounder) is an instrument on NOAA-18 and NOAA-19. It replaced the older AMSU-B. It has a resolution of 90px per line and 5 channels.
Data from the instrument is present in HRPT and can be decoded with my new software. Unfortunately, only MHS on N-19 is working, because N-18's NHS is dead.
The instrument can be used to monitor low clouds, percipation and water vaopr in the atmosphere. I attached a sample image to the email.
Back in August we posted about the release of Sanchez, a tool originally designed to apply a color underlay image to grayscale infrared images received from geostationary weather satellites such as GOES 16/17, Himawari-8 and GK-2K. The tool has recently been updated with some very nice new features.
One of the new features is the ability to composite together images obtained from multiple satellites in order to form a full equirectangular image of the earth with live cloud cover. Another feature is the ability to use two or more images from different satellites to reproject back to geostationary projection at a specified longitude, essentially creating an image from a virtual satellite.
Elektro-L is a range of Russian geostationary weather satellites. Elektro-L1 and L2 were launched in 2011 and 2015 respectively, and Elektro-L3 was launched more recently in December 2019. Currently only Elektro-L2 and L3 are in operation. Like it's NOAA GOES, Himawari and GK-2A cousins, Elektro-L satellites beam back full disk images of the entire earth. Elektro-L2 is positioned to cover South America, Africa and Europe, whilst Elektro-L3 covers the East of Africa, Eastern Europe, Russia, Middle East, Asia and the West of Australia.
Recently @aang254 has been Tweeting that he has managed to get an Elektro-L decoder working. The decoder is open source and available on GitHub and Windows builds are already available. He notes that he's still working on the demodulator, but that should be released tomorrow. This decoder is great news as now Europeans now have an opportunity to receive full disk images. There is no full guide yet on how to use the decoder, but we expect that one will be released soon.
We note that according to wmo-sat.info the Elektro-L satellites transmit at ~1693 MHz, and have a 2 MHz wide HRIT and 200 kHz wide LRIT mode. So the signals should be able to be received with an RTL-SDR and appropriate LNA.EDIT: Unfortunately it seems that wmo-sat.info may have incorrect information, and that Elektro-L requires X-Band hardware to receive these images. While not totally impossible, an X-Band satellite SDR setup is a bit more difficult to put together compared to the L-band SDR setup used by GOES and GK-2A.
Published my ELEKTRO-L Decoder (early release)!
You can find it here under GPLv3, it takes synced derandomized CADUs as input, but I'll add in a demodulator tomorrow no worries!
Windows builds included already!https://t.co/Txh22PZ2cG
Thank you to John First for submitting his guide all about the setup and use of the software required to receive NOAA weather satellite images on Windows 10 (pdf file) with an RTL-SDR dongle. John's guide covers the use of SDR# for receiving the signal, WXtoIMG for decoding the signal, and Orbitron for tracking the satellite and automatically tuning SDR# when a satellite is in range.
He also explains the use of the VB-Audio Virtual Cable for piping audio between SDR# and WXtoIMG, as well as the DDE Tracking and Scheduling Plugin for interfacing SDR# with Orbitron, and finally how to do NTP clock synchronization to ensure the local time is accurate.