2nd SpaceOps Workshop
Conjunction Analysis betweenConjunction Analysis between KOMPSAT-2 and Space Debris and
Collision Avoidance StrategyCollision Avoidance Strategy
*Su-Jin Choi, In-Sik Jung, Dae-Won Chung, Chang-Kyung Yu, g, g y g ,
2011 SpaceOps Workshop, STFC
14-16 June, 2011
LEO Satellite Mission Operations DepartmentLEO Satellite Mission Operations Department
Contents
Background – Status of Space Debris Environment
Contents
KOMPSAT & COMS program
Introduction & Motivation
Automated Conjunction analysis & collision Avoidance System
History of collision worksy
Conjunction Analysis Results
Collision Avoidance StrategyCo s o o da ce S a egy
COLA Maneuver Optimization
Work-flow of Collision MitigationWork flow of Collision Mitigation
Example of Closest Approach
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Space Debris Environment
Space Debris
Space Debris Environment
The collection of objects in orbit around Earth that were created by humans but no longer serve any useful purpose.
Space debris consist of
F t ti D b i Fragmentation Debris
Mission-related Debris
Rocket BodiesRocket Bodies
Non-operated Satellites
State of Space Objectp j
Since 1957, the number of space objects have increased rapidly.
In according to USSTRATCOM spaceIn according to USSTRATCOM, space objects larger than 10cm in the space are more than 15,000 as of April 2011.
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Space Debris Environment(Cont’)
Mass Distribution and Number of Space Debris
Space Debris Environment(Cont )
Note the operational S/C accounts for only approximately 10% of the mass in LEO.
Count Ratio of all Space Debris Mass Ratio of all Space Debris
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Space Debris Environment(Cont’)Space Debris Environment(Cont )
Contents EpochNumber of
Space Debris Altitude
Distribution of Name of Satellite
p pgenerated Space Debris
Satellite
Anti-Satellite Test
Jan, 2007 > 2,500 200 ~ 4,000km FY-1CTest
Collision btw. Satellites
Feb, 2009 > 1,500 250 ~ 1,500kmIridium 33
Cosmos 2251Satellites Cosmos 2251
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KOMPSAT Program
KOrea Multi-Purpose SATellite
KOMPSAT Program
KOMPSATKOMPSAT--3/3/3A3A KOMPSATKOMPSAT--55KOMPSATKOMPSAT--22
MultiMulti--Spectral Camera/Spectral Camera/IRIR SunSun--Synchronous, 685km/Synchronous, 685km/528km528kmResolution Resolution
SAR(Synthetic Aperture Radar) SAR(Synthetic Aperture Radar) SunSun--Synchronous, 550km Synchronous, 550km Resolution : 1m/5m/20mResolution : 1m/5m/20m
MultiMulti--Spectral CameraSpectral Camera SunSun--Synchronous, Synchronous, 685685kmkm Resolution Resolution
(0.7m : pan, 3.2m : color)(0.7m : pan, 3.2m : color) Launch : 2012/Launch : 2012/20132013
Launch : Aug. 2011Launch : Aug. 2011((11m : pan, m : pan, 44m : color)m : color) Launch : Jul. Launch : Jul. 20062006
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COMS ProgramCOMS Program
Communication, Ocean and Meteorological Satellite
• Mission– Meteorological Observation
Ocean Color Monitoring– Ocean Color Monitoring– Ka-band Communication Experiment
• Launch : April 2010Launch : April 2010
Ocean MonitoringMeteorological Services
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Introduction & Motivation
Since plenty of spacecrafts were launched into the space, space debris have became hazard threat for most of the operating satellites
Introduction & Motivation
became hazard threat for most of the operating satellites.
Many agencies developed conjunction analysis system and set its operation procedure
NASA : NASA Robotic Conjunction Assessment Process
ESA : Process for the identification and assessment of high-risk conjunction event
i i l d f lli i i kCNES : Contingency Operational Procedure for Collision Risk Management
JAXA : JAXA’s Conjunction Assessment Procedure
The necessity to monitor KOMPSAT-2 from space debrisThe necessity to monitor KOMPSAT-2 from space debris
After Chinese ASAT, conjunction analysis was required because the fragment of FY-1C were scattered near the KOMPSAT-2 orbit.
KARI developed ACAS(Automated Conjunction analysis & collision Avoidance System) to monitor collision risk and avoid it appropriately.
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ACAS
ACAS Architecture
ACAS
Conjunction Assessment Part
Space-track Catalog
Orbit Source
Connect Module
Orbit Processing Module
Report Management
Module
KOMPSAT-2 OD
JSpOC CSM
STK/CAT
ModuleOrbit Data
Connect Parameter
Conjunction Assessment
Results
Tracking Data
Results
Conjunction Assessment
COLA Planning PartResultsCOLA
Planning
FDS Engineer
COLA Planning Module
COLA Planning Validation ModuleCOLA
Planning Parameter
- CA ResultsCOLA Parameter-COLA
planning result
* CA(Conjunction Assessment)* COLA(Collision Avoidance) 92011-10-10
History of Collision Works
2007 February : Start Conjunction Assessment
History of Collision Works
Between KOMPSAT-1, 2 and FY-1C debris
Monthly basis
2009 October : ACAS V_1.0 built
KOMPSAT-2 VS. FY-1C, Iridium-33 and Cosmos 2251 debris
Daily basis using USSTRATCOM catalog and In-house generated TLE
2010 August : ACAS V_2.0 built
KOMPSAT-2 VS. all USSTRATCOM catalog
Daily basis using USSTRATCOM catalog and KOMPSAT-2 OD
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Conjunction Analysis Results(1/9)
Conjunction Analysis Period
Conjunction Analysis Results(1/9)
Aug. 2010 ~ Apr. 2011(9 month)
7 days prediction
Orbit Source
KOMPSAT-2 : Orbit determination by GPS navigation solution
Space Debris : USSTRATCOM catalog(more than 14,000)
Min. Distance Threshold : 5km
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Conjunction Analysis Results(2/9)Conjunction Analysis Results(2/9)
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Conjunction Analysis Results(3/9)Conjunction Analysis Results(3/9)
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Conjunction Analysis Results(4/9)Conjunction Analysis Results(4/9)
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Conjunction Analysis Results(5/9)Conjunction Analysis Results(5/9)
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Conjunction Analysis Results(6/9)
Total number of Space Debris according to USSTRATCOM catalog
Conjunction Analysis Results(6/9)
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Conjunction Analysis Results(7/9)
The number of Space debris violated 5km Threshold
Conjunction Analysis Results(7/9)
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Conjunction Analysis Results(8/9)
Orbital Distribution of Space Debris violated 5km Threshold
Conjunction Analysis Results(8/9)
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Conjunction Analysis Results(9/9)
Kind of Space debris violated 5km Threshold
Conjunction Analysis Results(9/9)
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Collision Avoidance Strategy
TCA prediction based on orbit information
Collision Avoidance Strategy
Acquisition of TCA information based on precise orbit
Definition of probability space based on accuracy of the orbit
Collision Avoidance/Return maneuver optimizationCollision Avoidance/Return maneuver optimization
Minimize fuel consumption, non-mission interval time
Maintain mission orbit
Optimization trajectory design considering thruster performance and constraints of the satellite
C lli i id lid tiCollision avoidance maneuver validation
Stochastic analysis via Monte-Carlo simulation
Optimal fuel estimation for COLA maneuverOptimal fuel estimation for COLA maneuver
Validating the maneuver using visibility of satellite attitude/orbit
Development of automated program based on performance
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COLA Maneuver Optimization
Optimize collision avoidance maneuver
COLA Maneuver Optimization
Determine COLA time and target orbit
Maintain local time of SSO according to COLA maneuver
Optimization problem optVΔi tV V VΔ < Δ ≤ ΔOptimization problem
Minimize Cost function
Fuel consumption
opt min optV V VΔ < Δ ≤ Δ
p
Non-operation time
Optimization parameters
오차전파공간
최소증가요구속도
실제증가요구속도
minVΔ
VΔ
MinimumDel V
Del V
Thruster direction
Thruster activation time
C t i t
충돌확률공간C
ollis
ion
prob
abili
ty
spac
e
Constraints
Orbit dynamics
Collision Space AvoidanceCollision Space Avoidance
Thruster power and burning time
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COLA Maneuver Optimization(Cont’)
COLA Maneuver Optimization Architecture
COLA Maneuver Optimization(Cont )
Numerical Method of parameter optimization : SQP, CEALM, etc
Determine Cost and Constraint violation using Satellite Tool Kit
Find ,to minimize
V PJ
Δ
:Position on the orbit to initiate avoidance maneuverP
with constraints C( , ) 0V PΔ ≤
,V PΔ
J
( , )C V PΔ
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COLA Maneuver Optimization(Cont’)
Stochastic analysis of the COLA using Monte-Carlo simulation
COLA Maneuver Optimization(Cont )
Validity check of the COLA optimization parameter
Estimate fuel consumption for COLA maneuver
Fuel estimation validation from optimization algorithm
Validating the maneuver using visibility of satellite attitude/orbit
Orbit and attitude display and validation check using MATLAB and STK
MATLAB
All optimization algorithm control and input/output interface control between COTS
Usage of various arithmetic and analysis tool
STK(Satellite Tool Kit)
presice orbit propagation and situational awareness
Powerful display of satellite attitude and orbit
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Work-flow of Collision MitigationWork flow of Collision MitigationStep 1 : Automated Screening
S t k C t l Miss Distance < 1km
Yes
No
Space-track Catalog
First Screening Time
Step 4 : CA Maneuver
Miss Distance < 100mMax Probability > 1e-3 YesAfter TOT
Maneuver GO?
NoKARI OOP
Step 2 : Intensive Screening
YesAfter TOT
Remaining TOT <= 2day
NoCSM SP
Additional Tracking Data
Step 5 : End of CA Maneuver
Yes
Yes
No
Miss Distance < 1km
Data
Step 3 : CA Maneuver Planning
Step 1 : Automated Screening
Yes
Maneuver GO?
No
Remaining 2 day of TOT
Remaining 1 day of TOT
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Example of Closest ApproachConjunction epoch (UTC) 2011-Mar-15 09:28:45
SSC ID 32063 (CZ-4 R/B) 29268 (KOMPSAT-2)
Example of Closest Approach
( / ) ( )
Semi-major axis [km] 7106.78 7066.96
Eccentricity 0.0057293 0.0015123
Inclination [deg] 98.2923 98.3192
RAAN [deg] 154.5828 318.9755
Argument of perigee [deg] 2.6155 340.5964
Mean anomaly [deg] 357.5326 19.4655
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