RENDEZVOUS AND DOCKING OF SPACECRAFT - ESA

RENDEZVOUS AND DOCKING OFSPACECRAFT1. INTRODUCTION TO RENDEZVOUS & CAPTURE IN SPACE2. VERIFICATION PRIOR TO FLIGHT, CONCEPTS & TOOLSByWigbert FehseTutorial Lectures on LEO & GEO Rendezvous at the 4th ICATT, Madrid 2010This course is based to a large extent on the book’Automated Rendezvous and Docking of Spacecraft’,published by Cambridge University Press(ISBN: 0521824923).No part of this lecture must be copied or used in any formwithout stating the source.1

WHERE DO WE NEED RENDEZVOUS, CAPTURE ANDCOUPLING IN SPACE?RENDEZVOUS, CAPTURE AND COUPLING IN SPACE WILL BE REQUIREDIN MOST SCENARIOS WHERE MORE THAN ONE SPACECRAFTIS INVOLVED, e.g.:• ASSEMBLY OF STRUCTURES IN ORBIT,• SERVICING OF SPACECRAFT, i.e. SUPPLY WITH CONSUMABLES,EXPERIMENTS AND OTHER GOODS,• TRANSPORT OF CREW & GOODS TO / FROM A MANNED SPACESTATION,• LANDING ON CELESTIAL BODIES AND RETURN TO EARTHOF (UN)/MANNED SPACECRAFT.WITHIN THE FRAME OF THIS LECTURE WE WILLCONCENTRATE ON APPLICATION OF RENDEZVOUS & CAPTUREIN LOW- AND GEOSTATIONARY EARTH ORBITS (LEO & GEO).Dr. W. Fehse — Introduction to RVD — Where is RVD needed — Version 20092

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTURE IN GEO ?Dr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20093

THE TASKA VEHICLE SHALL MEET IN ORBIT ANOTHER VEHICLEAND CONNECT TO IT.BOTH VEHICLES MUST HAVE AT THE SAME TIMEWITHIN CLOSE TOLERANCES:• THE SAME POSITION• THE SAME VELOCITY VECTOR• A PARTICULAR ATTITUDE RELATIVE TO EACH OTHERONLY UNDER THOSE CONDITIONS COUPLING CAN BE PERFORMED.Dr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20094

THE SCENARIO IN LEOTHE LEO SCENARIO, IN WHICH THE AUTOMATIC RVD TAKES PLACE,CONSISTS OF THE FOLLOWING ELEMENTS:• A MANNED SPACE STATION IN LOW EARTH ORBIT,• MANNED SPACECRAFT, WHICH REGULARLY BRING CREW FROMGROUND TO THE STATION AND BACK,• UNMANNED TRANSPORT VEHICLES, WHICH SUPPLY THE STATIONWITH CONSUMABLES AND PAYLOAD,• GROUND CONTROL CENTRES, WHICH MONITOR AND GUIDE THEFLIGHT OF THE APPROACHING VEHICLE AND OF THE STATION,• RELATED INFRASTRUCTURES FOR COMMUNICATION BETWEENGROUND STATIONS AND SPACECRAFT AND BETWEEN THE VARIOUSGROUND CENTRES THEMSELVES.Dr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20095

SYSTEM AND FUNCTIONS IN LEO ARD (SCHEMATIC)CHASERONBOARD CONTROL SYSTEM:GNC, MVM , FDIRRENDEZVOUS SENSORS:GPS, RGPS, RADAR, OPT. SENSORSREACTION CONTROL SYSTEMTHRUSTERSTM/TC COMM’s SYSTEMSpace/SpaceCommunicationsDocking MechanismInterfacesRendezvous SensorInterfacesTARGETONBOARD CONTROL SYSTEM:AOCSSENSOR FUNCTIONS:GPSTM/TC COMM’s SYSTEMVOICE COMM’s WITH GROUNDGround/SpaceSpace/GroundCommunicationsSPACE SEGMENTGROUND SEGMENTGround/SpaceSpace/GroundCommunicationsCHASER CONTROL CENTRECHASER MISSION CONTROLCHASER SPACECR. CONTROLCOMM’s WITH TARGET CCCOMM’s LINK CONTROLGround/GroundCommunicationsTARGET CONTROL CENTRETARGET MISSION CONTROLTARGET SPACECR. CONTROLVOICE COMM’s WITH TARGETCOMM’s WITH CHASER CCCOMM’s LINK CONTROLDr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20096

THE INTERNATIONAL SPACE STATION (ISS) SCENARIOTHE PRESENT SPACE STATION SCENARIO CONSISTS OF:• THE INTERNATIONAL SPACE STATION ’ISS’– USA, RUSSIA, JAPAN, WESTERN EUROPE AND CANADA WILLCONTRIBUTE MODULES / ELEMENTS TO THE ISS• CREW TRANSPORT- AND RESCUE VEHICLES:– THE US SHUTTLE,– THE RUSSIAN SOYUS CREW TRANSPORTER– (CREW TRANSPORT VEHICLES STUDIED BY NASA CEV - ORIONAND BY RUSSIA AND EUROPE CSTS )• UNMANNED TRANSPORT VEHICLES:– THE RUSSIAN PROGRESS,– THE AUTOMATED TRANSFER VEHICLE (ATV) OF ESA (2008)– THE JAPANESE H-2 TRANSFER VEHICLE (HTV) (2009)Dr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20097

7. 7. Social ContributionsSocial ContributionsDoing Our Best to Protect the EnvironmentEnlightenment and EducationIn order to promote effective environmental preservation activities, it is important toraise the employee's awareness of the environment. In that extent, a process of continuousand repeated education is necessary.The Nippon Chemi-Con Group raises employee's awareness and provides educationat various stages of the employment.EnlightenmentAs part of its enlightenment-rising activities, the company publishes a monthlynewsletter that includes an "Ecology information Center" environmental article thatdiscusses various global environmental problems and the environmental activities ofthe company. We have also established an environmental information BBS on ourhomepage and are transmitting information on the latest environmental movements,etc.EducationOur Group provides regular education to employees to deepen their understanding ofenvironmental issues. All new employees undergo a process of environmental trainingto learn about our environmental policy, the trends of laws and regulations incountries around the world, and the requirements of the world, and the requirementsof the customer. We provide education and training related to ISO14001, Environmentalaudit, and chemical substances management.Communication with Local ResidentsStrengthening the Relationship between Our Business Sites and the Local CommunityTakahagi PlantClose communication with local communities is vital to enable the smooth and continuousproduction operations of these production sites. Nippon Chemi-Con groupcompanies actively conduct environmental activities, such as environment cleaningcampaigns and environmental-related events.Fukushima ElectrolyticIndustry Satoshi KikuchiDirector(Chairman of EnvironmentalCommittee)Nippon Chemi-Con CorporationA word from the Chairman ofthe Environmental CommitteeThe Nippon Chemi-Con Group acquired its first certificationof environmental management system in 1995,and over 10 years has passed. The environmental preservationactivities in the initial period assumed emissioncontrol and law requirements importance. In the 21stcentury, responsibilities of corporation's environmentalactivities are extended to "Energy conservation" and"Environmental warranty of the products". Those responsibilitiesare now essential in order to continue corporateactivities. In such social environment, the corporationmust pursue the ideal state, and not only the complianceto the laws and regulations, but affirmative and quick responsesto the changes are important.We hope that more people will understand the ideas andactivities introduced in this environmental report and cooperatewith us. Anticipating such understanding and cooperation,we are aiming at more intensive environmentalpreservation activities. We are looking forward tohearing from your frank opinion on this report.Company OutlineCompany nameMain office locationRepresentativesDate of foundationBusiness sites in Japan: Nippon Chemi-Con Corporation: 5-6-4, Osaki, Shinagawa-ku, Tokyo: Ikuo Uchiyama, President: 1931: 15 Production sites, 13 sale officesBusiness sites around the world : 15 locations in 8 countriesBusiness line: The manufacture and sale of aluminum electrolytic and othercapacitors, precision parts, and electronic equipment.A note on the design of this publication"Technology harmonizes with earth environment, and aims at coexistence."The cover page was designed from the idea that our eco-conscious aluminumelectrolytic capacitors are harmonized in the nature and are protecting theearth environment in the future.A word from the editor42 employees and their family members participated in the Environmental volunteer. (2008/2)Chemi-ConFukushima29 employees and their family members participated in the Environmental Eco-walk. (2007/6)Niigata PlantIn this Environmental report, business activities and environmental managementactivities are intelligibly summarized focusing on the figures and viewsthat Nippon Chemi-Con Group aims at. We also presented our new productsthat contribute to the environmental preservation. We would be pleased if informationthis report provides makes more people help understanding our environmentalmanagement activities.Contact Offices Relating to This Report141-8605564TEL : 03-5436-7633FAX : 03-5436-7596Nippon Chemi-Con Corporation Environment Department5-6-4, Osaki, Shinagawa-ku, Tokyo 141-8605, JapanTEL +81-3-5436-7633FAX +81-3-5436-7596102 employees and their family members participated in the Environmental Eco-walk. (2007/11)39 employees and their family members participated in the Environmental volunteer. (2007/6)Please visit our Website to learn more about our company's business activities data, environmental activities, and other company-related issues.http://www.chemi-con.co.jp/13 ENVIRONMENTAL REPORT 2008 ENVIRONMENTAL REPORT 2008 14

SYSTEM AND FUNCTIONS IN GEO RVD (SCHEMATIC)Launcher Interface RingCHASERONBOARD CONTROL SYSTEM:GNC onlyRENDEZVOUS SENSORS:OPT. SENSORS onlyREACTION CONTROL SYSTEMTHRUSTERS & WHEELSTM/TC COMM’s SYSTEMCapture ToolCameraApogeeBoostMotorTARGET(Comm’s Satellite)AOCSTHRUSTERS & WHEELSTM/TC COMM’s SYSTEMno dedicated interfacesfor sensors and dockingGround/SpaceSpace/GroundCommunicationsSPACE SEGMENTGROUND SEGMENTGround/SpaceSpace/GroundCommunicationsCHASER CONTROL CENTRECHASER MISSION CONTROLRENDEZVOUS & DOCKING CONTROLimage processing, GNC, MVM, FDIRCHASER SPACECR. CONTROLCOMM’s WITH TARGET CCCOMM’s LINK CONTROLGround/GroundCommunicationsTARGET CONTROL CENTRETARGET SPACECR. CONTROLCOMM’s WITH CHASER CCCOMM’s LINK CONTROLDr. W. Fehse – Introduction to RVD – Tasks, Scenario, Players – Version 20099

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTURE IN GEO ?Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200910

¨©¡¡¡¡ ¢¢£££¢¢¢£££¢¤¤¥¦§MAIN PHASES OF A RENDEZVOUS MISSIONTARGET STATIONMATING (DOCKING OR BERTHING)STRUCTURAL CONNECTIONInsertion into structural latch interfacesAchievement of rigid structural connectionCAPTUREPrevention of escape of capture interfacesAttentuation of shock & residual motionCLOSE RANGE RENDEZVOUSFINAL APPROACHApproach to capture pointAchievement of capture conditionsCLOSINGReduction of relative distance to targetAcquistion of final approach lineFAR RANGE RENDEZVOUSTransfer from phasing orbit to first aim pointin close vicinity of target, relative navigationPHASINGReduction of orbital phase angle betweenchaser and target S/C, absolute navigationLAUNCHInjection into orbital plane of targetAchievement of stable orbital conditionsGROUNDDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200911

CO-ORDINATE FRAMESTo describe rendezvous orbits and trajectories we usethree different co-ordinate frames:a3NNa = x 1 loa = za = y3 op 2 oporbital motiona = y2 loa1Equatora2EquatoriInclinationAscending Nodea = x1 opa 3 = z loEarthγEarth Inertial FrameOrbital Plane FrameLocal Orbital Frameorbit angles w.r.t.inertial spaceposition&velocitiesin orbitrelative position &velocities to targetDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200912

LAUNCH INTO THE ORBIT PLANE OF THE TARGET• OWING TO THE ROTATION OF THE EARTH, TWO TIMES A DAY THELAUNCH SITE MOVES INTO THE ORBITAL PLANE OF THE TARGETVEHICLE.• HOWEVER, BECAUSE OF SAFETY RESTRICTIONS (NO FLIGHT OVERINHABITED AREAS), MOST LAUNCH SITES CAN ONLY LAUNCH IN ONEDIRECTION, e.g. OVER OPEN SEA.• ALSO, WITH A LAUNCH IN EAST-DIRECTION, THE VEHICLEBENEFITS FROM THE ROTATION OF THE EARTH, WHICHPROVIDES A GRATIS ∆V OF ≈ 463 m/s AT THE EQUATOR.• THIS RESULTS IN ONE OPPORTUNITY PER DAY, WHERE THE LAUNCHDIRECTION MEETS THE ORBIT PLANE AND ORBIT DIRECTION.• BECAUSE OF THE DEVIATION OF THE EARTH FROM A TRUE SPHERE,THE ORBIT WILL DRIFT WITH TIME (DRIFT OF NODES).AS A RESULT, THE CHASER SPACECRAFT HAS TO BE LAUNCHED INTOA VIRTUAL TARGET ORBIT PLANE, SUCH THATAT THE TIME OF ARRIVAL, CHASER AND TARGET VEHICLESWILL HAVE DRIFTED INTO THE SAME ORBITAL PLANE.Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200913

Definition of Orbital ElementsEarth Centred Inertial FrameNΩiMEAN OF VERNALEQUINOXASCENDINGNODEEARTHΩi= RIGHT ASCENSION OF ASCENDING NODE (RAAN)= INCLINATIONDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200914

DEFINITION OF PHASE ANGLEOrbital Plane FrameTARGETPOSITIONTARGET ORBITCHASER ORBITCHASERPOSITIONPHASE ANGLEEARTHDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200915

APOGEE AND PERIGEE RAISE MANOEUVRESOrbital Plane FrameApogee 2VApogee∆ aPerigee 1Orbit 2Apogee 1Orbit 1 r a2a Orbit 122a1r a2a 1EarthEarth2a2r pPerigee∆VpOrbit 2r pPerigee 2Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200916

TRAJECTORIES IN EARTH CENTRED ANDTARGET CENTERED FRAMESORBITAL PLANE FRAME(Earth−centred coordinatesin the orbit plane)TARGET CENTERED ROTATING FRAME(local orbital coordinates move with the target)V−barxTARGET POSITIONAPOGEETARGET ORBIT∆ h∆ hCHASER ORBITTARGET ORBITR−barzPERIGEECHASER ORBITDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200917

HOHMANN TRANSFER∆=∆Vx2Apogee∆Vx2X (V−bar)2aV aOrbit 1Orbit 2Orbit 2raTransferOrbitTransferOrbit∆ z = 4 ω ∆ Vx 1∆Vx1Orbit 1∆ x = 3 ωπ ∆Vx1r pPerigeeEarth∆V p=∆Vx1Z (R−bar)IN ORBITAL PLANE FRAMEIN TARGET CENTRED FRAMEDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200918

Hill EquationsFor circular orbits, the motion between a body in orbit and the origin of thelocal orbital frame (e.g. that of the target) is described by the Hill Equations.ẍ − 2ωż = 1 m cF xÿ + ω 2 y = 1 m cF y (1)¨z + 2ωẋ − 3ω 2 z = 1 m cF zParameter:ω = orbital ratem c = mass of body (e.g. chaser)The right side of the equations describes the imposed accelerationsF x,y,zm c= γ x,y,zDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200919

Clohessy-Wiltshire Equationsx(t) =( )4ẋ0ω − 6z 0sin(ωt) − 2ż (0ω cos(ωt) + (6ωz 0 − 3ẋ 0 )t + x 0 + 2ż )0· · ·ω+ 2 ω 2γ z(ωt − sin(ωt)) + γ x( 4ω 2(1 − cos(ωt)) − 3 2 t2 )y(t) = y 0 cos(ωt) + ẏ0ω sin(ωt) + γ yω2(1 − cos(ωt)) (2)( )(2ẋ0z(t) =ω − 3z 0 cos(ωt) + ż0ω sin(ωt) + 4z 0 − 2ẋ )0· · ·ω+ 2 ω 2γ x(sin(ωt) − ωt) + γ zω2(1 − cos(ωt))The Clohessy-Wiltshire Equations are a particular solution of the Hill Equations.This form of the equations is valid- for pulses (instantaneous changes of velocity at start and end) and- for constant values of γ x,y,z .Results are sufficiently accurate for distances in z-direction between chaser and targetof up to a few 1000 m.Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 201020

USE OFCLOHESSY-WILTSHIRE EQUATIONSAND OF HILL EQUATIONSTHE CLOHESSEY-WILTSHIRE (CW) EQUATIONS PROVIDE ANEASY WAY TO CALCULATE POSITIONS AND VELOCITIES ANDTHE DELTA-V OF TRAJECTORIES.THEY ARE EXTREMELY USEFUL TO e.g.• DEVISE APPROACH STRATEGIES,• ASSESS TRAJECTORY SAFETY,• CALCULATE OVERALL DELTA-V BUDGETS etc.WE MUST NOT FORGET, HOWEVER, THAT THE CW-EQUATIONS AREONLY APPROXIMATIONS (PULSES, CONSTANT FORCES).FOR EXACT RESULTS (REAL THRUSTERS & DISTURBANCES)NUMERICAL INTEGRATION OF THE HILL-EQUATION IS INEVITABLE.THIS WILL BE NECESSARY IN PARTICULAR FOR MOSTVERIFICATION TASKS.Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 201021

PHASING STRATEGY IN LEO, EXAMPLETARGETLOCATIONFIRST AIMPOINTHOHMANNTRANSFERSCIRCULARISATIONMANOUEVREPERIGEE RAISEMANOEUVRETARGET ORBITPERIGEE RAISEMANOEUVREPERIGEE RAISEMANOEUVREFAR RANGE RVPHASINGLAUNCHAPOGEE RAISEMANOEUVRELAUNCHERTRAJECTORYGROUNDDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200922

IMPULSIVE TRAJECTORIESTANGENTIAL MANOEUVRESRADIAL MANOEUVRESX (V−bar)∆ x = _4ω ∆Vz1X (V−bar)∆Vx1∆ x = 6 πω ∆ Vx1∆Vx2∆Vz∆ z = _ 1ω ∆Vz∆Vz2 11Z (R−bar)∆Vx2Z (R−bar)fly−around toR−bar approachon −R−bar sideX (V−bar)∆Vx1∆ x = 3 _ω π ∆Vx1∆ z = _ 4 ω ∆ Vx1∆Vx1X (V−bar)∆ z = _ 1ω ∆Vz1∆ x = _2ω ∆Vz1∆Vz1Z (R−bar)∆Vx2fly−around toR−bar approachon +R−bar sideZ (R−bar)∆VxDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200923

STRAIGHT LINE AND QUASI-STRAIGHT LINETRAJECTORIESContinuous force2ω VxX (V−bar)∆Vx2Motion Vx∆Vx1XV−bar∆V ∆V ∆V ∆V∆V∆VTargetV-bar LINEZ (R−bar)R−barZTargetXX (V−bar)Motion Vz∆Vz12ω V z+ +Continuous x−force(V + Z )z 0t23ωz−forceV−bar∆V∆V∆V∆V∆V∆V∆V∆V∆V∆V∆Vz 2∆VR-bar LINEZ (R−bar)R−barZDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200924

THE PREDOMINANT DISTURBANCES IN LEO AND GEOSunTHE DIRECTION OF THE DRAG FORCE ISALWAYS OPPOSITE TO THE FLIGHT DIRECTIONα . =360 deg24 hγ SUNγDRAGV−barCoPF DRAGV−barCoPFDRAGR−barR−barTHE DIRECTION OF THE SOLAR FORCE ISALWAYS OPPOSITE TO THE SUN DIRECTIONDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200925

LONG TERM TRAJECTORY WITH DIFFERENTIAL DRAGEXAMPLE: 0.5 m/s R-BAR CAM IN 400 km ORBIT, z 0 = 15 m, C BcC Bt= 5,Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200926

EFFECTS OF THE SOLAR PRESSURE IN GEO (repeated)Important:(Figures are obtained by numerical integration of the Hill equations.The Clohessy-Wiltshire equation are valid only for constant forces.)1. Motion after releasedue to solar pressure,start 12:00 h2. Tangent. boost traject.diff. solar press., 3 rev.+0.002 m/s, start 12:00 hNote: These are just 3 examples !Shape of trajectories depends highly on starting timeand boost size and direction !3. Radial boost traject.,diff. solar press. 3 rev.+0.01 m/s, start 12:00 hDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 201027

DRIVERS FOR RENDEZVOUS STRATEGIES IN THESHORT RANGETHE MAIN DRIVERS FOR AN APPROACH STRATEGY ARE:• LOCATION OF DOCKING/BERTHING PORTS w.r.t. V-BAR AND R-BAR• DIRECTION OF APPROACH AXIS & ATTITUDE OF TARGET• CAPABILITIES (RANGE, FOV, ACCURACY) OF SENSORS• TRAJECTORY SAFETY CONSIDERATIONS• APPROACH CONTROL ZONES IMPOSED BY THE TARGET• COMMUNICATION WINDOWS WITH GROUNDDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200928

DRIVERS FOR RENDEZVOUS STRATEGIES IN THESHORT RANGE:DOCKING AND BERTHING PORT LOCATIONSDOCKING PORT LOCATIONSline of finaltranslationline of finaltranslationdocking ports can havea significant distancefrom the actual V−baror R−barV−bar+ V−bar Portsensor interfacesline of finaltranslationsensor interfacesm+ V−bar Port+ V−bar Portsensor interfaces− R−bar Portm mline of finaltranslationCoMmmm+ R−bar PortR−barsensor interfaces−V−bar Portmline of finaltranslation− V−bar Portsensor interfacessolar arraysand other apendagesnot shown !line of finaltranslationBERTHING BOX & PORT LOCATIONSBerthing Boxacquired byV−bar approachtransfer toberthing portby manipulatorV−barmsensor interfaces forfinal translation andberthing box acquisition+ V−bar Port+ V−bar PortR−bar PortmR−bar Porttransfer toberthing portby manipulatorBerthing Boxacquired byR−bar approachCoMR−bar+ V−bar PortR−bar Port− Vbar Portline of finaltranslationDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200929

DRIVERS FOR RVD STRATEGIES IN THE SHORT RANGE:OPERATIONAL RANGE OF RENDEZVOUS SENSORSaccuracy1000 m100 m10 mAGPS and RGPSlimited by multipath andshadowing effectsAbsolute GPS w. S/AAbsolute GPS w/o S/ARelative GPS1 % of range1 mRadar0.1 m0.01 mCamera Type SensorLaser Range Finder1 m 10 m 100 m 1 km 10 km 100 kmrangeDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200930

DRIVERS FOR RVD STRATEGIES IN THE SHORT RANGE:APPROACH CONTROL ZONES OF THE ISS1000mAPPROACH ELLIPSOIDKEEP−OUT ZONE200m+V−barhalf cone angle10 − 15 degr.2000mAPPROACH CORRIDORSAPPROACH ELLIPSOIDKEEP−OUT ZONEDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200931

ONBOARD FUNCTIONS AND COMMUNICATION LINKSDRSGPSONBOARD RVD CONTROL SYSTEMCOMM’sSYSTEM MGMTCOMPUTER& SOFTWAREGPSONBOARD GNCSOFTWAREGYROSOPT. RVSENSORSPROPULS.CONTROLCHASERDOCKINGSYSTEMRV SENSORH.O.TARGETH.O. = HUMAN OPERATORH.O.CHASERCONTROL CENTERGROUND LINK INFRASTRUCTUREH.O.TARGETCONTROL CENTERDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200932

COMMUNICATION RANGE OF GROUND STATIONS(Example: DEOS 400 km, i = 87 ◦ , RAAN = 0 ◦ , day = 01 - 02 January)Dr. W. Fehse — Introduction to RVD — From Ground to Capture — Version 201033

APPROACH STRATEGY EXAMPLE (ATV-TYPE)V−BARKEEP−OUT ZONE 200mAPPROACHCORRIDORTARGET S3250−500mAPPROACHELLIPSOID2000 mV−BAR APPROACHWAITING POINT3000 − 5000 mS2RADIAL BOOSTTRANSFERHOHMANNTRANSFERCOMMUNICATIONRANGE(FAR RANGE RV)(CLOSE RANGE RV)> 3000 m S1S0FINALAPPROACHCLOSING PHASEHOMING PHASERVS RGPS RGPS GPSR−BAR(FROM PHASING)Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200934

APPROACH STRATEGY EXAMPLE(JAPANESE HTV-TYPE)KEEP−OUT ZONEAPPROACHELLIPSOIDV−BARWAITING POINT200 m 2000 m3000 − 5000 mS2FINALAPPROACHRVSS4APPROACHCORRIDORS3HOHMANNTRANSFERHOHMANNTRANSFERCOMMUNICATIONRANGE> 2500 mR−BARCLOSING PHASERGPSHOMING PHASERGPSS1S0GPSDr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200935

APPROACH STRATEGY EXAMPLE(GEO SERVICING TYPE)70°S4150°V−bar, xS3Target satelliteS1330°165*315°9°9°Earth ShadowEclipseR−bar, z270°(Source: SENER, Smart-OLEV project)Dr. W. Fehse – Introduction to RVD – From Ground to Capture – Version 200936

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTURE IN GEO ?Dr. W. Fehse – Introduction to RVD – Capture Issues – Version 200937

DOCKING AND BERTHING (DEFINITION)MANIPULATORTARGETSTATIONGRAPPLE MECH.TARGETlateralmotionresidualattitudemotionsrel. attitudeGRAPPLE FIXTUREattitude angleof targetlateralmisalignm’trel. attitudeappr. velocityCHASERattitudemotionBERTHINGMECHANISMHALVESCHASERresidualresidualattitudemotionslateraltranslationalmotionsmotionBERTHING BOX. DOCKING BERTHINGCAPTURE & CONNECTIONCAPTURE & TRANSFER TO. ATTACHMENT POSITIONDr. W. Fehse – Introduction to RVD – Capture Issues – Version 200938

THE PROBLEM OF CAPTURELAW OF CONSERVATION OF MOMENTUM:FREE BODIES CONTACTING EACH OTHER WILL REBOUND AND SEPARATEAGAIN.TOTAL MOMENTUM Σ (M x V) OF THE COMPLETE SYSTEM REMAINSCONSTANT, IF NO MOTION ENERGY HAS BEEN CONVERTED INTO HEAT.vdAS A RESULT OF THE REBOUND, ONLY LIMITED TIME IS AVAILABLE TOPERFORM CAPTURE.Dr. W. Fehse – Introduction to RVD – Capture Issues – Version 200939

Momentum Exchange at ContactThe motions between two bodies after contact can be derived from the momentumlaw.For translational motion∫ t1t0Fdt = m · ∆VIf the point of impact is not located on a line connecting the CoM’s of the twobodies, also the change of angular momentum must be taken into account:I · ∆ω =∫ t1t0(r × F)dtF(t)V a0CoM aV b1F(t) V a0CoM bV b1rNon−CentralImpactCoM aCoM bω b1Central ImpactDr. W. Fehse – Introduction to RVD – Capture Issues – Version 200940

Shock Attenuation DynamicsBasic Spacecraft Features Important for Contact Analysisx0∆x 1x maxMbMaMb >/= MaMfe

FUNCTIONS OF A DOCKING MECHANISMRECEPTION : PROVIDES AFTER FIRST CONTACT THE MECHANICALGUIDANCE OF THE CAPTURE INTERFACES INTO A POSITION WHERECAPTURE TAKES PLACE.CAPTURE: ENSURES THAT THE CAPTURE INTERFACES WILL NOTESCAPE AFTER CONTACT DUE TO REBOUND.SHOCK ABSORPTION: REDUCES THE CONTACT SHOCK AND INCREASESTHE TIME FOR CAPTURE, DUE TO THE SPRING-DAMPER EFFECT ON THEMOTION OF THE CONTACT INTERFACES.MECHANICAL ALIGNMENT: REDUCES THE ALIGNMENT ERRORS TO ADEGREE NECESSARY FOR THE ENGAGEMENT OF STRUCTURAL LATCHES.PROVIDES PRECISION ALIGNMENT DURING STRUCTURAL LATCHING.STRUCTURAL LATCHING: ESTABLISHES A STIFF STRUCTURALCONNECTION, AS NECESSARY TO SUSTAIN AND TRANSMIT THE LOADSOF THE COMBINED VEHICLE.SEALING: ESTABLISHES A GAS- TIGHT CONNECTION BETWEEN THE TWOSPACECRAFT.Dr. W. Fehse – Introduction to RVD – Capture Issues – Version 200942

TYPES OF DOCKING MECHANISMTWO BASIC TYPES OF DOCKING SYSTEMS HAVE BEEN DEVELOPED:DOCKING SYSTEMS WITH CENTRAL CONTACT INTERFACESDOCKING SYSTEMS WITH PERIPHERAL CONTACT INTERFACESTHE CENTRAL DOCKING SYSTEMHAS ON THE ACTIVE SIDE AN ELASTICALLY SUSPENDED ROD (PROBE),WHICH ENTERS A HOLLOW CONE (DROGUE) ON THE PASSIVE SIDE.IT WILL BE CAPTURED AT THE CENTRE OF THE CONE BY PASSIVE(SPRING ACTUATED) LATCHES.THE PERIPHERAL DOCKING SYSTEMUSES PETAL-TYPE GUIDING STRUCTURES AT ITS CIRCUMFERENCE.THERE ARE SPACES BETWEEN THE PETALS, WHERE THE PETALS OF THEOPPOSITE SIDE FIT IN.WHEN INTERFACES ARE ENGAGED AT A CERTAIN DEPTH, CAPTURE ISEFFECTED BY PASSIVE OR ACTIVE LATCHES.Dr. W. Fehse – Introduction to RVD – Capture Issues – Version 200943

©©©©©©©©©©©©¡ ¢ ¢ ¡ §§§ ¨¨¨¨ ¨¨§§§ ¦¥¥¥¥¥ ¦ ¦ ¦ ¦¥¤¦¤¥¥¥££££££££ ¤ ¤ ¤ ¤ ¤£¤£££TYPES OF DOCKING MECHANISM (DIAGRAM)CENTRAL DOCKING MECHANISMPERIPHERAL DOCKING MECHANISMPETALS CAN BE INSIDEOR OUTSIDEAT HATCH OPENING, MECHANISM IS IN THE WAYIN CASE OF CENTRAL DOCKING MECHANISMDr. W. Fehse – Introduction to RVD – Capture Issues – Version 200944

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTURE IN GEO ?Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200945

ONBOARD FUNCTIONS AND COMMUNICATION LINKS(repeated)DRSGPSONBOARD RVD CONTROL SYSTEMCOMM’sSYSTEM MGMTCOMPUTER& SOFTWAREGPSONBOARD GNCSOFTWAREGYROSOPT. RVSENSORSPROPULS.CONTROLCHASERDOCKINGSYSTEMRV SENSORH.O.TARGETH.O. = HUMAN OPERATORH.O.CHASERCONTROL CENTERGROUND LINK INFRASTRUCTUREH.O.TARGETCONTROL CENTERDr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200946

THE AUTOMATIC ONBOARD CONTROL SYSTEMFOR RVD IN LEOTHE MOST IMPORTANT TASKS, THE AUTOMATIC CONTROL SYSTEM OFTHE APPROACHING VEHICLE HAS TO FULFIL, ARE:• GUIDANCE, NAVIGATION and CONTROL (GNC),i.e. IMPLEMENTATION OF THE MANOEUVRES, THE TRAJECTORIESAND THE ATTITUDES ACCORDING TO THE APPROACH STRATEGY.• MISSION and VEHICLE MANAGEMENT (MVM),i.e. THE SEQUENCING OF GNC MODES FORTRAJECTORY AND ATTITUDE ANDTHE ENGAGEMENT OF THE RELEVANT H/W AND S/W FUNCTIONS.• FAILURE DETECTION, ISOLATION and RECOVERY (FDIR)• COLLISION AVOIDANCE MONITORING ANDCOLLISION AVOIDANCE MANOEUVRE (CAM) ACTUATION• COMMUNICATION WITH GROUND AND WITH TARGET, i.e.SELECTION & TRANSMISSION OF ONBOARD DATA TO GROUND/TARGETAND RECEPTION, PROCESSING AND EXECUTION OF DATA FROM GROUND.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200947

CONTROL HIERARCHY AND SPACECRAFT FUNCTIONSIN AUTOMATED RENDEZVOUS AND DOCKINGTMMONITORING &HIGH LEVEL CONTROLBY OPERATORS IN CCTCSPACECRAFTONBOARDSYSTEMSCOMMUNICATIONS SYSTEMDATA MANAGEMENT SYSTEMAUTOMATIC ONBOARD RV−CONTROL SYSTEMPOWER CONTROL SYSTEMPLANT(VOLTAGE)SPACECRAFT STATEAUTOMATIC FDIRFAILURE DETECTION, ISOLATION& RECOVERY SYSTEMAUTOMATIC MVMMISSION & VEHICLE MANAGEMENT(MODE SWITCH./ EQU’PT ASSIGNM.)SENSORSGNCMODESPLANT (ATV)(POSITION, VELOCITIESATTITUDE, ATTITUDE RATESOF CHASER)ACTUA−TORSGNC (SPACECRAFT STATE CONTROL)CAMCONTROL FORCES/TORQUESTHERMAL CONTROL SYSTEMPLANT(TEMP.)Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200948

CLOSED LOOP GNC BLOCK DIAGRAMSENSORSGUIDANCEGNC FUNCTIONSACTUATORSRENDEZVOUSSENSORGPS RECEIVERNAVIGATIONFILTER−+CONTROLLERACTUATORMANAGEMENTTHRUSTERSWHEELSATTITUDESENSORSSPACECRAFT STATESTATE AS SEENBY SENSORSMEASUREMENTENVIRONMENT& DISTURBANC.DYNAMICS& KINEMATICSFORCES & TORQUESSPACECRAFTDYNAMICS, KINEMATICSDYNAMICDISTURBANCES& ENVIRONMENTDr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200949

GNC SYSTEM FOR ARD, DEGREES OF FREEDOMTHERE ARE 6 DEGREES OF FREEDOM (DOF) TO BE CONTROLLED, i.e.3 TRANSLATIONS AND 3 ROTATIONS.THE COMPLETE GNC SYSTEM, THEREFORE, CONSISTS OF6 CONTROL LOOPS.AS LONG AS TARGET AND CHASER ARE AT LARGE DISTANCE ANDMOVEMENTS ARE INDEPENDENT OF EACH OTHER, THE6 DOF CAN BE CONTROLLED TO A FAR EXTENT INDEPENDENTLYOF EACH OTHER.IN THE LAST PART OF THE APPROACH, i.e.WHEN THE DOCKING INTERFACE OF THE APPROACHING VEHICLE HASTO BE ALIGNED TO THAT OF THE TARGET STATION,ALL MOTIONS WILL EVENTUALLY BE COUPLED.FOR THIS CASE MULTIPLE-INPUT-MULTIPLE-OUTPUT (MIMO) CONTROLOR OTHER TECHNIQUES HAVE TO BE APPLIED FOR THE CONTROLOF THE COUPLED MOTION.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200950

THE MISSION + VEHICLE MANAGEMENT (MVM)FUNCTION FOR ARDTHE TASK OF THE MVM FUNCTION IS TO SCHEDULE THE VARIOUS• S/W MODES FOR FOR NAVIGATION, GUIDANCE AND CONTROL(PHASE + MODE MANAGEMENT) AND• THE EQUIPMENT CONFIGURATION FOR EACH STEP OF THEAPPROACH.THE MVM FUNCTION IS DRIVEN BY A MISSION TIMELINE TABLE,WHICH IS UPDATED ACCORDING TO THE ACTUAL EVENTS.THE MVM IS VERY CLOSELY INTERACTING WITH THE FAILUREDETECTION, ISOLATION + RECOVERY (FDIR) FUNCTION.ON REQUEST OF THE FDIR FUNCTION, IN CASE OF FAILURE OF ANEQUIPMENT OR OF FAULTY BEHAVIOUR OF THE COMPLETE STRING,IT EXECUTES THE REDUNDANCY SWITCHING OF SENSOR ANDACTUATOR EQUIPMENT.IT REGISTERS THE INSTANTANEOUS CONFIGURATION OF MODESAND EQUIPMENT AND THE REDUNDANCY STATUS WITHIN THATCONFIGURATION.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200951

PRINCIPLE OF MVM FUNCTION (simplified)TCTMFDIRFUNCTIONMISSIONTIME LINEMODE MANAGEMENTMODETABLEPHASE/MODETRANS.CRIT.MODE & EQUIP’T CONFIG. MONITORINGTCDISTRIB.ALGORITHM SCHEDULERINSTANT.GNCCONFIG.NAVIG.ALGO’SGUIDANCEALGO’SCONTROLALGO’SLLFDI−ALG. LLFDI−ALG. LLFDI−ALG.EQUIPMENT SCHEDULEREQU’T AEQU’T BEQU’T CEQU’T DHEALTH STAT.HEALTH STAT.HEALTH STAT.HEALTH STAT.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200952

FAULT TOLERANCE AND RECOVERY CONCEPTTHE FOLLOWING FAULT TOLERANCE REQUIREMENTS HAVE BEENESTABLISHED FOR OPERATIONS AT OR IN PROXIMITY OF A MANNEDSPACE STATION:• AFTER ANY COMBINATION OF 2 SINGLE FAILURES, CREW ANDSTATION MUST REMAIN SAFE.• AFTER ANY FIRST SINGLE FAILURE THE MISSION MUST STILLBE ACHIEVED.THIS HAS IMPORTANT REPERCUSSIONS ON BOTH TRAJECTORY DESIGNAND REDUNDANCY DESIGN OF THE ONBOARD SYSTEM.FOR THE ESSENTIAL FUNCTIONS THE ONBOARD SYSTEM MUST BETWO-FAILURE TOLERANT.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200953

RECOVERY FROM CONTINGENCIESTHE FOLLOWING ACTIONS ARE POSSIBLE:• SWITCH TO REDUNDANT EQUIPMENT, IF FAULTY EQUIPMENTHAS BEEN IDENTIFIED.• SWITCH TO REDUNDANT STRING, IF FAILURE COULD NOT BEISOLATED. THIS INCLUDES SWITCHING TO A REDUNDANTPROCESSOR WITH IDENTICAL S/W.• EXECUTION OF A COLLISION AVOIDANCE MANOEUVRE (CAM)OR INHIBITION OF TRAJECTORY CONTROL ACTUATION TO LEAVETHE VEHICLE ON A SAFE DRIFT ORBIT (IF AVAILABLE).RECOVERY FROM FAILURES OF COMPUTER- AND DATA BUSFUNCTIONS WILL BE HANDLED (VOTING) BY THE DATA MANAGEMENTSYSTEM RATHER THAN BY THE MVM FUNCTION.FOR S/W FAILURES, A SEPARATE MORE ROBUST AND SIMPLEPROCESSOR MAY BE USED FOR MONITORING, FAILURE DETECTIONAND RECOVERY.FUNCTIONAL REDUNDANCY HAS TO BE USED TO THE EXTENTPOSSIBLE, TO REDUCE THE COMPLEXITY OF THE SYSTEM.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200954

COLLISION AVOIDANCE MANOEUVRE (CAM)THE CAM IS A SINGLE RETROGRADE BOOST, WHICH MOVES THEVEHICLE IN THE FIRST INSTANCE IN A DIRECTION OPPOSITE TO THEAPPROACH DIRECTION.THE DELTA-V OF THE CAM HAS A CONSTANT VALUE(AT LEAST PER APPROACH PHASE).THE CAM MUST BE STRONG ENOUGH TO ENSURE THAT THERESULTING TRAJECTORY MOVES OUT OF A SAFETY ZONE AROUNDTHE TARGET STATION (e.g. THE APPROACH ELLIPSOID IN CASE OF THEISS) AND DOES NOT RETURN TO IT WITHIN A GIVEN TIME.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200955

THE NAVIGATION REQUIREMENTS FOR ARDVALUES TO BE MEASURED (LONG RANGE):AS LONG AS CHASER AND TARGET VEHICLE ARE AT FAR DISTANCEFROM EACH OTHER, IT IS SUFFICIENT TO MEASUREPOSITION AND ATTITUDE INDEPENDENTLY FOR EACH VEHICLEIN AN ABSOLUTE FRAME ,• POSITION IN AN EARTH FIXED COORDINATE SYSTEM,• ATTITUDE EITHER EARTH ORIENTED OR INERTIAL(e.g. SUN POINTING).WHEN THE CHASER HAS COME CLOSER TO THE TARGET VEHICLE(ORDER OF MAGNITUDE OF A FEW 10 KM)AND MANOEUVRES REQUIRE HIGHER ACCURACY,THE DIFFERENCE OF ABSOLUTE POSITION MEASUREMENTSWOULD LEAD TO TOO LARGE ERRORS.RELATIVE POSITION MEASUREMENTS BETWEEN THE TWO VEHICLESNEED TO BE PERFORMED FROM THEREON.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200956

THE NAVIGATION REQUIREMENTS FOR ARD (cont’d)PERFORMANCE REQUIREMENTS FOR ABSOLUTE AND RELATIVEATTITUDE:DURING ALL APPROACH PHASES PRIOR TO THE FINAL APPROACH,ONLY ABSOLUTE ATTITUDE NEEDS TO BE MEASURED(e.g. w.r.t. LOCAL VERTICAL / LOCAL HORIZONTAL).THE ABSOLUTE ATTITUDE HAS TO BE CONTROLLED TO ≤ 1 DEG.,MOSTLY BECAUSE OF THE NECESSARY ALIGNMENT OF THRUSTERS FORTRAJECTORY CONTROL.ABSOLUTE ATTITUDE MEASUREMENT ACCURACY MUST BE OF THEORDER OF 0.1 DEG.RELATIVE ATTITUDE MEASUREMENT IS REQUIRED WHEN THE CHASERVEHICLE HAS TO ACQUIRE THE DOCKING AXIS OF THE TARGETSPACECRAFT.RELATIVE ATTITUDE MEASUREMENT ACCURACY REQUIREMENT IS OFTHE ORDER OF 1 - 2 DEG.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200957

MEASUREMENT PRINCIPLES: GPSNAVIGATION SATELLITE CONSTELLATIONLOCUS OF EQUAL DISTANCES18S3513S1S21024812194673N171415162211912123220Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200958

MEASUREMENT PRINCIPLES: RGPSRELATIVE GPS (RGPS) MEASUREMENT PRINCIPLE:IN CASE OF DIFFERENTIAL GPS (AS USED e.g. FOR AIRCRAFT ANDSHIPS) ALL MEASUREMENTS ARE RELATED TO ONE RECEIVER,THE POSITION OF WHICH IS PRECISELY KNOWN.HOWEVER, THERE IS NO FIXED POSITION AVAILABLE IN SPACE.BOTH CHASER AND TARGET ARE MOVING WITH HIGH VELOCITYRELATIVE TO THE EARTH.THEREFORE, WITH RELATIVE GPS, THE RAW DATA OF THEGPS RECEIVERS OF CHASER AND TARGET ARE RELATED TO THEPOSITION ESTIMATES OF THE CHASER’S NAVIGATION FILTER.THE NAVIGATION FILTER PRODUCES A RELATIVE POSITIONESTIMATE, USING ALL NAVIGATION INFORMATION AVAILABLE,INCLUDING:• THE GPS RAW DATA OF BOTH VEHICLES,• ORBIT PROPAGATION WITH THE PRESENT STATE VECTOR,• THE COMMANDED THRUSTS .Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200959

MEASUREMENT PRINCIPLES: RGPSGPS RXCHASERGPS RAW DATA CHASERGPS SATEL.SELECTIONGPS SAT.DIFFERENTIALDATACALCULATIONRELATIVE GPSMEASUREMENTVECTORGPS RXTARGETGPS RAW DATA TARGETGPS SAT EPHEMERISABSOLUTE ATTITUDE & POSITIONABSOLUTENAVIGATIONFILTERTHRUSTERMANAGEM.INITIAL PARAMETERS(e.g. TARGET ORBIT EPHEMERIS)COMMANDEDCONTROL FORCESSTATEPROPAGATION,COVARIANCEPROPAGATIONRGPS NAVIGATION FILTERSTATE UPDATE&COVARIANCEUPDATERELATIVESTATE VECTOR− rel. position− rel. velocities− rel. clock bias− rel. clock driftCOMPARE BOXES ’SENSORS’ AND ’NAVIGATION FILTER’ ON CHART 47.In RGPS the sensor function includes GPS Receivers and Navigation Filter.Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200960

MEASUREMENT PRINCIPLE OF LASER RANGE FINDER(PULSE TYPE)LASER BEAMOUTGOINGINCOMINGRANGE & DIRECTIONψ, ϑRMIRROR 2MIRROR 1ϑψϑ(t)ψ(t)TRANSMITTER/RECEIVERSIGNALPROCESSOR∆tRANGELOS−DIRECTIONREL. ATTITUDERELATIVE ATTITUDEOUTGOING PULSEINCOMING PULSER1R2R3Dr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200961

MEASUREMENT PRINCIPLE OF CAMERA SENSOR(SCHEMATIC)CAMERA SENSOR MEASUREMENT CONCEPTRINGILLUMINATORLENSCCDCCDELECTRON.PROCESSORRANGEDIRECTIONREL. ATTITUDETARGET REFLECTORSCCD CAMERAPATTERNEVALUATIONALGORITHMSERPitchRollAR = RANGEA = AZIMUTHE = ELEVATIONYawDr. W. Fehse – Introduction to RVD – Automatic RVD Onboard Functions – Version 200962

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTURE IN GEO ?Dr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200963

FUNCTIONS AND OPERATORS INVOLVED IN ARD(repeated)DRSGPSONBOARD RVD CONTROL SYSTEMCOMM’sSYSTEM MGMTCOMPUTER& SOFTWAREGPSONBOARD GNCSOFTWAREGYROSOPT. RVSENSORSPROPULS.CONTROLCHASERDOCKINGSYSTEMRV SENSORH.O.TARGETH.O. = HUMAN OPERATORH.O.CHASERCONTROL CENTERGROUND LINK INFRASTRUCTUREH.O.TARGETCONTROL CENTERDr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200964

WHY DO WE WANT TO HAVE AN AUTOMATICONBOARD SYSTEM?COULDN’T WE DO IT BETTER REMOTELY CONTROLLED FROMGROUND?ANSWER:FOR THE APPROACH AND COUPLING OF THE CHASER TO THE TARGET,A LARGE NUMBER OF MANOEUVRES AND OPERATIONS ARE NECESSARY.• DUE TO THE LIMITED COMMUNICATION POSSIBILITIES BETWEENGROUND CONTROL CENTRE AND SPACECRAFT• AND BECAUSE OF THE RISK OF LINK FAILURESMANOEUVRES AND OPERATIONS HAVE TO BE PERFORMED TOA LARGE EXTENT AUTOMATICALLY ABOARD THE VEHICLE.Dr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200965

WHY DO WE WANT TO HAVE HUMAN OPERATORSINVOLVED ?ANSWER:WE WANT TO HAVE HUMAN OPERATORS INVOLVED,WHEREVER THEY CAN DECREASE COMPLEXITY OF THE SYSTEMAND IMPROVE SAFETY AND MISSION SUCCESS.AUTOMATIC DOES NOT MEAN COMPLETELY AUTONOMOUS !MONITORING AND ’GO-AHEAD’ COMMANDS ARE PART OF THENOMINAL OPERATIONS.THUS, THE ONBOARD SYSTEM MUST BE CAPABLE OF PROVIDINGAND RECEIVING INFORMATION TO AND FROM REMOTE OPERATORS.ALSO, INTERACTIONS BY GROUND AND BY CREW ARE PART OFTHE OVERALL RECOVERY CONCEPT IN CASE OF FAILURES.Dr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200966

THE ROLE OF HUMAN OPERATORS INAUTOMATIC RENDEZVOUS AND DOCKINGIN AN EARTH ORBIT THERE IS NO NEED TO PERFORM THERENDEZVOUS AND DOCKING PROCESS COMPLETELY AUTONOMOUSLY.ON THE CONTRARY, INTERACTION BY HUMAN OPERATORS ISALWAYS DESIRABLE, IF THIS LEADS TO• INCREASE OF SAFETY• INCREASE OF MISSION SUCCES PROBABILITY• DECREASE OF COMPLEXITYFOR THIS REASON, BOTHOPERATORS ON GROUND AND IN THE TARGET STATIONWILL BE INVOLVED IN THE RENDEZVOUS AND DOCKING PROCESS.Dr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200967

THE CONTROL HIERARCHY IN AUTOMATED RVDREMOTEMONITORING & CONTROLBY OPERATORS(GROUND & TARGET S/C)TCAUTOMATIC ONBOARD RV−CONTROL SYSTEMAUTOMATIC FDIRFAILURE DETECTION, ISOLATION& RECOVERY SYSTEMAUTOMATIC MVMMISSION & VEHICLE MANAGEMENT(MODE SWITCH./ EQU’PT ASSIGNM.)TMSPACECRAFT STATESENSORSGNCMODESACTUA−TORSGNC (SPACECRAFT STATE CONTROL)PLANT(POSITION, VELOCITIESATTITUDE, ATTITUDE RATESOF CHASER)CONTROL FORCES/TORQUESDr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200968

THE TASKS OF GROUND OPERATORS IN ARDIN THE NOMINAL MISSION CASEDURING THE NOMINAL MISSION, THE TASKS OF THE HUMAN OPERATORSIN THE GROUND CONTROL CENTRE ARE:• MONITORING OF– TRAJECTORY, ATTITUDE, RATES ANDSTATUS OF ONBOARD SYSTEM,– TIMELINE (ADJUSTMENT OF TIMELINE , IF NECESSARY),– VIDEO PICTURES IN THE LAST METRES OF FINAL APPROACHAND DOCKING (RUSSIAN APPROACH),• INPUT OF DATA AND COMMANDS TO THE CHASER VEHICLE– UPDATED ORBIT DATA OF TARGET VEHICLE ,– GO-AHEAD- (MISSION CONTINUATION) COMMANDINGAFTER HOLD POINTS,• VOICE COMMUNICATION WITH TARGET CREW AND WITHOPERATORS OF OTHER CONTROL CENTRES INVOLVED.IN ADDITION, IF NECESSARY, GROUND OPERATORS MAY HAVE TOPERFORM CALIBRATION AND TRIMM MANOEUVRES.Dr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200969

TRAJECTORY MONITORING DISPLAYPHASESTARTENDPITCHYAWROLLHohmannxx:xx:xxxx:xx:xxANGLEXXXXXXXXXXXXXXXXXXXXXR Y PDEVIATIONCONTINGENCYANG.RATEXXXXXXXXXXXXXXXXXXXXX−200Z (LVLH)0MENUNNNDISPLAYSNNNWARNING Traj. Syst. Thrust Com.HELPTimelineGMTxx:xx:xxMETX (LVLH) actual position−1500 −2000 −2500 −3000 −3500hold pointS 2ORBITholdpointmarginxx:xx:xxorb. night−4000GNC modeSENSOR typeXYZPOSITIONXXXXXXXXXXXXXXXXXXXXXVELOCITYXXXXXXXXXXXXXXXXXXXXX200400trajectorycorridoractual positionDEVIATION FROM PLANNEDXY600trajectory continuationif no S2 boostZZ800MISSIONSYSTEMMessages concerning mission eventsMessages concerning system events and warningsDr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200970

RENDEZVOUS CONTROL SYSTEM DISPLAYPHASESTARTENDHohmannxx:xx:xxxx:xx:xxCONTINGENCYWARNINGMENUTraj.NNN NNNDISPLAYSSyst. Thrust Com.HELPTimelineGMTORBITxx:xx:xxMETxx:xx:xxRVS 1 RVS 2Video 1 Video 2OPTICALIllumin.SENSORSATTITUDE SENSORSEarth S. Sun S.Gyro 1 Gyro 2Gyro 3 Gyro 4PROPULS. SYSTEMLargeThr. 1LargeThr. 2Small SmallThr. 1 Thr. 2DATA MANAGEMENT SYSTEMFTC 1 FTC 2 FTC 3 FTC 4S−Band 1 S−Band 2UHF 1 UHF 2Nav.Sat.1 Nav.Sat.2local linkCOMM’sSYSTEMRV−CONTROLMVM / FDIR S/W SYSTEMTraj. modeGui.modeTraj. modeAtt. modeAtt. modeNAVIGAT. GUIDANCE CONTROLThr.man.DockingSystemPowerTherm.MISSIONSYSTEMMessages concerning mission eventsMessages concerning system events and warningsDr. W. Fehse – Introduction to RVD – Role of Man in Automatic RVD – Version 200971

PART 1: INTRODUCTION TO RENDEZVOUS & DOCKINGTHE MOST IMPORTANT QUESTIONS TO BEANSWERED1. WHAT ARE THE TASKS, WHAT IS THE SCENARIO, WHO ARE THEMAJOR PLAYERS IN A RENDEZVOUS MISSION ?2. HOW DOES THE APPROACHING VEHICLE GET FROM GROUNDTO THE TARGET ?3. WHAT ARE THE MAIN ISSUES OF CAPTURE IN SPACE ?4. WHICH FUNCTIONS MUST BE AVAILABLE ABOARD TO DO ITAUTOMATICALLY (LEO) ?5. WHAT IS THE ROLE OF MAN IN THE AUTOMATIC RENDEZVOUSPROCESS (LEO)?6. WHAT ARE THE MAIN ISSUES OF RENDEZVOUS & CAPTUREIN GEO ?Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200972

WHAT IS DIFFERENT BETWEEN RVD IN GEO AND LEO ?THE MAJOR DIFFERENCES ARE IN THE FOLLOWING AREAS:1. ORBITAL DYNAMICS DURATION, DELTA-V2. ORBITAL DISTURBANCES: DRAG IN LEO, SOLAR PRESSURE IN GEO3. ILLUMINATION: PRACTICALLY NO ECLIPSES4. COMMUNICATION WITH GROUND: PERMANENT LINK POSSIBLE5. NAVIGATION: NO GPS, NO INTERFACES FOR SENSORS6. CAPTURE & LATCHING: NO DEDICATED INTERFACESTHESE DIFFERENCES WILL BE DISCUSSED IN MORE DETAILIN THE FOLLOWING CHARTS.Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200973

THE MAJOR DIFFERENCES: ORBITAL DYNAMICSTypical two-pulse manoeuvres with a duration of half an orbitalperiod will take 12 h in GEO as compared to 46 min in LEO(factor of 15 - 16).This makes the approach very slow and results in a duration of many daysfor the rendezvous phase in GEO, as compared to a couple of hours in LEO-RVD.The ∆V is proportional to ω, the orbital rate→ the required ∆V for the same distance is in GEO about 15 - 16 times smallerthan in LEO.• The fact that the required forces for a certain trajectory size are smaller, doesnot only imply less propellant but alsothat the thrusters must be smaller to keep thrust errors low.• In the same way the trajectory becomes alsomore sensitive to orbital disturbances.Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200974

THE MAJOR DIFFERENCES: ORBITAL DISTURBANCESTHE PREDOMINANT DISTURBANCES IN LEO AND GEOSunTHE DIRECTION OF THE DRAG FORCE ISALWAYS OPPOSITE TO THE FLIGHT DIRECTIONα . =360 deg24 hγ SUNγDRAGV−barCoPF DRAGV−barCoPFDRAGR−barR−barTHE DIRECTION OF THE SOLAR FORCE ISALWAYS OPPOSITE TO THE SUN DIRECTIONDr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200975

THE MAJOR DIFFERENCES: ILLUMINATIONThere will be no occurrence of an orbital night during the major part of a year.Only at ± 23 days around the equinoxes there will be at midnight relatively shortperiods of eclipses (of a maximum of 74 min at the day of the equinox).There is no need in any of the envisaged GEO missions to perform RVD on thoseparticular days at that time.According to the 24 h orbit, for an Earth-pointing satellite in GEO the Sun directionchanges along the day the same way as for a fixed position on the equator on ground.The maximum lateral Sun-angle for an equatorial orbit is that of the ecliptic,changing over the year by ± 23.5 deg, with 0 deg at the equinoxes.Optimal illumination conditions for -R-bar docking around 9:00 h or 15:00 h.At those times sunlight comes from behind the chaser and from the side,illuminating optimally the target docking port.Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 201076

THE MAJOR DIFFERENCES:COMMUNICATION WITH GROUNDIf the ground station of the servicer is near to the foot point of thetarget vehicle, direct and continuous communication with groundwill be possible during RVD.There are no systematic interruptions as in LEO.This is an important advantage over LEO RVD, where even underbest conditions and availability of a relay satellite a part of the orbitwill be without communications with ground.Also, due to the quasi-fixed position over ground,high bandwidth communication is possible in both directions,including video transmission from space to ground.Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200977

THE MAJOR DIFFERENCES: NAVIGATIONNo useful navigation satellite reception in GEO.No sensor interfaces on GEO satellites.GEO rendezvous vehicles will have to use either RF-sensors of the radar-type oroptical sensors.• RF-sensors are both heavy and bulky, when there areno active interfaces on the target.• Optical sensors generally have a much shorter range than RF-sensors, butrequire less power, since they can use Sun illumination.As RF-Sensors have probably to be excluded for mass, size and power consumption,there is in principle a gap in the medium range between a few 10 km and ≈1 km.Since in GEO servicing missions no dedicated interfaces will beavailable on the target for optical rendezvous sensors,not the same performance can be expectedas known from LEO rendezvous missions.Dr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200978

THE MAJOR DIFFERENCESGENERAL PROBLEM: NO TARGET INTERFACESSatellites in GEO for communications and formonitoring of phenomena on the Earth(Weather and Earth Observation)are not designed to support rendezvous and docking.As additional equipment for RVD results in additional cost,not only for the equipment but also forthe launch of the additional mass,and as RVD is not required for the nominal mission,GEO satellites will also in future not be designed to support RVD.NO DEDICATED DOCKING- AND SENSOR INTERFACESDr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200979

POTENTIAL CAPTURE INTERFACESAs a result, only the nozzle of apogee boost motor is available as suitablecapture interface, unless the entire satellite body is captured e.g. by large arms orby a net.The principle of capture using theABM nozzle as interface is shown below.Also in case of spinning satellites, this will be the sole interface available for capture.However in this case the capture interface on the chaser or even the entire chaservehicle would have to be spun up.APOGEE BOOST MOTOROF GEO SATELLITECAPTURE TOOL OFSERVICING VEHICLESERVICING VEHICLEPrinciple of Capture Tool for Apogee Boost MotorDr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200980

ALLOCATION OF TASKS TO SPACE- AND GROUNDSEGMENT IN GEO RVDATTUDE CONTR.SYSTEMACTUATORSOwing to the possibility ofcontinuous communicationand toslow trajectory dynamics,most of control tasks can beallocated to ground.The objective is to have asfew as possible functions on board,in order to keepcomplexity, mass & power consumptionof the vehicle low,and to keep the cost forspacecraft, launch and operationas low as possible.SPACESEGMENTGROUNDSEGMENTCLOSED LOOPTRAJECT. GNCVIDEO/IMAGECOMPRESSIONPRIMARYGUIDANCE NAVIGATION &CONTROL PROCESSINGSUPPORTINGANALYSIS&SIMULATIONSCAMCOMMUNICATIONS, TM/TC INTERFACECOMMUNICATIONS, TM/TC INTERFACEATTITUDESENSORSTRAJECTORYSENSORSMISSION & VEHICLEMANAGEMENTPROCESSINGMAN−MACHINE INTERFACE PROCESSINGGeneral control concept ina GEO servicing scenarioDr. W. Fehse – Introduction to RVD – Main Issues of GEO RVD – Version 200981

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200982

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLSISSUES ADDRESSED:• GENERAL VERIFICATION ISSUES OF SPACE PROJECTS• VERIFICATION & VALIDATION OF RV-CONTROL SYSTEMIN THE DEVELOPMENT PHASES• STIMULATION FACILITIES FOR NAVIGATION• VERIFICATION OF CAPTURE IN THE DOCKING PROCESS• VALIDATION OF SIMULATION MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200983

GENERAL VERIFICATION ISSUES FOR SPACETECHNIQUES & TECHNOLOGYPHYSICAL CONDITIONS OF ORBITAL FLIGHT CANNOT BEREPRODUCED ON GROUND IN ALL ASPECTS (0-g, ORBITAL DYNAMICS).• A MAJOR PART OF THE VERIFICATION TASKSCANNOT BE PERFORMED BY DIRECT PHYSICAL TESTINGPRIOR TO THE REAL MISSION.VERIFICATION HAS TO RELY ON TOOLS AND FACILITIES, CONTAININGMATHEMATICAL MODELLING OF• SPACECRAFT KINEMATICS AND DYNAMICS,• ACTUATORS, SENSORS, COMMUNICATION EQUIPMENT etc.,• EFFECTS OF ORBITAL ENVIRONMENT ON SENSORS, ACTUATORS etc.,• CONTACT DYNAMICS OF 2 BODIES IN SPACE (2 x 6 DOF).VALIDATION OF THESE MATHEMATICAL MODELS w.r.t. PROPERTIESAND EFFECTS OF THE REAL WORLD IN ORBIT IS ONE OF THE ESSENTIALTASKS OF THE VERIFICATION PROCESS.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200984

GENERAL RVD VERIFICATION ISSUES (cont’d)AS A CONSEQUENCE,USING DEDICATED TOOLS AND FACILITIES,FOR THE VERIFICATION OF RV-SYSTEMS AND ITEMS,IT HAS TO BE DEMONSTRATED PRIOR TO ORBITAL OPERATIONSTHAT BOTH• SYTEM AND ITEMS TO BE FLOWN IN ORBIT ARE VERIFIEDCONCERNING THE FUNCTION AND PERFORMANCEAS NECESSARY FOR THEIR PARTICULAR MISSION.AND• TOOLS AND FACILITIES USED FOR VERIFICATION AREVALIDATED FOR THEIR PARTICULAR VERIFICATION TASK.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200985

THE AIM OF VERIFICATION AND VALIDATIONVERIFICATION AND VALIDATION ARE TASKS, WHICH BY NATURE WILLALWAYS BE LIMITED IN THEIR EXTENT.THERE WILL NEVER BE A 100% VERIFCATION OR VALIDATION !IT WILL BE IMPOSSIBLE TO CHECK ALL POTENTIAL VALUES ANDCOMBINATIONS OF PARAMETERS OR ASPECTS.THE ISSUE OF VERIFICATION AND VALIDATION CAN, THEREFORE,• NEVER BE THE ACHIEVEMENT OF AN ABSOLUTE PROOF, BUT• RATHER THE ACHIEVEMENT OF THE HIGHEST POSSIBLECONFIDENCE LEVEL THAT SYSTEMS, ITEMS OR FUNCTIONS WILLPERFORM AS REQUIRED UNDER REAL WORLD CONDITIONS.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200986

DEFINITION OF VERIFICATION AND VALIDATIONVERIFICATION IS DEFINED AS THE PROOF THAT• AN ITEM, FUNCTION OR PROCESS WORKS AND PERFORMSACCORDING TO ITS SPECIFICATION.VALIDATION IS DEFINED AS THE PROOF THAT• AN ITEM, FUNCTION OR PROCESS WILL PERFORM AS EXPECTED, OR• THE DESCRIPTION OF THE BEHAVIOUR OF AN ITEM, FUNCTION ORPROCESS BY MATHEMATICAL MODELLING WILL MATCH THE BEHAVIOURUNDER REAL WORLD CONDITIONS.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200987

DEFINITION OF DEMONSTRATIONDEMONSTRATION IS THE PROOF IN FRONT OF WITNESSESTHAT A FEATURE BEHAVES AS IT IS EXPECTED TO BEHAVE.THIS CAN INCLUDE :• DEMONSTRATION OF THE FEASIBILITY OF A CONCEPT,• DEMONSTRATIONS RELATED TOVERIFICATION & VALIDATION OF ITEMS,• DEMONSTRATION OF OTHER ISSUES, e.g.CAPABILITIES IN GENERAL.DEMONSTRATIONS CONCERNING RVD ISSUES CAN RANGE FROM• SIMULATIONS,• VIA PHYSICAL TESTS,• UP TO DEMONSTRATION FLIGHTS IN ORBIT.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200988

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLS• GENERAL VERIFICATION ISSUES OF SPACE PROJECTS• VERIFICATION & VALIDATION OF RV-CONTROL SYSTEMIN THE DEVELOPMENT PHASES• STIMULATION FACILITIES FOR NAVIGATION• VERIFICATION OF CAPTURE IN THE DOCKING PROCESS• VALIDATION OF SIMULATION MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200989

WHAT NEEDS TO BE VERIFIED FOR RVD ?FOR THE PARTICULAR MISSION TASK OF RENDEZVOUS + DOCKING,PROPER FUNCTION AND PERFORMANCE OF THE FOLLOWING FEATURESMUST BE VERIFIED:• THE ALGORITHMS OF THE ONBOARD- AND GROUND SYSTEMS CON-TROLLING THE RVD PROCESS,• THE CONTROL SOFTWAREIN WHICH THESE ALGORITHMS ARE IMPLEMENTED,• THE SENSORS REQUIRED FORTRAJECTORY AND REL. ATTITUDE CONTROL,• THE FUNCTION AND PERFORMANCE OF THEINTEGRATED SYSTEM,• THE SUCCESSFUL CAPTURE OF THEDOCKING OR BERTHING INTERFACES• THE PROPER INTERACTION OF REMOTE CONTROL FUNCTIONS(GROUND OR TARGET STATION) WITH THE ONBOARD SYSTEM.MANY OTHER ITEMS OR FEATURES OF THE CHASER SPACECRAFT AREALSO INVOLVED, BUT ARE NOT SPECIFIC TO THE RENDEZVOUSCONTROL SYSTEM.SUCH ITEMS OR FEATURES ARE NOT CONSIDERED HERE, AS THEY AREPART OF THE NORMAL SPACECRAFT VERIFICATION PROCESS.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200990

VERIFICATION AND VALIDATIONIN THE DEVELOPMENT PHASESTHE METHODS OF VERIFICATION HAVE TO BE CHOSEN ACCORDING TOTHE ISSUES WHICH ARE AT STAKE IN THE PARTICULAR PROJECT PHASE:FEASIBILITY PHASE:• ARE MISSION CONCEPT AND REQUIREMENTS FEASIBLE ?DESIGN PHASE:• IS THE PRELIMINARY DESIGN ABLE TO REALISE THE CONCEPT ANDTO FULFIL THE REQUIREMENTS ?DEVELOPMENT PHASE (QUALIFICATION):• DOES THE DESIGN IMPLEMENTATION IN H/W AND S/W FULFIL THEFUNCTION AND PERFORMANCE REQUIREMENTS FOR THE MISSION ?FLIGHT ITEM MANUFACTURE PHASE:• DO THE FLIGHT ITEMS ”AS BUlLT” CORRESPOND FULLY, i.eIN PHYSICAL ASPECTS, IN FUNCTION AND IN PERFORMANCE, TOTHE ONES QUALIFIED ?Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200991

VERIFICATION IN THE DEVELOPMENT PHASES (cont’d)IN THE FOLLOWING CHARTS THE VERIFICATION STEPS OF A RENDEZVOUSCONTROL SYSTEM IN THE DEVELOPMENT LIFE CYCLE WILL BE SHOWNON THE EXAMPLE OF THE GNC SYSTEM.THE DEVELOPMENT OF THE MVM- AND FDIR-FUNCTIONS WILL STARTSEPARATELY. IT WILL BE MERGED WITH THE GNC, WHEN THECOMPLETE RV-CONTROL SOFTWARE WILL BE INTEGRATED.RVD-SPECIFIC EQUIPMENT, SUCH AS SENSORS, WILL BE DEVELOPEDIN PARALLEL AND THEIR PERFORMANCE WILL FIRST BE VERIFIEDBY STATIC TESTS IN THEIR OWN TEST FACILITIES.THEREAFTER, THEY WILL BE VERIFIED IN THE DYNAMIC MEASUREMENTENVIRONMENT ON STIMULATION FACILITIES (see below).EVENTUALLY THEY WILL BE MERGED INTO THE COMPLETERV-CONTROL SYSTEM FOR FUNCTIONAL TESTINGAT THE END OF THE DEVELOPMENT PHASE.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200992

VERIFICATION IN THEFEASIBILITY STUDY PHASEWHAT NEEDS TO BE VERIFIED IS THE FEASIBILITY OF :• TRAJECTORY AND ATTITUDE STRATEGY,• TOTAL DELTA-V REQUIREMENT,• THRUSTER CONFIGURATION, THRUST LEVEL,• PROPELLANT BUDGET,• NAVIGATION PERFORMANCEWHAT TOOLS ARE REQUIRED:• TRAJECTORY SIMULATIONS w/o MODELLING OF THE GNC LOOP,• SIMULATIONS WITH SIMPLIFIED GNC AND S/C MODELLING.AT START, THRUST LEVEL, PROPELLANT BUDGET etc. WILL BE DERIVEDFROM THE DELTA-V RESULTS BY APPLYING EMPIRICAL FACTORS,NAVIGATION PERFORMANCE ESTIMATED FROM AVAILABLE SENSOR DATA.A SIMULATION WHICH MODELS THE COMPLETE GNC LOOP OR THE OTHERAUTOMATIC FUNCTIONS IS NOT YET REQUIRED.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200993

VERIFICATION IN THE DESIGN PHASEWHAT NEEDS TO BE VERIFIED:• FEASIBILITY OF THE DESIGN CONCEPTS FOR GNC, MVM AND FDIR,• FEASIBlLITY OF REQUIRED PERFORMANCE FOR GNC,• FEASIBILITY OF DESIGN IMPLEMENTATION WITH THE ENVISAGEDHARDWARE,• PROBABILITY OF CAPTURE WITH THE GIVEN CAPTURE INTERFACEDESIGNWHAT TOOLS ARE REQUIRED:CLOSED LOOP SIMULATIONS WITH GNC/MVM ALGORITHMS RUNNINGAGAINST MODELLED ENVIRONMENTIN THE FIRST STEPS OF DESIGN, GNC, MVM AND FDIR ALGORITHMS WILLBE DESIGNED AND ANALYSED SEPARATELY.LATER, GNC- AND MVM ALGORITHMS WILL HAVE TO BE MERGED INTO APROTOTYPE CONTROL SOFTWARE.FOR FIRST VERIFICATION OF CAPTURE ALL FEATURES WILL BEMODELLED IN A SINGLE SIMULATION S/W.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200994

VERIFICATION IN THE EARLY DESIGN PHASEGNC ALGORITHMS WILL FIRST BE TESTED IN SIMULATIONS, IN WHICH• SPACECRAFT DYNAMICS AND DISTURBANCES,• SENSORS,• ACTUATORS• DATA MANAGEMENT etc. H/W AND S/WARE MODELLED GLOBALLY ACCORDING TO THEIR BEHAVIOUR, RATHERTHAN TO THEIR DETAILED DESIGN.LATER, THESE MODELS WILL SUCCESSIVELY REPLACED BY MODELSREPRESENTING THE ACTUAL DESIGN.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200995

CLOSED LOOP GNC SIMULATION, SINGLE PLATFORM(EARLY GNC ALGORITHMS AND BEHAVIOUR MODELS)RVSMODELGUIDANCEALGORITHMSMEASUREMENTENVIRONMENTMODELSGPSRECEIVERMODELNAVIGATIONFILTERALGORITHMSCONTROLLERALGORITHMSTHRUSTERMANAGEMENTALGORITHMSATTITUDESENSORMODELSGNC ALGORITHMS TO BE DEVELOPEDSIMULATION COMPUTERSIMPLIFIED SENSOR MODELSACCORDING TO BEHAVIOURDYNAMICSMODELSDYNAMICDISTURBANCEMODELSTHRUSTERMODELSIMPL. THRUSTER MODELSACCORDING TO BEHAVIOURDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200996

VERIFICATION IN THE FINAL DESIGN PHASEWHAT TOOLS ARE REQUIRED (cont’d):IN A NEXT STEP GNC, MVM AND FDIR DESIGNS HAVE TO BE MERGED,TO ESTABLISH A FIRST PROTOTYPE OF AN RV ONBOARD CONTROLSOFTWARE.IT HAS THAN TO BE VERIFIED IN A CLOSED LOOP SIMULATION THATTHIS FIRST PROTOTYPE OF A RENDEZVOUS CONTROL SOFTWAREWILL WORK PROPERLY AND WILL PROVIDE THE REQUIREDPERFORMANCE IN THE ENVIRONMENT OF THE SIMULATED ONBOARDSYSTEM.FOR THIS PURPOSE THE SIMULATION MUST INCLUDE DETAILEDMODELS OF THE ONBOARD SYSTEM, i.e. OF• THE DATA MANAGEMENT AND COMMUNICATION ARCHITECTURE• THE ACTUAL DESIGN OF THE EQUIPMENT (SENSORS, THRUSTERS)(THIS IS IN CONTRAST TO THE GLOBAL BEHAVIOUR SIMULATION OF THEEQUIPMENT IN STEP 1)THIS SIMULATION IS STILL ALL S/W (NO H/W IN THE LOOP) AND DOESNOT NEED TO RUN IN ’REAL TIME’.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200997

CLOSED LOOP GNC SIMULATION, SINGLE PLATFORM(FINAL GNC ALGORITHMS AND DESIGN REPRESENTATIVE MODELS)RVSMODELGUIDANCEALGORITHMSGNC ALGORITHM SOFTWAREFOR ALL GNC MODESFINAL ALGORITHMSMEASUREMENTENVIRONMENTMODELSGPSRECEIVERMODELNAVIGATIONFILTERALGORITHMSCONTROLLERALGORITHMSTHRUSTERMANAGEMENTALGORITHMSIMPROVEDMEASUREMENTENVIRONMENTMODELSATTITUDESENSORMODELSDESIGN REPRESENTATIVESENSOR MODELSDYNAMICSMODELSTHRUSTERMODELSIMULATION COMPUTERDYNAMICDISTURBANCEMODELSDESIGN REPRESENTATIVETHRUSTER MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200998

MERGING OF GNC, MVM AND FDIR IN O/B COMPUTERMVM & FDIR SOFTWAREGUIDANCES/W CODENAVIGATIONFILTERS/W CODEGNC SOFTWARETHRUSTERCONTROLLERMANAGEMENTS/W CODE S/W CODEAUTOMATIC FDIRFAILURE DETECTION, ISOLATION& RECOVERY SYSTEMAUTOMATIC MVMMISSION & VEHICLE MANAGEMENT(MODE SWITCH./ EQU’PT ASSIGNM.)SENSORH/WGNCMODESACTUA−TOR H/WMODE/EQU’PT SWITCHING COMMANDSRVS MODELMEASUREMENTENVIRONMENTMODELSGPS RECEIVERMODELGNC COMPUTER H/Wincluding:OPERATING SYSTEM S/WGENERAL SERVICES S/WATTITUDESENSORMODELSDESIGN REPRESENTATIVESENSOR MODELSDYNAMICSMODELTHRUSTERMODELENVIRONMENT SIMULATION COMPUTERDYNAMICDISTURBANCEMODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 200999

VERIFICATION IN THE DEVELOPMENT PHASEWHAT NEEDS TO BE VERIFIED:1. PROPER FUNCTION AND PERFORMANCE OF COMPLETERV-CONTROL SYSTEM IMPLEMENTED IN H/W AND S/W.2. FUNCTION AND PERFORMANCE OF THE NAVIGATION H/W AND S/WIN A REALISTIC MEASUREMENT ENVIRONMENT.3. PROPER FUNCTION OF THE ONBOARD SYSTEM TOGETHER WITHTHE REMOTE CONTROL FUNCTIONS (GROUND/SPACE).WHAT TOOLS ARE REQUIRED:FOR POINT 1:REAL TIME SIMULATIONS WITH THE DATA MANAGEMENT H/W (COM-PUTER AND DATA BUS) IN THE LOOP.(see CLOSED LOOP SIMULATION W. O/B COMPUTER) .Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009100

CLOSED LOOP GNC SIMULATION WITH O/BCOMPUTERRVS MODELGNC COMPUTER H/WGUIDANCES/W CODEalso including:OPERATING SYSTEM S/WGENERAL SERVICES S/WMVM & FDIR S/WMEASUREMENTENVIRONMENTMODELSGPS RECEIVERMODELNAVIGATIONFILTERS/W CODECONTROLLERS/W CODETHRUSTERMANAGEMENTS/W CODEATTITUDESENSORMODELSDESIGN REPRESENTATIVESENSOR MODELSDYNAMICSMODELTHRUSTERMODELENVIRONMENT SIMULATION COMPUTERDYNAMICDISTURBANCEMODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009101

VERIFICATION IN THE DEVELOPMENT PHASEWHAT TOOLS ARE REQUIRED (cont’d):FOR POINT 2(FUNCTION AND PERFORMANCE OF THE NAVIGATION H/W AND S/WIN A REALISTIC MEASUREMENT ENVIRONMENT):SIMULATIONS WITH PHYSICAL STIMULATION, PROVIDING AREALISTIC MEASUREMENT ENVIRONMENT TO THE SENSOR H/W, i.e.• MOTION AND ILLUMINATION TO THE OPTICAL RV-SENSORACCORDING TO THE REAL MOTION OF THE S/C AND TOPOTENTIAL DISTURBANCES (SUN IN FOV, REFLECTIONS)• R/F DATA INPUT TO THE GPS RECEIVERS ON CHASER ANDTARGET SIDE ACCORDING TO GPS SATELLITE CONSTELLATION ANDPOSITION + ATTITUDE OF THE TWO VEHICLES(see next chart).Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009102

CLOSED LOOP GNC SIMULATION WITHREAL-TIME GNC S/W AND SENSOR H/WThe GNC function in the O/B-computer may be replaced by a real-time simulation.stimulationSENSOR HARDWARETRAJECTORYSENSORGUIDANCEONBOARD COMPUTERincluding:OPERATING SYSTEM S/WGENERAL SERVICES S/WMVM & FDIR S/WMEAS. STATEPHYSICALSIMULATIONNAVIGATIONFILTERCONTROLLERTHRUSTERMANAGEMENTMEASUREMENTENVIRONMENTSTIMULATIONFACILITYMEASUREMENTSTATECALCULATIONATTITUDESENSORMODELSDYNAMICSTHRUSTERMODELDYNAMICDISTURBANCEMODELSENVIRONMENT SIMULATION COMPUTERDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009103

VERIFICATION IN THE DEVELOPMENT PHASEWHAT TOOLS ARE REQUIRED (cont’d):CLOSED LOOP SIMULATION WITH ONBOARD SYSTEM AND THEREMOTE CONTROL FUNCTIONS ON GROUND AND IN THETARGET STATION IN THE LOOP (incl. HUMAN OPERATORS).GENERAL REMARKS:NOTE 1: ALTHOUGH IT IS HIGHLY DESIRABLE TO INCLUDE AS MUCH ASPOSSIBLE REAL H/W IN THE SIMULATION, IT IS NOT POSSIBLE TO TESTTHE ONBOARD SYSTEM WITH THE ACTUATOR HARDWARE IN THE LOOP.NOTE 2: THE TOOLS OF THE DESIGN PHASE WILL ALSO BE NEEDED INTHE DEVELOPMENT PHASE TO DESIGN, ANALYSE AND VERIFY THE MANYSMALLER AND LARGER DESIGN CHANGES DURING DEVELOPMENT.NOTE 3: SIMULATIONS WITH GROUND- AND SPACE SEGMENT IN THELOOP WILL ALSO GO THROUGH SEVERAL STEPS OF INCREASINGINVOLVEMENT OF ACTUAL H/W AND S/W.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009104

VERIFICATION IN THE FLIGHT ITEMMANUFACTURE PHASEWHAT NEEDS TO BE VERIFIED:• FUNCTION/PERFORMANCE OF ITEMS/SYSTEM MANUFACTURED FORFLIGHT IN COMPARISON WITH QUALIFICATION RESULTS OF THEDEVELOPMENT PHASE.WHAT TOOLS ARE REQUIRED:• IT WILL NOT BE NECESSARY TO REPEAT ALL TEST FORQUALIFICATION.• H/W ITEMS WILL BE TESTED INDIVIDUALLY IN THEIR OWNACCEPTANCE TEST PROGRAMME• THE RV-CONTROL S/W WILL IN ADDITION TO COMPREHENSIVES/W TESTING BE ACCEPTANCE TESTED IN THE REAL TIMESIMULATION WITH THE DATA MANAGEMENT H/W IN THE LOOP• TESTS OF SENSOR H/W FOR SENSITIVITY TO MEASUREMENTENVIRONMENT NOT NECESSARY FOR ACCEPTANCE.SENSITIVITY IS CONSIDERED TO BE DESIGN DEPENDENTRATHER THAN MANUFACTURE DEPENDENT.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009105

VERIFICATION IN THE FLIGHT ITEMMANUFACTURE PHASE (cont’d)WHAT NEEDS TO BE VERIFIED:• FUNCTIONING OF COMPLETE CHAINAN END- TO-END TEST WITH ALL H/W AND S/W IN THE LOOP(ONLY FUNCTION - NOT PERFORMANCE) NEEDS TO BE PERFORMED ONSPACECRAFT LEVEL DURING ACCEPTANCE OF THE VEHICLETO VERIFY PROPER FUNCTIONING OF THE COMPLETE CHAIN.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009106

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLS• GENERAL VERIFICATION ISSUES OF SPACE PROJECTS• VERIFICATION & VALIDATION OF RV-CONTROL SYSTEMIN THE DEVELOPMENT PHASES• STIMULATION FACILITIES FOR NAVIGATION• VERIFICATION OF CAPTURE IN THE DOCKING PROCESS• VALIDATION OF SIMULATION MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009107

STIMULATION FACILITIES FOR RENDEZVOUS SENSORSTO VERIFY FUNCTION AND PERFORMANCE OF THE NAVIGATIONH/W AND S/W, STIMULATION FACILITIES ARE REQUIRED, WHICH• PROVIDE THE PROPER MEASUREMENT INPUTS TO THESENSOR SYSTEM ACCORDING TO THE REAL FLIGHT CONDITIONS,• PROVIDE THE REALISTIC WORST CASE DISTURBANCESACCORDING TO THE MEASUREMENT ENVIRONMENT OFTHE REAL WORLD.VALIDATION OF THE SYSTEMATIC PART OF THE STIMULATION, i.e.THE SIGNAL THAT THE SENSOR RECEIVES ACCORDING TO POSITION ANDATTITUDE OF THE VEHICLES, IS GENERALLY STRAIGHT FORWARD.VALIDATION OF THE UNSYSTEMATIC PART OF THE STIMULATION,i.e. THE MODELLING OF THE DISTURBANCES DUE TO THEMEASUREMENT ENVIRONMENT, IS DIFFICULT AND REQUIRES A LOT OFPRACTICAL IN-FLIGHT EXPERIENCE.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009108

CLOSED LOOP GNC SIMULATION WITHREAL-TIME GNC S/W AND SENSOR H/WFor the test of optical sensors the onboard computer may not be necessary.The dynamic input to the facility may be read from a file.stimulationSENSOR HARDWARETRAJECTORYSENSORGUIDANCEONBOARD COMPUTERincluding:OPERATING SYSTEM S/WGENERAL SERVICES S/WMVM & FDIR S/WMEAS. STATEPHYSICALSIMULATIONNAVIGATIONFILTERCONTROLLERTHRUSTERMANAGEMENTMEASUREMENTENVIRONMENTSTIMULATIONFACILITYMEASUREMENTSTATECALCULATIONATTITUDESENSORMODELSDYNAMICSTHRUSTERMODELDYNAMICDISTURBANCEMODELSENVIRONMENT SIMULATION COMPUTERDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009109

RGPS VERIFICATION SETUPSTIMULATOR SENSOR H/WGNC FUNCTIONCHASER POSITIONDISTUR−BANCESTARGETORBITALSTATEGPS SAT’SPOSITIONSTIMULATORTARGET GPS−RECEIVERH/WNAVIGATIONFILTERRV CONTROL SOFTWARE (CHASER)GUIDANCEFUNCTIONCONTROLFUNCTIONGPS SAT’SPOSITIONSTIMULATORDISTUR−BANCESCHASER GPS−RECEIVERH/WGYROS(MODEL)DISTUR−BANCESTARGET POSITIONCHASERORBITAL STATES/CDYNAMICS &KINEMATICSGPS−LAB FUNCTIONSRV SYSTEM SIMULATOR FUNCTIONSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009110

STIMULATION FACILITY FOR OPTICAL SENSORS: EPOS(This figure shows the old EPOS facility with a gantry robot type of motion system)Gantry Robot 6 DOF, Target Mount 3 DOF, Illumination System 4 DOFDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009111

STIMULATION FACILITY FOR OPT. SENSORS: EPOSx(EPOSx is based on a 500m flow dynamics test facility for shape analysis of ships)Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009112

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLS• GENERAL VERIFICATION ISSUES OF SPACE PROJECTS• VERIFICATION & VALIDATION OF RV-CONTROL SYSTEMIN THE DEVELOPMENT PHASES• STIMULATION FACILITIES FOR NAVIGATION• VERIFICATION OF CAPTURE IN THE DOCKING PROCESS• VALIDATION OF SIMULATION MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009113

VERIFICATION OF CAPTURE IN THE DOCKINGPROCESSTO ACHIEVE SUCCESSFUL CAPTURE, THE FOLLOWING TASKS HAVE TOBE ACHIEVED:1. THE GNC SYSTEM OF THE CHASER VEHICLE MUST GUIDE ITSCAPTURE INTERFACES INTO THAT OF THE TARGET VEHICLEWHITHIN CERTAIN LATERAL AND ANGULAR ALIGNMENTBOUNDARIES AND MAX. LINEAR AND ANGULAR RATES.2. WITHIN THIS RANGE OF CONTACT CONDITIONS THE DOCKINGMECHANISM MUST SUCCESSFULLY CAPTURE ITS INTERFACES ONTHE OTHER SIDE, SUCH THAT NO ESCAPE IS POSSIBLE.3. AFTER INITIAL CAPTURE, THE MECHANISM MUST BRING INTOPOSITION AND ALIGN THE INTERFACES IN SUCH AWAY THATENGAGEMENT OF THE STRUCTURAL LATCHES CAN COMMENCE.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009114

VERIFICATION OF CAPTURE IN THE DOCKINGPROCESS (cont’d)THE VERIFICATION OF THE FIRST TASK IS PART OF THEGNC PERFORMANCE VERIFICATION, DISCUSSED BEFORE.IF IT CAN BE SHOWN THAT1. THE GNC IS ABLE TO BE WITHIN CERTAIN PERFORMANCEBOUNDARIES AT CONTACT,2. THE MECHANISM IS ABLE TO CAPTURE WITHIN THAT RANGE OFCONTACT CONDITIONS,TASKS 1 (GNC) AND 2 (CAPTURE) CAN BE VERIFIED INDEPENDENTLYOF EACH OTHER, i.e. THERE IS NO NEED FOR A COMBINED TEST.VERIFICATION OF TASK 3 (STRUCTURAL LATCHING) CAN ANYWAYBE DONE INDEPENDENTLY OF TASK 2.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2010115

COMPUTER SIMULATION OF CAPTURE(USED IN THE EARLY PROJECT PHASES)SIMULATION COMPUTERINITIALCONDITIONSrel. positionrel. attituderel. motioninitiation of captureDOCK. MECH.FRONT−ENDS:RELATIVEKINEMATICSCONTACTPOINT & TIMErelativeposition & attitudeof front−endsCAPTUREMODEL:FRONT−ENDS& LATCHESKINEMATICSATTENUATIONSYSTEM:RELATIVEFORCES &TORQUESTO SPACECR.CHASERDYNAMICSTARGETDYNAMICSSPACECRAFTRELATIVEKINEMATICScapture criteriafulfilled: yes / norelative forces& torquesrelative position,attitude & ratesrelative position, attitude and rates of spacecraftINITIAL CONDITIONS WILL BE OBTAINED FROM GNC SIMULATIONSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009116

VERIFICATION OF CAPTURE INTERFACESIN THE DEVELOPMENT PHASE CAPTURE HAS TO BE VERIFIED WITH• THE HARDWARE OF THE CAPTURE MECHANISM (DOCK. OR BERTH.)• THE ACTUAL DYNAMIC CONDITIONS AT CONTACT.THE RELATIVE MOTION CONDITIONS OF THE TWO VEHICLESAT CONTACT IN TERMS OF• CONTACT VELOCITY VECTOR• LATERAL MISALIGNMENT• ANGULAR MISALIGNMENTWILL BE OBTAINED FROM THE RESULTS OF THE GNC SIMULATION.THE DYNAMIC REACTION OF THE TWO SPACECRAFTAFTER CONTACT WILL BE DETERMINED BY SIMULATION.IN THE TEST THE RESULTING RELATIVE MOTION HAS TO BE EXECUTEDBETWEEN THE TWO HALVES OF THE CAPTURE INTERFACES.Dr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2010117

CAPTURE VERIFICATION FACILITYFORCE SENSORSATTENUATION SYSTEMDOCKING I/F CHASERTEST ITEM6 DOFFORCE &TORQUEDOCKING I/F TARGETCHASERDYNAMICSTARGETDYNAMICSSTEWART PLATFORMINITIAL CONDITIONSRELATIVEMOTIONLINEARACTUATORSTABLEPOSITIONLINEARACTUATOREXTENSIONDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009118

PART 2VERIFICATION & VALIDATION PRIOR TO FLIGHT,CONCEPTS AND TOOLS• GENERAL VERIFICATION ISSUES OF SPACE PROJECTS• VERIFICATION & VALIDATION OF RV-CONTROL SYSTEMIN THE DEVELOPMENT PHASES• STIMULATION FACILITIES FOR NAVIGATION• VERIFICATION OF CAPTURE IN THE DOCKING PROCESS• VALIDATION OF SIMULATION MODELSDr. W. Fehse — Introduction to RVD — Verification, Concepts & Tools — Version 2009119

VALIDATION OF SIMULATION MODELSIN LATER STAGES OF DEVELOPMENT, SIMULATION MODELSOF EQUIPMENT MAY BE REPLACED BY THE EQUIPMENT ITSELF.SOME FEATURES AND ITEMS, HOWEVER, HAVE TO BE REPRESENTEDALWAYS BY MATHEMATICAL MODELS, AS THEIRPHYSICAL REPRESENTATION IS NOT POSSIBLE ON GROUND.SUCH FEATURES AND ITEMS ARE:• THE ORBITAL DYNAMICS,• THE DYNAMIC DISTURBANCES,• THE BEHAVIOUR OF THE ACTUATORS.OTHER FEATURES, SUCH AS THE MEASUREMENT ENVIRONMENTOF THE SENSORS, ARE IN SOME SIMULATIONS REPRESENTEDBY MATHEMATICAL MODELS, IN OTHERS BY PHYSICALSTIMULATION TOOLS.ALL THESE MODELS AND STIMULATION TOOLS NEED TO BEVALIDATED IN ORDER TO BE USED FOR VERIFICATION PUPOSES.IT MUST BE SHOWN THAT THE MODELS AND TOOLS REPRESENTTHE REALITY TO THE EXTENT NECESSARY FOR THEPARTICULAR VERIFICATION TEST.Dr. W. Fehse — Introduction to RVD — Verification — Version 2008120

CLOSED LOOP SIMULATION WITH O/B COMPUTER(repeated)THE MODELS OF THE ENVIRONMENT SIMULATION MUST BE VALIDATEDRVS MODELGNC COMPUTER H/WGUIDANCES/W CODEalso including:OPERATING SYSTEM S/WGENERAL SERVICES S/WMVM & FDIR S/WMEASUREMENTENVIRONMENTMODELSGPS RECEIVERMODELNAVIGATIONFILTERS/W CODECONTROLLERS/W CODETHRUSTERMANAGEMENTS/W CODEATTITUDESENSORMODELSDESIGN REPRESENTATIVESENSOR MODELSDYNAMICSMODELTHRUSTERMODELENVIRONMENT SIMULATION COMPUTERDYNAMICDISTURBANCEMODELSDr. W. Fehse — Introduction to RVD — Verification — Version 2009121

MODELS IN GNC SIMULATIONCHASER PERTURBAT.ORBITATTITUDEAIRDRAGMODELGRAVITY FIELDMODEL (J2)GRAV. GRADIENTMODELCHASER DYNAMICSCHASER POSITIONDYNAMICS(INTEGRATION)SLOSH./FLEX.MODELSC.O.M.MODELMEASUREMENT ENVIRONMENT ANDSENSOR MODELSGPS CONSTELLATION& MEAS. ENVIRONM.MODELSUN/EARTH−SENS.MODELSCHASERGPS RECEIVERMODELPOSITIONRAW DATAGNCCOMMANDSPROPULSIONDRIVE ELECTR’CSCHASER ATTITUDEDYNAMICS(INTEGRATION)GYRO ASSEMBLYMODELABSOLUTEATTITUDETHRUSTER &ACCOMM. MODELCHASER ACTUATIONTARGET DYNAMICSORBITATTITUDEPLUME IMPINGEM.MODELGRAVITY FIELDMODEL (J2)AIRDRAGMODELTARGET PERTURBAT.TARGET POSITIONDYNAMICS(INTEGRATION)TARGET ATTITUDEDYNAMICS(INTEGRATION)GPS CONSTELLATION& MEAS. ENVIRONM.MODELRVS ACCOMMODAT.ON CHASERMODELDOCKING PORT,TARGET PATTERNKINEMAT. MODELTARGETGPS RECEIVERMODELRV−SENSORMODELPOSITIONRAW DATARANGE, LOSREL. ATTITUDETARGET ATTITUDECONTROL MODELDr. W. Fehse — Introduction to RVD — Verification — Version 2008122

VALIDATION OF SIMULATION MODELS (cont’d)SUCH VALIDATION CAN BE ACHIEVED BY COMPARISON OF:• THE OUTPUT OF A MODEL OR COMPLETE SIMULATIONWITH DATA DERIVED FROM REAL SPACE MISSIONS,• THE OUTPUT OF A MODEL OR COMPLETE SIMULATIONWITH PHYSICAL TEST DATA,• MATHEMATICAL MODELS OR SIMULATIONSWITH ACCORDING MODELS OR SIMULATIONSWHICH ARE ALREADY VALIDATED,• MATHEMATICAL MODELS OR SIMULATIONSWITH ONES GENERATED BY INDEPENDENT SOURCES.IT HAS TO BE STRESSED THAT A 100% VALIDATION WILL NEVER EXIST !THE QUESTIONS TO BE ASKED MUST BE ALWAYS:• VALIDATION w.r.t. WHAT FEATURE, TO WHAT EXTENT ?• IS IT SUFFICIENT FOR THE PURPOSE OF THE PRESENT VERIFICATIONTASK ?Dr. W. Fehse — Introduction to RVD — Verification — Version 2009123

CONCLUSIONSVERIFICATION AND VALIDATION ARE NOT CONSTRAINED TO APARTICULAR PHASE AT THE END OF A PROJECT.ON THE CONTRARY,VERIFICATION TASKS START AT THE VERYBEGINNING OF A PROJECT ANDCONTINUES IN EACH OF THE PROJECT PHASES.AT EACH STEP OF THE PROJECT DEVELOPMENT SEQUENCESOMETHING CAN GO WRONG.THE TASK OF VERIFICATION IS TO ENSURE THAT POSSIBLE MISTAKESIN CONCEPT, REQUIREMENTS, DESIGN AND MANUFACTUREARE DETECTED AS EARLY AS POSSIBLE.THE METHODS OF VERIFICATION HAVE TO BECHOSEN ACCORDING TO THE ISSUES WHICH ARE AT STAKEIN THE PARTICULAR PROJECT PHASE.WHERE IN THE FEASIBILITY PHASE OF A PROJECT GENERIC TOOLSCAN BE USED, WITH THE PROGRESSING PROJECT,SIMULATION MODELS MUST MORE AND MOREREPRESENT THE ACTUAL DESIGN OF ITEMS AND SYSTEMS USED.Dr. W. Fehse — Introduction to RVD — Verification —Version 2009124

DEVELOPMENT LIFE CYCLE OF A SPACE PROJECTTHE REAL WORLDTHE INTENDEDSPACE OPERATIONCustomer’s Ideaof the RealityMission Concept,Mission RequirementsSystem, Ops., Safety etc.RequirementsMISSION DEFINITIONPHASECONCEPT DEFINITIONPHASE(Phase A)Preparationof Concept andRequirementsby the CustomerSystem LevelSpecificationsSubsystem, EquipmentSpecificationsSubsystem, EquipmentDevel., Manufact. & Verific.System Integration &QualificationDESIGN PHASE(Phase B)DEVELOPMENT,QUALIFICATION &FLIGHT ITEM MANUF.PHASE(Phase C/D)IndustrialContractIncludesDevelopment &System VerificationIn−Orbit OperationOPERATIONALPHASEVALIDATION W.R.T. REAL WORLDVERIFICATION W.R.T. SPECIFICATIONDr. W. Fehse — Introduction to RVD — Verification — Version 2008125