Technology Development Update
(The Constellation-X Observer, Volume 2, Spring 2008)
Two mirror segment image of point source, showing a 14.7 arc sec HPD at 8 keV.
The Spectroscopy X-ray Telescope team has had a number of recent successes, most notably a test of a two-mirror system in the 600m beamline at NASA/ GSFC that achieved 14.7 arc sec HPD at 8 keV, in agreement with the optical metrology data. The pair of Ir-coated mirror segments were temporarily supported by a speciallyconstructed cradle-mattress system that negates the effect of gravity which could otherwise severely distort the figure of the mirror segments. The good image and the good agreement between the X-ray measurement and prediction indicate:
- Directly slumped glass mirror segments are all but certain to meet the baseline Con-X requirement of 15 arc sec HPD. No post-slumping processing, be it epoxy replication or old-fashioned polishing, is required, realizing both budget and schedule savings for the project.
- The metrology process used for mirror segment evaluation is understood.
- The effect of gravity and other forces that can degrade the figure of the thin mirror segments can be understood, modeled, and countered.
The next steps are to better understand the different terms that contribute to the 14.7 arc sec image quality and assess the extent to which these factors can be reduced to move to the 5 arc sec goal. We are also continuing to work on designs and test ideas for how to transfer and bond the mirror segment into a permanent housing.
A pair of SXT mirrors ready for X-ray test in a vacuum chamber. The mirrors are temporarily supported by coils to negate the effect of gravity.
