Lauri Newman (NASA), Matthew Hejduk (a.i. Solutions, Inc.), Ryan Frigm (a.i. Solutions, Inc.), Matthew Duncan (SpaceNav)
Keywords: conjunction assessment, operations
Abstract:
On-orbit collisions pose a significant mission risk to satellites operating in the space environment. Recognizing the likelihood and consequence of on-orbit collisions, NASA has taken several proactive measures to mitigate the risk of both a catastrophic loss of mission and the increase in the space debris population. In fall 2004, NASA GSFC established an Agency-wide, institutionalized process and service for identifying and reacting to predicted close approaches. The team responsible for executing this mission is the NASA Robotic Conjunction Assessment Risk Analysis (CARA) team. By fall 2005, this process had resulted in the execution of the first collision avoidance maneuver by a NASA unmanned satellite. In February 2008, NASA adopted a policy, documented in NASA Procedural Requirement 8715.6a ? Process for Limiting Orbital Debris that directed maneuverable satellites to have such an on-orbit collision mitigation process. In 2009, NASA decided to require support for all operational satellites. By January 2014, the CARA team has processed nearly 500,000 close approach messages from the Joint Space Operations Center (JSpOC) and has assisted our mission customers with planning and executing over 75 collision avoidance maneuvers for unmanned satellites in LEO, GEO, and HEO orbital regimes. With the increase in number of operational missions supported; growth in the orbital debris environment due to events such as the intentional destruction of the Fengyun 1-C satellite in 2007 and collision between Iridium-33 and Cosmos-2251; and improvements to the United States Space Surveillance Network (SSN) and its ability to track, catalog, and screen against small debris objects, the demands on the CARA process have consequently required the CARA Concept of Operations (CONOPS) to evolve to manage those demands. This evolution is centered on the ability to effectively and efficiently manage JSpOC, CARA, and Mission Operations resources, applying operational and analytical efforts for conjunction events that pose significant collision risk and rapidly discarding conjunction events that do not. While the overall CARA methodology is largely unaffected, this CONOPS evolution manifests itself in several aspects of the CARA process: required data and information, communication of those data and information, and courses of actions based on those data and information. The changes affect all relevant stakeholders, including the CARA team at NASA GSFC, GSFC-dedicated Orbital Safety Analysts at the JSpOC, and Mission Operations flight teams and management. In each step of the CARA process, the CONOPS ensures that necessary (whether situational or actionable) information be sent to stakeholders to facilitate an effective and efficient management of resources and appropriate protection of data. The most significant paradigm shift is the movement to risk-based reporting. Since the consequence of the on-orbit collision scenario can be catastrophic, the CARA risk-based framework hinges on the collision probability, Pc, as the encapsulation of collision risk. This CONOPS characterizes collision risk as Red (high collision risk), Yellow (potential for becoming a high collision risk), or Green (low collision risk) based on the operationally-computed Pc. Using this risk characterization schema, the amount and content of conjunction information and analyses is determined and communicated to mission stakeholders. Major technical analyses that have been conducted in support of this CONOPS include defining risk-based thresholds for red, yellow, and green criteria; determining when conjunction-related information may not be mature enough to be actionable; and accounting for uncertainties in all the inputs to the process so that a nuanced assessment of risk can be made. This paper summarizes the analyses executed and decisions rendered during the implementation of this evolved CONOPS. Historical conjunction events of note are used as example scenarios of each risk characterization.
Date of Conference: September 9-12, 2014
Track: Conjunction Assessment