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GOES-12 Eccentricity Control (Co-Location with Brasilsat B1)

GOES-12 Eccentricity Control (Co-Location with Brasilsat B1). Richard McIntosh a.i. solutions, Inc. AIAA SOSTC Workshop April 15, 2008. Co-Location Requirements. GOES-12 located at 75 deg W +/- 0.5 deg longitude.

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GOES-12 Eccentricity Control (Co-Location with Brasilsat B1)

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  1. GOES-12 Eccentricity Control(Co-Location with Brasilsat B1) Richard McIntosh a.i. solutions, Inc. AIAA SOSTC Workshop April 15, 2008

  2. Co-Location Requirements • GOES-12 located at 75 deg W +/- 0.5 deg longitude. • Brasilsat B1 given OK to move from 70 deg W to 75 deg W and maintain +/- 0.1 deg longitude. • B1 now occupies the middle 0.2 deg of GOES-12 box. • StarOne (B1 owners) suggested eccentricity vector control to avoid close approaches. • GOES maneuver control software not capable of planning East-West stationkeeping (EWSK) maneuvers that include eccentricity vector control. • NOAA desires to not perform any extra maneuvers for eccentricity control. • Analysis performed to determine how eccentricity control could be incorporated into the normal 1-burn EWSK operations.

  3. Eccentricity Control Strategy Recommended By StarOne Eccentricity Vector ex = e cos(Ω+ω) ey = e sin(Ω+ω)

  4. ΔV from SRP Raises Apogee V ECC VECTOR SRP V ΔV from SRP Lowers Perigee Effect of Solar Radiation Pressure on Eccentricity

  5. Natural Eccentricity Circle (size depends on Area/Mass) EX = e cos(Ω+ω) EY = e sin(Ω+ω)

  6. Eccentricity Control • Eccentricity vector will tend to follow the natural circle throughout the year. • Desired control circle size is usually smaller. • Objective is to try to make a short arc of the natural circle closely follow the control circle over the next EWSK cycle. • EWSK frequency: • GOES-12 every 11 or 12 weeks • B1 every 3 weeks

  7. Sun at End β Δα = Change in Sun RA over 1 East-West Maneuver Cycle EY Sun at Start β EX Δα Control Circle Natural Circle

  8. EY Next E-W Cycle β Δe β EX Δα Control Circle Natural Circle

  9. Equations (1 of 3)

  10. Equations (2 of 3) Δe RA1

  11. Equations (3 of 3) Note: Delta-Vs are normally in negative velocity direction for 75 West

  12. 1-Burn vs 2-Burn Control 1-Burn -0.268 m/s 2-Burns -0.478 and +0.211 m/s

  13. Single Burn at Perigee

  14. 2-Burn Control 0.0003 Circle

  15. 2-Burn Control 0.0002 Circle

  16. GOES-12 4-Year Simulation1-Burn East-West Maneuvers

  17. Conclusions • Analysis has shown that sufficient eccentricity control can be accomplished by GOES-12 with little or no impact to the normal EWSK operations (single-burn). • Only requirement is a change in the time of the burn (move from the normal perigee burn location). • NOAA has incorporated the equations presented here into a spreadsheet that computes the nominal time of the burn. • GOES-12 successfully performed the first EWSK maneuver with eccentricity control on July 24, 2007. • Subsequent EWSK maneuvers have shown that the single-burn strategy provides adequate eccentricity control. • Further analysis needs to be done to verify that the desired spacecraft separation can be maintained in the long term.

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