Overview of R&D efforts

CARA directs R&D efforts in all CA-related areas, but the principal focus is on collision risk assessment (RA), meaning determination of which events are truly risky and thus require mitigation. In this area, CARA has established a number of important findings over the last five years:

• Two Line Elements (TLEs) are not sufficient for CA mitigation decisions (CATAC statement, 2016)
• Maximum Probability of Collision (Pc) not sufficient as a stand-alone RA parameter (Hejduk, 2016)
• Calculated Pc is a durable RA parameter (Hejduk and Snow, 2019)
• Determined tests for proper use of 2-D Pc calculation approach (Hall, 2019a)
• Developed fast, appropriate Monte Carlo techniques for situations in which 2-D Pc calculation is not reliable (Hall et al., 2018)
• Evaluated approaches for eliminating correlated error between primary and secondary object covariances (Casali, 2018)
• Developed approaches to establishing Pc confidence intervals through covariance error histories (Hejduk and Johnson 2016; Elrod 2019)
  • Established collision consequence as an important and useful component of CA risk (Hejduk et al. 2017, Lechtenberg 2019)
• Other research areas are adjusted to fluctuate with this rapidly evolving field of study, but include such topics as:
  • Orbit Determination (OD) product adequacy (e.g., Degenerate and unrealistic covariances; commercial data)
  • CA screenings (e.g., Proper screening volume sizing; screening filtering techniques; autonomous spacecraft CA)
  • Pc calculation (e.g., 2-D Pc Limitations; non-Gaussian error volumes; Monte Carlo techniques)
  • Special studies (e.g., Effects of SF radar, mega-constellation deployments)

Archived Technical Papers

The CARA program has published numerous conference papers. These technical papers summarize the analysis and research and development work done by the CARA team in the technical subjects surrounding CA and operations. Access to the archived technical papers, organized by year of publication, is found here: https://github.com/nasa/CARA_Analysis_Tools/tree/master/technical_papers .

Policy Documents

There are two policies that pertain to the CARA process. The most recent versions of these documents are available on NODIS.

NPR 8715.6b:

NPR 8715.6 is the NASA Procedural Requirement for Limiting Orbital Debris. Although its purview extends from mission design to mission disposal, the requirements levied within seek to limit debris generated from putting a mission into space. Examples include a lifetime requirement for end-of-life disposal orbits. NPR 8715.6 requires all operational non-human spaceflight-related NASA missions to utilize the CARA service.

NID 7120.132:

NID 7120.132 is the Collision Avoidance for Space Environment Protection published in Dec 2020 to codify existing practice and implementation in policy form at a lower level than what is covered by NPR 8715.6. Various roles and responsibilities, largely implemented yet not documented in policy, are now defined. In order to ensure NASA is proactively managing collision risk, additional planning requirements are established to focus attention on conceptual and pre-implementation actions that will manage operational impacts. For contracts and partnerships, the NID provides additional guidance to help ensure NASA continues to lead in protecting the space environment through managing collision risk. Eventually, the NID will be replaced by an NPR, and any duplication with NPR 8715.6 will be resolved at that time.