modeling the large and small orbital debris populations ... · modeling the large and small orbital...

National Aeronautics and Space Administration

Modeling the Large and Small Orbital Debris Populations for Environment Remediation

J.-C. Liou, PhDNASA Orbital Debris Program Office

Johnson Space Center, Houston, Texas

3rd European Workshop on Space Debris Modeling and Environment RemediationCNES HQ, Paris, France, 16-18 June 2014

https://ntrs.nasa.gov/search.jsp?R=20140006500 2018-10-19T15:04:57+00:00Z

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Outline

• Options for Environment Remediation in LEO

• Knowledge of the Environment

• Modeling the Future Large and Small Orbital Debris Population Growth

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Options for Environment Remediation in LEO

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Stability of the LEO Debris Environment

• The Inter-Agency Space Debris Coordination Committee (IADC) investigated the stability of the orbital debris population in LEO several years ago– Six Agencies (ASI, ESA, ISRO, JAXA, NASA, UKSA) used six

different models for the study– A final study report was prepared and placed at the IADC

website (http://www.iadc-online.org) in January 2013– A study summary was presented to the UN Committee on the

Peaceful Uses of Outer Space (COPUOS) Scientific and Technical Subcommittee (STSC) in February 2013

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Conclusions of the IADC Study

• Even with a 90% compliance of the 25-year rule and no future explosions, the LEO debris population is expected to increase in the next 200 years– Monte Carlo (MC) statistics: 644/725 MC runs, 89% probability– Population growth is primarily driven by collisions between 700

and 1000 km altitudes– Catastrophic collisions are likely to occur every 5 to 9 years

• To better limit the growth of the future debris population and to reduce collision activities in LEO, new mitigation measures, such as active debris removal, should be considered

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Options for Environment Remediation

• Removal of massive intact objects, with high collision probabilities, to address the root cause of the future debris population growth problem

• Removal of ~5-mm to 1-cm debris to mitigate the main threat for operational spacecraft

• Prevention of major debris-generating collisions involving massive intact objects as a potential short-term solution

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0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150 2170 2190 2210

Effective Num

ber of O

bjects (>10

cm)

Year

LEO Environment Projection (averages of 100 LEGEND MC runs)

Reg Launches + 90% PMD

Reg Launches + 90% PMD + ADR2020/02


(Liou, Adv. Space Res, 2011)

A good implementation of the commonly-adopted mitigation measures and an ADR of about five objects per year can “stabilize the future environment”

Controlling Debris Growth with ADR

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Targets for Removal

1,000

10,000

100,000

1,000,000

10,000,000

0.1 1 10 100

Cumulative N

umbe

r

Size (cm)

Notional Size Distribution of LEO‐Crossing Objects

Main driver for population growth

1 cm

5 cm

10 cm

50 cm1 m

5 mm

Main threat to operational S/C

Degradation threat to operational S/C

~80% of all >5 mm debris are in the 5-mm to 1-cm regime

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Knowledge of the Orbital Debris Environment

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0

1000

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7000

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9000

10000

11000

12000

13000

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15000

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17000

1957

1959

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1969

1971

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1987

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Num

ber o

f Obj

ects

Year

Monthly Effective Number of Objects in Earth Orbit by Object Type

Total Objects

Fragmentation Debris

Spacecraft

Mission-related Debris

Rocket Bodies

Growth of the Cataloged Populations

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0

1

2

3

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7

1957

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2011

2013

Mas

s in

Orb

it (m

illio

ns o

f kg)

Year

Monthly Mass of Objects in Earth Orbit by Object Type

Total Objects

Spacecraft

Rocket Bodies

Fragmentation Debris


Mass in Space

No sign of slowing down!

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• Both number and mass distributions are important parameters for environment assessments– Health of the environment– Effectiveness of mitigation and remediation measures

• Other factors, such as threat to critical space assets need to be considered as well

Key Messages

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How Much Junk Is Currently Up There?

• Due to high impact speed in space (~10 km/s in LEO), even sub-millimeter debris pose a realistic threat to human spaceflight and robotic missions 1-cm Al sphere @ 10 km/s = 400 lb safe @ 60 mph 5-mm Al sphere @ 7 km/sec could penetrate a 2.54 cm thick Al wall

• Total mass: ~6300 tons LEO-to-GEO (~2700 tons in LEO)

Softball size or larger (≥10 cm): ~20,000 to 22,000(tracked by the U.S. Space Surveillance Network, SSN)

Marble size or larger (≥1 cm): ~500,000

Dot or larger (≥1 mm): >100,000,000(a grain of salt)

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Knowledge of the Historical and Current Environment

• For the ≥10 cm population– The sources and components (including the large and massive

rocket bodies and spacecraft) are well understood• Good historical launch records• The U.S. Space Surveillance Network tracks and maintains the orbits

of the objects in the U.S. satellite catalogs

• For the ~5-mm to 1-cm population– The sources and components are NOT well characterized

• Only limited data are available based on statistical sampling of a small fraction of the environment

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The Orbital Debris Family

10 m 100 m 10 cm 1 m 10 m1 mm 1 cm

Size (diameter)

R/Bs, S/C

Breakup Fragments

Al2O3 (slag)Al2O3

NaK

Paint Flakes MLI Pieces

Objects in the Near-Earth Environment

(Boundaries are notional)


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Current NASA Orbital Debris Database

10 m 100 m 10 cm 1 m1 mm 1 cm

Particle Diameter

100

1000

10,000

36,000

10 m

2000

Goldstone radars(>32.2º)

Haystack radar(>30º)

Haystack Auxiliary (HAX) radar (>42.6º)

U.S. Space Surveillance Network

HST-WFPC2 (580x610 km, 93-09)

STS (300x400 km, 95-11)

(Boundaries are notional)

MODEST telescope

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Modeling the Future Orbital DebrisPopulation Growth

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Predicting the Future

• Key uncertainties in environment projection– Initial population– Future sources

• Rocket bodies and spacecraft (launch frequency, orbits, masses, dimensions, materials, mission lifetimes, etc)

• Fragmentation debris (breakup frequency and outcome)• Non-fragmentation debris

– Solar activity– Post-mission disposal compliance– Monte Carlo approach

Two general approaches for future projection:– Examine extreme cases to bound the problem– Analyze nominal cases based on reasonable assumptions

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0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150 2170 2190 2210

Effective Num

ber of O

bjects (>10

cm)

Year

LEO Environment Projection (averages of 100 LEGEND MC runs)

Reg Launches + 90% PMD



(Liou, Adv. Space Res, 2011)

A good implementation of the commonly-adopted mitigation measures and an ADR of about five objects per year can “stabilize the future environment”

Controlling Debris Growth with ADR

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About the “Five Objects Per Year”

• The “removing five objects per year can stabilize the LEO environment” conclusion is somewhat notional. It is intended to serve as a benchmark for ADR planning.

• Assumptions in the LEGEND ADR simulations– Nominal launches during the projection period– A 90% compliance of the 25-year rule and no future

explosions– ADR operations start in 2020– Target selection is based on each object’s mass and Pcoll

– No operational constraints on target selection– Immediate removal of objects from the environment– Average solar activity cycle

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Approach Adopted for the IADC Studies

• Reasonable assumptions– Future launches can be represented by a recent eight-year

traffic cycle, average spacecraft mission lifetime is 8 years, explosions can be minimized, good compliance of the 25-year rule, etc.

• Best available tools from each participating agency– Each participating member agency uses its official/best models

for the solar flux prediction, orbit propagation, collision probability calculation, and satellite breakups

• Nominal cases– Monte Carlo results are analyzed– Study conclusions are drawn from the nominal/average results

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Analyzing the Monte Carlo Results

• Options to present Monte Carlo simulation results– Averages– Averages with ’s– Tabular format– Scatter plots– Distributions– Averages and extremes– Individual projections– Others

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Examples

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Additional Difficulty for Modeling Small Debris Population

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

400 500 600 700 800 900 1000 1100 1200

Num

ber o

f Objects per 50 km

Bin

Altitude (km)

Evolution of Cosmos 2251 Fragments (5 mm to 1 cm)

2009 (~163,000)

2011 (~100,000)

2013 (~87,000)

2015 (~67,000)

2017 (~59,000)

2019 (~43,000)

− At any given altitude below ~900 km, small debris continue to “rapidly” spiral toward lower altitude, and the same region continues to be replenished by debris spiraling down from higher altitude

− The small debris environment is highly dynamic and could have strong short-term (i.e., monthly to yearly) episodic variations

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Concluding Remarks

• Future environment projection is a difficulty task

• There exist different approaches to provide insights into the future to guide the development of mitigation and remediation measures

• Any study results must be clearly presented with the assumptions and the Monte Carlo nature of the outcome

• In reality, the assessments of the environment and the need for remediation efforts must be evaluated on a regular basis

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