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© GMV, 2015 Property of GMV
All rights reserved
FORMATION FLYING GUIDANCE FOR SPACE DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
ASTRONET II INTERNATIONAL FINAL CONFERENCE
T. V. Peters (GMV)
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
OVERVIEW
Presentation loosely organized around mission phases, taking examples from different projects– Engineering issues– GNC aspects, with emphasis on guidance
Material from following projects:– Detumbling: detumbling space debris after capture– Patender: net capture tests– COBRa: influencing debris (orbit and) attitude by plume impingement– Android: demonstrate robotic and net capture of space debris– eDeorbit: de-orbit Envisat
2015/06/16 Page 2
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
INTRODUCTION
Introduction– Space debris distribution– Space debris dynamics– Debris capture options
Mission phases for robotic capture– Mid-range rendezvous– Inspection from spiral orbit– Attitude synchronization– Capture and detumbling
Conclusion
2015/06/16 Page 3
© GMV, 2015 Property of GMV
All rights reserved
INTRODUCTION
FORMATION FLYING GUIDANCE FOR SPACE DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
DEBRIS CLASSIFICATION
Removal options– Removal of tiny & small debris not practical– Removal of large objects removes potential sources of fragments in case of
collision• Target selection is based on debris generating potential
Conclusion: remove large objects
2015/06/16 Page 5
Type Characteristics HazardTiny Not tracked, <1 cm Shielding exists,
damage to satellites may occur
Small Not tracked, diameter 1 – 10 cm, 98% of lethal objects, ~400.000 objects in LEO
Too small to track and avoid, too heavy to shield against
Medium Tracked, diameter >10 cm, <2 kg, 2% of lethal objects, ~24.000 objects in LEO, > 99% of mass (incl. large objects)
Avoidance manoeuvres performed most often for this category
Large Tracked, >2 kg, <1% of lethal objects, > 99% of mass (incl. medium objects)
Primary source of new small debris, 99% of collision area and mass
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
DEBRIS DISTRIBUTION
Debris population– Total mass estimated at 6300
tons– High concentration at 82-83°
inclination• COSMOS 3M
SSO particularly important for and Earth observation and science– SSO inclination-paired with 82-
83° inclination orbit– Heightens collision probability
• Orbit planes may align, leading to head-on collisions during entire orbit instead of only at nodes
2015/06/16 Page 6
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
DEBRIS ATTITUDE DYNAMICS
No systematic survey for attitude Several sources of data are available
– The spin rate of upper stages tends to slow down (1 & 2)• Spin-ups have been observed, likely due to outgassing events (2)
– Envisat (3 & 4)• Spin-up event occurred some time between april 2012 and november 2013• Rotation rate has been slowing down since then
– Rocket upper stages have generally been observed in a flat spin (i.e., non-axial) (5)• Initial spin state of rocket bodies tends to be axial• Therefore it is expected that a transition to a major axis spin occurs at some
point due to energy damping
2015/06/16 Page 7
1. Boehnhardt, H., Koehnhke, H. and Seidel, A. 1989, The acceleration and the deceleration of the tumbling period of Rocket Intercosmos 11 during the first two years after launch, Astrophysics and Space Science, vol. 162, no. 2, p. 297-313.
2. Williams, V., Meadows, A.J., 1978, “Eddy current torques, air torques and the spin decay of cylindrical rocket bodies in orbit”, Planetary and Space Science, vol. 26, 1978, p.721-726
3. Bastida Virgili, B., Lemmens, S., Krag, H., 2014, Investigation on Envisat attitude motion, e.Deorbit Workshop4. Kucharski, D., Kirchner, G., Koidl, F., Fan, C., Carman, R., Moore, C., Feng, Q., 2014, “Attitude and Spin Period of Space Debris
Envisat Measured by Satellite Laser Ranging”, IEEE Transactions on Geoscience and Remote Sensing, Vol. 52 , Issue 12, pp. 7651 – 7657, DOI 10.1109/TGRS.2014.2316138
5. Santoni, F., Cordelli, E., Piergentili, F., 2013, "Determination of Disposed-Upper-Stage Attitude Motion by Ground-Based Optical Observations", Journal of Spacecraft and Rockets, Vol. 50, No. 3, pp. 701-708, doi: 10.2514/1.A32372
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
DEBRIS ATTITUDE DYNAMICS
Envisat Rotation axis known Characteristic decay time ~4.5 years
COSMOS Rotation around major axis Characteristic decay time between
100 and 470 days, with a mean of 161 days and median of 129 days
2015/06/16 Page 8
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
CAPTURE METHODSCapture method Sensitivity to rotation rate Rotation related issues Structural issues
Net low fast de-spin required to avoid tether wind-up around target
may require measures to avoid breaking off pieces of target
Grappling high synchronization required requires structural hard point
Docking with nozzle high synchronization required requires non-steerable nozzle
Tentacles high synchronization requiredmay require structure not covered by MLI for firm grip
Harpoon (Rigid) high synchronization required
requires strong structure for contact (e.g., honeycomb panels) and avoidance of propellant tanks
Harpoon (Non-rigid) lowfast de-spin required to avoid tether wind-up around target
requires strong structure for contact (e.g., honeycomb panels) and avoidance of propellant tanks
Pushing sock air-bag high requires pre-capture de-spinmay require measures to avoid breaking off pieces of target
Foam projection highcentrifugal forces may disrupt foam; requires pre-capture de-spin
may require structure not covered by MLI for firm grip (i.e., MLI may tear off)
Ion-beam Shepherd lowlow sensitivity to spin rate; method may be used to control rotation
none
Electrostatic tractor (only for GEOs)
lowlow sensitivity to spin rate; method may be used to control rotation
none
Magnetic tractor lowlow sensitivity to spin rate; method may be used to control rotation
none
2015/06/16 Page 9
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
ROBOTIC ARM CAPTURE
Precursor activities dealt with cooperative targets (attitude controlled, visual markers, grappling interfaces) – ETVS-VII– Orbital Express (DARPA program)
FREND (DARPA) performed on-ground demonstration of capture of uncooperative target debris
Other missions/concepts being investigated:– DEOS (passive v.s. active chaser AOCS
investigated)– eDeorbit (several robotic arm and
tentacles configurations proposed, as well as net-based capture)
– ANDROID (double demonstration of robotic arm and net)
2015/06/16 Page 10
ETS-VI I (NASDA/JAXA) Orbital Express (DARPA)
DEOS eDeorbit concept from ESA CDF study
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
NET CAPTURE
Net Several studies to mature net
capture technology (net design, net deployment strategy and mechanisms)– Patender
• Scalable to debris mass and size • Composed of a pyramidal, conical or
plane net stowed in a canister with four masses (bullets) attached to net vertices
• Pneumatic or spring-driven ejection of bullets
• Tether connection after capture Studies to investigate
controllability– AGADiR
• Controllability remains a difficult problem
2015/06/16 Page 11
-0.5
0
0.5
1
1.5
2
2.5
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1
22m 2I
1m 1I
12R
22RVbar
Rbar
© GMV, 2015 Property of GMV
All rights reserved
MISSION PHASES
FORMATION FLYING GUIDANCE FOR SPACE DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
ACTUATORS AND SENSORS
2015/06/16 Page 13
Actuators Depends on size of object Separate thrusters for orbit raising / lowering & rendezvous
– Orbit raising / lowering: • (2 x) 2 x 22 N (Android; stack mass 425 kg)• 2 x 500 N (eDeorbit; stack mass 9500 kg)• Acceleration per thruster 0.05 m/s2
– Rendezvous• (2 x) 8 x 1 N (Android; mass during rendezvous 298 kg)• 28 x 22 N (eDeorbit; mass during rendezvous 1700 kg)• Acceleration per thruster 0.01 m/s2 (eDeorbit) / 0.003 m/s2 (Android)
Sensors
Sensor ModelMass [kg]
Power [W]
Range [km]
Performance Source Comments
GPS Phoenix 0.02 0.85- up to 2 m DLRWAC DVS 2.4 130.02-150 1" TSD
LIDAR RVS 13.8 350.001-2
0.01 m short range; min range < 1m0.5 long range
JENA OPTRONIK scanning
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
MID-RANGE RENDEZVOUS
Far-range rendezvous performed using TLE and GPS
TLE accuracy after 1 week of propagation:– Radial: maximum error < 1.5
km => drift of 14 km per orbit• Bias .25 km + 1σ of .1 km =>
drift of 3.3 km per orbit– Cross-track: maximum error <
1.5 km– Along-track: maximum error <
30 km Is a detection & handover to
WAC possible?
2015/06/16 Page 14
Debris TLE
Abs NGPS based
-
Trans G
Relativestate
NORAD TLE
GPS DATA
ΔV
Att GTGT TRACK
Att. Cmd.
Rel NWAC based
WAC DATA
Rough estimateof relative state
Translation
Attitude
1. Legendre P., Deguine B, Garmier R., Revelin B., 2006, Two Line Element Accuracy Assessment Based On A Mixture of Gaussian Laws, AIAA 2006-6518, AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 21 – 24 August 2006, Keystone, Colorado
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
MID-RANGE RENDEZVOUS
Search phase Detection limit 0.25
pixels– Camera FOV 28°
Detection can occur between 33 - 151 km distance– Depending on size of target– Uncertainty cone of .5° –
2.5°• Well within WAC FoV
– Handover to WAC is possible
2015/06/16 Page 15
range [m]number of pixels covered
/ object sizecomments
2 4 9 151000 0.06 0.11 0.25 max range WAC
67000 0.13 0.25 0.56 max range WAC33500 0.25 0.50 1.13 max range WAC
2000 4 8 19 handover distance
20 419 835 185590% of WAC FOV filled
9 927 1833 388690% of WAC FOV filled
4.5 1833 3505 658390% of WAC FOV filled
2 3886 6583 9660 working distance
target
chaser
Detection range 50 - 150 km
1.5 km
2ϕ
z
x
±5 km
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
MID-RANGE RENDEZVOUS
Phase 1– Difference in SMA larger than
radial uncertainty in TLE• ±2 km difference in SMA
– Vision-based navigation requires some radial motion for faster convergence
– Small target may lead to late detection
Phase 2– Terminal orbit may require
specific relative geometry • Lighting conditions• Earth in background• Ground contact
– Modulate drift to accommodate terminal conditions
2015/06/16 Page 16
100 m
50 m500 m
z
x
S1
S3aS3b
S4S5
~ 4000 m
S2a
S2b
4 km
.5 km2 km
z
x
S0S1
33 – 150 km
# of orbits
<1 km
# of orbits available for detectiondetection distance [km]
33 67 150δS.M.A. [km]
0.5 5.94 13.16 30.772 1.49 3.29 7.69
3.5 0.85 1.88 4.40
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
MID-RANGE RENDEZVOUS
2015/06/16 Page 17
Plan generation
Mean orbit Kepler orbittarget orbit
chaser LVLH state
Table of times, referencestates & ΔV’s
reference trajectorycorrectiontime check
time
ΔV computation
Reference trajectory
ΔV
Guidance function
Plan database
Situationassessment
mode manager commands
Guidance expert function
Plan generation
Mean orbit Kepler orbittarget orbit
chaser LVLH state
Table of times, referencestates & ΔV’s
reference trajectorycorrectiontime check
time
ΔV computation
Reference trajectory
ΔV
Guidance function
Full guidance Guidance as implemented
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
1.4
time [h]
V
[m
/s]
MID-RANGE RENDEZVOUS
Initial errors are quite large After first 5 hours (3 orbits) errors decrease
– Decrease occurs when chaser enters drift orbit – Large errors in position and velocity occur at
large distances Errors in position and velocity show a slight
increase over time– due to the fact that a unperturbed Keplerian
propagator is used to propagate relative trajectories• Keplerian orbit is initialized at start of simulation • starts diverging from true orbit over time
Causes of errors are known, and could be improved. – J2-based relative propagator could be used to
improve the reference trajectory– Guidance could be made to operate on
linearized differential orbital elements• Suffer less from linearization errors
– Guidance could periodically update its plan• Re-initializing Keplerian orbit used to generate
reference trajectory• Reference orbit will be closer to true orbit and
reference trajectory will be closer to truth
2015/06/16 Page 18
0 5 10 15 20 25 30-70
-60
-50
-40
-30
-20
-10
0
10Position error
time [h]
x [m
]
0 5 10 15 20 25 30-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08Velocity error
time [h]
v x [m
/s]
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
INSPECTION FROM SPIRAL ORBIT
Camera in target pointing when constraints are met
Several constraints shall be taken into account:– Eclipse times (no operation)– Sun exclusion angle (50deg)– Earth in the field of view (IP
problems)– Illumination conditions, angle
Sun Picard Mango below 90 deg (IP problems)
When all constraints taken into account only about 25% of the orbit is useful, +ZY in LVLH
2015/06/16 Page 19
-50-40-30-20-1001020304050
-10
0
10
3D LVLH Relative trajectory
X [m]
Y [
m]
-15 -10 -5 0 5 10 15
-15
-10
-5
0
5
10
15
3D LVLH Relative trajectory
Y [m]
Z [
m]-50-40-30-20-1001020304050
-10
0
10
3D LVLH Relative trajectory
X [m]
Z [
m]
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
INSPECTION FROM SPIRAL ORBIT
2015/06/16 Page 20
-40-20
020
4060
-20
-10
0
10
20-10
-5
0
5
10
15
X [m]
LVLH relative trajectory
Y [m]
Z [
m]
-40 -30 -20 -10 0 10 20 30 40 50-15
-10
-5
0
5
10
15
X [m]
LVLH relative trajectory
Y [
m]
-40 -30 -20 -10 0 10 20 30 40 50-10
-5
0
5
10
15
X [m]
LVLH relative trajectory
Z [
m]
-15 -10 -5 0 5 10 15-10
-5
0
5
10
15
Y [m]
LVLH relative trajectory
Z [
m]
Effect of perturbations (SRP and Drag) lead to non-constant drift rate– Needs to be taken into account in manoeuvre definition for
spiral orbit insertion if in drift-free orbit– Leads to more correction manoeuvres– Note: size of spiral orbit fairly small; 10 m vs. 20 – 50 m for
COSMOS - Envisat Possible input to spacecraft design to ensure small
differences in ballistic coefficient
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
SYNCHRONIZATION PHASE
Elements Target attitude propagation Reference frame transformations Quaternion spline curve for fly-around
to limit accelerations Straight-line approach using ramp-
constant-ramp velocity profile
Guidance plan consists of:1. Perform station keeping on Vbar2. Transfer to target ω-vector (h-vector is an
alternative)3. Station-keeping at target ω-vector4. Rotate to target co-rotating5. Perform transfer closer to target6. Station-keeping at w-vector7. Transfer to target body fixed frame position8. Station-keeping in body fixed frame position9. Transfer closer to target
2015/06/16 Page 21
XLVLH
ZLVLH
S1
S2
S3
S4
S5
A
1. Myoung-Jun Kim, Myung-Soo Kim, and Sung Yong Shin. 1995. A general construction scheme for unit quaternion curves with simple high order derivatives. In Proceedings of the 22nd annual conference on Computer graphics and interactive techniques (SIGGRAPH '95), Susan G. Mair and Robert Cook (Eds.). ACM, New York, NY, USA, 369-376. DOI=10.1145/218380.218486 http://doi.acm.org/10.1145/218380.218486
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
SYNCHRONIZATION PHASE
Synchronization simulated in simplified simulator– Propagation models
• Trajectory propagator contains J2 perturbation
• Attitude propagation propagates torque-free tumbling motion (no perturbations)
– Sensors and actuators• 1 N thrusters with thruster
management function• “Perfect” sensors
– GNC• Synchronization guidance• LQR controller• “Perfect” navigation
2015/06/16 Page 22
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
SYNCHRONIZATION PHASE
2015/06/16 Page 23
Camera view LVLH view
ω = 0.5 °/s
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
SYNCHRONIZATION
Guidance trajectory is precisely followed– Centimetre level accuracy in
position– Millimetre per second level
accuracy in position– Pointing error smaller than
0.1°– Better accuracy possible
with more aggressive controller
But, no navigation is included
2015/06/16 Page 24
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
SYNCHRONIZATION
ΔV required for synchronization– guidance ΔV is red– true ΔV is black
Four phases can be distinguished– transfer to the angular velocity vector
• fairly expensive; sharp increase in ΔV right at start
– station-keeping at the angular velocity vector• comparatively cheap; gradual increase in ΔV
– transfer to the body fixed frame – station-keeping in body fixed frame
• Station-keeping in target reference frame is cheaper than transfer
• But considerably more expensive than station-keeping at angular velocity vector
• Especially considering that station-keeping at angular velocity vector is performed at 10 m, while station-keeping in target body frame is performed at between 2 and 5 m
2015/06/16 Page 25
0 10 20 30 40 50 60 700
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
time [min]
V
[m
/s]
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
CAPTURE AND DETUMBLING
Capture and detumbling currently under investigation– Inverse kinematics dependent on
design of arm; full implementation provides low added value compared to cost • Some simplification (e.g. convenient
arm/joints configuration and allow small joint angles w.r.t. rigid)
– Contact model between robot hand and target approximated by translational and rotational spring damper Kc Dc system • no gripper is attached to end point of
manipulator, contact occurs just between two points
– state of spring damper could supply a metric on what is happening at contact
2015/06/16 Page 26
1. Dimitrov, D. N., Kazuya Y., 2004, "Momentum distribution in a space manipulator for facilitating the post-impact control," Intelligent Robots and Systems, 2004.(IROS 2004). Proceedings. 2004 IEEE/RSJ International Conference on, vol. 4, pp. 3345-3350. IEEE, 2004.
© GMV, 2015 Property of GMV
All rights reserved
CONCLUSION
FORMATION FLYING GUIDANCE FOR SPACE DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
© GMV, 2015FORMATION FLYING GUIDANCE FOR DEBRIS OBSERVATION, MANIPULATION AND CAPTURE
CONCLUSION
Brief outline of mission phases for a debris capture mission has been presented– Overview of results of several related projects
Envisat most likely candidate for a debris removal mission– Exceptional for high rotation rate– Special measures to be taken for attitude synchronization
Smaller ADR demonstration mission with a smaller target should be implemented
2015/06/16 Page 28
© GMV, 2015 Property of GMV
All rights reserved
Thank you
T. V. Peters
Email: [email protected]
www.gmv.com