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\large
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\centerline {\bf 5.3\_V2.0 CLOSE BIG VENT VALVE } 
\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: June 29,1999}\\
\noindent{\bf Filename: close\_bvv} \\


\noindent {\bf BRIEF FUNCTIONAL DESCRIPTION:} \\
\normalsize
The big ( previously known as ``large'') vent valve is planned to be 
opened once on orbit.
It is not planned to be closed.  Nevertheless, the mechanism is
capable of closing and opening again.  The following procedure has
been developed in case of an unforseen situation which would require
closing the big vent valve.


\vspace{0.25in}
\noindent The sequence of actions will be: 
\be
\item enable the valve close mechanism B and verify actuator temperatures
\vspace{-0.10in}
\item Open valve mechanism B
\vspace{-0.10in}
\item monitor the temperature and motion of the actuator
%\vspace{-0.10in}
%\item verify the close and open bits change
\vspace{-0.10in}
\item Turn off valve close mechanism B when the motion is complete
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\item verify the actuator temperature drops after the motion is complete
\vspace{-0.10in}
\item disable the valve close mechanism B
\ee


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\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes that the PSMC has power from the spacecraft. \\
Assumes that at least one side of the DPA is on.\\

\vspace{0.25in}
\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize
Assumes that \axaf\/ ISIM RCTU is powered on and in telemetry format
1, 2 or 4. \\


%\newpage 

\vspace{0.25in}
\normalsize
\noindent {\bf OPERATIONAL CONSTRAINTS/CAUTIONS:} \\
\normalsize
The open and close mechanism must not be enabled at the same
time. Consult the ``Open Big Vent Valve'' procedure for details.\\


\vspace{0.15in}
\normalsize
\noindent {\bf REFERENCES:} \\
\normalsize
\noindent ACIS Long Form Functional Test Procedure (36-01301.01)\\
\noindent 1.7\_V1.5 Open Big Vent Valve procedure\\

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

{\bf V1.2}
\begin{itemize}
\item changed filenames from ``open\_vv'' to ``open\_bvv''
\item deleted steps at the beginning and end which powered up and down
the DPA side A, the procedure now assumes that one side of the DPA is
on
\item changed the commands in steps 4.1 and 6.1 to be ``1VVCCBOF'' and
``1VVCBDS''
\end{itemize}

{\bf V1.3}
\begin{itemize}
\item changed the expected value of the logic verifiers due to error
in the web version of the ACIS IP\&CL
\end{itemize}

{\bf V1.4}
\begin{itemize}
\item changed TLM FMT requires to 1,2 or 4
\item changed time required for step 3.1 to 2 minutes and for step 5.1
to 20 minutes
\item changed expected values of HW serial digital TLM verfiers from
0/1 to ENB/DIS, CLOS/NCLO and OPEN/NOPE. 
\end{itemize}

{\bf V2.0}
\begin{itemize}
\item ACIS Team signed-off version
\item changed ``large'' to ``big'' in text descriptions
\end{itemize}



\newcommand{\tablecaptiontext}{Big Vent Valve Closing Procedure}
\input{close_bvv.tab}

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