Radio-Frequency Sensor Fusion for Relative Navigation of Formation Flying Satellites G. Allende-Alba (TUM/IAPG) S. D‘Amico (DLR/GSOC) O. Montenbruck (DLR/GSOC)
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
Technische Universität München
Contents ¾ Formation flying (FF) and relative navigation in space ¾ Motivation ¾ Techniques
¾ Results and disussion ¾ Conclusions and future work
Artist’s impression of future applications of formation flying satellites based on the PRISMA mission results (Source: SSC)
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
FF and relative navigation in space: motivation ¾ Spacecraft formation flying applications ¾ SAR interferometer and gravimeter ¾ Multi spacecraft telescope ¾ On-orbit servicing and rendezvous
¾ Formation control -> relative navigation ¾ Autonomous systems require information with high levels of ¾ Robustness ¾ Reliability ¾ Availability
Artist’s impression of the DARWIN constellation. (Source: ESA). Artist’s impression of a typical on-orbit servicing mission. (Source: ATK) 5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
FF and relative navigation in space: techniques ¾ Differential GPS ¾ Based on spaceborne GPS sensor ¾ Various degrees of accuracy
¾ Vision-based ¾ Proximity and rendezvous operations
¾ Laser metrology
Artist’s impression of the VBS in PRISMA (Source: SSC)
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
The PRISMA mission ¾ Demonstration of techniques for FF and rendezvous ¾ Novel relative navigation sensors
¾ Launched on June 15th, 2010 ¾ Sun-synchronous orbit ¾ Altitude of 750 km
¾ Joint effort ¾ ¾ ¾ ¾ ¾
Swedish National Space Board (SNSB) Swedish Space Corporation (SSC) / OHB-Sweden German Aerospace Center (DLR) National Center for Space Studies (CNES) Technical University of Denmark (DTU)
¾ Space segment consists of 2 spacecraft
Artist’s impression of the PRISMA satellites in orbit. (Source: DLR)
¾ Mango (chaser) ¾ Tango (target)
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Sensor fusion: introduction
¾ Absolute position of Mango and Tango ¾ Earth-Fixed EarthCentered reference frame
¾ Relative distance (d) ¾ Line of sight (LOS) ¾ RF reference frame
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Sensor fusion: architecture
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Sensor fusion: measurements Assessment of FFRF LOS measurements (DLR‘s POD as reference) Oct 28th (16:00) – Oct 30th (18:30), 2010 Large angular excursion (measurement error) caused by multipath during maneuver execution
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
Non-constant bias attributed to variations in sensor temperature
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Technische Universität München
Sensor fusion: measurements Assessment of (D)GPS measurements (DLR‘s POD as reference) Oct 28th (16:00) – Oct 30th (18:30), 2010
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Sensor fusion: relative navigation filter
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Results and discussion ¾ Accuracy of relative navigation solution ¾ Premise for analysis of filter properties ¾ Should be similar regardless of the sensor(s) being used
¾ Using both sensors at same orbit phases ¾ Increased robustness ¾ Increased reliability
¾ Handover between sensors at different orbit phases ¾ Increased availability
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Results and discussion Initial assessment of accuracy Oct 28th (16:00) – Oct 29th (01:00), 2010
Formation in free drift and stand-by (approx. avg. ISD of 300 m) Sensor
Error in position (cm)
Error in velocity (mm/s)
Radial
Along-track
Cross-track
Radial
Along-track
Cross-track
FFRF
0.1±2.7
-0.3±2.3
1.4±12.6
-0.010±0.10
0.001±0.04
0.063±0.15
GPS
0.2±1.6
0.1±0.6
0.3±0.8
0.010±0.22
0.002±0.07
0.006±0.21
FFRF+GPS
0.3±1.5
0.1±1.0
0.3±0.6
-0.001±0.09 -0.001±0.04 -0.001±0.07
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Results and discussion Handover tests Oct 28th (16:30) – Oct 30th (18:30), 2010
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba
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Technische Universität München
Conclusions and future work ¾ Sensor fusion allows the generation of relative navigation solution with increased: ¾ Robustness (tolerance to bad data points) ¾ Flexibility (single design for different mission scenarios) ¾ Reliability and availability (tolerance to measurement gaps or data outages)
¾ FFRF/GPS sensor fusion provides concepts for precise relative navigation in HEO ¾ Simple design of the relative navigation filter ¾ Feasibility of the approach ¾ Limitations in dynamical modelling and maneuver handling
¾ Integral design using measurements from GPS/FFRF/VBS sensors ¾ Generation of precise kinematic GPS measurements using PPP techniques could enable sensor fusion for real-time relative navigation
5th International Conference on Spacecraft Formation Flying Missions and Technologies. May 29-31 (2013) > G. Allende-Alba