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The 58th Session of International Astronautical Congress (IAC)

September 24-28, 2007
Hyderabad, India


Statistical Analysis Of the ESA Optical Space Debris Surveys

Thomas Schildknecht, Tim Flohrer, Reto Musci
Astronomical Institute, University of Bern, Switzerland

Rüdiger Jehn
ESA ESOC, Darmstadt, Germany

Introduction

Motivation

  • Primary objective of all space debris measurement programs
    • improved knowledge on the debris environment in specific orbital regions
      • number of objects
      • object sizes distributions
      • nature and origin of the objects
      • additional characteristics
  • Ideally: maintained catalogue of space debris, but
  • Statistical data
    • derive spatial fluxes
    • input data for spacecraft designers
    • asses collision risks
    • devise efficient space debris mitigation measures
  • Fluxes from statistical optical observation data
    • All methods require that some parameters or statistical properties of the debris population have to be assumed.

ESA 1-m Telescope (OGS)

OGS (Optical Ground Station)
  • 1m aperture
  • f=4.4 m
  • 4k x 4k CCD
  • FOV 0.7
Used for:
Surveys, faint objects follow-up

The ESA Survey Data

2006 Survey

GEO observation scenario 2006

GTO observation scenario 2006

PROOF Simulations

  • Simulate observations for model populations
    • use detailed observation scenarios of 2006
    • 4 Monte Carlo runs
  • GEO population with homogeneously distributed orbital elements:
    • analyze selection biases in the orbital element space
    • artificial clusters?
  • GEO catalogue population
    • direct comparison with 2006 survey
    • coverage in the orbital element space
  • MASTER population
    • independent validation of the MASTER-2005 model
  • GOAL:
    • from simulation: Ndet/Nobj
    • from observations: NUCT(detections) → Nobj

Homogeneous GEO Population

  • 1000 objects with equally distributed orbital elements:
    • semimajor axis: [40164km, 44164km]
    • eccentricity: [0, 0.1]
    • inclination: [0, 17]
    • node: [0, 360]
    • perigee: [0, 360]
    • mean anomaly: [0, 360]
  • No S/N limit → only "geometry"

GEO scenario

Simulated 1000
Detections 119
Objects 92
Ndet/Nobj 1.3

GTO scenario

Simulated 1000
Detections 334
Objects 277
Ndet/Nobj 1.2

GEO & GTO
Simulated 1000
Detections 453
Objects 369
Ndet/Nobj 1.3

Catalogue Population

GEO and GTO scenario

GEO
Detections 461
Objects 212
Ndet/Nobj 2.2

GTO
Detections 349
Objects 229
Ndet/Nobj 1.5

GEO & GTO
Catalogue 349
Objects 347
Survey 320

MASTER-2005 Population

GEO scenario; Survey CTs, MASTER "TLE detections"

MASTER
Det. TLE 460
Obj TLE 195
Ndet/Nobj 2.2

Survey
Det. CT 476
Obj CT 187
Ndet/Nobj 2.6

TLE/CT 1.06

Consistent

GTO scenario; Survey CTs, MASTER "TLE detections"

MASTER
Det. TLE 378
Obj TLE 242
Ndet/Nobj 1.5

Survey
Det. CT 332
Obj CT 229
Ndet/Nobj 1.5

Objects
TLE/CT
1.06

Consistent

GEO scenario; Survey UCTs, MASTER fragments

MASTER
Det. Frag 628
Obj Frag 450
Ndet/Nobj 1.4

Survey
Det. UCT 461
Obj UCT ?
Ndet/Nobj ?

Detections
Frag/UCT
1.36

Too many
Master Fragments

GTO scenario; Survey UCTs, MASTER fragments

MASTER
Det. Frag 838
Obj Frag 242
Ndet/Nobj 3.5

Survey
Det. UCT 579
Obj UCT ?
Ndet/Nobj ?

Detections
Frag/UCT
0.66

Too few
Master Fragments

Detections-to-objects ratios

Catalogue
Survey
Scenario
GEO
Homogeneous
MASTER
Population
GEO 1.3 1.4 2.2
GTO 1.2 1.2 1.5
GEO/GTO 1.3 1.5 2.3

1040 UCT detections in 2006 survey

  • Ndet/Nobj = 1.3 (catalogue pop.) → ~800 objects
  • Ndet/Nobj = 1.5 (MASTER pop.) → ~700 objects
  • Ndet/Nobj = 2.3 (homog. pop.) → ~450 objects

Conclusions

  • Fictitious homogeneous GEO population:
    • Sampling homogeneous in (i-Ω) orbital element space
    • 35% of the simulated objects detected
  • GEO catalogue population:
    • ~40% of the catalogue population detected in the simulation
    • ~36% of the catalogue were actually observed (320 out of 879)
  • MASTER-2005 population
    • over-predicts the number of fragments in orbital planes similar to the catalogue population
    • predicts too few debris for other orbital planes (missing high area-to-mass ratio population in the model!)
  • ESA 2006 survey
    • has seen 450 to 800 uncatalogued debris objects, ~700 assuming MASTER population characteristics

29 2007

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