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Thread: Satellite D15 Discussion

  1. #11
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    Quote Originally Posted by Tom Speer View Post
    It only started moving this morning. Patience.
    Oh ....

    Thought it began moving on 9/16, so this was actually the 2nd day into the drift...

  2. #12
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    Quote Originally Posted by HoTat2 View Post
    Yes, I see now T15 is definitely drifting westward ...

    But I do hope it is indeed "accelerating", since at only the current .1°/day, it's going to take about 20 days at this rate to reach 103W nom. ...
    The way they move is to raise/lower orbit and allow the Earth to revolve slower/faster underneath it. If it is only partway to the desired altitude it won't "move" as fast, and a bigger altitude change will "accelerate" that movement. In reality they probably just do a small burn to get it moving higher/lower, another small burn to stop it when they get to the desired altitude, wait while the Earth moves at a different speed underneath, then at the appropriate time do a small burn to begin the move back to GEO and one final burn to halt. Probably only requires a tiny amount of fuel since the amount of time required to raise/lower orbit isn't a big deal in the overall scheme of things so there's little gain by burning more to do the raise/lower faster.

  3. #13
    Super Moderator Tom Speer's Avatar
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    Sometime around 8 to 9am EDT today, T15 passed about 11 miles over D9S, the westward drift (relative to the earth) is picking up speed.
    Tom Speer, N2HF, the curious otter. Part of the DataDigesters team.

  4. #14
    Super Moderator Doctor j's Avatar
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    The latest TLE 262.2169 has it moving ~ .25 degrees per day
    Should be "home" (102.85 W) in less than 1 week (6PM 9/25 by present motion)

    Doctor j
    Last edited by Doctor j; 09-19-2019 at 05:22 PM.

  5. #15
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    The first Epoch was one of those rarer ones where it caught a snapshot during the transfer to a new orbit elevation.

    They give the satellite a burn at an angle 90 degrees to the earth to either accelerate or decelerate . Then 180 degrees later, they will do another burn to change the now elliptical orbit back to a circular orbit at the new elevation

    Hohmann transfer orbit.svg - illustration of a Hohmann transfer orbit

  6. #16
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    Yea ...

    Use to have a hard time understanding that for some reason ...

    Where you actually have to increase the satellite's velocity at the perigee and then apogee points of the "transfer ellipse" respectively to move it from a lower circular orbit to a higher one.

    And vice-versa by reducing velocity at apogee then perigee points of the transfer ellipse to move the satellite from a higher to lower circular orbit.
    Last edited by HoTat2; 09-19-2019 at 09:44 PM.

  7. #17
    Edgecutter bakers12's Avatar
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    Satellite D15 Discussion

    D15 has started its westward drift. Orbitron currently estimates its position at 101.3742° W. Since there isn't a separate D15 thread (that I noticed) I'm posting it here.
    Dear God, Please send clothes for all those poor ladies in Daddy's computer. Amen.

  8. #18
    Super Moderator Gary Toma's Avatar
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    Good Idea !! Here's a new separate thread...

  9. #19
    Super Moderator Tom Speer's Avatar
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    This morning, at 8:15 EDT, the N2YO prediction from the TLEs shows D15 at 102.75 W, 0.04S. still moving West. It is slightly to the south of D10, and 13 miles higher, still drifting westward. They will probably let it get slightly to the west of its licensed location of 102.85 before initiating the transfer orbit firings to get it down to geosynchronous altititude. I'm no expert in orbital mechanics, but I would expect the first transfer orbit burn sometime in the next 24 hours.
    Tom Speer, N2HF, the curious otter. Part of the DataDigesters team.

  10. #20
    Super Moderator Tom Speer's Avatar
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    We're waiting for fresh TLE orbital data. Based on the last data, from whiie DirecTV 15 was in its drift orbit, it would be at 103.00 degrees W this morning. Since it is heading to 102.85, it should have had a transfer orbit burn overnight, or very soon now.
    Tom Speer, N2HF, the curious otter. Part of the DataDigesters team.

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