The observing program transitioned from Cycle 1 to Cycle 2 in November 2000, 2 months later than expected due to a reduction in allowable observing time per orbit due to the increased effective size of the radiation belts. The observing efficiency has averaged 67% compared with a pre-launch goal of 70%. Improvements were made during the year to modify the star acquisition sequence following a slew resulting in a 1.5% increase in observing efficiency or an additional 300 Ks per year. A total of 10 Targets Of Opportunity have been observed since launch, both pre-approved through the peer review and from the Director's Discretionary program.
In keeping with the spirit of discovery, the Education and Public Outreach group have worked with NASA and the science community to make over 50 press releases since launch and have maintained a dynamic and informative web-site throughout the period.
The spacecraft has continued to perform extremely well with several notable operational milestones. The 1999 Fall and 2000 Fall and Spring earth eclipse seasons were handled with nominal power and thermal performance, and the first lunar eclipse passage occurred on 8 November 2000 and involved off-pointing the solar arrays to avoid an over-voltage condition of the power system following eclipse exit. No spacecraft safe modes have occurred in the last year. The observing schedule was interrupted 4 times due to large solar events which either triggered the autonomous instrument safing sequence, or resulted in ground intervention to stop the daily loads and safe the Science Instruments (SIs).
The only spacecraft anomalies have been the failure of the HETG A and B-side retract limit switches. The exact failure mode is still unknown, however the result is that the normal software commanded operations will not function properly. The LETG commanding is also affected since the software uses the state of the HETG position to determine if it's safe to move the LETG. Operational work-arounds are in place for autonomous HETG and manual LETG operation, and flight software modifications are nearing completion that will restore full autonomous operation to both gratings.
The SIs have continued to perform well. The rapid ACIS row-dependent energy resolution degradation as a result of proton damage (aka CTI degradation) seen early in the mission has been halted and work is on-going to develop possible techniques for mitigating the loss in energy resolution. The HRC timing and background problems (see HRC article) have been understood and efforts made to respond with software and processing fixes and additional calibration data.
The Operations Ground System has operated without problems and the ground team successfully completed a major operating system and software upgrade in November 2000 with no impact to operations.
The Science Processing Team have improved the average throughput of data from observation to observer from 3 weeks to less that 2 weeks and have almost completed the first major re-processing of Chandra data. The re-processing covers data from launch to August 2000 and incorporates a series of software fixes and improved calibrations. Metrics for the data system indicate that the archive is growing at a rate of approximately 500 GB per year, and is supporting an increasing request rate.
The CIAO analysis system has undergone significant change with the release of version 2.0 in December 2000. The CIAO 2.0 release includes 18 new tools and a major release of the CalDB and CIAO 2.2 is scheduled for the Fall of 2001. The first on-site CIAO workshop was held in January 2001 and based on the success, a second is planned for April.
We look forward to continued smooth operations and exciting science results in 2001-2002.
- Roger Brissenden