Solar Activity

[+EraSeek]

Use your WAAS today. Going to be a bumpy ride for the ionosphere.

http://solar.sec.noaa.gov/rt_plots/kp_3d.html

[+Worf's Pack]

Thanks for the info I can use that page at work.

[+budd-rdc]

If I have time, I ought to visit an ADJUSTED benchmark to see the effects on my non-WAAS GPSr.

 

Thanks for the link.

[+deimos444]

I am probably just being a dumbhead again but what effect does surface charging and increased atmospheric drag have on signal acquisition or reliability?

[+reveritt]

Break out the aluminum foil hats!

[+carleenp]

I am probably just being a dumbhead again but what effect does surface charging and increased atmospheric drag have on signal acquisition or reliability?

Taken from this article about using GPS to measure space weather:

 

For GPS users, the impact of space weather can usually be attributed to disturbances in the ionosphere as well as the plasmasphere, which in turn can cause degradation in range measurements and in severe circumstances, loss of lock by the receiver of the GPS signal. As GPS signals propagate through the ionosphere, the propagation speed and direction of the GPS signal are changed in proportion to the varying electron density along the line of sight between the receiver and the satellite. The accumulated effect, by the time the signal arrives at the receiver, is proportional to the integrated TEC, the number of electrons in a column stretching from the receiver to the satellite with a cross-sectional area of one square meter. This in turn affects the GPS range observable: a delay is added to the code measurements and an advance to the phase measurements. To achieve very precise positions from GPS, this ionospheric delay/advance must be taken into account.

Edited July 12, 2005 by carleenp

[+Yamahammer]

For GPS users, the impact of space weather can usually be attributed to disturbances in the ionosphere as well as the plasmasphere, which in turn can cause degradation in range measurements and in severe circumstances, loss of lock by the receiver of the GPS signal. As GPS signals propagate through the ionosphere, the propagation speed and direction of the GPS signal are changed in proportion to the varying electron density along the line of sight between the receiver and the satellite. The accumulated effect, by the time the signal arrives at the receiver, is proportional to the integrated TEC, the number of electrons in a column stretching from the receiver to the satellite with a cross-sectional area of one square meter. This in turn affects the GPS range observable: a delay is added to the code measurements and an advance to the phase measurements. To achieve very precise positions from GPS, this ionospheric delay/advance must be taken into account.

So that explains my DNF's!!! That's my story and I'm sticking to it!!!

 

[+EraSeek]

I am probably just being a dumbhead again but what effect does surface charging and increased atmospheric drag have on signal acquisition or reliability?

Let's see if I can pull this out of my memory hat. Mind you, I may be totally wrong without researching it. Surface charging, as I understand it can do a couple of things. Fry the satellite's electronics, and/or cause havoc with communications with the satellite. Increased atmospheric drag I believe refers to the fact that (although the sats are way the heck out there) the magnosphere is warped and compressed by the presure of the solar storm's onslought. The sats are traveling through this compressed atmosphere of ions, thus slowing their travel and displacing them from their proper predicted positions. This article, though difficult for me to read speaks a lot of the LOSS OF SAT LOCK due this condition, and that makes sense.

 

Most often what happens in a normally disturbed ionosphere is that the signal is delayed due to passing thru this active enviornment. Timing is everything!! with a GPS. A delay of 1 nanosecond can set your position off by 1 meter ( or is it 1 foot?). A nanosecond is one-billionth of a second! During a sever storm, I am sure this is much the case as well, but during a sever storm loss of sats and wild positioning is also much more likely to occur.

[twjolson & Kay]

So that explains my DNF's!!! That's my story and I'm sticking to it!!!

Never heard that one before....

[+Tidalflame]

Are there any archives of this? I'd like to see if some of my DNFs are actually related to this...

[+TeamRJJO]

For GPS users, the impact of space weather can usually be attributed to disturbances in the ionosphere as well as the plasmasphere, which in turn can cause degradation in range measurements and in severe circumstances, loss of lock by the receiver of the GPS signal. As GPS signals propagate through the ionosphere, the propagation speed and direction of the GPS signal are changed in proportion to the varying electron density along the line of sight between the receiver and the satellite. The accumulated effect, by the time the signal arrives at the receiver, is proportional to the integrated TEC, the number of electrons in a column stretching from the receiver to the satellite with a cross-sectional area of one square meter. This in turn affects the GPS range observable: a delay is added to the code measurements and an advance to the phase measurements. To achieve very precise positions from GPS, this ionospheric delay/advance must be taken into account.

For what it's worth.....

 

During my time in the GPS master control station, we observed somewhat limited effects of ionospheric scintillation on the GPS signal. The effects were most pronounced at locations close to the equator, during local sunset, between the months of October and January. At the monitor station in Colorado Springs, we saw almost no impact.

 

So in a nutshell, I'm doubting that North American cachers are going to see much of an effect from this storm.

 

Peace,

TeamRJJO

[+EraSeek]

During my time in the GPS master control station, we observed somewhat limited effects of ionospheric scintillation on the GPS signal.  The effects were most pronounced at locations close to the equator, during local sunset, between the months of October and January.  At the monitor station in Colorado Springs, we saw almost no impact.

 

So in a nutshell, I'm doubting that North American cachers are going to see much of an effect from this storm.

 

Peace,

TeamRJJO

Yes the article says it is usually most pronounce near the poles and the equator. That is fascinating that you worked a a master station. Tell me if you can, during a normal day WAAS can correct you from maybe 12 or 20' down to a few feet. During a major solar storm does WAAS keep up? Does it correct that well?

 

Well I guess to answer my own question, your previous answer would suggest there would not be much to keep up with.

Edited July 13, 2005 by EraSeek

[+deimos444]

Thanx to everyone for the educational answers.

As a mechanical guy I am sometimes confused about the electrical side.

[+TeamRJJO]

Yes the article says it is usually most pronounce near the poles and the equator. That is fascinating that you worked a a master station. Tell me if you can, during a normal day WAAS can correct you from maybe 12 or 20' down to a few feet. During a major solar storm does WAAS keep up? Does it correct that well?

 

Well I guess to answer my own question, your previous answer would suggest there would not be much to keep up with.

There's two parts to the answer:

 

1. Since WAAS broadcasts on the same frequency as the GPS signal we all use, if a storm was severe enough to cause ionospheric scintillation that takes out the GPS signal, it would likely be a problem for WAAS as well.

 

2. What you would see during scintillation would NOT likely be navigation errors. The bit errors that scintillation causes also make the received navigation message fail the built-in parity checks. So, if your user set is designed in accordance with the GPS payload-to-user specification, your receiver wouldn't use that satellite's signal at all. In reality, your receiver would likely have a tough time maintaining signal lock on the satellites, especially those at lower elevation angles. But again, this is a very localized effect.

 

Peace,

TeamRJJO

[+EraSeek]

Great info. Always wish to understand as much as I can. This helps. Thanks TeamRJJO!

[+fizzymagic]

Right. The problem is not ionospheric scintillation, but the TEC of the ionosphere, which slows down the propagation of the signal significantly, giving bad pseudorange numbers and therefore position errors.

 

Solar storms affect GPS readings in two ways: first, via the above-mentioned ionospheric signal retardation, and second, via the drag on the satellites changing the orbital ephemeris.

 

I don't know how significant the latter is, but the former can be substantial. WAAS-enabled GPS receivers will do better during solar storms, but they can still have significant problems if the TEC is changing faster than the WAAS update rate.

[+EraSeek]

So as I understand it ionospheric scintillation is basically a sever flashing of the ionosphere where the signal itself gets wacked out of the ballpark by heavy, intense, localized disturbances and would cause loss of signal, whereas what we will usually experience is simply where the total electron content is increased during a solar storm causing a drag on the signal, slowing it, like diving into water, and thereby causing a timing/position error.

[+TeamRJJO]

Another way of stating it would be that scintillation occurs during (large) fluctuations in TEC.

 

Peace,

TeamRJJO