NASA-STD-8719.14B.pdf

Approved: 2019-04-25

MEASUREMENT SYSTEM

IDENTIFICATION: Metric

NASA TECHNICAL STANDARD

NASA-STD-8719.14B

National Aeronautics and Space Administration

Approved: 2019-04-25 Superseding NASA-STD-8719.14A

Process for Limiting Orbital Debris

NASA-STD-8719.14B – 2019-04-25

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DOCUMENT HISTORY LOG

Status Document

Revision Approval Date Description

Baseline 2007-08-28 Initial Release

Change Change 1 2007-09-06 Administrative correction to remove supersession

Change 2 2009-06-10 Update to clarify requirements with respect to update of NPR 8715.6A (with Change 1) and

NASA-HDBK 8719.14. Clarification of battery passivation and required ODAR/EOMP signatures.

JWL4

Change 3 2009-07-23 Update to clarify requirement for battery passivation in paragraph 4.4.4.1.2.g.

JWL4

Change 4 2009-09-14 Administrative update to add hyperlinks to

SMARTS data system for Chapters 1 & 4.

JWL4

Rev A 2011-12-08 Text clarification: 1.2.e-i, 2.1.2, 2.2, 4.4.4.1.2, 4.6.2.2/.3, 4.7.1.d, A.3 (Sect 2)

Removed duplicate requirements in various paragraphs, removed Preliminary EOMP

(B.1.1), and removed App C, D, & E

Additional requirements: Pre-Acquisition and

Small Sat ODARs: 3.3, 4.2.1.j/.k; A.4, A.5;

Hazardous materials: 4.7.1.b, 4.7.3.f, 4.7.4.i./.j, 4.7.5.e, A.1 (Sections 7A & 14A), A.3 Table A.3-

1 (Section 7A), & B.1 (Section 7A)

JWL4

Change 1 2012-05-25 Administrative update to add hyperlinks to

SMARTS data system for paragraphs 4.2.1, 4.6.1, A.1, A.3, A.4, and B.1.

Administrative update to remove references to requirement 4.6-5 which was deleted in

Revision A in paragraphs 4.6.c, 4.6.3, 4.4.4, A.1.6 Section 6, & B.1.5 Section 6.

Administrative typo correction in B.1.5 Front.

Administrative update of a few paragraph formats.

JWL4

Revision

B

2019-04-25 Revised to make compatible with NPR 8715.6

Revision B

a) Material in NPR 8715.6A, but removed from or relocated within NPR 8715.6B, expands previous regions where policy is applicable to include stable Sun-Earth and Earth-Moon

Lagrange points, and Lunar and Mars orbit, simplifies the documentation content and delivery schedule, and the required signatures at different stages of certain document deliveries

b) Miscellaneous small edits

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TABLE OF CONTENTS

DOCUMENT HISTORY LOG

TABLE OF CONTENTS

LIST OF APPENDICES

LIST OF FIGURES

LIST OF TABLES

1. SCOPE

1.1 Purpose

1.2 Applicability

2. APPLICABLE AND REFERENCE DOCUMENTS

2.1 Applicable Documents

2.2 Reference Documents

3. ACRONYMS AND DEFINITIONS

3.1 Acronyms

3.2 Definitions

4. REQUIREMENTS

4.1 Objectives of Orbital Debris Assessments and Planning

4.2 Conducting Debris Assessments: An Overview

4.3 Assessment of Debris Released During Normal Operations

4.4 Assessment of Debris Generated by Explosions and Intentional Breakups

4.5 Assessment of Debris Generated by On-orbit Collisions

4.6 Postmission Disposal of Space Structures

4.7 Assessment of Debris Surviving Atmospheric Reentry

4.8 Additional Assessment Requirements for Tether Missions

LIST OF APPENDICES

ORBITAL DEBRIS ASSESSMENT REPORTS (ODAR)

EOMPS

LIST OF FIGURES

Figure 4.3-1. Apogee vs. Perigees for 25 Year Decay With F(10.7) = 100 and 150 Figure 4.6-2. IADC Rationale for GEO minimum perigee equation Figure A.2-3. PDR/CDR ODAR Review Check Sheet

Figure A.2-4. Final ODAR Review Check Sheet (2 Pages) Figure B.2-1. In-Flight EOMP Review Check Sheet

LIST OF TABLES

Table 4.2-1. Orbital Debris Technical Area Organization Table 4.2-2. Orbital Debris Technical Area Issues and Corresponding Requirements Table A.3-1. Mandatory Sections in an Abbreviated ODAR

PROCESS FOR LIMITING ORBITAL DEBRIS

1. SCOPE

1.1 Purpose

1.1.1 This document serves as a companion to NPR 8715.6 and provides specific technical requirements for limiting orbital debris and methods to comply with the NASA requirements for limiting orbital debris generation. This standard helps ensure that spacecraft and launch vehicles meet acceptable standards for limiting orbital debris generation.

1.1.2 This standard is primarily designed to limit the creation of new orbital debris and, therefore, to limit the risk to other current and future space missions. The methodologies described herein can be used by programs and projects to evaluate and to improve their own mission reliability and success with respect to vulnerabilities associated with the orbital debris and meteoroid environment. The assessments described in this standard are required per NPR

8715.6 and are reviewed for completeness as a part of the flight approval processes.

1.1.3 This standard details requirements for (1) limiting the generation of orbital debris, (2) assessing the risk of collision with existing space debris, (3) assessing the potential of space structures to impact the surface of the Earth, and (4) assessing and limiting the risk associated with the End of Mission (EOM) of a space object. In addition to requirements in Section 4 and methods for assessment, this standard provides the format for the required debris assessment and reports which must be submitted to the Office of Safety and Mission Assurance as required in

NPR 8715.6.

Note: NASA-HDBK-8719.14 serves as a reference document to assist orbital debris practitioners and program/project management in understanding orbital debris. Topics in NASA-HDBK-8719.14 include the orbital debris environment, measurements, modeling, shielding, mitigation, and reentry. It is strongly encouraged that the NASA-

HDBK be used with the implementation of NPR 8715.6 and NASA-STD-8719.14.

1.1.4 This document is primarily intended for use in assessing orbital debris that is in Earth orbit. For spacecraft and launch vehicles traveling beyond Earth orbit, the beginning of Sections

4.3-4.8 state how the requirements in this standard are applicable.

1.2 Applicability

1.2.1 This standard is applicable to NASA Headquarters (HQ) and NASA Centers, including

Component Facilities and Technical and Service Support Centers. This standard applies to the Jet

Propulsion Laboratory (a Federally-Funded Research and Development Center), other contractors, recipients of grants and cooperative agreements, and parties to other agreements only to the extent specified or referenced in the applicable contracts, grants, or agreements.

1.2.2 This standard is applicable to programs and projects responsible for NASA or NASA-sponsored objects launched into space as set forth in NPR 8715.6. This standard only applies to objects which will exceed 130 km (~70 mi) in altitude and achieve or exceed Earth orbital velocity.

Note 1: Sponsored by NASA are those objects developed or operated by NASA, under contract from NASA, or under agreement with NASA.

Note 2: The National Space Transportation Policy of 2013, gives the Department of

Transportation (DOT) the authority to oversee orbital debris mitigation practices for

Federal Aviation Administration (FAA)-licensed launches. Furthermore, for the purpose of this standard, NASA is not a sponsor of launch vehicles furnished by the

Department of Defense or foreign partners.

Note 3: NASA missions, spacecraft, and launch vehicles that were under contracts or passed Preliminary Design Review prior to the release of this standard may follow the requirements in NASA-STD-8719.14A.

1.2.3 Any decision to waive or vary from the requirements in this standard requires the concurrence of the Chief, Safety and Mission Assurance (SMA).

1.2.4 In this standard, "shall" denotes a mandatory requirement, "may" denotes a discretionary privilege or permission, “can” denotes statements of possibility or capability, "should" denotes a good practice, and "will" denotes an expected outcome.

1.2.5 NPR 7120.5 and NPR 8715.6 require the use of this document for development of

Orbital Debris Assessments (ODA), Orbital Debris Assessment Reports (ODAR), and End of

Mission Plans (EOMP).

2. APPLICABLE AND REFERENCE DOCUMENTS

2.1 Applicable Documents

2.1.1 General

If there is a conflict between a requirement in this NASA standard and the requirements of an applicable NASA Procedural Requirement (NPR) or NASA Policy Directive (NPD), the requirement in the NPD or NPR will always take precedence over the requirement of this standard. The applicable documents are accessible via the NASA Online Directives Information

System at https://nodis3.gsfc.nasa.gov/ or the NASA Technical Standards System at https://standards.nasa.gov or may be obtained directly from the Standards Developing

Organizations or other document distributors.

2.1.2 Government Documents

NPD 1000.5 Policy for NASA Acquisition

NPD 8010.3 Notification of Intent to Decommission or Terminate

Operating Space Systems and Terminate Missions https://nodis3.gsfc.nasa.gov/ https://standards.nasa.gov/

NPD 8020.7 Biological Contamination Control for Outbound and

Inbound Planetary Spacecraft

NPR 7120.5 NASA Space Flight Program and Project Management

Requirements

NPR 8020.12 Planetary Protection Provisions for Robotic Extraterrestrial

Missions

NPR 8715.3 NASA General Safety Program Requirements

NPR 8715.6 NASA Procedural Requirements for Limiting Orbital

Debris and Evaluating the Meteoroid and Orbital Debris

Environments

NASA-HDBK-8719.14 Handbook for Limiting Orbital Debris

2.2 Reference Documents

The documents listed in this section contain supporting information to assist in the implementation of this standard as cited in the text of Section 4.

United Nations Document V.09-88517, UN Space Debris Mitigation Guidelines of the

Committee on the Peaceful Use of Outer Space, January 2010. Available at http://www.unoosa.org/pdf/publications/st_space_49E.pdf

National Space Policy of the United States of America (June 2010); available at https://obamawhitehouse.archives.gov/sites/default/files/national_space_policy_6-28-

10.pdf

Space Policy Directive-3, National Space Traffic Management Policy (June 2018), available at https://www.whitehouse.gov/presidential-actions/space-policy-directive-3-national-space-traffic-management-policy/

U.S. Government Orbital Debris Mitigation Standard Practices, February 2001.

Available at http://orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf

U.S. Air Force Space and Missile Center (SMC) Orbital Debris Handbook, (July, 2002)

(https://apps.dtic.mil/dtic/tr/fulltext/u2/a435172.pdf).

JSC-27862, Postmission Disposal of Upper Stages (December 1998) (available through the NASA Orbital Debris Program Office (ODPO)).

Debris Assessment Software (DAS)

(https://www.orbitaldebris.jsc.nasa.gov/mitigation/das.html).

http://www.unoosa.org/pdf/publications/st_space_49E.pdf https://obamawhitehouse.archives.gov/sites/default/files/national_space_policy_6-28-10.pdf https://obamawhitehouse.archives.gov/sites/default/files/national_space_policy_6-28-10.pdf http://orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf https://apps.dtic.mil/dtic/tr/fulltext/u2/a435172.pdf https://www.orbitaldebris.jsc.nasa.gov/mitigation/das.html

Inter-Agency Space Debris Coordination Committee (IADC-02-01) Space Debris

Mitigation Guidelines, September 2007

(http://www.iadc-online.org/index.cgi?item=docs_pub).

3. ACRONYMS AND DEFINITIONS

3.1 Acronyms

CARA Conjunction Assessment Risk Analysis

CDR Critical Design Review

CSpOC Combined Space Operations Center (Formerly JSpOC)

DAS Debris Assessment Software

DCA Debris Casualty Area

EOM End of Mission

EOMP End of Mission Plan

GEO Geosynchronous Earth Orbit

GTO Geosynchronous Transfer Orbit

HQ Headquarters

IADC Inter-Agency Space Debris Coordination Committee

JSpOC Joint Space Operations Center

LEO Low Earth Orbit

MEO Medium Earth Orbit

MMOD Micrometeoroids and Orbital Debris

ODA Orbital Debris Assessment

ODAR Orbital Debris Assessment Report

ODPO NASA Orbital Debris Program Office

OSMA Office of Safety and Mission Assurance

PDR Preliminary Design Review

PPO Planetary Protection Office http://www.iadc-online.org/index.cgi?item=docs_pub

SMA Safety and Mission Assurance

SSO Sun Synchronous Orbit

TOPO Trajectory Operations Planning Office

3.2 Definitions

Apogee: The point in the orbit that is the farthest from the center of the Earth. The apogee altitude is the distance of the apogee point above the surface of the Earth.

Ascending Node: The point in the orbit where a satellite crosses the Earth's equatorial plane in passing from the southern hemisphere to the northern hemisphere.

Credible Failure Mode: A failure mode identified by failure mode and effects analyses or equivalent analyses, for which a quantitative failure probability is available and exceeds 0.000001 (1:1,000,000).

Decommissioning: The process of closing out the mission, including data archiving, hardware logistics, and management issues. Decommissioning follows passivation of the spacecraft.

Disposal: An end-of-mission process for moving a spacecraft (if necessary) to an orbit or trajectory considered acceptable for orbital debris limitation.

Earth Orbital Velocity: Any velocity perpendicular to the Earth’s radius vector at or above 130 km that is in excess of 7,826 m/sec.

Eccentricity: The apoapsis altitude minus periapsis altitude of an orbit divided by twice the semi-major axis. Eccentricity is zero for circular orbits and less than one for all elliptical orbits.

Geosynchronous Earth Orbit (GEO): A circular GEO with 0° inclination is a geostationary orbit about the Earth; i.e., the nadir point is fixed on the Earth’s surface.

The nominal altitude of a circular GEO is 35,786 km and the nominal inclination range is +/- 15 degrees latitude.

Geosynchronous Transfer Orbit (GTO): A highly eccentric orbit with perigee normally within or near the LEO region altitude and apogee near or above GEO altitude.

Inclination: The angle an orbital plane makes with the Earth’s equatorial plane.

Launch Vehicle: Any space transportation mode, including expendable launch vehicles

(ELVs), and reusable launch vehicles (RLVs).

Low Earth Orbit (LEO): An orbit with a mean altitude less than or equal to 2,000 km, or equivalently, an orbit with a period less than or equal to 127 minutes.

Meteoroids: Naturally occurring particulates associated with solar system formation or evolution processes. Meteoroid material is often associated with asteroid breakup or material released from comets.

Mission Operations: Phase of a mission where the spacecraft is performing a useful function, including the design mission, primary mission, secondary mission, extended mission, and activities leading to disposal.

Orbital Debris: Artificial objects, including derelict spacecraft and spent launch vehicle orbital stages, left in orbit which no longer serve a useful purpose. In this document, only debris of diameter 1 mm and larger is considered. If liquids are to be released, they should explicitly be shown to be compliant with all mitigation requirements.

Orbital Lifetime: The length of time an object remains in orbit. Objects in LEO or passing through LEO lose energy as they pass through the Earth’s upper atmosphere, eventually getting low enough in altitude that the atmosphere removes them from orbit.

Orbital Stage: A part of the launch vehicle left in a parking, transfer, or final orbit

(excluding solar/interplanetary orbits with no potential intercept with Earth) during or after payload insertion; includes liquid propellant systems, solid rocket motors, and any propulsive unit jettisoned from a spacecraft.

Passivation: The process of removing stored energy from a space structure which could credibly result in eventual generation of new orbital debris after End of Mission. This includes removing energy in the form of electrical, pressure, mechanical, or chemical.

Perigee: The point in the orbit that is nearest to the center of the Earth. The perigee altitude is the distance of the perigee point above the surface of the Earth.

Postmission Disposal: The process of intentionally changing the orbit of a spacecraft after the end of the operational mission.

Prompt Injury: A medical condition received as a result of the falling debris which requires (or should have required) professional medical attention within 48 hours of the impact.

Right Ascension of Ascending Node: The angle between the line extending from the center of the Earth to the ascending node of an orbit and the line extending from the center of the Earth to the vernal equinox, measured from the vernal equinox eastward in the Earth’s equatorial plane.

Semi-major Axis: Half the sum of the distances of apogee and perigee from the center of the Earth (or other body) equal to half the length of the major axis of the elliptical orbit.

Spacecraft: This includes all components contained within or attached to a space borne payload such as instruments and fuel.

Space Debris: General class of debris, including both meteoroids and orbital debris.

Space Structures: Spacecraft and launch vehicle orbital stages. This includes all components contained within the object such as instruments and fuel.

Stabilized: When the spacecraft maintains its orientation along one or more axes.

Sun Synchronous Orbit (SSO): An orbit in which the angle between the Sun-Earth vector and the intersection of the plane of a satellite's orbit and the Earth's equator is a constant and does not change with the season.

Tether: A long flexible structure greater than 300 meters in length. Tethers can have a variety of purposes, but are typically used electro-dynamically for power generation or to impart changes in linear or angular momentum.

Note: Despite their slender nature, such structures have significant projected areas which, combined with their small cross sections, make them highly vulnerable to being cut or damaged. Such damage may compromise the ability to successfully retract/stow the entire tether. Due to their length, tethers present problematic issues for conjunction analyses and avoidance maneuvers.

Vernal Equinox: The direction of the Sun in space when it passes from the southern hemisphere to the northern hemisphere (on March 20 or 21) and appears to cross the

Earth’s equator. The vernal equinox is the reference point for measuring angular distance along the Earth’s equatorial plane (right ascension) and one of two angles usually used to locate objects in orbit (the other being declination).

4. REQUIREMENTS

4.1 Objectives of Orbital Debris Assessments and Planning

4.1.1 It is U.S. and NASA policy to limit the generation of orbital debris, consistent with mission requirements and cost effectiveness. NPR 8715.6 requires that each program or project conduct a formal assessment for the potential to generate orbital debris.

4.1.2 The NASA Orbital Debris Program Office (ODPO) supports programs and projects with orbital debris assessments. The SMA organization at each Center and NASA HQ can also assist programs and projects with the preparation of the required ODARs and EOMPs.

4.1.3 Section 4.2 of this standard requires that programs and projects use the orbital debris modeling tools provided (or agreed to) by the NASA ODPO in assessing orbital debris generation and risk in Earth orbit.

4.2 Conducting Debris Assessments: An Overview

4.2.1 The main objective of the NASA Orbital Debris Program is to limit the generation of debris in Earth orbit and limit the risk to human life due to generated orbital debris through prevention and analyses. Debris can damage other spacecraft, force spacecraft to perform evasive maneuvers, induce degraded capability to meet mission objectives, and become a hazard to people in orbit and to people on the ground. In addition to limiting generation of debris in Earth orbit, NPR 8715.6 requires that the generation of debris be limited in lunar orbit, in Mars orbit, and in the vicinity of Sun-Earth or Earth-Moon Lagrange Points. This NASA standard specifies and tailors the processes and validations necessary to meet the intent of that directive in each of the specified environments.

4.2.2 Limiting orbital debris involves the following:

a. Limiting the generation of debris associated with normal space operations;

b. Limiting the probability of impact with other objects in orbit;

c. Limiting the consequences of impact with existing orbital debris or meteoroids;

d. Limiting the debris hazard posed by tether systems;

e. Depleting to a non-explosive potential all onboard energy sources after completion of mission;

f. Limiting orbital lifetime in Low Earth Orbit (LEO), Geosynchronous Earth Orbit (GEO), Lunar, Mars, or stable Earth-Moon or Sun-Earth Lagrange points after mission completion or maneuvering to a disposal orbit; and

g. Limiting the human casualty risk from space system components surviving reentry as a result of postmission disposal.

4.2.3 This document, along with the associated current version of Debris Assessment

Software (DAS) or the higher fidelity Object Reentry Survival Analysis Tool (ORSAT), maintained by the NASA ODPO located at the Johnson Space Center (JSC), and the Bumper code maintained by the NASA Hypervelocity team, is to be used by the program or project manager as the primary reference in conducting orbital debris assessments. Alternate tools and models may be employed to satisfy the assessment requirements in limited circumstances, with approval from OSMA prior to the assessment.

4.2.3.1 Approved environmental models for the assessments are ORDEM 3.0 for orbital debris and MEMR2 for meteoroids.

4.2.4 ODA and ODARs

4.2.4.1 The detailed requirements and evaluation methods for ODARs are presented in

Sections 4.3 through 4.8.

4.2.4.2 The orbital debris assessment covers the following broad areas:

a. The potential for generating debris during normal operations or malfunction conditions;

b. The potential for generating debris from a collision with debris or orbiting space systems;

c. Postmission disposal.

4.2.4.3 These broad areas are categorized into six issues that are addressed in the assessment:

a. Debris released during normal operations;

b. Debris generated by explosions and intentional breakups;

c. Debris generated by on-orbit collisions during mission operations;

d. Reliable disposal of spacecraft and launch vehicle orbital stages after mission completion;

e. Structural components impacting the Earth following postmission disposal by atmospheric reentry;

f. Debris generated by on-orbit collisions with a tether system.

4.2.4.4 The assessment is organized in an ODAR using Appendix A.1.

4.2.4.5 ODAs being performed on components or portions of a spacecraft are documented in the Abbreviated ODAR using Appendix A.3.

4.2.4.6 It is strongly encouraged that programs limit the regeneration of existing programmatic assessments, but rather include them as an attachment to the ODAR.

4.2.4.7 NPR 8715.6 specifies the timing of deliveries of ODARs to NASA.

4.2.4.8 Although the first detailed ODAR is not required until Preliminary Design

Review (PDR), an “Initial ODAR” is required for each project to assist NASA management in considering potential orbital debris issues during Mission Concept Review (MCR) to estimate and minimize potential cost impacts.

4.2.4.9 ODAs being performed on space systems during a project’s Phase A are documented in the Initial ODAR using Appendix A.4.

4.2.4.10 NASA International Space Station (ISS) payloads that remain encapsulated by or permanently mounted on the ISS or other spacecraft are exempted from performing orbital debris assessments. Debris assessments are also not required of payloads that are temporarily installed outside the ISS and later returned as cargo in a vehicle. Debris assessments are required of NASA payloads and components that are expected to be released (jettisoned or deployed) from the ISS.

4.2.4.11 NASA Exploration vehicle payloads that remain encapsulated by or permanently mounted on the vehicle are exempted from debris assessments. Debris assessment requirements do not apply to payloads that are temporarily installed outside the vehicle. Debris assessments are required of NASA payloads and components that are expected to be released (jettisoned or deployed) from the Exploration vehicles.

4.2.5 EOMP

4.2.5.1 An EOMP is developed for limiting debris generation and limiting risk to the public and other active spacecraft during decommissioning, and disposal of all operational space objects.

4.2.5.2 The EOMP is a living document. It is maintained throughout mission operations to ensure that operational use does not preclude a safe decommissioning and disposal. The

EOMP identifies milestones in the operational life of the mission which affect the EOM processing. After those milestones, the EOMP and the health of the critical items defined in the EOMP should be evaluated and updated so that NASA management understands the constraints and options available at EOM for limiting orbital debris.

4.2.5.3 The EOMP is organized using Appendix B, Section B.1.

4.2.5.4 The EOMP contains statements covering what actions must be undertaken in the event of reductions of capabilities or consumables which may significantly and predictably threaten the ability to carry out the planned EOM disposal. This includes reduction of system capability to “single string” unless expressly agreed otherwise. Such actions are not intended to represent binding "trigger points" for disposal, but rather an identification and planning for disposal-critical parameters.

4.2.5.5 It is strongly encouraged that programs limit the regeneration of existing programmatic information, but rather include the ODAR and other assessments as attachments.

4.2.5.6 NPR 8715.6, Section 3.2.11, Table A specifies the timing of deliveries of EOMPs to NASA.

4.2.5.7 An EOMP may include other aspects of the EOM process (final disposition of data and hardware, for example) if the program finds that the EOMP is the most convenient means of recording this information. Other applicable sections may be placed after the sections specified in Appendix B.

4.2.6 Structure of the Requirements in this Document

4.2.6.1 Each of Sections 4.3 through 4.8 covers a separate orbital debris technical area.

Table 4.2-1 defines the organization for each technical area. Table 4.2-2 lists each orbital debris technical area.

Note: In Table 4.2-1, the ‘4.x’ is a pointer to Sections 4.3 to 4.8.

Table 4.2-1. Orbital Debris Technical Area Organization

Section 4.x.1 Definition of the Area

Section 4.x.2 Requirements for the Area

Section 4.x.3 Rationale for the Area Requirements

Section 4.x.4 Methods to Assess Compliance

Section 4.x.5 Brief Summary of Mitigation Measures Used in NASA for this Area

4.2.6.2 The sections titled "Method to Assess Compliance" (Sections 4.x.4) provide detailed steps for how compliance with each requirement is determined and measured. Actual compliance can be verified with the specially designed DAS for operations in Earth orbit.

Both the software and its documentation can be downloaded from the NASA ODPO website at https://orbitaldebris.jsc.nasa.gov/mitigation/das.html. NASA ODPO contact personnel are also identified on this web site. The models in DAS support the approach and techniques described in this standard. If methods or models other than DAS are used, a full description of the models used will need to be added to ODAR Front Matter (See Appendix A, Section

A.1.)

4.2.6.3 Table 4.2-2 provides a summary of each of the technical requirements which need to be addressed in the ODAR.

Table 4.2-2. Orbital Debris Technical Area Issues and Corresponding Requirements

Debris Assessment

Issues Reqm’t Requirement Summary Comments

Release of debris during normal mission operations

4.3-1 and

4.3-2

Limit number and orbital lifetime of debris passing through LEO

Limit lifetime of objects passing near GEO

Requirement includes staging components, deployment hardware, subsatellites, or other objects that are known to be released during normal operations.

Accidental explosions 4.4-1 and

4.4-2

Limit probability of accidental explosion during mission operations

Passivate to limit probability of accidental explosion after EOM

Requirement addresses systems and components such as range safety systems, pressurized volumes, residual propellants, and batteries.

Debris Assessment

Issues Reqm’t Requirement Summary Comments

Intentional breakups 4.4-3 and

4.4-4

Limit number, size, and orbital lifetime of debris larger than 1 mm and 10 cm (respectively)

Assess risk to other programs for times immediately after a test when the debris cloud contains regions of high debris density

Intentional breakups include tests involving collisions or explosions of flight systems and intentional breakup during space system reentry to reduce the amount of debris reaching the surface of the Earth.

Collisions with large objects during orbital lifetime

4.5-1 Assess probability of collision with intact space systems or large debris (>10cm)

Collisions with intact space systems or large debris may create a large number of debris fragments that pose a risk to other operating spacecraft. A significant probability of collision may necessitate design or operational changes.

Collisions with small debris during mission operations

4.5-2 Assess and limit the probability of damage to critical components as a result of impact with small debris

Damage by small debris impacts can result in failure to perform postmission disposal. A significant probability of damage may necessitate shielding, use of redundant systems, or other design or operational options.

Debris Assessment

Issues Reqm’t Requirement Summary Comments

Postmission disposal 4.6-1, 4.6-2, 4.6-3, and

4.6-4

Remove spacecraft and orbital stages from LEO to reduce collision threat to future space operations

Remove spacecraft and orbital stages from GEO to reduce collision threat to future space operations

Govern intermediate disposal orbits

Assess reliability of postmission disposal

Assess options for disposal beyond Earth’s orbit consistent with planetary protection requirements

The accumulation of spacecraft and orbital stages in Earth orbit increases the likelihood of future collisions and debris generation. The orbital lifetimes of spacecraft and orbital stages in LEO and near GEO must be limited.

The removal of objects at the

EOM is preferred, but specific disposal orbits may be used.

Reentry Debris

Casualty Risk

4.7-1 Limit number and size of debris fragments that survive atmospheric reentry

This requirement limits human casualty expectation.

Collision risk posed by tether systems

4.8-1 Assess the probability of collision with resident space objects and limit orbital lifetime

Mitigate the effects of severed tether systems

Tether systems may pose special collision hazards with other objects in orbit.

Severed tethers may create additional hazards and hinder disposal plans.

Requirement applicability is indicated in the introduction to each requirement area in Sections 4.3 – 4.8.

4.2.7 Deviations to ODARs and EOMPs

Any non-compliance to the requirements for ODAR and EOMPs stated in this standard requires

NASA management approval of a waiver per NPR 8715.6.

4.3 Assessment of Debris Released During Normal Operations

4.3.1 Definition of Released Debris Technical Area

4.3.1.1 Orbital debris analyses assess the amount of launch vehicle and spacecraft debris released in normal operations. This requirement area applies to all space structures while in

Earth or lunar orbit. Operators are encouraged to limit the release of debris while in Mars orbit or in the vicinity of Sun-Earth or Earth-Moon Lagrange Points.

4.3.1.2 The goal is that in all operational orbits, space systems are designed not to release debris during normal operations. Where this is not feasible, any release of debris needs to be minimized in number, area, and orbital lifetime.

4.3.1.3 Historically, debris has been released as an incidental part of normal space operations. This type of debris is referred to as operational or mission-related debris and includes such objects as sensor covers, tie-down straps, explosive bolt fragments, attitude control devices, and dual payload attachment fittings. Space systems need to be designed to avoid the creation of any operational or mission-related debris. If the release of debris is unavoidable, the release should be done in a manner that limits the risk to other users of space. Debris 1 mm in diameter (mass approximately 1 mg) and larger for LEO and 5 mm and larger for GEO is a source of concern because these debris have sufficient energy to critically damage an operating spacecraft. Large, and especially long-lived debris can create a cloud of secondary debris fragments in the event of a collision with another resident space object.

4.3.1.4 The probability of a future collision occurring with debris depends on the number and size of the debris and on the length of time the debris remains in orbit. The requirements, therefore, limit the total number of such debris objects and their orbital lifetimes. Debris released during normal operations includes debris released during launch vehicle staging, payload separation, deployment, mission operations, and EOM passivation/disposal.

Spacecraft and spent orbital stages, as intact structures, are not considered mission-related debris themselves and are addressed later in Sections 4.5 and 4.6. For the purpose of this standard, however, satellites smaller than a 1U standard CubeSat are treated as mission-related debris and follow the same requirements for mission-related debris from LEO to

GEO.

4.3.1.5 Small debris, such as slag which is ejected during the burning of a solid rocket motor and liquids dispersed from a spacecraft, are not covered by the requirements of this standard.

4.3.2 Requirements for the Control of Debris Released During Normal Operations

4.3.2.1 NASA policy is that all NASA programs and projects assess and limit the amount of debris released as a part of the mission. This requirement area applies to all space structures in Earth orbit that release items/objects into Earth orbit that are larger than 1 mm in

LEO and 5 mm in GEO. However, satellites smaller than a 1U standard CubeSat are treated as mission-related debris rather than satellites. Slag ejected during the burning of solid rocket motors, and liquids dispersed from a spacecraft, are not covered by these requirements.

4.3.2.2 Requirement 4.3-1: Debris passing through LEO – released debris with diameters of 1mm or larger:

a. Requirement 4.3-1a: All debris released during the deployment, operation, and disposal phases shall be limited to a maximum orbital lifetime of 25 years from date of release.

b. Requirement 4.3-1b: The total object-time product shall be no larger than 100 object-years per mission. For the purpose of this standard, satellites smaller than a 1U standard

CubeSat are treated as mission-related debris and thus are bound by this definition to collectively follow the same 100 object-years per mission deployment limit.

4.3.2.3 Requirement 4.3-2: Debris passing near GEO: For missions leaving debris in orbits with the potential of traversing GEO (GEO altitude +/- 200 km and +/- 15 degrees inclination), released debris with diameters of 5 mm or greater shall be left in orbits which will ensure that within 25 years after release the apogee will no longer exceed

GEO - 200 km or the perigee will not be lower than GEO + 200 km , and also ensures that the debris is incapable of being perturbed to lie within that GEO +/- 200 km and +/-

15 zone for at least 100 years thereafter. For the purpose of this standard, satellites smaller than a 1U standard CubeSat are treated as mission-related debris and thus are bound by this definition to follow this requirement.

4.3.3 Rationale for Released Debris Area Requirements

4.3.3.1 The intent of Requirement 4.3-1 is to remove debris in LEO from the environment in a reasonable period of time. The 25-year removal time from LEO limits the growth of the debris environment over the next 100 years while limiting the cost burden to programs and projects. The limit of 25 years has been thoroughly researched and has been accepted by the

U.S. Government and the major space agencies of the world.

4.3.3.2 Debris in orbits with perigee altitudes below 600 km will usually have orbital lifetimes of less than 25 years. This requirement will have the greatest impact on programs and projects with perigee altitudes above 700 km, where objects may remain in orbit naturally for hundreds of years.

4.3.3.3 Requirement 4.3-1b limits the total number of debris objects released while taking into account their orbital lifetimes. Based on historical precedent and practice, an acceptable level of risk for released debris damaging another operational spacecraft is <10-6 (over the life of the decay). The value of 100 object-years was chosen because debris released during normal operations following this requirement will have a probability on the order of 10-6 of hitting and potentially damaging an average operating spacecraft.

4.3.3.4 Examples of LEO debris are the cover (0.3 kg and ~0.2 m2) released from the

SABER instrument on the TIMED spacecraft which was launched in 2001, and the Delta 2

Dual Payload Attachment Fitting (DPAF) employed on the ICESAT and CHIPSAT mission of 2003. In both cases the debris were left in orbits of less than 630 km and decayed from orbit well within the 25-year requirement.

4.3.3.5 Debris that is not removed from GEO altitude may remain in the GEO environment for many thousands of years or longer. Therefore, Requirement 4.3-2 limits the accumulation of debris at GEO altitudes and will help mitigate the development of a significant debris environment, as currently exists in LEO. The 200 km offset distance takes into account the operational requirements of GEO spacecraft (see Section 4.6). Special orbit propagation models are necessary to evaluate the evolution of disposal orbits to ensure that debris do not later interfere with GEO, as a result of major perturbations, such as solar and lunar gravitational perturbations and solar radiation pressure.

4.3.4 Methods to Assess Compliance

4.3.4.1 Compliance with Section 4.3 requirements is documented in the ODAR and

EOMP for all items/objects larger than 1 mm in LEO and 5 mm in GEO planned for release during any phase of flight.

4.3.4.2 Debris Passing Through LEO: 25-Year Maximum Lifetime (Requirement 4.3-1a)

4.3.4.2.1 The amount of time a debris object will remain in orbit depends on its initial orbit, on the area-to-mass ratio of the debris, and on solar activity. For an object with an apogee altitude above 5,000 km, the orbit lifetime will also be affected by lunar and solar gravitational perturbations.

4.3.4.2.2 The steps in performing the ODA for this requirement are as follows:

a. Determine the average cross-sectional area, area-to-mass ratio, and initial orbit for each debris piece released. The average cross-sectional area for atmospheric drag calculations for an object that is not stabilized in attitude is the cross-sectional area averaged over all aspect angles and is measured in square meters. The NASA

ODPO’s DAS provides a rigorous means of determining average cross-sectional area.

It can be approximated as follows:

(1) For convex-shaped debris, the average cross-sectional area is approximately

1/4 of the surface area. For a convex shape, all of the surface area elements are exposed to a complete hemisphere (2 steradians) of deep space. Examples of convex shapes are spheres, plates, and cylinders.

(2) For non-convex shaped debris, an estimate of the average cross-sectional area may be obtained in two ways:

(a) For nearly convex shaped debris; i.e., debris for which there is almost no shielding of one surface element from the deep space environment by another, use 1/4 of the effective total surface area of the debris. The effective total surface area is the total surface area decreased by the surface area shielded from deep space. Examples of nearly convex shapes are two convex shapes attached by a connecting element such as a cable or a convex shaped debris object with an appendage.

(b) For complex debris shapes, determine the view, V, that yields the maximum cross-sectional area and denote the cross-sectional area as Amax.

Let A1 and A2 be the cross-sectional areas for the two viewing directions orthogonal to V. Then define the average cross-sectional area as (Amax + A1

+ A2) / 2.

(3) If the debris will assume a stable attitude relative to the velocity vector, the average cross-sectional area for atmospheric drag calculations is the cross-sectional area presented in the direction of motion.

(4) The area-to-mass ratio for the debris object is the average cross-sectional area

(m2) divided by the mass (kg).

(5) The initial debris orbit is the orbit of the object releasing the debris unless the release occurs with ∆v greater than 10 meters per second. For debris released with significant ∆v (typically greater than 10 meters per second), the initial debris orbit may be significantly different from that of the object releasing the debris. DAS can be used to calculate the initial orbit in this case.

b. With the debris orbital parameters, area-to-mass ratio, and year of release into orbit, use DAS to determine the orbital lifetime.

4.3.4.3 Debris Passing Through LEO: Total Object-Time Product (Requirement 4.3-1b)

4.3.4.3.1 The total object-time product is the sum, over all objects, of the orbit dwell time in LEO. “LEO dwell time” is defined as the total time spent by an orbiting object below an altitude of 2000 km during its orbital lifetime. If the debris is in an orbit with apogee altitude below 2000 km, the LEO dwell time equals the orbital lifetime. The LEO dwell time for each object can be obtained directly using DAS and the orbital information collected for the evaluation of Requirement 4.3-1.

4.3.4.3.2 If the LEO dwell time for debris is calculated to be 25 years, then no more than four such debris can be released to be compliant with the 100 object-years limit.

Note that Requirement 4.3-1a limits the total orbital lifetime of a single piece of debris passing through LEO to 25 years, regardless of how much time per orbit is spent below

2000 km. If the orbital lifetime of the debris is only 20 years, then a total of up to five debris can be released and still satisfy Requirement 4.3-1b, as long as the maximum orbital lifetime of each debris does not exceed 25 years. Figure 4.3-1 depicts the relationship between perigee and apogee altitudes in determining orbital lifetime.

Generally, all ODARs should provide a DAS estimate for the mission’s particular ballistic number and solar conditions. The curve in Figure 4.3-1 for F(10.7) = 100 is indicative of likely verification of requirement 4.3-1a, but the project may need to consider that even longer decays are if decay begins in or is headed towards the full trough of a solar cycle. The solar flux is not fully predictable and will undulate on a roughly 11-year cycle, generally leading to variable decay times, as can be seen in the variability of parameters in this plot for the two representative fluxes. Note that two identical spacecraft beginning their end-of-mission decays at the same altitude--respectively at the peak and trough of the same solar cycle--will have widely different decay times. The spacecraft beginning its decay at the trough of the cycle will take longer. Thus, the decay for the specific EOM conditions must be calculated based upon specific solar flux conditions and spacecraft mass properties at the forecast time, and must be updated for end-of-mission plans if mission timing changes.

4.3.4.4 Debris Passing Near Geosynchronous Altitude (Requirement 4.3-2)

4.3.4.4.1 In general, debris passing near GEO can be categorized as in nearly circular or in highly eccentric orbits. An example of the former would be debris released by a spacecraft after the spacecraft has already been inserted into an orbit near GEO. The

GOES 2 spacecraft employed a design of this type. To ensure that the debris is compliant with Requirement 4.3-2, the spacecraft must be sufficiently above or below GEO at the time of debris release to assure that within 25 years, and for 100 years thereafter, the debris is outside of the GEO +/- 200 km and GEO +/- 15 band. The orbit propagator within DAS can determine the minimum altitude above GEO or the maximum altitude below GEO to ensure that the debris is not perturbed into GEO +/- 200 km and GEO +/-

15 within 100 years.

4.3.4.4.2 Debris may also originate from a launch vehicle orbital stage which has directly inserted its payload into an orbit near GEO; e.g., the IUS upper stage used on the

TDRS 7 mission. The goal is that no debris is released and that the orbital stages are sufficiently removed from GEO at the time of debris release to minimize the risk to other

GEO objects, as described in the previous paragraph.

Figure 4.3-1. Apogee vs. Perigees for 25 Year Decay With F(10.7) = 100 and 150

Note: Figure 4.3-1. The limiting conditions of allowable apogee and perigee in constant solar flux conditions for a variety of area/mass ratios, under which requirement (4.3-1a) is met (25-year decay after EOM). CD of 2.2 and constant planetary geomagnetic index of 3.0 are assumed. The 25 year decay requirement at EOM is met for any particular spacecraft if the conditions are at or to the left of the plotted line for that spacecraft’s area/mass ratio, under the assumption that the monthly average solar flux is increasing past the listed F(10.7) value at the time that decay starts.

4.3.4.4.3 Debris may in limited cases also be released into highly eccentric

Geosynchronous Transfer Orbit (GTO) with perigees near LEO or at higher altitudes and with apogees near GEO, but must be consistent with requirement 4.6-3. (For debris with perigees passing through LEO, requirements 4.3-1a and 4.3-1b take precedence.) High perigee GTOs (above 2000 km) have been designed for use on several occasions by

Proton launch vehicles and GOES 13. Debris released at the time of payload separation on a mission of this type would fall under Requirement 4.3-2. Debris can be left in an eccentric orbit traversing GEO, if orbital perturbations will cause the object to leave GEO within 25 years. The orbit propagator within DAS can be used to determine the long-term orbital perturbation effects for specific initial orbital conditions and, hence, to determine compliance with Requirement 4.3-2 by ensuring the debris will not reenter the GEO protection zone within 100 years.

4.3.5 Brief Summary of Mitigation Measures Used in NASA for this Area

4.3.5.1 If a program or project does not fall within the above requirements, a number of mitigation measures may be taken. These include:

a. Releasing debris in orbits with lower perigee altitude to reduce orbital lifetime;

b. Designing debris with larger area-to-mass ratio to reduce orbital lifetime;

c. Releasing debris under conditions in which lunar and solar perturbations will reduce lifetime; and

d. Limiting release of debris by making design changes, changing operational procedures, or confining debris to prevent release into the environment.

e. Design sensor covers, bolt fragments, and similar objects to that they will be passively retained instead of being released.

4.3.5.2 Ground based simulations and testing can be used to better understand the effects of such design, operational, and confinement approaches.

4.3.5.3 For a lunar, Mars, Sun-Earth Lagrange Point, or Earth-Moon Lagrange Point mission, the program or project should design the mission to limit the release of debris during normal operations in a manner that is consistent with the mission requirements and cost consideration.

4.4 Assessment of Debris Generated by Explosions and Intentional Breakups

Orbital debris analyses assess accidental explosion probability and intentional breakups during and after completion of mission operations. Section 4.4 is not intended to mandate the use of techniques that could cause unreasonable passivation errors or malfunctions that involve nonreversible passivation methods.

4.4.1 Definition of the Explosion and Intentional Breakup Technical Area

4.4.1.1 Spacecraft and launch vehicle orbital stage explosions have been the primary contributor to the hazardous orbital debris environment. Some explosions have been accidental with onboard energy sources providing the energy such as residual propellants or pressurants left in orbital stages. However, some intentional breakups have occurred as tests or as a means of disposing of spacecraft.

4.4.1.2 In order to limit the risk to other space systems from accidental breakups after the completion of mission operations, all onboard sources of stored energy of a space system, such as residual propellants, batteries, high-pressure vessels, self-destructive devices, flywheels, and momentum wheels are depleted or safed when they are no longer required for mission operations or postmission disposal. Depletion should occur as soon as this operation does not pose an unacceptable risk to the payload (see Section 4.6.2.4).

4.4.1.3 Meeting this requirement necessitates reliable designs to prevent explosions during operations as well as after operations are completed.

4.4.1.4 Accidental Explosions

4.4.1.4.1 Accidental explosions of spent orbital stages have been the primary source of long-lived debris greater than 1 cm in diameter in LEO. The assessed source of energy for most of these events has been residual propellants, including liquid oxygen and hypergolic propellants. U.S. Delta 1 second stages were a principal source of such debris before corrective measures were implemented, but similar failures have been observed with European, Chinese, Russian, French, Indian, and Ukrainian orbital stages. Such failures have occurred as soon as a few hours and as long as 23 years after launch. The explosion of a 2-year-old Pegasus orbital stage in 1996 produced the greatest number of cataloged fragmentation debris to that date and was probably caused by the failure of a pressure regulation valve connecting a high pressure nitrogen supply with a lower pressure propellant tank. Several spacecraft breakups have been linked to battery failures.

4.4.1.4.2 Accidental explosions, primarily related to propulsion system malfunctions, during orbital deployment or orbital operations have also been documented. However, historically these events have attracted greater attention and more extensive preventive measures.

4.4.1.5 Intentional Breakups

4.4.1.5.1…