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More Galaxy 15 (PRN 135) news


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I need someone to explain this (in small words)

 

Depending on their position at the time of failure, these satellites tend to migrate toward one of two libration points, at 105 degrees west and 75 degrees east. Figures compiled by XL Insurance of New York, an underwriter of space risks, say that more than 160 satellites are gathered at these two points, which Bednarek described as the orbital equivalent of valleys.
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I need someone to explain this (in small words)
It means that steering wheel fell off the satellite, and that since it won't stay in its own lane it tends to create problems for other drivers, and eventually, geosync satellites whose steering wheels fall off all wind up in basically the same parking lot. :D Edited by ecanderson
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doesn't that only relate to points between two stellar objects (such as sun/earth or earth/moon), and not to points relative to only one stellar object (such as a certain longitudes of the earth)?

That's what I understand a Lagrangian point is too. The wikipedia explanation of "Libration" doesn't seem to apply either.http://en.wikipedia.org/wiki/Libration

 

As a guess it might be that variations in the earths gravity (due to mass concentrations) might cause satellites to be attracted to certain points in the orbit.

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Yes, confusing. Obviously there is some reason for this "libration points at 105 degrees west and 75 degrees east" and I have seen several references to it but I have not found an explanation of it yet.

 

Because that is the way Q wants it?

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I need someone to explain this (in small words)
It means that steering wheel fell off the satellite, and that since it won't stay in its own lane it tends to create problems for other drivers, and eventually, geosync satellites whose steering wheels fall off all wind up in basically the same parking lot. :D

Did you mean?

It means that steering wheel fell off the satellite, and that since it won't stay in its own lane it tends to create problems for other drivers, and eventually, geosync satellites whose steering wheels fall off all wind up in basically the same parking lot. :wacko:

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Yes, confusing. Obviously there is some reason for this "libration points at 105 degrees west and 75 degrees east" and I have seen several references to it but I have not found an explanation of it yet.

FWIW I asked about this on an Astronomy forum (link) and this was explained as follows:

 

"The Earth is lumpy, and if I am not mistaken the resulting irregularities in the gravitational field give us these sweet spots where the satellites are more resistant to perturbations from the Sun and the Moon. Those perturbations cause the satellites to drift away from their original longitudes in the first place when they run out of station-keeping fuel."

 

and

 

"Yes, these points are directly opposite each other on Earth's equator, and reflect the slight elliptical nature of the mass distribution around the equator. Geostationary satellites positioned elsewhere are on the slope of a very slight potential well, and will trickle "downhill" without regular station-keeping."

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Good info here. I imagine most of the participants are aware of it, but for any who are not, I'll point out that GPS satellites are not geostationary.
Life would be surely be easier if that were possible. My TomTom wouldn't need to download their QuickGPSFix data weekly to keep ahead of the almanac info. :D Imagine a world without ephemeris data.

 

Wouldn't it be nice if every spot above the earth could be a geostationary position? Shame about that physics stuff... always getting in the way of our fun.

 

That said, the WAAS satellites were indeed expected to "stay put" with a little help, unlike the regular GPS constellation which wanders all over the place.

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Good info here. I imagine most of the participants are aware of it, but for any who are not, I'll point out that GPS satellites are not geostationary.

Two are, or were at least. This one is now un-geostationary. :anicute: The WAAS satellites are the geostationary ones. The rest of the GPS constellation, in three orbital altitudes, are lower and not geostationary.

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The saga continues for the Galaxy 15 satellite (PRN 135 / WAAS 48) originally at 133 degrees west. "The stray satellite will pass through the 131 degrees west position around May 31 ..." (link). It's interesting how the other geostationary satellites are being moved around to avoid interference issues.

 

Meanwhile it's still seems to be functioning OK in it's WAAS role according to the WAAS Satellite Status map (link).

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I read that they shut down the WAAS relay temporarily to send it a kill signal, but it didn't work. So apparently we still have WAAS for now. Not that my Garmin Oregon knows the difference...

 

Any ideas on if the FAA has a backup WAAS satellite ready? All I've been able to find on the Internet so far is "maybe".

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I read that they shut down the WAAS relay temporarily to send it a kill signal, but it didn't work. So apparently we still have WAAS for now. Not that my Garmin Oregon knows the difference...

 

Any ideas on if the FAA has a backup WAAS satellite ready? All I've been able to find on the Internet so far is "maybe".

 

There is no such thing as a WAAS satellite, per se.

WAAS is a separate communications package hosted by an Intelsat Galaxy satellite.

Therefore, it may be more of an issue of finding another host satellite for another WAAS package.

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There is no such thing as a WAAS satellite, per se.

WAAS is a separate communications package hosted by an Intelsat Galaxy satellite.

Therefore, it may be more of an issue of finding another host satellite for another WAAS package.

Does a satellite broadcasting WAAS correction need to have certain hardware on it? I read things like "Galaxy 12 does not have the payload (L-band) necessary to broadcast WAAS corrections" which I assume meant some hardware limitation, but I guess I could be wrong about that. I know it's not dedicated to WAAS only, that is only one of its functions (though now it sounds like it is its only function).

 

So what is the proper terminology for a satellite broadcasting WAAS?

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I read things like "Galaxy 12 does not have the payload (L-band) necessary to broadcast WAAS corrections" which I assume meant some hardware limitation, but I guess I could be wrong about that.
No, you're 100% correct. The WAAS signal uses the 20cm band, just like the rest of the GPS system, and Galaxy 12 doesn't support those frequencies ... it's a C-band only (60cm) satellite.
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I read that they shut down the WAAS relay temporarily to send it a kill signal, but it didn't work. So apparently we still have WAAS for now.

I wish someone would tell my Triiton 2000 that. I've had it for three weeks now and have as yet to pick up a WAAS satellite. Or a twelfth GPS satellite.

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It still lives :D SpaceFlightNow.com (link)

 

It has drifted to 117.6°W (from 133°W) so far and it looks like it may continue it's WAAS role until the new satellite (PRN133) becomes operational later this year and maybe even later.

 

When Galaxy 15 does power itself down, officials say there is a small chance they could reboot the satellite and recover its functionality.
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It still lives :anicute: SpaceFlightNow.com (link)

 

It has drifted to 117.6°W (from 133°W) so far and it looks like it may continue it's WAAS role until the new satellite (PRN133) becomes operational later this year and maybe even later.

 

When Galaxy 15 does power itself down, officials say there is a small chance they could reboot the satellite and recover its functionality.

 

I haven't seen it on any of my GPSr's. It has caused more trouble with CATV head-end reception issues than it is worth!!!! I wish I could shoot it down!!

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I haven't seen it on any of my GPSr's. It has caused more trouble with CATV head-end reception issues than it is worth!!!! I wish I could shoot it down!!

You'd see it as #48, not #133. As it drifts further east, it will actually be a good one for you. I look forward to it moving more to about 104 degrees so it won't be shadowed when I'm up close to the Rockies on the Front Range.
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I haven't seen it on any of my GPSr's. It has caused more trouble with CATV head-end reception issues than it is worth!!!! I wish I could shoot it down!!

You'd see it as #48, not #133. As it drifts further east, it will actually be a good one for you. I look forward to it moving more to about 104 degrees so it won't be shadowed when I'm up close to the Rockies on the Front Range.

 

Actually it shows up as WAAS 135. Delorme's PN series do not use the SV numbers like Garmin.

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I just noticed that easterly bound WAAS 48, has almost caught up with 51.

48 is at 107.94

51 is at 107.27

It looks like that 48 will track just south of 51 as it passes it. (if - means south)

Can't blame my 60CSx for using 46 for the last few says, as 48 and 51 duke it out.

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I just noticed that easterly bound WAAS 48, has almost caught up with 51.

48 is at 107.94

51 is at 107.27

It looks like that 48 will track just south of 51 as it passes it. (if - means south)

Can't blame my 60CSx for using 46 for the last few says, as 48 and 51 duke it out.

 

So long 48, and thanks for all the fish....

Edited by Hank30721
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My older units are acting as expected, with the "shutdown" of WAAS 48. The Meridian, after more than half an hour, keeps on searching for 48. Too bad that one can't go inside, via 03, and cancel just one WAAS Sat, rather than both, as it's all or nothing. Another hack in the future to change to 46.

The GPS 60 grabbed 51 right off, then in the second slot it searched for 48 for about a minute, then to 33 for about a minute, then to 46. The bar never goes solid and the icon flashes, but it has been doing the corrections ok. Sometimes with 14 sats visible, the unit only uses one WAAS slot/bar, and it has kicked 51 off, keeping 46, but the +- accuracy drops from 13 ft to 5 ft, like it does with 51.

Side note: I have had the WAAS Sat kicked off of a 60CXs, when there were about 14 sats visible, just like Garmin said that it might, in a back page of the manual.

Now I wonder how the new Maggie X10 units will handle the change.

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My older units are acting as expected, with the "shutdown" of WAAS 48. The Meridian, after more than half an hour, keeps on searching for 48. Too bad that one can't go inside, via 03, and cancel just one WAAS Sat, rather than both, as it's all or nothing. Another hack in the future to change to 46.

The GPS 60 grabbed 51 right off, then in the second slot it searched for 48 for about a minute, then to 33 for about a minute, then to 46. The bar never goes solid and the icon flashes, but it has been doing the corrections ok. Sometimes with 14 sats visible, the unit only uses one WAAS slot/bar, and it has kicked 51 off, keeping 46, but the +- accuracy drops from 13 ft to 5 ft, like it does with 51.

Side note: I have had the WAAS Sat kicked off of a 60CXs, when there were about 14 sats visible, just like Garmin said that it might, in a back page of the manual.

Now I wonder how the new Maggie X10 units will handle the change.

 

I responded in the x10 thread in case you don't see it. I'll try and get a good lock with the 610 asap and watch the birdees. 46 has been hit and miss from what I've seen so far but havent got to spend a great deal of time. Last Saturday I was out most of the day but running out of time and ended up grabbing coords with the Garmin since i had several waypoints stored for a friend on the Mag that i didnt want to risk.

 

The 610 is a really nice unit and not sorry I bought it even though it was bought due to temporarily losing the Garmin.

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Just to clear up some misinformation...

 

That said, the WAAS satellites were indeed expected to "stay put" with a little help, unlike the regular GPS constellation which wanders all over the place.

 

GPS satellites do not wander all over the place. Each one is assigned a specific orbital plane and a slot within that plane. Think of a plane as a circle around the earth. A slot is a position on that circle. A GPS satellite will circle the earth roughly twice a day.

 

The WAAS satellites are the geostationary ones. The rest of the GPS constellation, in three orbital altitudes, are lower and not geostationary.

 

As someone else mentioned, "There is no such thing as a WAAS satellite, per se." I just wanted to add that the satellites which carry the WAAS payload are not a part of the NAVSTAR GPS constellation.

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PRN 135 / WAAS 48 may return.www.intelsat.com

Galaxy 15 Status Update

On 23 December, the power from the Galaxy 15 battery completely drained during its loss of earth lock and the Baseband Equipment (BBE) command unit reset, as it was designed to do. Shortly thereafter Galaxy 15 began accepting commands and Intelsat engineers began receiving telemetry in our Satellite Operations center. We have placed Galaxy 15 in safe mode, and at this time, we are pleased to report it no longer poses any threat of satellite interference to either neighboring satellites or customer services.

 

After completing initial diagnostic tests, we will load updated commanding software to the satellite. We expect to relocate the satellite to an Intelsat orbital location where engineers at our Satellite Operations Control Center will initiate extensive in-orbit testing to determine the functionality of every aspect of the spacecraft. We will provide an update through normal sales channels, and MyIntelsat, if and when the satellite recovery mission is successful.

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News like this really grounds a person. We have so much fun with our sport of geocaching or just getting lost in the woods and using the GSP to get us out that it is easy to forget all of the complexity that goes into making it all possible. It is also somewhat ironic that we are guided by satellites to and from our destination and yet one of those satellites is getting lost. I'm glad there are people whose job it is to keep those satellites in place.

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