The 14th Annual

Improving Space Operations WorkshopApril 15-16 2008

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)

00

Star One’s Fleet and Trends

107.5

Anik F1

AMC12

/SOC12

37.5

8470

92

BSat3BSat2 (inc’d)

65

SOC2

68

Launch(Apr

2008)

75

SOC1

55.5

89

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 >

0.0136°

Deviation from Nominal Set-up

Relative Motion

-30

-20

-10

0

10

20

30

-30 -20 -10 0 10 20 30

R (Km)

-30

-20

-10

0

10

20

30

-30 -20 -10 0 10 20 30

R (Km)

N (

Km

)

-30

-20

-10

0

10

20

30

-30 -20 -10 0 10 20 30

R (Km)

= 30° min dist = 8.3 Km = 60° min dist = 4.5 Km

= 75° min dist = 2.3 Km

N (

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°

Incl

inati

on

Longitude

+0.5°

0.5°

lssz0.1°

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

evandro.andrade@starone.com.br

Tel.: (55) (21) 2121-7003

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!!!