PREFACE
Collision
with orbital debris is a hazard of growing concern as historically accepted practices and procedures have allowed man-made objects to accumulate in orbit. To limit future debris generation, NASA Management Instruction (NMI) 1700.8, Policy to Limit Orbital Debris Generation, was issued in April of 1993. The
NMI required each program to conduct a formal assessment of the potential to generate orbital debris. NMI 1700.8 was superceded in 1997 by NASA Policy Directive (NPD) 8710.3. This standard serves as a companion to NPD 8710.3 and provides each NASA program with specific guidelines and assessment methods to assure compliance with
the NMI.
Each
main debris assessment issue (e.g., Postmission Disposal) is developed in a separate chapter. For the reader who needs just an overview of the debris issues, guidelines descriptions in chapter 2
should be consulted.
The
standard was developed jointly by the Office of Safety and Mission Assurance (Code Q) and the Johnson Space Center Space orbital debris research group. Comments, questions, or suggestions concerning this document should be directed to
Code QS.
Frederick D. Gregory
Associate Administrator for Safety and Mission Assurance
1. INTRODUCTION
1.1 SCOPE AND PURPOSE
This document
serves as a companion to NASA Policy Directive (NPD) 8710.3 and provides specific guidelines and methods to comply with the NASA policy to limit orbital debris generation. The guidelines serve to help ensure that launch vehicles, upper stages, and payloads meet acceptable standards for limiting orbital debris generation. This document should be used by the program manager or project manager as the primary reference in conducting debris assessments. The standard establishes guidelines and provides supporting analysis tools for: (1) limiting the generation of orbital debris, (2) assessing the risk of collision with existing space debris, and (3) assessing the potential of spacecraft-generated debris fragments to impact the Earth's surface. In addition to guidelines and methods for assessment, this volume provides formats for the debris assessment reports. Two appendices are used to define frequently used terms and to provide summary background
information.
Another document, entitled "Reference
Manual for Orbital Debris Assessments," provides
more in-depth background and technical information.
In addition, debris assessment software is available
to support the assessment of particular guidelines
and to evaluate mitigation measures.
1.2 OVERVIEW OF NASA MANAGEMENT
INSTRUCTION 1700.8
NASA Management Instruction (NMI)
1700.8 states "NASA's policy is to employ
design and operations practices that limit the
generation of orbital debris, consistent with mission
requirements and cost-effectiveness." The
NMI requires that each program or project conduct
a formal assessment for the potential to generate
orbital debris.
The debris assessment must address
the potential for orbital debris generation that
results from normal operations and malfunction
conditions, and on-orbit collisions. The assessment
must also address provisions for postmission disposal.
Malfunction conditions refer to those credible
failure scenarios or conditions that can result
in the direct generation of orbital debris or that
can disable the spacecraft to preclude postmission
disposal. Examples of orbital debris generated
during normal operations include items such as
lens covers, shrouds, and staging components that
are released into the environment. An on-orbit
explosion is an example of debris generation by
malfunction. Examples of debris generation by collisions
include immediate debris generation by collisions
with large objects and by loss of control of a
spacecraft or payload as a result of impact with
small debris during mission operations.
To satisfy the NMI, the program
or project manager may need to plan for such things
as:
- Depleting on-board energy sources
after completion of mission
- Limiting orbit lifetime after
mission completion to 25 years or maneuvering
to a disposal orbit
- Limiting the generation of debris
associated with normal space operations
- Limiting the consequences of
impact with existing orbital debris or meteoroids
- Limiting the risk from space
system components surviving reentry as a result
of postmission disposal
1.3 OBJECTIVES OF DEBRIS ASSESSMENTS
Each program or project should attempt to meet
all pertinent guidelines. It is understood, however,
that satisfying these guidelines must be balanced
with the necessity to meet mission requirements and
to control costs. If a guideline cannot be met because
of over-riding conflict with mission requirements
or prohibitive cost impact, this should be specifically
noted in the assessment with rationale and justification
provided.
As a matter of practice, it is desirable for the
program or project to work with the Office of Safety
and Mission Assurance during the assessment process.
Ideally, the program or project should also use the
expertise at NASA centers. The Office of Safety and
Mission Assurance at each center can direct programs/projects
to groups that can provide assistance with debris
assessments. These groups have resources for analyzing
complex debris problems which may not be covered
in the detail necessary in this standard or in the
debris assessment software.
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