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% Ed sez for the duration of the heating cycles
% from -32C to +70C, 3/4 deg/s
% from +70C to whatever, 0.5 deg/s
%
% new information on 9/29/99
%  Starting temp   Pulse duration  Act temperature     Shaft angle
%
%   Cold            140  sec            66°C         70 deg +/- 5
%
%    27°C           100 sec             71°C         65 deg +/- 5
%
%    27°C           135                 85°C         35 deg +/- 5
%
%    27°C           170 sec             98°C         10 deg +/-
%   5
%

\begin{document}
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%\input pstricks.tex
%\input psfig
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\large
%\vspace*{-0.5in}
\centerline {\bf 2.17\_V2.0 CLOSE ACIS DOOR ON ORBIT } 
\centerline {\bf (in 4 shots) } 
\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: September 30,1999}\\
\noindent{\bf Filename: close\_door} \\

\noindent {\bf BRIEF FUNCTIONAL DESCRIPTION:} \\
\normalsize
The ACIS camera housing door was planned to be opened only once on
orbit; however recent events dictate that the SOT/FOT should develop
a procedure to close the door. The door mechanism uses the same paraffin 
actuators as the big vent valve mechanism.  Extreme caution
must be exercised with these actuators, from the ACIS Long Form
Functional Test Procedure document:

\begin{quote}
\em{Because the Optical Blocking Filters are fragile and cannot 
withstand much differential pressure, mechanism motions may only 
be initiated when the differential pressure is less than 1 torr.
Be safe; check both transducers.  The mechanisms are driven by 
Starsys hot wax actuators. Power is applied directly from the 
space craft bus to heat the wax and, therefore, the time for a 
given motion to complete is dependent upon the bus voltage. To 
avoid failure of an actuator due to overheating--which would occur 
if the completion-of-motion switches failed, for instance--we 
monitor the actuator temperature. If the actuator temperature 
exceeds 135C, a command to abort the motion should be sent. Recovery 
from such a condition is never routine; no further motions should
be attempted without thorough analysis of the procedural failure.
 It is also imperative that the commanded actuator be allowed to 
cool below 50C before the opposing actuator is commanded, lest the 
afore-mentioned egregious situation occur.  It is not an error to 
command a valve open which is already open, etc., since the PSMC 
logic will know from the motion switches that the mechanism is 
already in the commanded state and not (falsely) apply power to 
the actuator.
}
\end{quote}

The side A HW serial digitial TLM has an extra bit to monitor the status of the
actuator.  However, the logic which determines the value of this bit
is sufficiently obtuse, that it is typically easier to use side B.
%The door typically took 3.5~minutes to open with a 28VDC bus
%voltage during ground testing; it will go faster with 32VDC on the
%bus.  
The peak temperature of the actuator should be $100\pm10$~C; 
damage can occur if the temperature
exceeds 135~C. An on-board regulator disconnects the voltage if the
temperature reaches 130~C.  Therefore, ground intervention to abort
the actuator motion should not be necessary or even possible, but 
is maintained as a backup to this automatic cutoff.  As the 
actuator warms above 70~C, it begins to move and the door closed
bit should switch to one. {\bf At the time of writing, it is
anticipated that the door will not be completely closed but will be
left in a ``cracked-open'' position. This procedure does NOT warm up
the detector housing to room temperature like the door opening
procedure does.}



The door close actuator will be cycled four times nominally before the
door motion is complete.  A library of  SCSs will be pre-built 
by the FOT which will contain the necessary commands to operate the
actuator with heating cycle durations ranging from  50 -- 200~s.
Each SCS will contain the actuator heater on command, the appropriate 
time delay, the actuator
heater off command, a 1~s delay, and another actuator off command .
The FOT will also have the actuator heater off command queued up and
ready to be sent as quickly as possible in case of an emergency.
%Each suceeding cycle keeps the actuator
%heater on for a longer time.  
The first cycle is intended to be long
enough to just melt the wax and have the plunger of the actuator move
a small amount.  The initial temperature of the actuator for the first
cycle will be $-32$~C.  The following cycles will be inititated
after the actuator temperature read less than $+30$~C.  Therefore, the
first cycle begins with a significantly colder temperature than the
suceeding cycles.  The second cycle is
intended to melt the wax, trip the ``closed'' 
limit switch (so that it reads ``NCLO'' for not closed) and rotate the
shaft by a few degrees without beginning
to close the door.  The third cycle is intended to melt the wax
and rotate the shaft by enough that the door
closes  to $35\pm5$~degrees.  The last cycle is intended to close
the door to a desired shaft rotation angle of $10\pm5$~degrees.
During the execution of the procedure, the SOT will decide on the
appropriate duration for each heating cycle and instruct the FOT to
uplink the appropriate SCS.

After each one of these cycles, the desired motion may not be
observed.  If this is the case, a contingency procedure may be called
for.  The contingency procedures which have been prepared are to 
repeat the heating cycle with a different duration
than one of the planned 4 heating
cycles (all times will be available in 5s increments) and simply to
turn off the heater (hopefully this is unnecessary). 


\vspace{0.25in}
\noindent The sequence of actions will be: 
\be
%\item enable and turn on DPA PSs A \& B and DEA side A {\it if necessary}
%\vspace{-0.10in}
%\item heat the DA housing to -60C if necessary {\it if necessary}
%\vspace{-0.10in}
\item start a DEA HKP run if necessary
\vspace{-0.10in}
\item switch spacecraft telemetry format to 4
\vspace{-0.10in}
\item enable the door mechanism side B and verify actuator temperatures
\vspace{-0.10in}
\item Execute first heating cycle
\vspace{-0.10in}
\item Verify expected behavior (the temperature and motion of the actuator)
%\vspace{-0.10in}
%\item verify the close and open bits change
\vspace{-0.10in}
\item Monitor actuator cooldow
\vspace{-0.10in}
\item Decide if next heating cycle time is correct, if yes proceed, if
no execute contingency
\vspace{-0.10in}
\item Execute second heating cycle
\vspace{-0.10in}
\item Verify expected behavior 
\vspace{-0.10in}
\item Monitor actuator cooldow
\vspace{-0.10in}
\item Decide if next heating cycle time is correct, if yes proceed, if
no execute contingency
\vspace{-0.10in}
\item Execute third heating cycle
\vspace{-0.10in}
\item Verify expected behavior 
\vspace{-0.10in}
\item Monitor actuator cooldow
\vspace{-0.10in}
\item Decide if next heating cycle time is correct, if yes proceed, if
no execute contingency
\vspace{-0.10in}
\item Execute fourth heating cycle
\vspace{-0.10in}
\item Verify expected behavior 
\vspace{-0.10in}
\item Monitor actuator cooldow
\vspace{-0.10in}
\item disable the door mechanism B
\vspace{-0.10in}
\item switch spacecraft telemetry format to 1 or 2
\ee


%\vspace{0.25in}
\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes the small and big vent valves have been open for 
many days. \\
Assumes that the instrument is in the canonical thermal standy state
[{\bf Note the DH temperature is -60~C, not room temperature as in the
door opening procedure}]. \\
Assumes the DA  heater on side B is on.\\
Assumes that the RCTU starts in format 1 or 2, is swithced to format 4 for
the door opening and is then put back into format 1 or 2.

\vspace{0.25in}
\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize
The waiver that releases Paul of all responsibility in the case that the
door never opens again must be signed by Martin Weisskopf, Chandra
Project Scientist, Gordon Garmire, ACIS Principal Investigator, Mark
Bautz, ACIS Project Scientist, and Harvey Tannanbaum, CSC Director.


%\newpage 

\vspace{0.25in}
\normalsize
\noindent {\bf OPERATIONAL CONSTRAINTS/CAUTIONS:} \\
\normalsize
The small and  big vent valves must already be open. \\
The open and close mechanism must not be enabled at the same time.\\
{CARD ACIS-002} \\
{CARD ACIS-007} \\


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

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

{\bf V1.0}
\begin{itemize}
\item initial version, copied from the 2.10 Door Open procedure
\end{itemize}

{\bf V1.1}
\begin{itemize}
\item added pulse durations and expected shaft rotation angles from
email from Ed Boughan
\item changed expected starting temperature of actuator housing
temperatures 1OAHAT and 1OAHBT in step 3.2 to -30 and -32~C
\end{itemize}

{\bf V1.2}
\begin{itemize}
\item updated the expected durations, maximum temperatures, and
shaft rotation angles of the heating cycles
\item updated the text description to be consistent with the procedure
\end{itemize}

{\bf V2.0}
\begin{itemize}
\item ACIS team signed-off version
\item added Bob's comments that the procedure is run with the DH at
-60~C, not room temperature as the door opening procedure.
\end{itemize}

\newcommand{\tablecaptiontext}{Close ACIS Door on Orbit }
\input{close_door.tab}

\end{document}
