Space Debris Environment Impact Rating System

1 University of Southampton2 PHS Space Ltd.

H.G. Lewis1, S.G. George1, B.S. Schwarz1 &

P.H. Stokes2

Introduction: ACCORD • FP7-funded project: University of Southampton & PHS Space

Ltd. • Aims:

– Provide a mechanism for communicating the efficacy of current debris mitigation practices

– Identify opportunities for strengthening European capability • Activities:

– Surveying the capability of industry to implement debris mitigation measures

– Reviewing the capacity of mitigation measures to reduce debris creation

– Combining capability and capacity indicators within anenvironment impact rating system

Alignment of Capability and Capacityfor the Objective of Reducing Debris

Environment Impact Rating System• Tool to evaluate how spacecraft design & operation impacts

the long-term debris environment• Communicate how mitigation measures and good design

practices can improve environmental impact• Based on a single score:

– Combines measures of compliance, capacity and capability of various mitigation techniques

– Incorporates current state of debris environment• Final system will be available online as voluntary (and

confidential) tool for industry• A prototype rating system for the LEO environment is

presented here

Environment Impact Rating SystemTwo aspects:1. Space “Health” Index

– Provides context and calibration forenvironmental impact rating

– Score out of 100

2. Environmental Impact Rating– Measure effect of future spacecraft on debris

environment– Input data provided by manufacturer/operator– Score out of 100

4

“Health” Index

Environmental Impact Rating

Calibration

1.

2.

User InputsSPACECRAFT DATA, APPLIED

MITIGATION MEASURES

“Health” ~

Assess the “health” of the space environment with respect to 2 goals:

1. Widespread Implementation of Mitigation MeasuresA. Protection of ServiceB. Legacy of Service

2. Benign Space Debris Environment

For each goal, the index calculates a score (out of 100), which is a measure of how well the goal has been realised

1. Space “Health” Index

Leads to a measure of a “healthy” space environment to be used in the impact rating calculation

A measure of the long-term sustainability of outer space activities

1. Space “Health” IndexOutside influences affect achievement of goal:

– ‘Pressures’ cause deviation away from goal

– ‘Resiliences’ direct status towards goal

For each goal, the index calculates:• ‘Present’ status

measured value, relative to a defined reference point

• Predicted ‘Near-Future’ status estimated using trend of status over previous 5 years, pressures and resiliences

6Technique adapted from Ocean Health Index Halpern et al. (2012, Nature)

Goal

Present Status

Near-Future Likely Status

Measured Value

ReferencePoint

5 YearTrend

PressuresResiliences

1. Space “Health” Index• Focus, to-date, on LEO: divided into 35 regions:

– 7 altitude bands (categorised by perigee)– 5 inclination bands:

• Equatorial (0º-19º)• Intermediate (20º-84º)• Polar (85º-94º)• Sun-Synchronous (95º-103º)• Retrograde (104º-180º)

• “Health” score derived for each goal in each region

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Combined to give overall “health” of LEO

(deg)

Goal 1A: Protection of ServiceCompliance with mitigation guidelines & good practices that are implemented to avoid loss during operations

– Impact shielding, collision avoidance• Reference:

– 100% compliance for all measures by all spacecraft in region• Pressures:

– Technical and financial challenges• Resiliences:

– Availability of data, tools, techniques and supporting guidelines• Source of Data:

– ACCORD industry survey, ACCORD compliance analysis

Goal 1B: Legacy of ServiceCompliance with mitigation guidelines & good practices that are implemented to preserve the space environment

– Post-mission disposal, passivation, limiting release of MRO• Reference:

– 100% compliance for all measures by all spacecraft in region• Pressures:

– Technical and financial challenges• Resiliences:

– Availability of data, tools, techniques and supporting guidelines• Source of Data:

– ACCORD industry survey, ACCORD compliance analysis

Goal 2: Benign Space Debris EnvironmentCurrent state of the debris environment and future trends:

– Number of ≥ 10 cm debris objects• Reference:

– Population of objects ≥ 10 cm on 1st May 2009– Population of objects ≥ 10 cm on 1st May 2014 (no collisions

scenario)• Pressures:

– Technical and financial challenges of implementing mitigation measures

• Resiliences:– The requirement to comply with mitigation guidelines and

standards• Source of Data:

– MASTER 2009 population and DAMAGE future projection

Data SourcesDAMAGE Simulations:

– Capacity of mitigation measures to limit creation of further debris• 16 Mitigation scenarios (PMD, PASS, MRO, CA; plus

combinations)• Effectiveness of mitigation measure normalised between 0 (no

mitigation) and 1 (full mitigation) in terms of no. objects & no. catastrophic collisions

ACCORD Industry Survey– Technical and financial challenge of implementing mitigation

measures (Capability)• Survey responses normalised to give score between 0 and 1

– Level of implementation of mitigation measures among spacecraft manufacturers and operators

• Survey responses normalised to give score between 0 and 1 11

Data Sources

http:// www.fp7-accord.eu

Quantify impact of a prospective spacecraft on the space environment

User-Specified Inputs(for prospective spacecraft):

– On-Orbit Mass– Perigee Altitude– Orbital Inclination– Mitigation Measures

Implemented– How Individual Measures

are Implemented in Design

Lead to: 3 parameters, which combine togive single score for spacecraft (out of 100)

2. Environmental Impact Rating

Defines LEO

Region

Orbit DataAltitude

Inclination

Mitigation Measures

Used

How Mitigation

Measures are Implemented

UserInputs

Rating Calculation

Rating Parameters:1. Debris score for the prescribed

orbital region (how “crowded” the region is)

2. The capacity of appliedmitigation measures to limit the generation of new debris (from DAMAGE)

3. How the prospective spacecraftaffects the “health” index in thegiven orbital region (re-calculate “health” index)

2. Environmental Impact Rating

Environmental Impact Rating

Defines LEO

Region

Orbit DataAltitude

Inclination

Mitigation Measures

Used

How Mitigation

Measures are Implemented

UserInputs

Crowding of Debris in

LEO Region

Capacity of Mitigation to Limit Future

Debris

Modification to “Health”

Index for LEO Region

“Health”Index

All scores expressed out of 100

Example:Generic Earth Observation Spacecraft

Inputs:• Mass: 1000kg• Altitude: 795km• Inclination: 98

Applied Mitigation Measures:

• Collision Avoidance• Passivation• Limiting MRO Release

Impact Rating: 23 %

Change in “health” of region:Change in “health” of LEO:

Suggested ‘actions’ to improve rating

+0.16 %+0.01%

Representative ‘Certificate’

Conclusions and Future Work• A prototype Environmental Impact Rating System for space

systems has been developed comprising two aspects:– Space “Health” Index– Environmental Impact Rating

• Based on data gathered from industry and other sources, in addition to simulations performed using DAMAGE

• Future work:– Improve the assumptions made in the prototype– Community and industry engagement is anticipated (and

welcomed) to address these assumptions and ensure the applicability of the finished system

– Final system will be implemented in a web-tool and hosted client-side to ensure privacy

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Contact:

Dr. Hugh G. LewisAstronautics Research Group

University of SouthamptonUnited Kingdom

E: hglewis@soton.ac.ukT: +44 (0) 23 8059 3880

W: http://www.soton.ac.uk/~hglewis

http:// www.fp7-accord.eu

Funding provided by the European Union Framework 7 Programme (Project No. 262824). Thanks to Carsten Wiedemann (TU Braunschweig), Adam White (University of Southampton), Richard Tremayne-Smith, and Holger Krag (ESA Space Debris Office)