Presentation on theme: "The 14 th Annual Improving Space Operations Workshop April 15-16 2008 Brasilsat Goes Longitude Sharing Evandro Paiva de Andrade Celestial Mechanics Team."— Presentation transcript:
The 14 th Annual Improving Space Operations Workshop April Brasilsat Goes Longitude Sharing Evandro Paiva de Andrade Celestial Mechanics Team Engineering Division - Star One S/A
Star One’s Fleet Brasilsat B1 (BSat1) and Goes12 Co-location Future Co-locations
Star One’s Satellite Types Four BSS376-W spinners: BSat1 (1994), BSat2 (1995), BSat3 (1998) and BSat4 (2000) Two SpaceBus 3000B3: StarOne-C1 SOC1 (2007) and SOC2 (2008) 0
Star One’s Fleet and Trends Anik F1 AMC12 /SOC BSat3 BSat2 (inc’d) 65 SOC2 68 Launch (Apr 2008) 75 SOC G-28 IS 805 BSat1(inc’d) BSat4 Goes12 Mid-2008 inc’d: inclined orbit
BSat1 and Goes12 Co-location BSat1 arrived at 75° W in March 24, 2007 NOAA switched eccentricity (ecc) control strategy from one thruster firing near perigee to one thruster firing sun-synchronous, which allowed eccentricity vectors synchronization and, therefore, eccentricity/inclination (ecc/inc) co-location Weekly orbit data exchange
BSat1 – Inclined Orbit 5 ° 10 ° 15° Aries Ecliptic Pole =90° Geosynchronous Orbit Normal Evolution Inc Vector Secular Perturbation inc naturally defined
Ecc/Inc Co-location BSat1 one year ecc evolution ecc // inc Eccentricity strategy
Strategy Set Up sma* ecc sma* inc R N Comfortable minimum distance 10 Km ecc // inc sma:semi-major axis of the orbit min(sma* ecc, sma* inc) ecc > 23.7E-05 inc > °
Deviation from Nominal Set-up Relative Motion R (Km) R (Km) N (Km) R (Km) = 30° min dist = 8.3 Km = 60° min dist = 4.5 Km = 75° min dist = 2.3 Km N (Km) Intermediate angles between ecc and inc
Actual Data ecc inc Good alignment !!!
Collision Avoidance Maneuver Acceptable minimum close approach margin between GOES12 and BSat1 2 km Close approach prediction between 2 km and 5 km alert for a potential issue trigger more frequent communication between Star One and NOAA Close approach prediction of anything less than 2 Km trigger collision avoidance maneuver to be performed by Star One
W Flybys and Minimum Distance GOES-12 Current strategy has guaranteed a minimum of 14 km between the satellites Goes12 north-south maneuvers done outside box of 75°±0.1 W and timed in such a way that any in-plane coupling will not make Goes12 enter BSat1 box before the following E-W maneuver
Furthering Closeness BSat3 (orbit not-inclined) will be brought to 75 W by June 2008 Ecc/inc co-location strategy fails when Goes inc < 0.1 One alternative is to combine ecc/inc and longitude separation co-location strategies. Star One agrees to continue with the responsibility of performing collision avoidance maneuvers if the minimum close approach margin is outranged.
Longitude Separation Strategy Goes12 enters ±0.1° inclination box outside of the eclipse season, what favors an adequate planning of Goes12 West maneuvers aiming at the co-location by longitude separation strategy during this phase. This would minimize need for coordination between Star One and NOAA
Box Demarcation +0.1° -0.1° Inclination Longitude +0.5° 0.5° lssz 0.1° Equator 75° W Meridian ecc/inc separation strategy zone lssz: longitude separation strategy zone -0.5°
Next Steps Finalize discussions that include satellites in standard geostationary orbit Develop any required longitude sharing procedures or memoranda Formalize agreement through the exchange of technical letters
Evandro Paiva de Andrade Tel.: (55) (21) Celestial Mechanics Team - Engineering Division - Star One Rio de Janeiro - RJ – Brazil Helpful contributions from: DSc Cintia Quireza, MSc Mauricio Bottino, Lincoln Oliveira, Reinaldo Pinto and PhD Annelisie Aiex THANKS!!!