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D10 Satellite TECH THREAD - HD Testing Schedule / Press Releases / Location

Discussion in 'DIRECTV General Discussion' started by Sixto, Jul 6, 2007.

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  1. Sep 6, 2007 #1841 of 2718
    Ken984

    Ken984 Active Member

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    Bossier...
    Its impossible to say, I would hope that they are purposeful in making it exactly perfect so they can try the rest of the systems.
     
  2. Sep 6, 2007 #1842 of 2718
    davring

    davring Hall Of Fame

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    I know they would not be making any more moves than absolutely necessary, you can't call the fuel truck to top off the tank. I understand that fuel is critical to the life of the sat, if it runs out it becomes quite useless. If I am wrong someone please step in and set me straight. :)
     
  3. Sep 6, 2007 #1843 of 2718
    James Long

    James Long Ready for Uplink! Staff Member Super Moderator DBSTalk Club

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    The question would be if they are actually burning fuel.
    They could have given it a nudge and just let it drift.
    It isn't like every mile costs an exact amount of fuel.
    It is the starting and stopping that costs.
     
  4. Sep 7, 2007 #1844 of 2718
    donshan

    donshan Godfather

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    :D I worked several hours this afternoon with the Spaceway 1 TLE history data set to see if any drift could be detected. I thought I would post the initial results for others to check and comment on, because they seem to indicate Spaceway 1 drifted very slightly West during July and early August, but has been more or less stationary at 102.8 W +/- since mid August.


    I found the calculations more tedious that I expected because I found I needed to set my The Sky astronomy program to the exact same Julian day and day fraction as the TLE data set. I set up an Excel spreadsheet to do the time calculations and correct for my -7 hr from UTC and in the end rounded to the nearest hour to save some time. Changing the minutes and seconds in the calculation only changed the outer decimals. I hope it is right but there were a lot of copy/pastes and formulas to enter so this is a first draft for comments.

    The Sky has a time skip forward function that can be set to scales of seconds, minutes, hours, or days. I set it for hours and watched Spaceway 1 wobble back and forth during 24 hours in a simulation. This showed me visually what others have posted, that these orbits are not perfect in keeping SW1 exactly fixed over one spot on earth.

    The message for looking at D10 moves is that, it too is moving back and forth vs. earth longitude in its present slot. Calculating the position at times after the TLE set will probably show this same back and forth. So one person's position data can vary from another depending on the time that they did the computer calculation.

    Also bear with me as this is the first time I have ever tried this!:)

    This time input was informative as it showed rounding the day/time makes a difference in the decimal accuracy of the calculated Spaceway 1 longitude and other data. I have included 3 decimals on the longitude, but those values vary with the hour of the calculation. Also I did not post the latitude as it is close to zero in all calculations indicating SW 1 is over the equator.

    It took D* about four weeks to "drift" Spaceway 1 over less than 0.1 degree! SW1 drifted about half as far as D10 needs to go to get to 102.775 W. OMG! I hope it doesn't take weeks to drift D10 too!:eek2::eek2:

    I think I see some extra fuel being burned!:D

    Although as I understand with the Xenon Ion propulsion most off the energy comes from electric power off the solar panels.

    "Maximum Warp Power Scotty!"

    http://www.boeing.com/defense-space/space/bss/factsheets/xips/xips.html
     
  5. Sep 7, 2007 #1845 of 2718
    cnmsales

    cnmsales Hall Of Fame

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    This would line up with the Sept 19th date.
     
  6. Sep 7, 2007 #1846 of 2718
    Smthkd

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    Not if they started early per there request to the FCC as being ahead of schedule. This would put them more at the 16th like Earl and others are saying!
     
  7. Sep 7, 2007 #1847 of 2718
    harsh

    harsh Beware the Attack Basset

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    If you read the terms and conditions of an STA, there may be severe penalties if a testing satellite interferes in any way with the function of a working satellite. This would doubtless include DIRECTV 10 interfering with Spaceway 1.

    It is also likely that if the maneuvering system is found to be unstable, they don't want to get it anywhere near another satellite.
     
  8. Sep 7, 2007 #1848 of 2718
    Chip Moody

    Chip Moody Legend

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    Yeah, so much so that I feel compelled to say "Oh, duh!" :)

    Thanks...

    - Chip
     
  9. Sep 7, 2007 #1849 of 2718
    kaysersoze

    kaysersoze Duplicate User (Account Closed)

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    So are we talking about 2 different kinds of transmissions, because I thought the sat was being tested prior to being at the 102.6 slot?
     
  10. Sep 7, 2007 #1850 of 2718
    Smthkd

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    102.6 is the testing slot! The permanent slot will be 102.8 (unless they get they final approval for 102.775. They already have temporary permission for this slot - 102.775- until the approval)!
     
  11. Sep 7, 2007 #1851 of 2718
    Ken984

    Ken984 Active Member

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    Bossier...
    The length of time it took Spaceway 1 to drift was probably due to the fact it was in service and broadcasting, if they moved it faster it may have disrupted service. Hopefully it will be as "quick" as they have said "3 days".
     
  12. Sep 7, 2007 #1852 of 2718
    MIAMI1683

    MIAMI1683 New Member

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    Lefty or Ken, once the move is started (assuming it hasn't) will there be alot of time spent trying to get the orbit perfectly circular again?
     
  13. Sep 7, 2007 #1853 of 2718
    LameLefty

    LameLefty I used to be a rocket scientist

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    It depends on how precisely they can increase apogee to begin the drift, then decrease it again to slide back into a correct GSO altitude at the operational slot, without inducing any other major disruptions to the orbit (such as increasing inclination). We won't know until "the Move" starts, and I don't think it has yet unless new TLEs come out showing a major change in position.

    I'm going to be out of the office doing my real job most of this morning, so I'll trust Ken, Don and the others to post info as it turns up. :)
     
  14. Sep 7, 2007 #1854 of 2718
    donshan

    donshan Godfather

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    Good point. They could have used the low thrust Xips over many weeks because they had plenty of time to do it. I was hoping to find a specific day that they did a "burn" and changed the orbit of Spaceway 1 to move it. I did not find that. To move D10 in three days maybe they plan to use the "liquid apogee engine".

    From the Boeing fact sheet on the D10, it has two types of propulsion, a) "liquid apogee engine- 100 lbf", plus b) two Xips units for station keeping( with two spares). That factsheet lists the D10 mass as 13,360 Lbs at launch, but that changes to "8,157 lbs -in orbit beginning of life.". The most obvious reason to "lose" 5203 lb. is the fuel used for the initial orbit adjustment maneuvers. with the liquid engine. If they planned fuel use well maybe they have chemical fuel left that was a planned allocation for burns for this final 3 day move to get to 102.775 W quickly. If so we may see a different pattern in the D10 TLE data to move D10 in three days than for SW 1 over weeks. They will then have the two Xips units reserved for 15 years of station keeping and would not need the apogee engine again until maybe one last "end of life " burn.

    The "real" rocket scientists here should comment on my amateur speculations. :D
    Such as are the Xips units powerful enough to move D10 in three days or is the liquid appogee engine required to do it that quickly?

    If they do an apogee engine burn the D10 data may show a bigger TLE difference more quickly than was in SW1 TLE data.
     
  15. Sep 7, 2007 #1855 of 2718
    F1 Fan

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    You mean tracking D10 and keeping DBSTalk informed is not your real job?:eek2:

    Seriously I want to thank you, Ken, Don and others for keeping us informed and teaching us amateurs on the way. I have been "tracking" D10 since launch with your help in here.
     
  16. Sep 7, 2007 #1856 of 2718
    dhowse

    dhowse Cool Member

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    Donshan,

    The propellent used by the main kick motor is probably the same fuel used by the small station keeping thrusters. When it comes to fuel management "gooooo slooooow" is the name of the game. The orbital analysts that figure this stuff up (10# brain guys) spend a lot of time optomizing the burn plans to use the least amount of fuel. Don't forget, the two main things that determine a satellite's usable operational life are battery capacity and fuel. Conserving fuel now means more fuel available later in the mission. The longer youu stay operational in orbit the more use ($'s) you get from your satellite.

    Doug
    And yes, I am a rocket scientist.
     
  17. Sep 7, 2007 #1857 of 2718
    dhowse

    dhowse Cool Member

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    As far as TLE's: For Geo birds they are not updated that often (something like every two weeks or so if I recall). D10 could already be in its operational location. You just won't know it until a new TLE comes out.

    EaglePC: Believe it or not collision avoidance pretty much operates on the Big sky, little satellite principle. It's up to the satellite operators to avoid collisions. Of course it's in their best interest as well. The problem is when you have a dead bird near your or bital slot. It makes orbital maneuvers that much more interesting. That's why you pay your orbital analysts big bucks.

    Doug
     
  18. Sep 7, 2007 #1858 of 2718
    donshan

    donshan Godfather

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    I only know what I read about it at Boeing's site and D10 is built on the Boeing 702 and D10 has both a "liquid apogee engine" and two XIPS which use different fuels, don't they? XIPS uses xenon gas and electric power from the solar panels. This link has a graphic of the station keeping XIPS system:

    http://www.boeing.com/defense-space/space/bss/factsheets/xips/xips.html

    and D10 specs on page 2:

    http://www.boeing.com/defense-space/space/bss/factsheets/702/dtv10-11-12_factsheet.pdf

    Boeing quote from the first link, with bold emphasis added:

     
  19. Sep 7, 2007 #1859 of 2718
    oakwcj

    oakwcj Lower Echelon

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    Up to this point, there have been new TLE's on at least a daily basis. Since DirecTV's application for Special Temporary Authority stated that it would take a few days to drift the D10 into place, I'd be really surprised if it were already at 102.775, given that it's only been 24 hours since the last TLE.
     
  20. Sep 7, 2007 #1860 of 2718
    Ken984

    Ken984 Active Member

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    Bossier...
    My understanding is that Norad updates the TLE for the sats daily(sometimes multiple times), IF they detect changes, SpaceTrack usually has them listed fairly quickly, am I totally wrong in my thinking?
     
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