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 An Interview with
Dr. Harvey Tananbaum, Director
Chandra X-ray Center
August 29, 1995
Background:
The Advanced X-ray Astrophysics Facility (AXAF) is scheduled for
launch aboard the Space Shuttle in August, 1998. A crucial component
of the AXAF X-ray observatory is the four pairs of nested cylindrical
mirrors. They must be shaped, ground and polished to tolerances of a
few parts in ten million making them the smoothest mirrors ever
built.
Q: Could you give us an update of the progress
this year on the mirrors for the AXAF X-ray telescope?
We have had a very positive year. We finished working on all the
glass (for the mirrors). The grinding, the shaping, the polishing,
the smoothing--all of the work at Hughes Danbury (Hughes Danbury
Optical Systems) was completed before the first of the year, a few
months ahead of schedule. We exceeded the contract requirements and
goals by a significant factor.
Q: Does this mean that the scientific capability
of the telescope will be better than expected?
A lot, lot better. The images will be very sharp across the entire
energy range of X-rays to be observed by AXAF and the data will be
easier to analyze.
Q: To what do you attribute this
accomplishment?
We are reaping the rewards of the efforts funded by NASA over the
last two decades for work on X-ray optics. Many of the scientists
involved in that work, such as telescope scientist Leon Van
Speybroeck, have been intimately involved at every step of the way
on this project. And the performance of the scientists, engineers
and managers at Hughes Danbury was outstanding. The improvement in
know-how to make the mirrors from one set of mirrors to the next
was fantastic. The first mirror took 6 or 7 polishing runs to
finish. The last ones took 2 or 3. It is a shame that we don't have
a follow-up mission so we can keep the team together.
Q: What is the next step?
As the mirrors have been completed, they have been shipped to
Optical Coatings Laboratory, Inc. in California to be coated with
iridium to improve their efficiency for collecting and focussing
X-rays. This is also a very challenging and critical procedure. The
coating must preserve the smoothness of the mirrors, and they must
remain absolutely clean afterwards.
Q: How is the coating going?
The third mirror (out of eight overall) is scheduled for coating
the first week in September and from all indications, the work is
going very well, meeting or slightly exceeding all of the
specifications.
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