RESULTS OF PRISMA / FFIORD EXTENDED MISSION AND ... · ISFFMT 2013 / Munich / Germany/ May 29-31, 2013 RESULTS OF PRISMA / FFIORD EXTENDED MISSION AND APPLICABILITY TO FUTURE MISSIONS

ISFFMT 2013 / Munich / Germany/ May 29-31, 2013

RESULTS OF PRISMA / FFIORD EXTENDED MISSION AND APPLICABILITY TO FUTURE MISSIONS

M. Delpech1, J.C.Berges1, F.Malbet2, T. Karlsson3

1 CNES, 2 IPAG, 3 OHB-Sweden

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SFFMT 2013 / Munich / Germany / May 29-31, 2013

Content

■ Context & Motivation■ PRISMA overview■ Experiments description

Vision based RDVMetrology transition & Vision based based proximity controlµ-NEAT pathfinder

■ Applicability to ADR scenario■ Conclusion

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Context and motivation

■ PRISMA nominal mission enabled numerous contributions in formation flying and autonomous rendezvous (validation of sensors, algorithms, operations)

Formation flying• GPS navigation and all GPS based tasks (DLR, OHB-S)• RF navigation and all RF based tasks (CNES with the FFIORD experiment)

Autonomous RDV• Vision based RDV with a non cooperative object (OHB-S)• Proximity operations in a cooperative context (OHB-S)

All experiment objectives were fulfilled

■ PRISMA extended mission started in August 2011 with opportunities of new experiments(including new software)

■ CNES responded positively to demonstrate capabilities required in future missionsVision based RDV (RDV)Metrology transition (FF, RDV)Re-pointing manoeuvers (FF, RDV)push the PRISMA system to its limits

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PRISMA overview

Position reference measurement: POD from GPS (DLR) accuracy < 1 cm (3D)

Tango S/C

Propulsion:

6 x 1N hydrazine thrusters (MIB = 0.7 mm/s)

DVS

VBS FR

VBS CR

Mango S/C

FFRFantennas

GPSantenna

GPSantenna

Relative sensing

• FFRF (CNES): range + LOS (1 cm / 1°)

• 2 smart vision sensors (DTU) with IP functionalities

• VBS FR: target direction + camera attitude at long range

• VBS CR: pos + attitude in cooperative mode (LEDs)

• GPS (DLR): relative navigation 10 cm OB accuracy

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Vision based RDV (1)Experiment plan

Objective• Acquire flight expertise in Angles-only Navigation RDV with non cooperative objects (ex: ADR),

possible back-up for FF missionDescription• Navigation: EKF (6 states vector) with Yamanaka Ankersen relative dynamic model + target orbit propagator• Guidance: waypoint oriented strategy (manœuvre dates defined on the ground)

• Navigation uncertainty: 10-12% range - 100 m / 10 cm/s on RN position/ rate coordinates

• Fuel constraint:Long duration RDV with no crosstrack manœuvresConservative filter tuning to reduce dispersions

Desired trajectory 10 km -> 0.1 km

Plan• 4 rehearsals• 3 m/s total budget

Experiment #1Experiment #2Experiment #3

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Vision based RDV (2)Flight results

Experiment Duration (hours)

Range accuracy

(%)

Expected Delta V (cm/s)

Real Delta V (cm/s)

RdV 4 km to 100 m (OL) 16.2 1.8% N/A N/A

RdV 4 km to 100 m (CL) 16.2 2% 54.0 42.6

RdV 10 km to 100 m (CL) 18.5 3 % 98.5 86.8

RdV 10 km to 50 m (CL) 19.5 5.5% 74.0 73.6

• All rendezvous were achieved successfully

• VBS behaviour was satisfactory at long and medium range(target detection and tracking)

• Fuel usage remained within allocated budget

• Range uncertainty reduction is not significant above 2 km

• Limited range accuracy at short range due to the targetdirection uncertainty

Range profile


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Vision based RDV (3)Flight results

Relative range error and uncertaintyRDV #4 (10 km -> 50 m)

Short rangedegradation

LVLH frameinitial attitude

error


Initial attitude error of the LOF

Run in replay mode with different tuning

Target picturedat 10 km

Target picturedat 3 km

Target size:50 pixelsat 50 m

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Direction bias causes transversal error variations upto 1 m in the 50-100m range domain

Station keeping was not demonstratedAccuracy good enough to place the chaser in relativeorbit-keeping near the target

target size -> 50 pixels at 50 m

Vision based RDV (4)Short range performance

Regions of interest

100 m 50 m

Lessons learned• angles-only navigation efficiency demonstrated - even inpresence of periodic data loss i.e. eclipses (replay mode)

• robust image processing techniques are neededat short range to improve safety/performance


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Proximity operations withmetrology transition (1)

transition

A B

Parking orbit

VBS Navigation

TangoMango

FFRF Navigation

DescriptionSingle navigation filter with metrology handover (no data fusion) - EKFGain update with smoothing phase to deal with biasand noise variations Position control is kept identical in both regimes(LQR) Possibility to use an alternate navigation function in the loop (OHB-S) for comparison purposes

ObjectiveExercise metrology transitions to emulate some phases of future FF missionsRF (coarse sensor) optical (fine sensor)Attempt to achieve fine position control

LimitationControl period = 200 s with 0.7 mm/s MIBhigh control sensitivity to relative position rate errors


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Experiment Navigation error (cm)POD as ref

Control error (cm)VBS nav as ref

Control error (cm)POD as ref

PROX @ 20 m (OHB nav)

Bias [0.8 2.4 3.1]Std [5.6 1.4 1.2

Bias [2.8 0.1 0.1]Std [14 4.4 5.3]

Bias [4.1 2.4 2.9]Std [14 4.5 5.2]

PROX @ 15 m (CNES nav)

Bias [2.0 12 6.4]Std [1.9 3.8 2.0]

Bias [0.2 1.1 1.6]Std [2.2 5.3 2.9]

Bias [2.2 11 8.2]Std [2.5 6.0 3.3]

FFRF VBS

4 transition experiments wereperformed with a satisfactoryfunctional behaviour

FFRF VBS FFRF

control accuracy is not improved w.r.t. FFRF navigation


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LED detection process frequently perturbed VBS measurements suffer from temporary noise increase (distance) and bias variations that affect control performance Positioning stability could not reach the level obtained with FFRF measurements even throughground replay testsHigh performance is achievable but requires cleaner optical conditions (robustness of the

optical target detection to be improved)

Target satellite at 15 m distanceVBS measurement error (POD reference)

Solar panel

Bias variation

Noise increase

RF antenna


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µ-NEAT Pathfinder (1)

• L2 Lagrange point mission• 2 FF spacecraft (Telescope and Detector)• Spacecraft distance: 40 m / 12 m• Up to 20 reorientation manoeuvres per day • Telescope pointing accuracy: 3 arcsec• Detector positioning accuracy: 2 mm / 1 cm• 200 targets visited 50 times

Context: Missions proposed to ESA: NEAT (M-class) / µ-NEAT (S-class)

detection and characterization of exo-planetsin the Habitable Zone

0.8 m

Sun

Tango

Mango12 m

Objective: perform a sequence of re-pointing manœuvres / observationphases to be achieved in a typical day of µ-NEAT mission

Earth

xy

Mango S/C

Z

Direction cones within which Mango must be located to avoid antenna switches

Configuration

Constraints


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µ-NEAT Pathfinder (2) Guidance & Control

Trajectory: sequence of linear segments for re-pointingmanœuvres and fixed positions for the observations phases

Guidance module: 1 - Generation of desired position and velocity input @ 1 Hz in

specified frame (inertial) 2 - Conversion in LVLH frame to feed the control algorithm:

- observation phase: circular trajectory at orbital rate- re-pointing manœuvre: portion of helix

d1

R1

z

y

d2

R2

U1

U2

x Re-pointingmanoeuvre

Observation phase n°k

LVLHframe

Observation phase n°k+1

Control module:- LQR algorithm with a LTI relative dynamic model (CW-Hill)

GXMMXKKu dvpvp ++−= ].[][K: regulator gainM: gain to follow a profileG: feedforward gain

M matrix is tuned for each type of input profile to achieve the best possible performance (reference tracking control)

• Control cycle: 100 s

• dV budget: 16 cm/s / orbit (observation phase)


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µ-NEAT Pathfinder (3)Experiment scenario

2 sessions (each duration = 3 consecutive orbits or 5 hours)Session 1: RF navigation with 9 targets 2000 s per target (600 s re-pointing + 1400 s observation) Session 2: GPS navigation with 4 targets including the Moon for illustration, purposes

Sequence designed to maximize star tracker availability

Man Id Manœuvremagnitude (°)

Translation magnitude (m)

1 26.8377 5.41

2 21.7218 4.44

3 28.5856 5.74

4 18.7034 3.84

5 24.7205 5.02

6 21.7623 4.45

7 16.1635 3.34

8 21.2071 4.34

9 23.8714 4.85


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µ-NEAT Pathfinder (4)Flight results

1st session: RF navigation (best control performance)


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µ-NEAT Pathfinder (5)Illustration with DVS images

Expertise is applicable to the field of Active Debris Removal (guidance & control aspects and system constraints)


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Applicability to others missions (1)

ContextCNES system studies on active debris removal (Orbital Transfer Vehicle) – vehicle architecture,capture conceptAnalysis of critical phases in simulation (sensing strategy, system constraints)

ActivitiesSimulator design relying on PRISMA heritage

•Re-use of existing functionalities•Collected metrology data to improve sensor fidelity

Illustrative scenario• RDV from 6-7 km followed by inspection phase at 15 m • Camera down to ~100 m• Low resolution LIDAR for proximity operations

LIDAR picture of Tango S/C

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Applicability to others missions (2) Simulation results

Angles only navigation

• Range observability improvement

• Performance robustness inpresence of eclipses

Forced trajectories @ short range• 50 s control rate

• Control accuracy in 4-5 cm (1 σ)during revolutions

transition

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Conclusion

■ PRISMA extended mission allowed to show the capabilities / flexibility of the overallsystem and increase the CNES technical return

second vision based autonomous RDV experiment (first by OHB-S)angles-only navigation is a valid technique to RDV with a non cooperative object

transition between RF and optical metrology stagesevaluate issues in terms of navigation / control performance

first demonstration of LEO formation flying with inertial pointingillustrate the margin of improvement achievable on higher orbits

■ The applicability of this technical return was illustrated in the field of Active DebrisRemoval (sensor flight data, GNC functions) to speed-up the evaluation of approachcandidate scenarii

■ Perspectives: Next studies like NEAT will benefit from the same experience (phase 0 to be started soon in CNES)

Documents

RESULTS OF PRISMA / FFIORD EXTENDED MISSION AND ... · ISFFMT 2013 / Munich / Germany/ May 29-31, 2013 RESULTS OF PRISMA / FFIORD EXTENDED MISSION AND APPLICABILITY TO FUTURE MISSIONS