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{\bf 1.21\_V2.0 EVENT HISTOGRAM ON THE INTERNAL CAL SOURCE}\\
{\bf WITH ACIS-S  }
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\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: June 27, 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 telemetry format called ``Event Histogram'' is expected to
be used heavily when ACIS is in the next-in-line mode.  Even though
this procedure explicitly calls for the internal cal source for this
particular test, this mode will probably be most useful for the
external cal source during flight. 
The PBs are designed to optimize the telemetry utilization in format
1; however the procedure will work in format 2 also.
The procedure assumes $\sim25$~m of TLM FMT 2 time after the
startScience command has been sent to guarantee that the bias maps
get down and 5~m of TLM FMT 2 time before the stopScience command is
sent to clear the event buffer.
The instrument can stay in TLM fmt 1 for many  hours during the 
science run itself but at least 90~m in TLM FMT 1 are desired to make the data
acquisition sensible.

\vspace{0.25in}
\noindent The sequence of actions will be: 
\be
\item warm boot and start DEA housekeeping if necessary
\vspace{-0.10in}
\item configure the instrument to collect spectroscopy array data
\vspace{-0.10in}
\item start the science run including a complete dump of the 
configuration information and wait 25~m for the bias maps to get down
in TLM FMT 2
\vspace{-0.10in}
\item switch the spacecraft to TLM FMT 1
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\item acquire data {\em for at least 90~m in TLM FMT 1}
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\item switch the spacecraft to TLM FMT 2, wait five minutes
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\item end the science run
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\item return to thermal standby if necessary
\ee


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\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes that the instrument is in the canonical thermal standby mode.\\
Assumes that the ``standard Rev. A and optional Rev. A'' patches
have been loaded. \\

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\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize
Assumes the spacecraft starts the procedure in TLM FMT 2 and switches
to TLM FMT 1 for the bulk of the run, and then back to FMT 2 five
minutes before the end of the run. \\

%\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 V1.2}
\begin{itemize}
\item changed filenames from ``ccd\_evhist\_s'' to ``evhist\_sarray''
\item deleted command ``WSFEPALLUP'' in step 1
\end{itemize}

{\bf V1.3}
\begin{itemize}
\item added a new step 1 to perform a warm boot and start a DEA HKP
run
\item changed PB mnemonic in step 3.1 
\item moved the dumps after the start science run command in step 3.2
\item added a step 4 to switch the TLM fmt from 2 to 1
\item added a step 6 to return to thermal standby if necessary
\end{itemize}

{\bf V2.0}
\begin{itemize}
\item ACIS Team signed-off version
\item  added step 3.14 to wait 25~m for the bias maps to come down while
staying in TLM FMT 2
\item added step 6 to switch back to TLM FMT 2, 5 minutes before
issuing the stopScience command
\item added step 7 to end the science run
\item changed expected version number of flight SW to 27 in step 1.5
since the Event Histogram mode is needed for this procedure
\item changed expected value of ``1STAT7ST'' in step 1.6
\item edited comment in ``Description'' column in step 3.2 to indicate
that no data will be aquired from the S2 CCD
\item added comment in step 8.2 to verify that the FEPs and video
boards are off
\item edited ``Brief Functional Description'', ``Sequence of
Actions'', ``Special Initial Conditions'',
and ``Assumed Instrument State'' to be consistent with these changes
\end{itemize}

\newcommand{\tablecaptiontext}{Event Histogram on the Internal Cal
Source with ACIS-S}
\input{evhist_sarray.tab}

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