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\large
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\centerline {\bf 1.30\_V2.0 INTERNAL CALIBRATION SOURCE AND BACKGROUND
MEASUREMENT }
\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: August 3, 1999}\\


\noindent {\bf BRIEF FUNCTIONAL DESCRIPTION:} \\
\normalsize
ACIS contains an Fe55 source inside its camera housing which 
continually illuminates the focal plane when the ACIS door is closed.
The source is highly
collimated so that most of the events occur on the S2 and S3
CCDs.  The Mn~L line strength will be compared to the Mn~K line
complex strength to judge any differences in sensitivity, compared
to ground calibrations.  The
count rate for the Mn~L line on the S3 chip will be 
$0.4~{\rm counts~s^{-1}}$ given an August 1999 launch date.  
The requirement is to acquire
10,000~counts in the Mn~L line; therefore an integration time
of 25~ks is required.  Since the other CCDs will not see a significant
number of Mn X-ray, we will use this time to collect background data on
them.  Half of the time will be spent on the I array and the other
half on the S array.  There are four science runs in the procedure.
The first collects I array data in Faint mode with a g7 grade filter
and no event amplitude cutoff.
The second collects S array data in Faint mode with a g7 grade filter
and no event amplitude cutoff.
The third collects I array data in Faint mode with a b255 grade filter
and a 3700~ADU event amplitude cutoff.  It also employs a window block
to reject events from I1 abd I2.
The fourth collects S array data in Faint mode with a b255 grade filter
and a 3700~ADU event amplitude cutoff.  It also employs a window block
to reject events from S4 and S5.


\vspace{0.25in}
\noindent The sequence of actions will be: 
\be
\item warm boot and start DEA housekeeping if necessary
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\item configure the instrument to collect imaging array data
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\item execute the faint mode science run (no g7, no event amplitude cutoff)
\vspace{-0.10in}
\item configure the instrument to collect spectroscopy array data
\vspace{-0.10in}
\item execute the faint mode science run (no g7, no event amplitude cutoff)
\vspace{-0.10in}
\item configure the instrument to collect imaging array data
\vspace{-0.10in}
\item execute the faint mode science run (no b255, event amplitude
cutoff at 3750 ADU, window out I1 and I2)
\vspace{-0.10in}
\item configure the instrument to collect spectroscopy array data
\vspace{-0.10in}
\item execute the faint mode science run (no b255, event amplitude
cutoff at 3750 ADU, window out S4 and S5)
\vspace{-0.10in}
\item return to thermal standby mode if necessary
\vspace{-0.10in}
\ee


\vspace{0.15in}
\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes that the instrument is in the cannonical thermal standby mode.\\
Assumes that the ACIS door is closed.\\
Assumes that the standard patches have been loaded {either the
standard patches alone or the standard patches bundled with the
optional patches}. \\


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\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize


%\newpage 

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\normalsize
\noindent {\bf OPERATIONAL CONSTRAINTS/CAUTIONS:} \\
\normalsize


\vspace{0.15in}
\normalsize
\noindent {\bf REFERENCES:} \\
\normalsize

\normalsize
\noindent {\bf CHANGE HISTORY:} \\
\normalsize

{\bf V2.0}
Original version, edited from procedure 1.23\_V2.1.
\begin{itemize}
\item step 7.1, changed the SW command mnemonic from ``WT00144014'' to
``WT00146014'' and the command identifier
\item step 7.2, changed the SW command mnemonic from ``W200009014'' to
``W20001A014'' and the command identifier
\item step 9.1, changed the SW command mnemonic from ``WT000CE014'' to
``WT000148014'' and the command identifier
\item step 9.2, changed the SW command mnemonic from ``W200009014'' to
``W20001A014'' and the command identifier
\end{itemize}

\newcommand{\tablecaptiontext}{Internal Calibration Source and
Background  Measurements}
\input{intcal_bkg.tab}

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