Suzaku Status report - 10 August 2005

["U\. S\. Suzaku GOF" <suzakunews@olegacy.gsfc.nasa.gov>]

Suzaku Status report - 10 August 2005

After a successful launch of Suzaku (Astro-E2) on July 10, 2005 the 
X-ray Spectrometer (XRS) was activated and performed to 
specifications for almost three weeks, with 7 eV resolution recorded 
from the calibration source. An anomaly appeared on July 29, three 
days after the dewar main shell vent valve was opened. Several abrupt 
temperature changes were observed in parts of the dewar and other 
signatures that were clear signs of a momentary puff of helium gas in 
the dewar vacuum space. All of the temperatures recovered very 
quickly after the event as the gas rapidly adsorbed onto the cold 
surfaces of the helium cryostat and the detector system, but the 
event substantially degraded the spectral resolution of the array. 
Heating the detector system to greater than 6 K effectively degassed 
the array and recovered the original 7 eV resolution performance. 
More events were seen over the following days, with the frequency 
increasing. Degassing again recovered the original spectral 
resolution. On August 8 there were two more of these events, the 
second of which overwhelmed the dewar vacuum, caused a thermal short 
between the helium and neon tanks, and resulted in the liquid helium 
boiling off and completely venting to space.

Without the helium cryogen, the XRS instrument can no longer provide 
the planned science. The AO1 General Observer Program that was 
planned for the mission can no longer be achieved and will not be 
performed. The associated NASA grants will not be awarded. A mishap 
investigation board is being formed to understand the cause of this 
loss and to make recommendations for future missions.

There are two other instruments that are still functioning, the XIS 
and HXD, which provide a new and exciting science capability. It is 
now necessary to plan a new observation program, optimized to these 
instruments. Further information on an upcoming opportunity for 
participation in this revised program and possible associated NASA 
grants funding will be forthcoming over the coming weeks.

We regret the loss of this important science opportunity. While the 
technology is challenging, the perfect operation of the instrument in 
space for almost three weeks is in itself a marvelous technical 
achievement. It demonstrates that it is possible to make this 
technology work in space, and shows that the science promise of XRS 
will eventually be realized, as new flight opportunities become 
available.

Richard Kelley
Suzaku NASA Principal Investigator

Nicholas White
Suzaku NASA Project Scientist

Please see http://suzaku.gsfc.nasa.gov and 
http://www.astro.isas.ac.jp/astroe/index-e.html for further 
information on Suzaku.
--
A service of the U.S. Suzaku Guest Observer Facility, NASA/GSFC.

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