Navegação óptica espacial
José Manuel N. V. Rebordão
Faculdade de Ciências da Universidade de Lisboa
Ciência 2009, 30 de Julho de 2009
Abstract
 Autonomous navigation of spacecrafts is a mandatory technology in the
context of a wide variety of space missions, such as rendezvous and
docking, landing or constellation management. Sensing systems, in particular
active or passive optical sensors, play an unique role to feed GNC systems
with suitable spatial and temporal data. In addition noise characteristics
are critical to select and parameterise signal processing filters and ensure
smooth navigation.
 Since Portugal became a member of ESA, optical navigation has been
addressed by Portuguese research units and companies, working in most of
the cases in close collaboration with EADS-Astrium, and several projects
were awarded to develop and consolidate technologies and to generate
performance models to guide the specifications and development of the
GNC chain. Slowly but effectively, the TRL level has been increasing,
leading to flight experiments and demonstrations in realistic environments
under preparation to flight in ESA / Proba 3.
 Several optical navigation techniques will be presented in the context of
the control of constellation configurations, terrain-related navigation,
rendezvous between autonomous spacecrafts and generation of hazard
maps to enable the selection of the less hazardous landing site, supported
by optical metrology and imaging or lidar data.
2009
Optics / Photonics in Space
Instrumentation / Payload (‘all’ n)

Analogue & Digital optics

Focal plane / sensors

P/L design assessment, performances & telemetry
Spacecraft / System
2009

Attitude and navigation sensors

GNC sensors

Configuration management

Harness

Optical communications

Structure monitoring (FO sensors)

OGSE
What type of Missions ?
Autonomous missions


Solar system exploration
Man cannot be on-the-loop
Constellation of spacecrafts (S/C)



Real-time configuration control
System of several specialized S/C
Multi-aperture Instruments
Metrology
2009
Functions to be performed
Relative navigation wrt



Terrain
Stars (star mappers, star trackers, sun sensors)
Planets & small bodies (Earth sensors)
Landing

Hazard mapping (in the context of Hazard Avoidance)

Range and attitude estimation

Configuration determination
Rendezvous & Docking
Instrument enablers
Ranges, angles ( and corresponding velocities and accelerations)


Configuration keeping
Manoeuvring control
Pointing, change of geometry / baseline, …
2009
Optics plays a role
Supplying derived data to the GNC system
Complementing / filtering / improving other
navigation sensors with redundant data

IMU
Embedded in a chain of several variable
accuracy and time response sensors
(metrological chain)


2009
RF
Others (optical, …)
Main interfaces / dependencies
ADCS

Attitude Determination & Control Systems
GNC

Guidance, Navigation & Control
System level



2009
Type and degree of S/C stabilization
Location in S/C
Thrusters influence
Types
Passive

Camera-based / imaging
Terrain
Celestial bodies
Other spacecrafts (patterns of lights, 3D, …)
Active



2009
LIDAR
Interferometric
Lateral sensing
Constrains and critical tradeoffs
 Mechanisms

Zooming  variable resolution
Angular steering  focus of attention

LIDAR

 Power
 System


Redundancy
Radiation hardening
 Processing power & Bandwidth

(>>) 1 – 10 Hz
Image-related
Intelligent processing
Number of devices

Timing



 Mission-related
Thermal  illumination, shadows, …
Eclipse / non-eclipse
2009
Examples
 Landing / Hazard mapping

Passive
VBrNav HASE

Active
 Navigation & Positioning

AUTONAV AEROFAST

NPAL

PLANAV
LiGNC  LAPS
 Rendezvous & Docking

VBrNav  GNCO  PROBA 3
 Constellation / Instrument
configuration

 ESA Missions

PROBA 3

Mars Return Sampler

Next Moon Lander
2009

High Precision Optical Metrology
(DARWIN)  Fabry-Perot
Metrology  PROBA 3
FEMTO (XEUS)  Mode Locked
Semiconductor Lasers
Navigation & Positioning
ESA - AutoNav
Autonomous on-board navigation for interplanetary
missions
Partners
ESA, EADS Astrium (Fr), GMV (Sp), BDL
Funding
ESA
Contracts
ESA  EADS Astrium  INETI
Start
September 2001
End
July 2004
Simulation of the navigation optical camera, to be
included into the general system simulator;
generation of images of star fields, planets and
asteroids.
Image analysis of star fields, asteroids and planets in
order to measure the attitude of spacecraft and
contour / limb of asteroids, enabling autonomous
relative navigation.
2009
Autonav – Faint object detection
 To locate a non-resolved faint punctual object using multiple
time integration (MTI) approach to increase the SNR, and 3x
validation based on the linearity of displacement.



20 to 30 images are accumulated in sequence, …
made overlap using guide stars and added to increase SNR
The process is repeated three times to discriminate faint fixed stars
from faint moving bodies (asteroids or comets)
 Magnitude 13 objects should be detected with MTI
 The soonest asteroids are detected, the more accurate
navigation is!
IP_Init_LOS_Measurement
IP_MTI_LOS_Measurement
- Reference image;
- Search window
(ROI)
For n frames:
Locate guide stars
Attitude Measurement
(ref. image)
Geometric superposition of
ROIs
Provide ref. image
with ICRS
coordinates
and guide stars
(identified
catalogue stars)
Accumulate data within the
ROI
IP_Final_LOS_Measurement
REAL TIME
2009
ROI radiometric
processing
Find candidate points
within ROI
List of candidate LOS:
- positions (ICRS and sub-pixel image coords)
- instrumental magnitudes
Single or multiframe image
(1,...,n), for MTI
Autonav – Bright object detection
 Small objects & phase correction
 Full object within FOV
150
200
250
300
350
200
250
300
350
400
450
500
0
50
 Limb measurement
100
150
200
-250
250
300
-200
350
-150
50
100
150
200
250
-100
-50
0
0
50
100
150
200
250
300
50
100
150
200
250
300
-150
2009
-100
-50
0
50
100
150
200
300
350
400
450
500
FP7 - AEROFAST
AEROcapture for Future spAce tranSporTation
Partners
Astrium (Fr), Deimos Engenharia,
Corticeira Amorim (PT), Samtech (B), U.
Rome, STIL (Bu), I. Lotnictwa (Pl),
SRCPAS (Pl), ONERA (Fr), Kybertec (CZ)
Funding
FP7
Contracts
EADS Astrium SAS  INETI
Start
September 2008
End
2010
Solar system missions (e.g., Mars) relying on return
missions (humans and cargo) must rely on
aerocapture to be mass effective and use
atmospheric drag to slow space vehicles.
Aerocapture demands extremely accurate navigation
2009
Image-based optical navigation (images of planet
limbs, stars and asteroids) to support GNC.
ESA - Planav
Beagle 2 as seen
from Mars Express
Image based navigation tool for Mars landing
Partners
ESA, Deimos Engª (P)
Funding
ESA (Task Force Portugal – ESA)
Contracts
ESA  Deimos Engª  INETI
Start
August 2003
End
December 2003
Utilization of the geophysical cameras of
Beagle in the opposite direction, to track Mars
moons Phobos and Deimos, against a fixed
background of bright stars.
Analysis of the visibility of stars and moons,
to ensure that the Kalman filter receives an
adequate number of observables, in order to
reduce the positional error of Beagle 2.
2009
Precise
determination of
Beagle 2 landing
position in Mars
ESA - NPAL
Navigation for planetary approach and landing
Partners
ESA, EADS Astrium (Fr), O. Galileo (It),
U. Dundee, SSSL (Uk), Atmel (It)
Funding
ESA
Contracts
ESA  EADS Astrium  INETI
Start
December 2001
End
July 2004
Image analysis of planetary surfaces
(feature detection and tracking) in
order to enable navigation relative to
the terrain (kinematics).
50
100
150
200
250
Modelling and testing image
processing algorithms hardcoded in
one ASIC (FEIC camera)
300
350
400
450
500
2009
50
100
150
200
250
300
350
400
450
500
NPAL – Relative Navigation issues
 Supported by vision




Last 20 km in about 60 s.
Relative surface velocity
from ~750 m/s to 0.
FOV 70º
1024x1024. 50 Hz
 Thermal constrains:


Landing at dawn
Sun very close to the
horizon (< 5º)
long shadows.
2009of EADS Astrium SAS
Courtesy
NPAL – Relative Navigation issues
 With a single measurement, the LOS to a feature point is
known, but not its depth.
 Tracking the point with a dynamical filter allows progressive
determination of depth. For that:

Displacement and rotation of the S/C between two consecutive
measurements MUST be known.
Rotation  gyroscopes
Displacement requires v, but errors in v grow, because v is integrated from a.
 The vehicle state estimation is performed through sequential
Kalman filtering (one sub-optimal implementation, Sparce
Weight Kalman Filter, tested)
 ~ 50 points are used in the state vector
2009
Terrain-relative navigation. What for?
For safe landing with vision-based risk
assessment (hazard mapping) and Hazard
Avoidance
Passive systems (camera)
VBrNav  HASE  NextMoon
Active systems (lidar)
LiGNC  LAPS  NextMoon
Vision Based Landing: objectives
Objective: Landing on a planet
without atmosphere (Mercury) on a
only 10% hazard-free surface
Hazard avoidance (HA) is responsible for
hazard detection and path-planning to
avoid the detected hazards with
constraints on fuel and spacecraft
control authority.
Courtesy of EADS Astrium SAS
2009
Vision based Landing: Hazard Avoidance
(HA)
 Hazard Mapping: process of
analysing terrain topography and
detecting hazards through IP
algorithms applied to the
monocular optical images taken by
the onboard navigation camera.
 Piloting: concepts of data fusing,
planning and decision-making used
for the selection of a safe
Landing Site (LS).
 Guidance: concepts used to steer
the spacecraft to the Landing
Site (it can change during flight).
2009
ESA – VBrNav / HM
Vision-Based relative Navigation techniques framework
Partners
ESA, LusoSpace, Deimos Engª (P), EADS Astrium (F)
Funding
ESA (Task Force Portugal – ESA)
Contracts
ESA  Deimos Engª  INETI
Start
February 2004
End
March 2006
Development of landing hazard maps
(in view of Mercury or Mars landing),
based on optical images using shape
from shading methods.
2009
HM issues
 Topography (slope) estimation using
different IP methods



Motion Stereo
Optical flow
Shape from Shading (SFS) 
Merging with Navigation DEM0
 Image analysis to derive



Shadows
Texture (boulders and craters)
 Hazard fusion
2009
Pangu topo
Reconstructed DEM
De-striped DEM
Pangu slope map
Recovered slope map
Slope differences (log)
Camera Image
Reconstructed Image
Difference Image (log)
ESA - LiGNC
LIDAR Guidance, Navigation and Control
Partners
ESA, EADS Astrium (Fr), Deimos Engª,
Solscientia (P), U. Dundee (Uk)
Funding
ESA
Contracts
ESA  EADS Astrium  INETI
Start
September 2001
End
July 2005
LIDAR data processing to:
- generate topographic maps of the
landing regions,
- build up landing hazard maps
- estimate dynamically navigation
kinematical parameters.
2009
ESA - LiGNC
2009
XLIF
YLIF
ESA – LAPS
LIDAR-based Autonomous Planetary landing System
Partners
EADS Astrium SAS (Fr), ABSL Space
Products (Uk), Vision-Box (Pt), U.
Dundee (Uk)
Funding
ESA
Contracts
ESA  EADS Astrium  FCUL
Start
2008
End
2010
New Lidar developed for planetary topography
Image processing (IP) consolidation
Updating LiGNC IP algorithms for LAPS needs:
Adaptation to LIDAR outputs
Real-time implementation and optimization
(with Vision-Box)
Tests
2009
ZLIF
Rendezvous & Docking
VBrNav / RVD
GNCO & GNCO Maturation
PROBA 3
ESA – VBrNav / RDV
Vision-Based relative Navigation techniques framework
Partners
ESA, LusoSpace, Deimos Engª (P)
Funding
ESA (Task Force Portugal – ESA)
Contracts
ESA  Deimos Engª  INETI
Start
February 2004
End
March 2006
GNC (Guidance, Navigation & Control) for
Rendezvous & Docking between autonomous
S/C (in view of Mars Return Sample mission)
 Design Drivers






2009
Early detection of the target for a specified radial
dispersion (50, 100 m) at a specified range (1, 1.5, 2
km)
±1º attitude uncertainty of the chaser
Space qualified CCD (1024x1024, 15 mm)
No zoom, only 1 fixed camera
Minimum number of light spots on the target
Eclipse
ESA – GNCO MATURATION
Guidance for Non-Circular Orbits
Partners
Deimos Engenharia
Funding
ESA (Task Force Portugal – ESA)
Contracts Deimos Engenharia  FCUL
CAN RR 3D coordinates
-3
CAN RR Focal plane coordinates
x 10
1
3.08
3.06
3.04
0.5
3.02
Start
January 2006
3
2.98
0
2.96
End
December 2010
2.94
2.92
-0.5
0.05
Mars Return Sampler mission
-1
0
-0.05
y
-0.08
-0.06
-0.02
-0.04
x
Modelling optical navigation sensors
and image processing chain
Development of performance models
Laboratory test bed
Real-time test bed with WH in the loop
Passive spherical, non-stabilized white
canister with RR
2009
0
0.02
0.04
0.06
0.08
-6
-4
-2
0
2
4
-4
x 10
ESA – PROBA 3
Autonomous Rendezvous Experiment
Partners
Deimos Engenharia, …
Funding
ESA
Contracts
Deimos Engenharia  INETI
Start
2009
End
2012
2009
PROBA-3
PROBA-3
Constellation / Instrument
configuration
ESA - HPOM
High precision optical metrology (Darwin)
Partners
ESA, EADS Astrium (Fr + D), SIOS,
TPD/TNO (Nl), EADS-CASA (Sp)
Funding
ESA
Contracts
ESA  EADS Astrium  INETI
Start
December 2001
End
December 2005
DARWIN is based on an InfraRed Space
Interferometer (MAT) to detect planets in nonsolar planetary systems.
Optical metrology (FSI, frequency sweeping
interrferometry) for formation flying missions
New concepts for compensation of metrological
networks in space.
2009
FSI - Frequency Sweeping Interferometry
 ESA / FP-MET – Fabry-Perot Metrology
 Non ambiguous measurement
Laser &
Detection
Optical Head
 No need for frequency stabilization
 Low hardware complexity
(transferred to software)
 Compactness
 Synthetic wavelength down to the mm range
 mm level accuracy at short ranges
 Measurement of drift between S/C
2009
FSI Head
FSI for Multiple Aperture telescopes
.
 Synthetic optics, Michelson configuration
 Stabilization of the interference patterns
 Metrological chain to control the optical delay lines
 FSI for coarse compensation, relative metrology for RT stabilization
2009
FSI for
distance
measurement
CandidateTechnology
for ESA PROBA 3
(2013)
Vacuum tests in 2009
2009
ESA - FEMTO
Absolute long distance measurement with (sub)μm accuracy for formation flight applications
Partners
ESA, TPD/TNO (Nl), LCVU (Nl),
ASTRIUM (D)
Funding
ESA
Contracts
ESA  TPD/TNO  INETI
Start
January 2007
End
December 2009
Realisation and fundamental technological
limitations of pico (ps, 10-12s) and femto-second
(fs, 10-15s) metrology
Assessment of the maturity of the technology
Applicability of fs-metrology to different space
mission scenarios
2009
Complexity and impact at system level
Baseline Metrology for XEUS
 XEUS (X-ray
Evolving Universe Spectroscopy): two
separate spacecrafts flying in formation with a focal
length of 35 m, without the use of a large deployable
bench or a telescope tube system.
 XEUS Optical metrology must measure all 6 degrees of
freedom of DSC (Detector S/C) relative to MSC
(Mirror S/C),
 The solution to measure 6 DOF is to use a Trilateration
scheme to obtain the lateral displacements and
angular orientation of the DSC wrt the MSC with an
absolute distance metrology system.
2009
Parameter
Value and
Range
Uncertainty (2σ)
Required – Predicted
z (ISD)
35 m ± 1 m
300 µm – 10 µm
x&y
0m±1m
170 µm – 125 µm
pitch & yaw
0 degrees
10 arcsec – 1 arcsec
roll
0 degrees
>>10 arcsec – 10 arcsec
ESA- Mode Locked Semiconductor Lasers
Mode locked Semiconductor Lasers for Optical
Precision Metrology
Partners
EADS Astrium (D), Reflekron (Fi)
(observers)
Funding
ESA – ITI (Industrial Triangular
Initiative)
Contracts
ESA  FCUL
Start
2008
End
2010
Modelocked Semiconductor Laser accurate
timing stabilization
Pulse Cross-correlation for time-of-flight
distance measurement
Application to space and to Formation Flying
missions metrology
2009
Final comments
(excluding Configuration-type issues)
Solid-state lasers
Multi-camera

Redundancy
 Zooming

Mechanisms !
Changing FOV / resolution
 Steerability
 Eclipse / non-eclipse phases
 Huge amount of on-board



2009
Processing capability
Telemetry
Intelligence
APS cameras !
Acknowledgements
INETI  FCUL








Bento Correia (now @ Vision Box)
Alexandre Cabral
Paulo Motrena
Manuel Abreu
João Coelho
Conceição Proença
João Dinis
Elena Duarte
END !
ESA
EADS Astrium GNC team
Deimos Engenharia GNC team
2009