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%\input dspace12.tex
%\input pstricks.tex
%\input psfig
\newcommand{\be}{\begin{enumerate}}
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\newcommand{\axaf}{{\em AXAF}}
\def\la{\hbox{\rlap{$<$}\lower0.5ex\hbox{$\sim$}\ }}


\large
%\vspace*{-0.5in}
\centerline {\bf 1.1\_V2.0 OPEN SMALL VENT VALVE } 
\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: June 23,1999}\\
\noindent{\bf Filename: open\_svv} \\
%\vspace{0.25in}

\noindent {\bf BRIEF FUNCTIONAL DESCRIPTION:} \\
\normalsize
The small ( previously referred to as ``little'') vent valve is
planned to be opened once 
on orbit.  The current plan would open the valve while \axaf\/ is
still in the shuttle bay, 40~mins after the payload bay doors have
been opened.  The valve is opened to allow any residual
gas in the ACIS detector housing to 
escape. There are two redundant vent valves located in parallel
downstream of a porous plug.  Thus, the opening of either of these valves
will be sufficient but it is planned to open both. Since
the pumping speed is limited by the porous plug, no advantage in time
or final pressure can be realized by opening both valves.  There is no
telemetry verifier that the valves have opened.  The only way to
verify the opening of the valves is to monitor the reading of the internal
pressure monitor.  Once opened the little valve should not be closed,
since the risk of contaminants reaching the focal plane through this
path is negligible. Initialy, the pressure will drop by a factor of
two every 30 minutes.  Typically in ground operations, 3 hours was the
standard waiting time or until the rate of change was less than 1 torr
per 30 minutes.  The eventual pressure should read $0\pm2$ torr.

\vspace{0.25in}
\noindent The sequence of actions will be: 
\be
\item enable and turn on DPA power supply side A
\vspace{-0.10in}
\item turn on the pressure transducers A \& B, check the pressure, validate expectations
\vspace{-0.10in}
\item enable and open the little valve mechanism A \& B
\vspace{-0.10in}
\item disable the little vent valve mechanism A \& B
\vspace{-0.10in}
\item turn off and disable the DPA power supply side A
\vspace{-0.10in}
\item monitor the pressure as spacecraft telemetry is available
\vspace{-0.10in}
\item turn off the pressure transducers A \& B
\ee


\vspace{0.15in}
\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes that the PSMC has power from the spacecraft. \\


%\vspace{0.25in}
\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize
%The environment must be clean enough to allow opening of the valve. \\
%Assumes that \axaf\/ ISIM RCTU is powered on and in telemetry format 6. \\
Assumes that the spacecraft has power and connections for commanding
and telemetry while in the shuttle bay. \\
Assumes the telemetry is in FMT~6.\\

%\newpage 

%\vspace{0.25in}
\normalsize
\noindent {\bf OPERATIONAL CONSTRAINTS/CAUTIONS:} \\
\normalsize
There is no telemetry verifier and therefore it is crucial that the
internal pressure be monitored.  Both pressure monitors may be read
out, so they are both typically used. \\
CARD ACIS-005 \\


%\vspace{0.15in}
\normalsize
\noindent {\bf REFERENCES:} \\
\normalsize
ACIS Long Form Functional Test Procedure (36-01301.01) \\

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

{\bf V1.2}
\begin{itemize}
\item changed filenames from ``open\_lvv'' to ``open\_svv''
\end{itemize}

{\bf V1.3}
\begin{itemize}
\item changed title of procedure to say ``Small Vent Valve''
\item changed expected value of verifiers in step 1.2 from ``E'' to
``ENB'' and ``5.0'' to ``4.9--5.5''
\item changed criticality of verifier ``1DPP0AVO'' to 1 in steps 1.2
and 5.2
\item changed expected value of verifiers in steps 2.1 and 2.2 from
``1'' to ``ON''
\item changed expected value of verifiers in steps 2.3 and 2.4 from
``0--2~T'' to ``0-10~T'', changed criticality to ``2''
\item changed duration in step 2.3 to 6 minutes
\item changed expected value of verifiers in steps 3.1 and 3.3 from
``1'' to ``ENB''
\item changed expected value of verifiers in steps 4.1 and 4.2 from
``0'' to ``DIS''
\item changed expected value of verifiers in step 5.1 from
``OFF'' to ``ON''
\item changed expected value of verifiers in step 5.2 from ``0~V''
to ``$0.0\pm0.2$~V'', ``28.0--32.0~V'', and ``0.0--0.1~A''
\item changed expected value of verifiers in steps 6.1 and 6.2 from
``0~T'' to ``0-2~T'', changed criticality to ``2''
\item changed verifiers to be checked in steps 7.1 and 7.2 from
1PRDBAON \& 1PRDBBON to 1HOPAPR \& 1HOPBPR
\item deleted ``CMD EGSE'' and ``SEQ KEY'' from the LaTeX table
\item edited the text in the {\it Brief Functional Description}
\end{itemize}

{\bf V1.4}
\begin{itemize}
\item changed expected values of the initial pressure to ``-12 to +2
T'' in steps 2.3 and 2.4
\item changed order of Enable and On commands in section 3 so that
both valves are enabled first and then both valves are commanded open
\item put verifiers that DPA is off after step 5.1 instead of step
5.2, removed verifier 1DPPSA
\item added filename identification at top of procedure
\end{itemize}

{\bf V1.5}
\begin{itemize}
\item changed expected values of the DPA A input voltage and current in
step 1.2 to 28.0--34.0~V and 0.35--0.43~A
\end{itemize}

{\bf V2.0}
\begin{itemize}
\item ACIS Team signed-off version, identical to previous version 1.5
\end{itemize}


\newcommand{\tablecaptiontext}{Small Vent Valve Opening Procedure}
\input{open_svv.tab}

\end{document}



