Chandra Advanced CCD Imaging Spectrometer Update

TELESCOPES

Chandra

Boston - Nov 13, 2003
As has been noted for "some time", molecular contaminants have been slowly building up on a filter that shields the CCD chips in the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer (ACIS) from optical and ultraviolet light.

The effect of this buildup has been to gradually decrease the efficiency of the detector at low X-ray energies to roughly 60% of their value at launch in July of 1999. Observations at medium and high X-ray energies are affected by less than 10%.

Observations of objects that radiate primarily low energy X-rays, such as the coronas of stars and some supernova remnants, will take longer to reach the same sensitivity as an uncontaminated detector. The great majority of Chandra observations rely on medium and high-energy X-rays for which the contamination effects are minimal.

The contaminants are thought to be hydrocarbon substances whose source could be a Chandra spacecraft lubricant. Based on detailed analyses and extensive experience with other NASA missions, the Chandra team anticipated that molecular contaminants would slowly be released from material in the spacecraft when it was in orbit. The observed level of contamination is consistent with the high end of the expected range.

To deal with this possibility, a heater system was incorporated into the design of ACIS to allow the contaminants to be baked-off as needed while in orbit, as is done routinely on other missions. The Chandra team is currently performing detailed analysis in preparation for a possible bakeout planned for April or May 2004.

Since the build-up of additional contaminants is rather slow, it is important to analyze the nature of the contaminant to the extent possible, to optimize the bakeout process and to make sure there were no additional risks to be encountered during the bakeout. Even though analysis and previous experience indicate very little risk in this regard, a very conservative approach has been adopted, and various laboratory tests using spare components are underway.

Chandra's other detector, the High Resolution Camera, and the mirror assembly are maintained at relatively warm temperatures (10 degrees Celsius, and 20 degrees Celsius, respectively) so they have experienced very little build-up of contaminants. By comparison, ACIS's CCDs operate -120 Celsius, while its filters are maintained between -60 and -50 degrees Celsius.

TELESCOPES

Chandra X-Ray Observatory Vision Getting Blurred By Grease

London - Nov 06, 2003
The British science weekly New Scientist is reporting that the Chandra X-Ray Observatory "is suffering from a mysterious build-up of grease on an optical filter in front of one of its cameras, blocking almost half the light at some frequencies."

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.