That's a pretty impressive number of scrabble points for a project acronym, and I guess bonus points for building that acronym on top of another acronym (GNSS = Global Navigation Satellite System, generic term for America's GPS).
I know government projects have a long, storied history of such wordplay. Anyone have any fun stories on coming up with a really elaborate one? I wonder if chatGPT will unleash a new era of creativity with these...
“Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism”
Also… goodbye privacy but, you know… Patriotism!
I get that it's a play on "canning something", but as a strong believer in nominative determinism, it comes as no surprise to me that companies in fact still can spam me.
One point of clarification: GNSS is a term that has broader application than you describe, as it encompasses constellations from other countries and political associations as well. For example:
* Galileo - European Union's GNSS system, named after the astronomer * BeiDou - China's GNSS system * GLONASS - Russia's GNSS system * JAXA - Japan's GNSS system
One backronym that I liked from my time doing my PhD was RELAMPAGO, which is a Spanish word for "lightning," but which some group of scientists gave this definition: "Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations". It was a very cool campaign that produced a ton of amazing data, and catalyzed many dissertations (including one of my close friend's).
Sort of a reverse Xerox/Google/Velcro situation.
But lots of old school pros like surveyors will still refer to it as 'Navstar', which has resurged with the introduction of competing GNSS systems from other countries. Especially if you want to avoid the GPS/GNSS confusion.
There's debate about whether NAVSTAR itself was ever an acronym/backroom, or just a name.
"NAVigation System using Timing And Ranging"
Can confirm I've already submitted at least one bid with a chatGPT-derived acronym, complete with an X for scrabble points.
I'll chalk that one up as an argument in favour of "LLMs will take over the world", as coming up with cool acronyms involving sciency-sounding words genuinely might be one of the most important jobs in the space industry
Frankly GPS is so outmoded as to be a questionable source of meaningful data for things like ionospheric metrics. Beidou is light years ahead in both speed and fidelity.
But last I checked, the serious geologists I worked with had an almost religious aversion to "precursor signals". Has the state of the art changed there?
On the other hand, earthquakes are very notable events and probably cause all kinds of observational biases that make people interpret other phenomena as related. “Earthquake lights” might just be transformers shorting out, for example.
They're measuring it by looking for phase differences in the received L-band (~2GHz) signals, rather than amplitude. That eliminates lots of noise. And they're looking for a particular pattern, which lets you get way below the noise floor. For example, the signal strength of the GNSS (GPS) signal itself might be -125 dBm, while the noise level is -110 dBm [2]. That means the signal is 10^-12 _milliwatts_, and the noise is about 30 times larger. But by looking for a pattern the receiver gets a 43 dB processing boost, putting the effective signal well above the noise.
>> They're measuring it by looking for phase differences in the received L-band (~2GHz) signals
The "L-Band signals" are GNSS signals, for example GPS L1 and L2, which use a carrier wavelength of 1575.42 MHz and 1227.6 MHz, respectively. Both L1 and L2 signals are emitted at the same time, but experience differing levels of delay in the ionosphere during their journey to the receiver. The delay is a function of total electron content (TEC) in the ionosphere and the frequency of the carrier wavelength. Since we already know precisely how carrier frequency affects the ionospheric delay, comparing the delay between L1 and L2 signals allows us to calculate the TEC along the signal path.
Another way to think of it is: we have an equation for signal path delay with two unknowns (TEC, freq). Except, it is only one unknown (TEC). Use two signals to solve simultaneously for this unknown. Use additional signals (like L5) to reduce your error and check your variance.
[1] https://www.swpc.noaa.gov/phenomena/total-electron-content
edit: The atmosphere between the surface and the ionosphere forms a natural low-pass filter as well. I imagine typical ocean waves as seen by us are way too high-frequency to make it up to the ionosphere.
There are other, natural disturbances in the ionosphere, such as traveling planetary waves[2], but they have a significantly longer wavelength. As such the paper[3] mentions filtering them out using a high-pass filter.
In the paper they show some preliminary results trying to invert the parameters in order to estimate the height of the tsunami based on the measured ionosphere disturbance based on synthetic data, and the baseline amplitude is 10cm (4 inches), which the model comes quite close to.
[1]: https://earthobservatory.nasa.gov/blogs/fromthefield/2014/04...
[2]: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...
[3]: https://link.springer.com/article/10.1007/s10291-022-01365-6
Does anyone know if it would be feasible nowadays to just use starlink (or other LEO satellites) as a GNSS constellation? Even without precise onboard-clocks, would it not be possible to just bounce clock signals from earth as long as latency is known?
Ah, but how do you know latency, without accurate clocks? :) Accurate clocks facilitates measuring latency, which is used to calculate distance. :)
Starlink probably could learn the position of every satellite very accurately based on latency and signal strength and angle data from all the ground stations alone if they wanted to, if they don’t already.
Many areas that suffered the waves had earlier felt the earthquake that caused it (including here in India) and the sea receded in some places. Almost no one was alarmed by this or understood what was to follow. Even the news media didn't initially understand what they were reporting.
That situation has changed now. Sufficient buoys are deployed along with public warning systems. People are also much more sensitive to the warning signs. I don't think anybody will be caught by surprise like that in the future. That said, any new concepts and advancements are welcome. The more the merrier.
PS: We're coming up on the 20th anniversary of that disaster - the 26th of this month. Please remember the more than 128K people that perished on that day. Some of them were younger than much of the HN audience. May the victims and the lessons of that day never be forgotten.
> Given that GNSS satellites typically travel in medium Earth orbit, approximately 20,000 km or 12.4 miles above the surface, GNSS systems are well suited for detecting fluctuations in ionospheric density. > > Further, because ground stations can detect GNSS satellites from such a significant distance (up to 1,200 km),...
Should that be 2000 km and 1240 mi?
Using MEO means that they'll need fewer satellites for global coverage at acceptable elevation angles than they would in LEO, and since navigation signals are very low data rate, power is usually not a limiting factor either.
I don't understand, something happens every day. It's been running for years. Are the predicting it our not?
Have they timestamped a prediction/analysis beating other methods and had it confirmed afterwards?
How often is it wrong, how often is it right when they make calls real time?
They are detecting events quickly.