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\chapter*{Preface\markboth{Preface}{Preface}}
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E/dE predictions up-dated based on MARX 2.20.

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\hfill {\it- Dan Dewey, September XX, 1998} \hfill

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{\it HETG ground calibration information and post-publication
updates are available on-line at:}

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{\tt http://space.mit.edu/HETG/xrcf.html}~~.
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% Preface from Preliminary version
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{\it September 30, 1997}

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{\bfseries \LARGE Preface to Preliminary Version}

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This document is a preliminary version of the HETG Ground Calibration
Report.  The purpose of this preliminary release is to document the
status of the HETG performance and calibration based on an initial
sampling of XRCF data.  For this reason many sections and analyses are
neccessarily incomplete, see Table~\ref{tab:status}.

The preliminary results reported here demonstrate that the HETG is
performing largely as designed and expected, {\it e.g.}, see
Figures~\ref{fig:xrcf_res_power}, \ref{fig:effmegheg1}, and
\ref{fig:effmegheg0}.  This
is a significant conclusion that could only come from the full system
(HRMA-HETG-ACIS-S) testing carried out at XRCF.

The XRCF testing also proved valuable in identifying two minor
effects, due to fabrication non-idealities, that were not predicted
and would have been confusing to impossible to diagnose in flight;
these are the MEG misaligned gratings (Section~\ref{sec:mis_align})
and the HEG scattering (Section~\ref{sec:scatter}).  Finally, there
remains a small (``5mm'') discrepancy between the XRCF data and the
relative periods and locations of the HETG and LETG
(Section~\ref{sec:periods_angles}).

The information and results presented here are the work of both
the HETG Science Team and the ASC.

A next revision is planned for February 1, 1998 (to support the
ASC's April release of the ``Calibration Data Guide'') and a complete
report will be issued June 1, 1998.  Please address comments and
corrections to the Editor, {\tt dd@space.mit.edu}.

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\hfill {\it- Dan Dewey, September 30, 1997} \hfill

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{\it These analyses are in process; further up-to-date ``notebook''-style
information is available at:}

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{\tt http://space.mit.edu/HETG/xrcf.html}~~.
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