10 - SuJin Choi - Conjunction Analysis between KOMPSAT-2

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

22011-10-10

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.

32011-10-10 2011 SpaceOps Workshop, STFC

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


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

52011-10-10

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


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



Since plenty of spacecrafts were launched into the space, space debris have became hazard threat for most of the operating satellites


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.


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


Conjunction Analysis Results(1/9)

Conjunction Analysis Period


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


Conjunction Analysis Results(2/9)Conjunction Analysis Results(2/9)









Total number of Space Debris according to USSTRATCOM catalog




The number of Space debris violated 5km Threshold




Orbital Distribution of Space Debris violated 5km Threshold




Kind of Space debris violated 5km Threshold



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



Optimize collision avoidance maneuver


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


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


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


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

Yes242011-10-10 2011 SpaceOps Workshop, STFC

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



Documents

10 - SuJin Choi - Conjunction Analysis between KOMPSAT-2