We congratulate Harvey Tananbaum and Martin Weisskopf for jointly winning the 2004 Bruno Rossi Prize of the High Energy Astrophysics Division of the American Astronomical Society. The citation notes their vision, dedication, and leadership in the development, testing, and operation of the Chandra X-ray Observatory.
The Chandra program passed a major milestone in September 2003 with the start of a new contract between NASA and SAO. The new contract, which runs through July 2009, continues science center and operations activities for the second five years of the mission. The contract transition proceeded smoothly thanks to the hard work of administrative staff at NASA, SAO and its subcontractors.
The scheduled viewing efficiency averaged 64% during the last year, allowing the observing program to transition from Cycle 4 to Cycle 5 in November. There were 14 schedule interruptions due to high levels of solar activity, which had an overall impact of about 4% on the observing schedule. The mission planning team responded efficiently to all the solar replans and minimized the science lost. Planners also responded efficiently to the six Target Of Opportunity (TOO) observations that required schedule interruptions.
The spacecraft continued to operate well overall with no safe modes or major anomalies. Operational highlights included completing two eclipse seasons with nominal power and thermal performance, uplinking a software patch to improve power subsystem management for eclipses, lowering the Aspect Camera CCD operating temperature (from -10 to -15 deg C) to reduce dark current, uplinking a software patch to reduce the number of load stoppages due to false radiation triggers upon radiation belt entry, and successfully passing the Leonid meteor shower in November. (See the article "Stormy Weather" for a discussion of an unusual event this year.)
The operations team handled a number of spacecraft anomalies during the year, including completing the response to an anomalous thruster, and swapping to the redundant Inertial Reference Unit (IRU) due to an increasingly noisy gyroscope. The decision to swap to the backup IRU in July was made after one of the gyros in the prime IRU showed increasing levels of current noise. The gyro remains functional but is considered to have a limited lifetime. The swap ensures that there is a functioning backup that can be used in the event of a safe mode. The other three gyros (each IRU has two) are functioning nominally and the spacecraft can be configured to operate with cross-strapped gyros if needed. The swap was completed without loss of science time.
The science instruments also continued to operate well overall. The science team has carefully monitored a degradation in the ACIS detection efficiency at low-energies, which is thought to be due to a build up of contamination on the outside of the ACIS optical blocking filter. Studies are near completion about performing a bakeout designed to remove a significant fraction of the material. The Science Processing team maintained their excellent record for throughput of data with an average time of 6 days from observation to delivery of data. The Chandra archive holdings grew by 0.3 TB to 1.9 TB (compressed) during the year and now consists of 7.2M files.
The Science Data System team released CIAO 3.0 in August and completed a major data system release (7.0) in September. CIAO 3.0 was a major infrastructure release for data analysis that included a new port to MacOS X, a set of high priority new tools and access to many of the CIAO modules via S-Lang to enhance scripting capabilities for users. The Education and Public Outreach team was very active with 17 press releases, two Space Science Updates (SSU) and a video release issued through NASA HQ, and many other image releases. The interest in the Chandra web site and educational products remained very high last year, with interest peaking around the SSUs.
We look forward to continued smooth operations and exciting science results in 2004-2005.