1. COLLOCATION OPERATIONS &
AIAA SOSTC 2008
ISSUES IN FLIGHT DYNAMICS:
COLLOCATION OPERATIONS &
MISSION ANALYSIS
A SUPPLIER’S PERSPECTIVE
Gonzalo Garcia, VP of Operations, USA
Assaf Barnoy, Lead Flight Dynamics Engineer

2. AGENDA

3. AGENDA Introduction to GMV Introduction to focusSuite
Introduction to Flight Dynamics and Collocation Analysis
Collocation Assessment: Matool
Collocation Operations: COLLOC, INICOL, and CLOSEAP
Lessons Learned
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4. INTRODUCTION TO GMV

5. GLOBAL REACH, GLOBAL PRESENCE
Global Locations
GMV staff permanently located in 7 countries
GMV systems deployed in 5 continents, 18 countries
Pronounced world business
US subsidiary (ITAR OK)
Main Customers
Space Agencies
Industrial Primes
Integrators
Commercial Satellite operators
Space App. Communities
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6. OUR OFFER
Mission Analysis studies and mission analysis tools (station keeping, collocation, launch window analysis, …)
Operational systems for satellite control (inc. on-station and LEOP):
Real-Time TM/TC M&C
Flight Dynamics
Mission Planning and Scheduling
Special operational needs (e.g. collision prediction/analysis, rendezvous, interstellar)
Satellite capacity management:
Satellite capacity management
Payload Reconfiguration
CFDP
Operations support
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7. INTRODUCTION TO focusSuite

8. FLIGHT DYNAMICS: focusSuite PRODUCT LINE
focusSuite is an off-the-shelf product, which supports multi-mission, multi-satellite flight dynamics operations and mission analysis
focusSuite’s benefits include functionality, reliability, flexibility and user friendliness
focusSuite provides full lifecycle (assessment to launch to de-orbiting) flight dynamics operations support through a collection of flight proven mission independent and mission/spacecraft specific functionality
focusSuite provides high degree of configurability allowing to provide custom solutions
focusSuite also provides a generic framework that allows for extensibility of product development and evolution
focusSuite includes an Open API which increases productivity, stability, and accessibility, including integration into a service oriented architecture (SOA)
SUITE
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9. focusSuite: A COMPLETE PRODUCT LINE
FDS product line
focusSuite: advanced multimission, multisatellite FD infrastructure providing core functions
focusGEO: GEO operations
focusLEOP: LEOP operations
focusLEO: LEO operations
focusCn: satellite constellations
and more
focusCloseap: collision risk prediction
COLLOC: Collocation Assessment
INICOL: Collocation Initialisation control
MATOOL: Station Keeping and collocation assessment
Selected to operate over 120 satellites
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10. focusSuite: ARCHITECTURE
GUI
Autofocus
External
App.
Three-tier architecture, to promote flexibility and modularity, allow distribution and scalability:
1st Tier: Presentation (clients)
2nd Tier: Process management
3rd Tier: Data management / Computation. Normally includes legacy code based on reliable flight dynamics algorithms
Advanced API for interaction with Process Manager
Operator Manual Access (GUI)
Automatic Procedures (Autofocus)
External Applications (including SOA)
focusAPI
Process Manager
Event
Manager
Data
Manager
focusSuite
Modules
focusGEO
Modules
focusLEO
Modules
focusCn
Modules
COLLOC
INICOL
CLOSEAP
MATOOL
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11. INTRODUCTION TO FLIGHT DYNAMICS AND COLLOCATION11

12. COLLOCATION OPERATIONS
When planning to collocate spacecraft the following factors should be considered:
The number of participating spacecraft
The size of the control windows
The duration/frequency of the station keeping control cycle
Various other constraints on thruster design, such as the firing duration, minimum time between maneuvers, Sun-Earth angle, etc.
All of which translate to direct effect on the
operator:
Benefit in added capacity
Added redundancy
More complex station-keeping operations
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13. COLLOCATION REQUIREMENTS
There are two levels of requirements that must be considered:
Mission Requirements
Keep the satellites inside the control box during their lifetime
Fit the geometrical configuration of the control strategies and fulfil their design requirements
Minimize the fuel consumption of each satellite
Safety & interference criteria
The probability of an approach closer than a given threshold (safety margin) between any pair of satellites shall be negligible
The probability of disturbance on infra-red sensors, sun sensors, solar arrays or antennas shall be negligible
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14. COLLOCATION STRATEGIES: Longitude Separation
Complete Longitude Separation
Partial Longitude Separation OR
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15. COLLOCATION STRATEGIES: Inclination/Eccentricity Separation
Separation in Inclination
Separation in Eccentricity
Combined Inclination and Eccentricity separation
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16. COLLOCATION STRATEGIES: Inclination/Eccentricity Separation (cont)
Collocation by eccentricity offset ensures that radial and tangential separation are never low at the same time.
Radial Sep. = 0
Tangential sep. = max
Radial Sep. = max
Tangential Sep. = 0
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17. GMV’s SOLUTION TO COLLOCATION
GMV offers two levels of collocation support:
MATOOL: Mission Analysis Tool including Collocation, which analyzes collocation control to determine viability of collocation plan and proposes spacecraft operations control
COLLOC, INICOL, and CLOSEAP: Operational functions (part of focusGEO), which allow operators to observe and control a spacecraft collocation group
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18. COLLOCATION ASSESSMENT:
MATOOL

19. a station keeping and collocation analysis tool for
WHAT IS MATOOL?
a station keeping and collocation analysis tool for
MATOOL is
geostationary satellites.
Its main features include:
Full station keeping analysis (including delta V and mass consumption)
Extended simulation period (could span entire spacecraft lifetime)
Study of multiple spacecraft orbits, including inclined
Output is available in data files and plot format, and includes evolution data of orbital elements, manoeuvres, and inter-satellite variables for all satellite pairs
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20. MATOOL: MISSION ANALYSIS SUPPORT
Evaluation of the inclination control strategy (N/S) and the drift/eccentricity control strategy (E/W)
The performance of those strategies is evaluated based on orbit determination errors and thrusters behavior (thrust efficiency and cross-coupling effects)
Analysis and feasibility of the collocation strategy for several satellites, including safety constraints in terms of minimum inter-satellite distance and separation angles
Verification of the restrictions associated with the window control
Attitude constraints analysis
Complete lifetime estimation
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21. MATOOL: EXECUTION MODES
Collocation Parameters: The objective of this mode is to provide an initial estimate of the collocation control parameters for a cluster of satellites.
Proximity Analysis: The objective of this mode is to perform proximity analysis for a collocation group.
Complete Execution: The objective of this mode is to perform a long term simulation of the station-keeping strategy and collocation monitoring. This computes maneuver, orbit, and proximity evolution for all satellites.
Monte Carlo Analysis: A Monte Carlo
analysis option is available from the
Complete Execution mode. This method
makes use of random numbers and
probability statistics to investigate
problems.
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22. MATOOL: FUNCTIONALITIES
Maneuvers computation / orbit propagation / collocation analysis
Free Inclination drift management (no inclination control strategy)
Ionic/Chemical propulsion
External Maneuvers File integration. Results from other tools can be easily integrated for analysis
Generic Maneuver Calibration avoiding dependencies on a particular platform
Safety parameters estimation
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23. MATOOL: USER INTERFACE
Input Panel
Users have access to input parameters to define the mission profile, including number of satellite, orbit plans, maneuver station keeping information, and more
Tests Groups
Users can create multiple test groups/scenarios to address different missions, operational concepts, and collocation profiles
Analysis to Operations
Input parameters are 100% compatible with focusSuite operational products (focusGEO), thereby allowing for simple transition from analysis to operations
Analysis Output
Detailed analysis output is available in detailed execution walkthrough, data tables, and graphical displays
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24. MATOOL: USER INTERFACE
Longitude / Latitude Histograms
Show percentage of time spent within each subinterval within the box
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25. MATOOL: USER INTERFACE
Eccentricity evolution
Show evolution of eccentricity vector for all satellites in the collocation group. Both mean and osculating elements.
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26. MATOOL: USER INTERFACE
Inclination evolution
Show evolution of inclination vector for all satellites in the collocation group. Both mean and osculating elements.
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27. MATOOL: USER INTERFACE
Delta of inclination and eccentricity
Show separation in eccentricity and inclination vectors for all satellite pairs in the collocation group.
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28. MATOOL: USER INTERFACE
Inters-satellite separation
Show inter-satellite distance and angular separation for all satellite pairs in the collocation group.
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29. MATOOL: OPERATIONAL EXPERIENCE
EUTELSAT:
Mission analysis of the satellite fleet (20+ satellites), in particular for collocation analysis. Includes a collocation group of 5-6 satellites.
ESA:
Goal to analyze the feasibility of ‘cluster’ concept for a GEO mission
MATOOL used to assure a continuous inter-satellite link
SS/LORAL:
Mission analysis study performed by GMV and proposed operational concept delivered in formal report to SS/LORAL
Orbital Sciences Corporation:
Analysis tool for new GEO missions
Other GEO operators:
Superbird
Worldspace
OPTUS
HISPASAT
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30. COLLOCATION
OPERATIONS:
COLLOC
INICOL
CLOSEAP

31. COLLOC: COLLOCATION ANALYSIS
Purpose:
Performs a proximity check for satellites within a collocation group
Used also to monitor collocation groups of satellites from different operators
Options:
Under/Over-performance of maneuvers – used to allow for thruster efficiency in collocated satellites
Inter-satellites parameters (other satellites defined by Collocation File)
Angular satellite separation based on specified station visibility
Output:
Complete statistical review of the collocation of all satellites in cluster
If close approach is detected, a maneuver will be computed to avoid collision
Detailed graphical displays indicating collocation status

32. COLLOC: COLLOCATION ANALYSIS
COLLOC Report:
Single page printout includes orbit data for all participating satellites
Inter-satellite distance and angular separation for all satellite-pairs
Details about any avoidance manoeuvres needed, including improved collocation statistics
COLLOC Plots:
Orbit plots
Collocation plots
Latitude vs. Longitude plots
Latitude/Longitude histograms
Inter-satellite distance histogram

33. INICOL: COLLOCATION CLUSTER INITIALIZATION
Purpose:
Compute the maneuvers needed for the collocation strategy initialization and extraction
Options:
Collocation control parameters
Maneuver Mode: N/S, E/W (Drift & SK Initialization) and E/W (Only SK Initialization)
Constraints on operations (e.g. Next operational Station Keeping maneuver)
Output:
Computed maneuver(s) to achieve desired target
Collocation analysis with other spacecraft of proposed maneuver to determine close approaches
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34. INICOL: COLLOCATION CLUSTER INITIALIZATION
Two Operation Modes:
Satellite Insertion: To insert a satellite in a new or existent cluster finding the nominal position in Eccentricity, Longitude & Inclination
Satellite Extraction: To extract a satellite from a shared cluster in a safe manner
Proximity analysis is performed according to collocation data for all satellites in the cluster. Satellites defined by detailed orbital ephemeris (for controlled satellites) and longitude control boxes (for observed satellites).
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35. CLOSEAP: CLOSE APPROACH PREDICTION
Purpose:
Predict close approaches between the satellite and third party objects
Options:
Automatic download of latest TLE elements from SPACETRACK, including all observable objects
Phased approach allows for consideration of many parameters in a short span of time
Output:
Computed close approach report with any object
Probability of collision using covariance analysis
Collocation and orbit plots with any nearby object
Status messages sent by to selected users

36. CLOSEAP: CLOSE APPROACH PREDICTION
focusCloseAp
Automatic processing
Phased approach
LEVEL 1: BOX
LEVEL 2: SPHERE
LEVEL 3: ELLIPSOID

37. CLOSEAP: CLOSE APPROACH PREDICTION
Output: Plots
Separation plots between satellite and tracked objects
Orbit plots showing evolution of satellite and tracked objects
Avoidance manoeuvre

38. OPERATIONAL COLLOCATION EXPERIENCE
EUTELSAT:
Collocation group of 5-6 satellites has been operated with focusGEO successfully since 2001
HISPASAT:
At one point 4 satellites in collocation operated by focusGEO
WorldSpace:
Asiastar closely monitors close approaches to a collocated satellite from another operator using CLOSEAP / COLLOC
Soon:
Telenor and MEASAT will be monitoring collocated satellites with focusGEO
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39. LESSONS LEARNED

40. LESSONS LEARNED
A thorough detailed mission analysis study is necessary long before launch to define the optimal strategies that guarantee:
Minimum propellant consumption (= maximum life)
Fulfillment of separation constraints
A good combined strategy can make a big difference in expected life of the satellites
MATOOL is an excellent tool for that task. Used for different missions in the USA, Europe, Asia and Australia
The operational implementation of a collocation strategy requires the use of a multi-satellite system capable of planning the maneuvers of all satellites consistently. focusGEO does the job.
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41. Thank you