Hey, got up to 25 degrees today, McMurdo is probably warmer right now.
New Sat dish for McMurdo Station
- Thread starter n0nhp
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Then why steer the dish if it is geostationary. Certainly has more function than that.
That's the standard package from General Dynamics, its motorized and will cover most of the satellite arc. You would not want to get the wrenches out to peak it or make minor adjustments. It will track the satellite although I always parked any C band antenna up to about 11m since it doesn't need to track unless the satellite is inclined. An 11m Ku dish would have to track, otherwise you will see degradation as the satellite moves.
About late January, if the wind wasn't blowing, we'd be walking around in cutoffs and T shirts when it got over 32. We had a couple days over 40. When the humidity is single digits, it's all about sunshine.
n0nhp
Member
While I was the "Satcom Lead" (tech in charge of watching the Blinkin lights) Intelsat moved the bird we were on to make room for another satellite in the arc, It was a subtle move over two weeks duration but I actually got to steer the dish a bit. As satellites come and go and contracts come and go, the dish will be moved to accommodate.
About once every 90 days, the SOP was to nudge the az / el servos just to make sure they were still working and had not frozen up.
Bruce
techsender
Member
And you will need to do "center of box" tweaks probably twice a year. Brings back a lot of memories. Think the crew included Jose ?
A satellite, most any satellite once parked in center of box will be pushed and pulled around by earths gravity and solar winds where it starts moving in an ever growing figure 8 pattern. About every 2 weeks the people who fly the satellite will command the spacecraft back to center of box and this cycle repeats for the lifespan of the spacecraft. The main thing that determines the useable lifespan of a spacecraft is not its electronics or battery, its how much station keeping fuel it has on board at launch by design and from use during unusually busy station keeping maneuvers.
Most companies with C band dishes over about 9m in dia have the dish in a "step track" mode where it peaks itself anywhere from every 10min to 1hr depending on design parameters, the more often wearing out parts faster and less often putting you at some risk of signal degradation. The earth station I worked at for 18yrs (I retired as the principal RF engineer) I locked down our 11m C band antenna at center of box when first installed and its never been moved in over 20yrs now because there was no perceivable degradation as the satellite does its dance and I avoided lots of wear and tear by parking it.
For Ku band and higher the 3dB beamwidth of the antenna will be smaller than C band and most antennas over about 6m diameter will need to track the satellite. I had two 13m Ku, one 11m C, one 11m combo C/Ku two 9m Ka, two 8m Ka and a 7m Ku, all uplink and a bunch of receive only antennas at my site. The larger Ka band (28-30GHz) dishes are soo pointy they use a "monopulse" tracking which is a continuous servo track where if the antenna moves in the slightest its pushed back right on boresight to the satellite instantly.
For this new dish at McMurdo its complicated enough to require someone assigned to it on a 24/7 basis. If its step tracking and carrying important information, an accidental glitch in the tracking can swing the dish off the satellite and it takes someone who knows what their doing to put it back. There is also periodic maintenance checking RF levels a couple of times a day and changing gear oil and lube every 6mo, etc.
If its a transmit/uplink antenna there is a lot of support equipment and high power microwave RF to deal with and periodic maintenance on all that which takes an expert in the field to maintain, align and replace when needed. Over time the cost in maintenance personnel and replacement equipment will greatly exceed the original cost of the antenna.
Most companies with C band dishes over about 9m in dia have the dish in a "step track" mode where it peaks itself anywhere from every 10min to 1hr depending on design parameters, the more often wearing out parts faster and less often putting you at some risk of signal degradation. The earth station I worked at for 18yrs (I retired as the principal RF engineer) I locked down our 11m C band antenna at center of box when first installed and its never been moved in over 20yrs now because there was no perceivable degradation as the satellite does its dance and I avoided lots of wear and tear by parking it.
For Ku band and higher the 3dB beamwidth of the antenna will be smaller than C band and most antennas over about 6m diameter will need to track the satellite. I had two 13m Ku, one 11m C, one 11m combo C/Ku two 9m Ka, two 8m Ka and a 7m Ku, all uplink and a bunch of receive only antennas at my site. The larger Ka band (28-30GHz) dishes are soo pointy they use a "monopulse" tracking which is a continuous servo track where if the antenna moves in the slightest its pushed back right on boresight to the satellite instantly.
For this new dish at McMurdo its complicated enough to require someone assigned to it on a 24/7 basis. If its step tracking and carrying important information, an accidental glitch in the tracking can swing the dish off the satellite and it takes someone who knows what their doing to put it back. There is also periodic maintenance checking RF levels a couple of times a day and changing gear oil and lube every 6mo, etc.
If its a transmit/uplink antenna there is a lot of support equipment and high power microwave RF to deal with and periodic maintenance on all that which takes an expert in the field to maintain, align and replace when needed. Over time the cost in maintenance personnel and replacement equipment will greatly exceed the original cost of the antenna.
I did a bit of TV earth stations, head ends and such, so I know concrete settles and the birds do a bit of dance over time. Just no need for fully articulate dishes, just some tweaks on the jacks.
n0nhp
Member
Remember also, We are talking about a purchase by a U.S. Government agency operated by a contractor for same 
n0nhp
Member
The dome taking shape:
There are not a lot of factory authorized installation crews for these and I suspect this one is being built by Mechantech out of PA. I wish the camera could get a close up of some faces.
n0nhp
Member
Didn't quite get it capped in time:
It very seldom snows in McMurdo but when you need some dry weather, well let's just say Murphy has his little hand in the plans.
It very seldom snows in McMurdo but when you need some dry weather, well let's just say Murphy has his little hand in the plans.
n0nhp
Member
And the Golf Ball is capped off.
n0nhp
Member
And a very late update
future.usap.gov
With future plans included
Station News | United States Antarctic Program
Improving the communications infrastructure for the U.S. Antarctic Program (USAP) continues to be a priority for the National Science Foundation’s (NSF) Office of Polar Programs (OPP).
future.usap.gov
rescuecomm
Member
How do you know when an uplink dish is centered on the satellite?
The antenna system will monitor the satellite beacon then "step track" and peak on the satellite periodically to track its movement. The antenna controller will actually detune the signal very slightly in several directions, calculate the center then park the antenna on the satellite until the next scheduled peak, which could vary from 10 minutes to an hour or more depending on the satellite and the ground system design.
A satellite dish can also do continuous tracking in a "monopulse" mode where the beacon signal is received and converted into phase angles so the antenna controller knows exactly which direction to move to get back on the satellite. This is a continuous closed loop system and even blowing wind on the antenna will cause azimuth and elevation motors to run, trying to keep the antenna pointed exactly on the satellite.
Or if the dish is small enough where the 3dB down points are much larger than the satellite will ever move, the antenna might be manually peaked. In this case you contact the satellite owner to find out when the satellite will be in "center of box" then on that day and time you manually and carefully peak the antenna and lock it down, sometimes for the entire life of the antenna. In nearly all uplink/downlink sites there is a spectrum analyzer or at least a signal strength meter on a beacon receiver and satellite beacon levels are recorded during clear sky conditions when the antenna is peaked. This way you can tell at a glance if anything has degraded or needs attention, not counting rain fade.
All geosynchronous satellites get pulled around by gravity and solar wind causing them to move closer or further from the earth and slow down or speed up their orbit. Ground control stations will send commands to the satellite to fire thrusters about every 2 weeks to center the satellite and this is called station keeping. Its also a very dangerous procedure and any mistake can literally send the satellite out of orbit or rotate its antennas off into space and some satellites have been lost from messing up this procedure.
The amount of fuel a satellite launches with is the major factor in how long the satellite will live. Many perfectly good satellites are retired and abandoned because they ran out of fuel even though their electronics, solar panels and batteries are just fine.
A satellite dish can also do continuous tracking in a "monopulse" mode where the beacon signal is received and converted into phase angles so the antenna controller knows exactly which direction to move to get back on the satellite. This is a continuous closed loop system and even blowing wind on the antenna will cause azimuth and elevation motors to run, trying to keep the antenna pointed exactly on the satellite.
Or if the dish is small enough where the 3dB down points are much larger than the satellite will ever move, the antenna might be manually peaked. In this case you contact the satellite owner to find out when the satellite will be in "center of box" then on that day and time you manually and carefully peak the antenna and lock it down, sometimes for the entire life of the antenna. In nearly all uplink/downlink sites there is a spectrum analyzer or at least a signal strength meter on a beacon receiver and satellite beacon levels are recorded during clear sky conditions when the antenna is peaked. This way you can tell at a glance if anything has degraded or needs attention, not counting rain fade.
All geosynchronous satellites get pulled around by gravity and solar wind causing them to move closer or further from the earth and slow down or speed up their orbit. Ground control stations will send commands to the satellite to fire thrusters about every 2 weeks to center the satellite and this is called station keeping. Its also a very dangerous procedure and any mistake can literally send the satellite out of orbit or rotate its antennas off into space and some satellites have been lost from messing up this procedure.
The amount of fuel a satellite launches with is the major factor in how long the satellite will live. Many perfectly good satellites are retired and abandoned because they ran out of fuel even though their electronics, solar panels and batteries are just fine.
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rescuecomm
Member
Got it. Uplink antenna can rx a beacon signal. I missed that somewhere.
Its rare that it can't but I had one that couldn't. It was an 11m C-band only uplink/downlink antenna on a C/Ku satellite with only a Ku beacon. The system designer had a big idea to get Ku beacon data off a Ku dish at the same site on the same satellite and have monitor and control computers move the C-band dish along with the Ku dish. It never worked right so I manually peaked the C-band dish and locked it down. Problem solved.
n0nhp
Member
The SpecAn is also very helpful when your downlink suddenly drops by 3 to 6db and you look at it to see what's up, only to see another user bumped a control and is blowing the bird away with a 10 over uplink.. calls were made
Oh you MCPC guys sharing bandwidth. My company owned most of their own satellites or we booked entire transponders and didn't have to share bandwidth. We did have some 500MHz wide Ka transponders on two of our satellites and had to balance a bunch of 36Mhz carriers on those which was a big PIA but it was all our carriers.
I wonder what will be flowing through this new McMurdo dish? It would be fun (for me) to go there and get the thing all dialed in or perform customer acceptance testing, run antenna patterns, etc. Its been a couple of years since I had my hands on any of this stuff.
Edit: Oh, never mind, just saw this info above.
"The installation it is replacing is the main Data / Voice path to CONUS via geostationary commercial satellite and last I heard all voice was VOIP. So I doubt except for data on the internet, it will carry any ACARS or ADS-C traffic"
I wonder what will be flowing through this new McMurdo dish? It would be fun (for me) to go there and get the thing all dialed in or perform customer acceptance testing, run antenna patterns, etc. Its been a couple of years since I had my hands on any of this stuff.
Edit: Oh, never mind, just saw this info above.
"The installation it is replacing is the main Data / Voice path to CONUS via geostationary commercial satellite and last I heard all voice was VOIP. So I doubt except for data on the internet, it will carry any ACARS or ADS-C traffic"
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