The Chandra X-Ray Observatory mission planning process: managing and implementing constraints

Planning an observation schedule for ground-based and space-based telescopes alike requires careful constraint management and implementation. Scientific constraints, which meet an observer's desire to maximize science returns, must be weighed against the physical constraints and capabilities of the telescope. Since its launch in 1999, the Chandra X-Ray Observatory (CXO) has provided excellent science in spite of evolving constraints, including the proliferation of constraint types and varying degrees of restriction. The CXO observation schedule is generated on a weekly basis, yet the mission planning process maintains the flexibility to turn around a target-of-opportunity (TOO) request within 24 hours. This flexibility is only possible when all personnel responsible for schedule generation - flight operations engineers, science operations personnel, and program office support - are actively involved in constraint management. A proper balance of software tools, guideline documentation, and adequate subjective judgment is required for proper constraint implementation. The decision-making process employed by mission planning personnel requires accurate, complete, and current constraint information.