Longitude Sharing
Brasilsat
Goes
Evandro Paiva de Andrade
Celestial Mechanics Team
Engineering Division - Star One S/A
The 14th Annual
Improving Space Operations Workshop
April 15-16 2008
• 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
Mid-2008
SOC2
Launch
(Apr 2008)
BSat3
BSat2 (inc’d)
BSat1(inc’d)
BSat4
SOC1
107.5
92
89
84
G-28
75
Goes12
70
68
65
55.5
Anik F1
37.5
IS 805
inc’d: inclined orbit
AMC12
/SOC12
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
Inc Vector Secular
Perturbation
 =90°
Aries
5°
10 °
15°
Ecliptic Pole
Geosynchronous
Orbit Normal
Evolution
inc naturally defined
Ecc/Inc Co-location
Eccentricity strategy
BSat1 one year ecc evolution
ecc // inc
Strategy Set Up
• Comfortable minimum distance 10 Km
min(sma*ecc, sma*inc)

ecc > 23.7E-05
inc > 0.0136°
N
sma*inc
ecc // inc
R
sma*ecc
sma:semi-major axis of the orbit
Deviation from Nominal Set-up
Intermediate angles between ecc and inc
30
20
20
-10
10
0
0
-20
20
10
10
-30
30
N (Km)
30
N (Km)
N (Km)
Relative Motion
0
10
20
30
-30
-20
-10
0
0
10
20
30
-30
-20
-10
0
-10
-10
-10
-20
-20
-20
-30
-30
R (Km)
a = 30°  min dist = 8.3 Km
R (Km)
a = 60°  min dist = 4.5 Km
10
20
-30
R (Km)
a = 75°  min dist = 2.3 Km
30
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
Inclination
Box Demarcation
75° W
Meridian
0.5°
ecc/inc
separation
strategy zone
0.1°
Equator
lssz
-0.5°
-0.1°
lssz: longitude separation strategy zone
+0.1°
Longitude
+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
[email protected]
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!!!