FLTSATCOM

[Matt285]

Chanito posted earlier on an antenna topic and mentioned FLTSATCOM. What type of traffic is typically on there? Voice, CW, digital, RTTY. And also if you are monitoring how often are satellites in the right orbit for you to be able to copy. I know this is based on location and the angle of the pass. I guess I'd just ask how often you hear this traffic when monitoring on casual time. Thanks

[Matt285]

I should add that i'm asking about the satellite side and not air to ground and vice versa.

[NJQA]

 FLTSATCOM uses geostationary satellites...there is no “pass”...either your location is in the footprint or it isn’t.  You will hear some clear voice traffic (mostly Brazilian pirates) but most traffic will be encrypted digital.

[Matt285]

Ok thanks.

[Josh]

There's fh (frequency hopping) mode as well as the random digital modes in use by US forces, as well as the mentioned Brazilions of pirates. I suspect the best bang for the buck on the milsats would be an old scanner that covered the mil air band and then pop in all the sat bandplans and let one sit simmering on the milsats for the years to come. Sometimes cools stuff pops up, and keep in mind anyone who has the rf on the right freq can use these things so you never know who will show up. Mebbe even Russians!

[h96cs]

Of course there is cool stuff going on up there. Received this 5th February 2020, two days ago.

https://youtu.be/-bdMLh11b1o

I was quite amazed of receiving this, as most of the users I usually hear are brazilian pirates.
73's.

[anigwei]

Hi!

I live just 300 kilometers north from h96cs and I have no way to receive that signals! Why does h96cs receive it with a single scanner antenna and I have no way to receive it with similar antenna (I've tried a 144Mhz Yagi without success, a 144/433 Moxon, and a telescopic HT with same results).

Maybe those satellites have nulls within its footprint?

73

Of course there is cool stuff going on up there. Received this 5th February 2020, two days ago.

https://youtu.be/-bdMLh11b1o

I was quite amazed of receiving this, as most of the users I usually hear are brazilian pirates.
73's.

[nickcarr3151]

FLTSATCOM uses geostationary satellites...there is no “pass”...either your location is in the footprint or it isn’t.

Are you 100% sure about this?  FLTSATCOM 8 appears to be geo but FLTSATCOM 7 appears to be in an equatorial orbit. 

[NJQA]

FLTSATCOM uses geostationary satellites...there is no “pass”...either your location is in the footprint or it isn’t.

Are you 100% sure about this?  FLTSATCOM 8 appears to be geo but FLTSATCOM 7 appears to be in an equatorial orbit. 

Geostationary orbits are a form of equatorial orbit.

FLTSATCOM 7 is in a geo orbit.
https://space.skyrocket.de/doc_sdat/fltsatcom-2.htm

Maintaining a geo satellite with a near zero orbital inclination uses up station keeping fuel.  One tradeoff the designer has is to allow small amounts of inclination (for example +/- 5 degrees) to develop.  Doing this means you don’t have to perform station keeping maneuvers quite so often, saving fuel and extending the lifetime of the satellite.

To the observer on earth, this results in the satellite apparently “wandering” slightly in the sky, drawing a figure 8 pattern on the suborbital point on the earth.  Maintaining a bore site on the satellite would require a simple antenna tracking mechanism, but the beamwidth of most directional UHF antennas is broad enough that this isn’t necessary.  On Ka band it would be.

FLTSATCOM 7 and 8 are beyond their planned lifetime.  I wouldn’t be surprised to if a decision had been made to leave them in place as long as they were working, but to allow them to develop some orbital inclination.

When a geo satellite is “retired” it is placed in a graveyard orbit.   This requires less fuel than deorbiting the satellite.  The satellite is pushed a few 100 km farther out than the geo orbit and left there.  This frees up that geo slot for another satellite.

Also, you are talking about FLTSATCOM 8, not UFO8, right?

[nickcarr3151]

Well I'm confused then because when I plug the latest keps into Orbitron it shows FLTSATCOM 8 as stationary over India near its equator moving slowly S-N every day.  If I plug FLTSATCOM 7 in, it shows it over Hawaii -- but every day it shifts west-ward along the equator.  UFO 5, 6, and 9 are similar.

[NJQA]

Well I'm confused then because when I plug the latest keps into Orbitron it shows FLTSATCOM 8 as stationary over India near its equator moving slowly S-N every day.  If I plug FLTSATCOM 7 in, it shows it over Hawaii -- but every day it shifts west-ward along the equator.  UFO 5, 6, and 9 are similar.

OK,  that sounds like FLTSATCOM 8 is in a slightly inclined orbit, doing the figure 8 stuff.

Is it possible FLTSATCOM 7 is being moved?  To shift an orbital slot, the satellite is moved slightly closer to or farther from earth.  That causes it to move East or West.  When it gets to its new orbital slot, the satellite is parked back into the geo orbit.  This uses fuel so it is not done often.

FLTSATCOM 7 is old.  I suspect that it is just in an inclined orbit.

If you look here:
https://www.n2yo.com/satellite/?s=17181
You will see that it has an inclination of 14.5 degrees, which is a lot for a geo.

UFO8, seen here:
https://www.n2yo.com/satellite/?s=25258
has an inclination of 8.6 degrees.  There will be motion about the suborbital point, but not as much as for FLTSATCOM 7.

Compare the motion along the suborbital point for each of them.

If you compare this to, say, DIRECTV 15, as seen here:
https://www.n2yo.com/satellite/?s=40663
you will see an orbital inclination of 0 degrees and a sub orbital point that doesn't move.  This satellite has Ka band transponders and a user base that does not have tracking antennas.  It must stay in position, otherwise it will move outside the mainlobe of the user antennas.  More fuel will be expended to keep that satellite in position.

[NJQA]

One other thing.  It might seem like an inclined orbit is a negative thing for a Geo, and often it is, but it is sometimes useful.   On the satellites farthest excursions North/South, it may be visible for a little while to earth sites at high latitudes that normally would never be able to see geo satellites.

[NJQA]

FLTSATCOM 8, seen here:
https://www.n2yo.com/satellite/?s=20253
Has an inclination of 13 degrees and you can see much more N/S movement around the suborbital point.  It isn’t drifting West like FLTSATCOM 7.  My guess is that they are either moving 7 or they no longer have enough fuel for station keeping.

[sat_dxer]

FLTSATCOM 7 (USA 20)

Period to 1,456 min
Eccentricity .0041502
Mean Motion 0.98928/day

[nickcarr3151]

My guess is that they are either moving 7 or they no longer have enough fuel for station keeping.

After reading up on sat orbits a bit, this is what I was thinking.  Like I said though, a few of the UFO sats are doing the same.  Unless -- they are letting them wander a bit and then course correcting them after X period of days.