ASTRA 2002 - ROGER Paper Finalrobotics.estec.esa.int/ASTRA/Astra2002/Papers/astra2002_1.4-2.pdf ·...

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ASTRA Workshop 2002 © ROGER Study Team, 2002

M. Kassebom, D. Koebel, C. Tobehn

OHB-System AG, Universitätsallee 27-29, 28359 Bremen,Germanymailto: [email protected]

H. Petersen

Dutch Space, Newtonweg 1, 2333CP Leiden, The Netherlands

H. Stokes, D. Smith, C. Martin

Space Department, QinetiQ, Farnborough, Hampshire GU14 0LX, UK

A. Shaw

ESYS plc, Surrey Research Park, Guildford, Surrey GU2 7HJ, UK

ASTRA - Advanced Space Technologies for Robotics and Automation

ESA/ESTEC, Noordwijk, November 19 - 21, 2002

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■ Introduction

■ Simulation of the GEO Environment & Collision Risk Analysis

■ Intervention & Mission Concepts

■ Concept Analysis Trade-Offs

■ Generic Mission Constraints

■ Technical Solutions for Capture & Docking

■ Mission Profile & Target Number Analysis

■ Economic Analysis

■ Conclusions & Outlook

Table of ContentTable of Content



IntroductionIntroduction

■ The ROGER Study is an on-going ESA Study with the aim to assessthe economical and technical feasibility of a GEO service mission.

■ It has the following main objectives:

■ analysis of the GEO environment, including the establishment of a GEO orbitsimulator,

■ definition of scenario types and service levels for the ROGER mission,

■ analysis of the economical viability of the scenario types,

■ definition of the most promising baseline mission scenario,

■ investigation of the design and development of the related ROGER spacecraftand Robotic subsystem,

■ definition of a demonstration mission.



Simulation of the GEO EnvironmentSimulation of the GEO Environment

GEO SpacecraftFailures Data

Current GEO Status

Collision Risks

GEOSIMGEOSIM

A model to determine collision risksdue to the future evolution of controlled

and uncontrolled objects in GEO

Market Trends

Orbit Propagation

■ The GEO Simulation combinesdetailed GEO status data andtraffic projections with realisticorbit dynamic and collisionprediction algorithms.

■ The results of GEO simulationand collision analysis providesthe basis for possible ROGERmission scenarios and thejustification for the final missionbaseline selection.

[Source: QinetiQ]



Current and Future GEO Status (1)Current and Future GEO Status (1)

Currently (2002) Estimation for 2030

Evolution of Number of Uncontrolled Objects in GEO

[Source:QinetiQ, ESYS]



Current and Future GEO Status (2)Current and Future GEO Status (2)

0

10

20

30

40

50

60

0 20 40 60 80 100

120

140

160

180

200

220

240

260

280

300

320

340

Longitude East (5 degree bins)

No.

Obj

ects

20302002

Evolution of the Longitude Distribution of GEO Objects

[Source:QinetiQ, ESYS]



Collision Risk Analysis - ResultsCollision Risk Analysis - Results

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

1.6E-03

1.8E-03

2.0E-03

2000 2005 2010 2015 2020 2025 2030Year

Pro

babi

lity

Nominal

Low launch rate

High launch rate

0.0E+00

4.0E-04

8.0E-04

1.2E-03

1.6E-03

2.0E-03

2.4E-03

2.8E-03

2000 2005 2010 2015 2020 2025 2030Year

Pro

babi

lity

Nominal

Best re-orbit rate

Worst re-orbit rate

■ The number of objects on GEO andtherefore the future evolution of collisionrisk is governed by the balance betweenthe number of satellites launched and thenumber re-orbited at end-of-life.

■ The collision risk probability varies three-fold between the most optimistic, thenominal and the pessimistic re-orbit case(first picture).

■ Variations in the predicted launch trafficrate do not play a significant role in theevolution of the collision risk (secondpicture).

■ Note: These analyses exclude theconsideration of the untracked debrispopulation. [Source:

QinetiQ]



Collision Risk Analysis - RecommendationsCollision Risk Analysis - Recommendations

■ As a result of the GEO environment simulation and collision risk analysisthe following re-orbit policies & strategies can be recommended:

■ Mass removal is required for general GEO resident objects, although massremoval for GTO objects is less significant.

■ A mass removal effectively needs to keep the number of objects static. Theearlier such a programme is started the less the future risk will be.

■ A removal programme could be based on removing objects as they becomeuncontrolled or removing objects in high-risk longitudes.

■ There is no immediate need to consider older objects, with higherinclinations.



Intervention Concepts and Failure Event TypesIntervention Concepts and Failure Event Types

■ The ROGER study developed a list of potential mission scenarios, includingdifferent intervention concepts and failure event types to be served:

■ For each scenario various trade-offs were performed in order to derive theirtechnical and economical feasibility and to select a mission baseline for ROGER.

InterventionConcept

Description

Concept i) A re-orbiting only mission, focussed on removing potentiallyhazardous objects from the GEO region.

Concept ii) An intervention mission aimed at some mature aspects of servicing,based on basic robotic and docking technology, and advanced S/Cplatform design.

Failure Event Type 6 Temporary attitude failure by uncontrolled spin-up

Failure Event Type 8 Catastrophic premature fuel exhaustion or attitude control failure

Failure Event Type 9 Deployment failure, e.g. stuck in GTO

Concept iii) An intervention mission aimed at a more sophisticated level ofservicing, making use of advanced robotic capabilities.

Failure Event Type 3 Antenna or solar array release (major events)

Failure Event Type 4 Mechanical / thermal alignment problems (minor)

Failure Event Type 5 Other in-service mechanism problems (typically solar array drives)

Failure Event Type 7 Accessible electrical problems (e.g. solar array shorts)



Mission Scenario Trade-OffsMission Scenario Trade-Offs

Trade-offs were performed with respect to the following main aspects:

■ Technical Aspects:■ Identification of technical constraints,

■ Robotic solution vs. non-robotic solution,

■ Consideration of different propulsion systems for orbit manoeuvres,

■ Mission Aspects:■ Single target vs. multiple target mission,

■ Consideration of mission profile and resulting schedule,

■ Economic Aspects:■ ROM cost assessment for different scenarios and technical solutions,

■ Consideration of mission benefits and funding sources.



Basic Mission ConstraintsBasic Mission Constraints

■ Previous studies have investigated the rendezvous and docking with anuncontrolled target and concluded a basic technical plausibility.

■ Some basic constraints were identified wrt. the following aspects:

■ Kinematics of uncontrolled target object:■ Uncontrolled S/C will acquire a Flat Spin around the main inertia axis.

■ Assumption of the residual flat spin of GEO target objects:

■ This is considered to be manageable for available capture & docking technology.

■ Servicing of “quasi”-operational target objects (intervention concepts ii & iii):■ such target objects shall not be damaged or hindered during the capture and docking,

■ No further space debris shall be produced during the capture.

■ Advanced GNC requirements compared to other missions, incl. advancedrequirements for the attitude and orbit control.

RPMf SpinFlat 5.0≤⇒



Apogee Nozzle coupling

Robotic SolutionRobotic Solution

Lathe Clamp couplingmechanism

[Source: ESS/T Study]

■ Robotics:■ Identification of technical

solution based on the ERARobotic arm,

■ Baseline specification:~ 11m span, 6 DoF, 2 cameras.

■ Capture & Docking:■ Focus on the utilisation of the

Apogee Motor Nozzle and theLauncher Adapter Ring asgrappling points.

ERA Robotic Arm,provided by Dutch Space

➪ A Robotic Solution provides a greater flexibility for the chosen missionscenario (intervention concept), but has higher mass and powerrequirements at higher cost.



Non-Robotic SolutionNon-Robotic Solution

■ Non-Robotic Technologies:■ Several technologies and designs

have been investigated, such as:■ inflatable structures, e.g. wings,

■ throw-nets,

■ tethers.

➪ Non-robotic solutions can provide reduced mass and power requirementsat reduced cost,

➪ Non-robotic solutions are assumed to be only valid for the re-orbitmission; the multiple-target capability depends on the used technology.

■ Docking & Re-orbiting Scenario:■ Can also utilise simple robotic arms or extendable booms to provide coupling.

■ Throw-net like solutions provide the docking and re-orbiting by means of a tether (thedynamics of the coupled system have to be analysed in more detail here).

[Source: Dutch Space]

Outline sketch of non-roboticinflatable structures



Mission Profile & Duration of PhasesMission Profile & Duration of Phases

D: Inspection & Final Approach C: Homing B: Ground Guided

Phase(incl. Drifting to Target)

IAP

10 km

S1

1km

S2

100 m

S3

(Delta H = 300 km)

OTPITP

E: Capture&

Docking

Inspectionfly-by(optional)

Sensor Range

Injection Orbit(GTO)

PhasingOrbit

TargetTracking

ROGERTracking

ROGER drifts towards Target

TM/TC

ISA

A: LEOP & C/O

HorizontalRange fromTarget

Radial Distancefrom Target

Target on GEO

TransferInjection

ProgressiveTransfer

S/C-based Navigation

Ground-basedNavigation

ISA -IAP -S1 -S2 -S3 -

OTP -ITP -

Inter S/C AcquisitionInitial Aim Point (~10 km)Hold Point 1 (~1 km)Hold Point 2 (~100 m)Hold Point 3 (~50 m)Outer Target Point (~20 m)Inner Target Point (up to 2m)

Delta Hcirc ~ 475 km(for 180° phasing

in 30 days)

G: Re-orbit to GYO H: Retreat & Parking Orbit Acquisition ( GYO as parking orbit (TBC))

Back to B: Phasing Orbit

Acquisition

➩ Very detailed analysis of the duration of the different mission phases, as afunction of the used propulsion technology and the number of targets.



ROM Cost vs. Technology and No. of TargetsROM Cost vs. Technology and No. of Targets

■ Furthermore, a ROM Cost Analysis has been performed for the ROGER system,depending again on the implemented technology and the number of targets:

100

200

300

20 30 40

Number of Targets

Rec

urr

ing

Mis

sio

n C

ost

[M

io. E

uro

s]

Robotic Solution

Non-Robotic SolutionBi-Propellant

Ion Thrusters

Ion Thrusters

Bi-Propellant



Economic AnalysisEconomic Analysis

■ Principal driver for a ROGER business case are mission cost versus thepotential benefit for each target and servicing type.

■ The economic analysis included therefore a detailed investigation of thepotential benefit for each identified intervention concept and event type.

■ This includes: ⇒ insurance claims for in-orbit failure events,

⇒ cost-effectiveness of ROGER re-orbit service compared to the propellant effort of a operator’s voluntary graveyard transfer at EOL.

■ For the re-orbit service scenario it can be concluded:

■ there is potentially a sufficient number of GEO Sats being voluntarily re-orbited at EOL,

■ propellant saving can result in an operator’s additional revenue at EOL of 5 M - 15M ,

■ if the ROGER cost per target are in that range of benefit, it can be assumed that a re-orbitmission scenario is a viable business case for ROGER.



Conclusions & OutlookConclusions & Outlook

■ Detailed analyses have been performed to define a mission baselinescenario for ROGER which is:

■ politically desirable,

■ technically feasible,

■ economically viable.

■ The final mission scenario and the related detailed system design areactually under iteration.

■ Especially the following study tasks are being performed currently:

■ investigation of the design and development of the related ROGER spacecraftand the Capture & Docking subsystem,

■ definition of a demonstration mission.

■ A final economic evaluation of the ROGER mission will be performed atthe end of the study.

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