<title>Postmission disposal options for upper stages</title>

Abstract

NASA Management Instruction (NMI) 1700.8 directs each project office to limit orbital debris generation if this action is cost-effective and consistent with achieving mission objectives. To implement this policy, the NASA Office of Safety and Mission Assurance, the sponsor of NMI 1700.8, tasked NASA Johnson Space Center (JSC) to develop the NASA Safety Standard 1740.14: Guidelines and Assessment Procedures for Limiting Orbital Debris, August 1995. To mitigate the accumulation of mass in Earth orbit, NSS 1740.14 addresses the issues of postmission disposal of spacecraft and upper stages. According to the guidelines, these systems in general should be left in an orbit in which, using conservative projections for solar activity, atmospheric drag and gravitational perturbations will limit the lifetime in low Earth orbit (LEO) to no longer than 25 years after completion of mission. Consequently, JSC undertook a series of studies to investigate the most efficient and cost effective options for reducing orbit lifetime. In this paper we present an overview of the various options and give hints for the choice of the option best suited for specific mission types, e.g., depending on initial orbit, existing propulsion systems, existing electrical power level, electrical power and attitude control lifetime, and acceptable maneuver time and mass penalties.