Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

agupubs.onlinelibrary.wiley.com

Post reply on HN
Print view View original

51–60 of 92 posts

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#51

Post by ziftface »

gremy0 wrote: post #37
eganist wrote: post #7

I'm taking the liberty of reworking their "plain language summary." I aimed for maintaining accuracy with relaxed precision, but please correct me if I've lost too much of either in the process. I corrected a specific bit of imprecision in language in the source's plaintext summary not clearly distinguishing between vertical/y v. vertical/z, something the technical abstract clarified by stating "vertical altitude." -…

hmm, I put your "plainest" language answer into XKCD simple writer, and there was some complexity in there. In most simple language, the space truck was thrown up, not tossed forward, and this caused a sound wave that was followed with some interesting events in one of the high bits of the sky, between the space truck refuse air and the hotter-than-air stuff in the high sky, all of which need further study because of…

I'm actually really impressed by this, not bad

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#53

Post by cwkoss »

eganist wrote: post #7

I'm taking the liberty of reworking their "plain language summary." I aimed for maintaining accuracy with relaxed precision, but please correct me if I've lost too much of either in the process. I corrected a specific bit of imprecision in language in the source's plaintext summary not clearly distinguishing between vertical/y v. vertical/z, something the technical abstract clarified by stating "vertical altitude." -…

Is '~1 m' meters or miles?

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#54

Post by ethbro »

drag0nballz wrote: post #43
ethbro wrote: post #32

Earlier quoted context omitted.

I don't have firsthand knowledge, but I'd be surprised if mission critical military gear uses GPS for more than a secondary / corrective role. I can't imagine the signals play that well in a heavily-jammed environment. High probability rough GPS fix + radar / optical terrain comparison & dead reckoning for terminal guidance seems more likely.

I'm not sure if you consider this "mission critical" but US military drones use GPS for navigation. There have been several cases of them being captured via GPS jamming.

From what I heard, that extended to GPS spoofing.

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#55

Post by Asraelite »

bluGill wrote: post #35
jessaustin wrote: post #12

The worst such event on record caused errors of ~1 meter. I didn't think civilian GPS was that precise anyway, and that's why various schemes are used in conjunction with GPS for greater accuracy? Presumably, military GPS has similar schemes to deal with this sort of event?

Many commercial GPS systems can get to within 2cm ( I don't know if the correction GPS will see the same error and thus give the correct correction factor or not.

By "another GPS" do you mean a different satellite in the same network, or a different GNSS?

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#56

Post by dfsegoat »

tener wrote: post #44
eganist wrote: post #7

I'm taking the liberty of reworking their "plain language summary." I aimed for maintaining accuracy with relaxed precision, but please correct me if I've lost too much of either in the process. I corrected a specific bit of imprecision in language in the source's plaintext summary not clearly distinguishing between vertical/y v. vertical/z, something the technical abstract clarified by stating "vertical altitude." -…

We sure need to study the ability to affect the ionosphere. And then people will build weapons capable of doing it in suitable ways. Unless they already have those.

You mean, like HAARP? Not saying it is a weapon. But it certainly has the pedigree to perceived that way, from a program & pop-culture standpoint:

https://www.popsci.com/military-aviation-space/article/2008-...

* Note: University of Alaska fairbanks appears to have taken over HAARP and converted it to a "Fee based" research center -- much like a radiotelescope at other academic institutions I assume?

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#57

Post by louprado »

cwkoss wrote: post #53
eganist wrote: post #7

I'm taking the liberty of reworking their "plain language summary." I aimed for maintaining accuracy with relaxed precision, but please correct me if I've lost too much of either in the process. I corrected a specific bit of imprecision in language in the source's plaintext summary not clearly distinguishing between vertical/y v. vertical/z, something the technical abstract clarified by stating "vertical altitude." -…

Is '~1 m' meters or miles?

This is science!, therefore, metric system. Also GPS navigation errors of 1 mile would have been something you would have noticed.

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#58

Post by eganist »

cwkoss wrote: post #53
eganist wrote: post #7

I'm taking the liberty of reworking their "plain language summary." I aimed for maintaining accuracy with relaxed precision, but please correct me if I've lost too much of either in the process. I corrected a specific bit of imprecision in language in the source's plaintext summary not clearly distinguishing between vertical/y v. vertical/z, something the technical abstract clarified by stating "vertical altitude." -…

Is '~1 m' meters or miles?

m is standard for meters

mi is standard for miles

--

Good ask.

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#59

Post by peterwwillis »

Rebelgecko wrote: post #28
jessaustin wrote: post #12

The worst such event on record caused errors of ~1 meter. I didn't think civilian GPS was that precise anyway, and that's why various schemes are used in conjunction with GPS for greater accuracy? Presumably, military GPS has similar schemes to deal with this sort of event?

Military GPSs use multiple frequencies which helps them mitigate errors from the ionosphere. NOAA publishes enough space weather data to let commercial receivers make their own corrections, but I don't know if any actually do. In the relatively near future, GPS satellites will broadcast multiple frequencies for civilian use, once commercial receivers catch up everyone should be able to reduce the error due to atmosph…

Civilian devices can use two frequencies as well, they just don't for cost and complexity reasons. The new L5 frequency has been available for some time and new devices supporting it are coming out this year. There are also multiple augmentations users can use to increase their accuracy to even greater levels than military users: https://www.gps.gov/systems/augmentations/

Re: Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5

#60

Post by Stratoscope »

iaw wrote: post #24
m3kw9 wrote: post #9

Even plainer language: Rocket exhaust can have impact with atmosphere, we need to study it more on short and long term effects.

The ionosphere is not the same thing as the atmosphere. The ionosphere is a shell of super hot gas outside of the atmosphere.

The ionosphere is not outside the atmosphere, it's part of the atmosphere.

The atmosphere consists of many layers. From the ground up, these are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

You may be thinking of the thermosphere, which is indeed very hot (thus the name), albeit with such low density that it wouldn't transfer much heat to your spacesuit or spacecraft. But the thermosphere is part of the atmosphere too.

https://spaceplace.nasa.gov/thermosphere/en/

The ISS and other low earth orbit satellites are orbiting inside the thermosphere. Yes, the ISS is in the atmosphere and suffers from a small amount of atmospheric drag, so it requires occasional reboosts to maintain altitude.

The ionosphere isn't exactly a separate "layer" from these. It's a very tall region of ionized gas that starts near the top of the stratosphere and overlaps parts of the layers above. Its exact limits vary with solar conditions.

The ionosphere is actually made up of several layers of its own, defined by the solar energy wavelength that causes ionization in each layer. These are the D, E, and F layers, and occasional sub-layers within those. Hams and other shortwave radio operators are familiar with these ionospheric layers because of their different effects on radio propagation.

https://en.wikipedia.org/wiki/Ionosphere

https://spaceplace.nasa.gov/ionosphere/en/

https://www.nasa.gov/mission_pages/sunearth/science/atmosphe...

And I finally get to say about one of my own comments: "Username checks out."

https://en.wikipedia.org/wiki/Stratoscope

(I'm actually named after the Truetone Stratoscope radio antennas, not the balloon, but sometimes people do say I'm full of hot air.)

Post reply on HN