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Chandra X-Ray Observatory Sensor Has Contaminant Problem
By Jeremy Singer
Space News Staff Writer
posted: 04:00 pm ET
06 November 2003
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Untitled WASHINGTON -- Contaminant buildup on an optical filter aboard NASAs Chandra X-ray Observatory is increasing the time needed to get accurate readings from the spacecraft in the low-energy range of the X-ray spectrum, according to a program official. The problem is limited to Chandras Advanced Charge Coupled Device Imaging Spectrometer (ACIS), said Roger Brissenden, manager of the Chandra X-ray Center in Cambridge, Mass. In some cases, scientists are relying on Chandras High Resolution Camera for data that the ACIA was designed to collect, he said. The ACIS instrument is now operating at about 60 percent of its efficiency at launch in the low-energy spectrum, Brissenden said in a Nov. 6 telephone interview. However, the overall impact on Chandra is very small, he said. The contaminant is believed to be a hydrocarbon substance whose source could be a Chandra spacecraft lubricant, Brissenden said. Chandra program officials are now examining the possibility of heating the spacecraft in order to remove the buildup on the ACIS optical filter. That could take place in April or May 2004, he said. The filter is used to prevent optical light from flooding the X-ray sensor. The rate of accumulation is at the high end of pre-launch projections, Brissenden said. The difficulty related to the buildup was first reported by the magazine New Scientist.
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