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\large
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\centerline {\bf 5.12\_V1.0 BAKEOUT: FP to $-60$~C, DH to $+20$~C }
\vspace{0.25in}

\normalsize
\noindent{\it Last Revised: September 30, 2003}\\
\noindent{\bf Filename: bake\_FPm60\_DHp20} \\

\noindent {\bf BRIEF FUNCTIONAL DESCRIPTION:} \\
\normalsize

It has been determined that the ACIS optical-blocking filter (OBF) and/or
CCDs have developed a layer of contamination over the first four years
of the mission.  Ground tests at NGST indicate that the contaminant is
likely to release at temperatures at or above 0~C.  Thermal models
from LMA indicate that the center of the ACIS-S OBF can be raised to
0~C and the center of the ACIS-I OBF can be raised to $-7.5$~C if
the Detector Housing (DH) or Camera Body (CB) is heated to room
temperature and the focal plane is heated to $-60.0$~C.  The edges of
both OBFs will be close to room temperature in such a scenario.
Ground tests also indicate that the relevant timescales for the
contaminant release are on the order of a few hours.  The exact
release temperature and time constants are {\em not known} because
the exact composition of the contaminant on-orbit is not known.

Current thinking states that ACIS must be in the focal position for
this activity. It is expected that this activity will take an entire 
orbit or a large fraction of it, including the heating phase, the 
hot, stable phase and the cooling phase.  The activity should start
outside of the radiation belts and should have the FP cold again by
the time {\em Chandra} re-enters the radiation belts.

{\em NOTE:} It is important that the CCDs should stay as cold as
possible during this activity.  The CCD temperature should not be
allowed to exceed -60.0~C.

\vspace{0.15in}
\noindent The sequence of actions will be: 
\be
\item verify the initial Camera Body, Warm \& Cold Radiators and FP temperatures
\vspace{-0.10in}
\item enable FP bakeout and start heating FP to -60.0 C
\vspace{-0.10in}
\item Enable and turn on the DA housing bakeout heater once the FP
temperature has approached -60~C, heat DA housing to +25~C
\vspace{-0.10in}
\item Wait for the Camera Body temperature to stabilize at +25~C
\ee


%\vspace{0.25in}
\normalsize
\noindent {\bf ASSUMED INSTRUMENT STATE:} \\
\normalsize
Assumes the instrument is in the canonical thermal standby state (the
FEPs and video boards must be off !!!!).\\
Assumes that the SIM is at the ACIS-S position (SIM step \#~=~75624).\\

\vspace{0.25in}
\normalsize
\noindent {\bf SPECIAL INITIAL CONDITIONS:} \\
\normalsize


%\newpage 

\vspace{0.15in}
\normalsize
\noindent {\bf OPERATIONAL CONSTRAINTS/CAUTIONS:} \\
\normalsize
{\em THIS PROCEDURE LEAVES THE INSTRUMENT IN BAKEOUT MODE, IT MUST BE
ROUTINELY MONITORED DURING THIS TIME.}\\
The little and  large vent valves must already be open. \\
The turning off of the FEPs and analog electronics should be verified
before the heaters are turned on. \\
{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 SOT procedure 2.9\_V2.0 ``Full Bakeout'' \\
\noindent FOT procedure SAP\_61005 ``Full Bakeout'' \\


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

{\bf V1.0}
\begin{itemize}
\item adapted from SOT procedure 2.9\_V2.0 ``Full Bakeout'',
  corresponding FOT procedure is SAP\_61005.
\end{itemize}



\newcommand{\tablecaptiontext}{Full Bakeout Procedure }
\input{bake_FPm60_DHp20.tab}

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