What is this world coming to when a weather satellite that was designed for a two-year mission starts to fail 21 years after launch? I mean, really — where’s the pride these days?
All kidding aside, it seems like NOAA-15, a satellite launched in 1998 to monitor surface temperatures and other meteorologic and climatologic parameters, has recently started showing its age. This is the way of things, and generally the decommissioning of a satellite is of little note to the general public, except possibly when it deorbits in a spectacular but brief display across the sky.
But NOAA-15 and her sister satellites have a keen following among a community of enthusiasts who spend their time teasing signals from them as they whiz overhead, using homemade antennas and cheap SDR receivers. It was these hobbyists who were among the first to notice NOAA-15’s woes, and over the past weeks they’ve been busy alternately lamenting and celebrating as the satellite’s signals come and go. Their on-again, off-again romance with the satellite is worth a look, as is the what exactly is going wrong with this bird in the first place.
If the great Samuel Clemens were alive today, he might modify the famous meteorological quip often attributed to him to read, “Everyone complains about weather forecasts, but I can’t for the life of me see why!” In his day, weather forecasting was as much guesswork as anything else, reading the clouds and the winds to see what was likely to happen in the next few hours, and being wrong as often as right. Telegraphy and better instrumentation made forecasting more scientific and improved accuracy steadily over the decades, to the point where we now enjoy 10-day forecasts that are at least good for planning purposes and three-day outlooks that are right about 90% of the time.
What made this increase in accuracy possible is supercomputers running sophisticated weather modeling software. But models are only as good as the raw data that they use as input, and increasingly that data comes from on high. A constellation of satellites with extremely sensitive sensors watches the planet, detecting changes in winds and water vapor in near real-time. But if the people tasked with running these systems are to be believed, the quality of that data faces a mortal threat from an unlikely foe: the rollout of 5G cellular networks.
It’s not hard to detect meteors: go outside on a clear night in a dark place and you’re bound to see one eventually. But visible light detection is limiting, and knowing that meteors leave a trail of ions means radio detection is possible. That’s what’s behind this attempt to map meteor trails using broadcast signals, which so far hasn’t yielded great results.
The fact that meteor trails reflect radio signals is well-known; hams use “meteor bounce” to make long-distance contacts all the time. And using commercial FM broadcast signals to map meteor activity isn’t new, either — we’ve covered the “forward scattering” technique before. The technique requires tuning into a frequency used by a distant station but not a local one and waiting for a passing meteor to bounce the distant signal back to your SDR dongle. Capturing the waterfall display for later analysis should show characteristic patterns and give you an idea of where and when the meteor passed.
[Dave Venne] is an amateur astronomer who turns his eyes and ears to the heavens just to see what he can find. [Dave]’s problem is that the commercial FM band in the Minneapolis area that he calls home is crowded, to say the least. He hit upon the idea of using the National Weather Service weather radio broadcasts at around 160 MHz as a substitute. Sadly, all he managed to capture were passing airplanes with their characteristic Doppler shift; pretty cool in its own right, but not the desired result.
The comments in the RTL-SDR.com post on [Dave]’s attempt had a few ideas on where this went wrong and how to improve it, including the intriguing idea of using 60-meter ham band propagation beacons. Now it’s Hackaday’s turn: any ideas on how to fix [Dave]’s problem? Sound off in the comments below.
[9A4OV] set up a receiver using the HackRF board and an LNA that can receive the NOAA 19 satellite. Of course, a receiver needs an antenna, and he made one using a cooking pot. The antenna isn’t ideal – at least indoors – but it does work. He’s hoping to tweak it to get better reception. You can see videos of the antenna and the resulting reception, below.
The satellite is sending High-Resolution Picture Transmission (HRPT) data which provides a higher image quality than Automatic Picture Transmission (APT). APT is at 137 MHz, but HRPT is at 1698 MHz and typically requires a better receiver and antenna system.
There’s a magnificent constellation of spacecraft in orbit around Earth right now, many sending useful data back down to the surface in the clear, ready to be exploited. Trouble is, it often takes specialized equipment that can be a real budget buster. But with a well-stocked scrap bin, a few strategic eBay purchases, and a little elbow grease, a powered azimuth-elevation satellite dish mount can become affordable.
The satellites of interest for [devnulling]’s efforts are NOAA’s Polar-orbiting Operational Environmental Satellites (POES), a system of low-Earth orbit weather birds. [devnulling] is particularly interested in direct reception of high-definition images from the satellites’ L-band downlink. The mount he came up with to track satellites during lengthy downloads is a tour de force of junkyard build skills.
The azimuth axis rotates on a rear wheel bearing from a Chevy, the elevation axis uses cheap pillow blocks, and the frame is welded from scrap angle iron and tubing. A NEMA-23 stepper with 15:1 gearhead rotates the azimuth while a 36″ linear actuator takes care of elevation. The mount has yet to be tested in the wind; we worry that sail area presented by the dish might cause problems. Here’s hoping the mount is as stout as it seems, and we’ll look forward to a follow-up.
It would work for us, but a 4-foot dish slewing around in the back yard might not be everyone’s taste in lawn appurtenances. If that’s you and you still want to get your weather data right from the source, try using an SDR dongle and chunk of wire.
He doesn’t provide a method of tuning the radio signal, but at first you can use the audio samples he points to. The actual broadcasts happen on one of seven frequencies between 162.400 MHz and 162.550 MHz but the tones are also broadcast on TV and Radio alerts. Once you have the audio it is fed into a pair of XR-2211 Tone decoders. This provides just three interface pins for the Arduino to watch.
The annoying noise that grabs your attention at the beginning of a weather alert, or test of the alert system is actually what the SAME data packets sound like. From those tones this system will be able to decode what type of alert is being issued, and the geographic locations it affects. If you interested in more info about SAME head over to the Wikipedia article on the topic.
Can you believe that [hpux735] pulled this satellite weather image down from one of the National Oceanic and Atmospheric Administration’s weather satellites using home equipment? It turns out that they’ve got three weather satellites in low earth orbit that pass overhead a few times a day. If you’ve got some homebrew hardware and post processing chops you can grab your own images from these weather satellites.
The first step is data acquisition. [hpux735] used a software defined radio receiver that he built from a kit. This makes us think back to the software-radio project that [Jeri Ellsworth] built using an FPGA–could that be adapted for this purpose? But we digress. To record the incoming data a Mac program called DSP Radio was used. Once you do capture an audio sample, you’ll need something to turn it into an image. It just so happens there’s a program specifically for weather image decoding called WXtoImg, and another which runs under Linux called WXAPT. Throw in a little post processing, Robert’s your mother’s brother, and you’ve got the image seen above.
[Hpux735] mentioned that he’s working on a post about the antenna he built for the project and has future plans for an automated system where he’ll have a webpage that always shows the most current image. We’re looking forward hearing about that.