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© GMV, 2008 Property of GMV
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ISSUES IN FLIGHT DYNAMICS:
COLLOCATION OPERATIONS & MISSION ANALYSIS A SUPPLIER’S PERSPECTIVE
Gonzalo Garcia, VP of Operations, USAAssaf Barnoy, Lead Flight Dynamics Engineer
AIAA SOSTC 2008
© GMV, 2008 Property of GMV
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AGENDA
© GMV, 2008
Introduction to GMV
Introduction to focusSuite
Introduction to Flight Dynamics and Collocation Analysis
Collocation Assessment: Matool
Collocation Operations: COLLOC, INICOL, and CLOSEAP
Lessons Learned
AGENDA
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INTRODUCTION TO GMV
© GMV, 2008
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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© GMV, 2008
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
focus
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INTRODUCTION TO focusSuite
© GMV, 2008
• 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)
focusSUITE
FLIGHT DYNAMICS: focusSuite PRODUCT LINE
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© GMV, 2008
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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© GMV, 2008
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)
focusSuiteModules
DataManager
Process Manager
GUI
focusGEOModules
focusLEOModules
focusCnModules
Autofocus
focusAPI
ExternalApp.
focusSuite: ARCHITECTURE
EventManager
COLLOC INICOL CLOSEAP MATOOL
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INTRODUCTION TO FLIGHT DYNAMICS AND COLLOCATION
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COLLOCATION OPERATIONSWhen 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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© GMV, 2008
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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Complete Longitude Separation Partial Longitude Separation
COLLOCATION STRATEGIES:Longitude Separation
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OR
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COLLOCATION STRATEGIES: Inclination/Eccentricity Separation Separation in Inclination Separation in Eccentricity Combined Inclination and Eccentricity separation
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© GMV, 2008
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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COLLOCATION STRATEGIES: Inclination/Eccentricity Separation (cont)
© GMV, 2008
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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GMV’s SOLUTION TO COLLOCATION
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COLLOCATION ASSESSMENT:
MATOOL
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WHAT IS MATOOL?
MATOOL isgeostationary 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
a station keeping and collocation analysis tool for
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© GMV, 2008
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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© GMV, 2008
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 Carloanalysis option is available from the Complete Execution mode. This method makes use of random numbers and probability statistics to investigateproblems.
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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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© GMV, 2008
MATOOL: USER INTERFACEInput PanelUsers have access to input parameters to define the mission profile, including number of satellite, orbit plans, maneuver station keeping information, and more
Tests GroupsUsers can create multiple test groups/scenarios to address different missions, operational concepts, and collocation profiles
Analysis to OperationsInput parameters are 100% compatible with focusSuite operational products (focusGEO), thereby allowing for simple transition from analysis to operations
Analysis OutputDetailed analysis output is available in detailed execution walkthrough, data tables, and graphical displays
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MATOOL: USER INTERFACE
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Longitude / Latitude Histograms
Show percentage of time spent within each subinterval within the box
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MATOOL: USER INTERFACE
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Eccentricity evolution
Show evolution of eccentricity vector for all satellites in the collocation group. Both mean and osculating elements.
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MATOOL: USER INTERFACE
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Inclination evolution
Show evolution of inclination vector for all satellites in the collocation group. Both mean and osculating elements.
© GMV, 2008
MATOOL: USER INTERFACE
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Delta of inclination and eccentricity
Show separation in eccentricity and inclination vectors for all satellite pairs in the collocation group.
© GMV, 2008
MATOOL: USER INTERFACE
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Inters-satellite separation
Show inter-satellite distance and angular separation for all satellite pairs in the collocation group.
© GMV, 2008
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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COLLOCATIONOPERATIONS:
COLLOCINICOL
CLOSEAP
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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
COLLOC: COLLOCATION ANALYSIS
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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
© GMV, 2008
INICOL: COLLOCATION CLUSTER INITIALIZATION
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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
© GMV, 2008
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).
INICOL: COLLOCATION CLUSTER INITIALIZATION
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© GMV, 2008
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 email to selected users
© GMV, 2008
CLOSEAP: CLOSE APPROACH PREDICTION
LEVEL 2: SPHERE
LEVEL 3: ELLIPSOID
LEVEL 1: BOX
Internet OperationalOrbital Data
User 1 User 3User 2
TLEs
Ephemeris /State Vector + Manoeuvres
CollisionRisk
AssessmentReport
FDS
focusCloseAp
Automatic processing
Phased approach
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CLOSEAP: CLOSE APPROACH PREDICTION
Output: Plots
• Separation plots between satellite and tracked objects
• Orbit plots showing evolution of satellite and tracked objects
• Avoidance manoeuvre
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OPERATIONAL COLLOCATION EXPERIENCE
EUTELSAT:– Collocation group of 5-6 satellites has been
operated with focusGEO successfully since 2001HISPASAT:
– 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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LESSONS LEARNED
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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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