Scheduling observatory time to maximize both day-to-day science target integration time and the lifetime
of the observatory is a formidable challenge. Furthermore, it is not a static problem. Of course, every
schedule brings a new set of observations, but the boundaries of the problem change as well. As
spacecraft ages, its capabilities may degrade. As in-flight experience grows, capabilities may expand. As
observing programs are completed, the needs and expectations of the science community may evolve.
Changes such as these impact the rules by which a mission scheduled. In eight years on orbit, the Chandra
X-Ray Observatory Mission Planning process has adapted to meet the challenge of maximizing day-to-day
and mission lifetime science return, despite a consistently evolving set of scheduling constraints. The
success of the planning team has been achieved, not through the use of complex algorithms and
optimization routines, but through processes and home grown tools that help individuals make smart short
term and long term Mission Planning decisions. This paper walks through the processes and tools used to
plan and produce mission schedules for the Chandra X-Ray Observatory. Nominal planning and
scheduling, target of opportunity response, and recovery from on-board autonomous safing actions are all
addressed. Evolution of tools and processes, best practices, and lessons learned are highlighted along the
Soon after the start of science operations of the <i>Chandra X-ray Observatory</i>, it became apparent that weakly penetrating
(0.1-0.5 MeV) protons in the Earth's radiation belt were causing an unexpectedly rapid increase in the charge-transfer
inefficiency of <i>Chandra's </i>front-illuminated CCDs. Fortunately, the <i>Chandra</i> team developed, implemented, and
maintains a radiation-protection program that successfully reduced the rate of degradation of the CCDs' performance to
acceptable levels. Since implementing this program, the average rate of increase of the charge-transfer inefficiency has
slowed to 3.2×10<sup>-6</sup>/y (2.3%/y) for the front-illuminated CCDs and 1.0×10<sup>-6</sup>/y (5.8%/y) for the back-illuminated CCDs.
This paper reviews the <i>Chandra</i> radiation-management program, reports the current status, and describes changes
planned or implemented since the previous paper on this topic.
After over 6 highly successful years on orbit, the Chandra X-ray Observatory continues to deliver world class science to
members of the X-ray community. Much of this success can be attributed to an excellent space vehicle, however; the
creation of several unique software tools has allowed for extremely efficient and smooth running operations. The
Chandra Flight Operations Team, staffed by members of Northrop Grumman Space Technology, has created a suite of
software tools designed to help optimize on-console operations, mission planning and scheduling, and spacecraft
engineering and trending. Many of these tools leverage COTS products and Web based technologies. We describe the
original mission concepts, need for supplemental software tools, development and implementation, use of these tools in
the current operations scenario, and efficiency improvements due to their use.