The scheduled viewing efficiency averaged 67% during the last year, allowing the observing program to transition from Cycle 3 to Cycle 4 in November. The average was approximately 3% lower than expected, mostly due to 10 interruptions of the observing schedule caused by high levels of solar activity. Once again this year, the science and mission operations teams worked hard to perform rapid re-plans and ensure a highly efficient return to the science time-line after these events. There is some indication (at last) of a decline in solar activity following solar maximum.
Observers were active in both the Target Of Opportunity (TOO) and Director's Discretionary Time (DDT) programs. Thirteen TOO targets with 18 observations and 27 DDT targets with 45 observations were accepted. Of these targets, 14 were fast response requests and required a mission schedule interruption and re-plan.
The Education and Public Outreach group have had a banner year with an increased focus on press releases and NASA Space Science Updates. Additional staff have been added to the group to aid in the production of animations and graphics, and in researching and developing science stories. Twenty science press releases and multiple other image releases were made during the year, and 4 Space Science Updates were made through NASA HQ.
The spacecraft and Science Instruments have continued to operate well and with no major anomalies. An investigation is underway to determine the cause of a decreased efficiency in the output of one of the Momentum Unloading Propulsion System (MUPS) thrusters following a longer than predicted momentum unload in December. The flight team has worked creatively to ensure no impact to the science schedule during the investigation.
A series of on-orbit tests were completed with the Aspect Camera to determine how close to the bright earth limb the camera could acquire and track stars. The results allowed for a reduction in the 20 degree limitation to 10 degrees and will ease scheduling of attitudes near the earth both during perigee passage and for science observing.
There were no safe modes during the year, but one safing action occurred when the spacecraft transitioned to bright star hold following a long maneuver in January. The cause was traced to a slightly inaccurate on-board gyro scale-factor and alignment matrix. A newly calibrated set of values was uplinked in May to mitigate against similar cases in the future.
Also of operational note was the nominal performance of the Observatory though two eclipse seasons, and a lunar eclipse in May.
The Science Processing team maintained an excellent record for throughput of data from observation to release to the Observer with an average time of 6 days. The Chandra archive holdings are now 1.6 TB (6M files compressed), with a total of 64.6K files corresponding to 2.5 TB retrieved last year
The Data System team completed a major port of the system to Solaris 8 in July and made releases of an interface to the Chandra Ray Tracer software (ChaRT) and an update to WebChaSer in December. CIAO 2.3 was released in November and includes a new tool that can be used to apply the CTI (charge transfer inefficiency) adjustment procedure. This correction restores some of the resolution lost due to radiation damage to the ACIS detectors early in the mission.
We look forward to continued smooth operations and exciting science results in 2003-2004.