%+
% Name:
% bias_parity_error_spec_1.1.tex
%
% History:
% 2010 Jul 19, created (v0.1), Glenn E. Allen
% 2010 Aug 18, removed maxpix and fixed maxerr (v0.2), GEA
% 2010 Aug 19, added a figure showing the number of errors per frame
% (v0.3), GEA
% 2012 Nov 02, described what to do for CC mode (v0.4), GEA
% 2012 Nov 20, (v1.0), GEA
%-
\documentclass{article}
\usepackage{/nfs/inconceivable/d0/SRC/LATEX/STY/cxo_memo_logo}
\usepackage[dvips]{graphics}
\usepackage{epsfig}
\usepackage{/nfs/inconceivable/d0/SRC/LATEX/STY/gea}
\usepackage{pstricks}
\newrgbcolor{red}{1 0 0}
\begin{document}
% 1. Header
\memobasic{
Jonathan McDowell, SDS Group Leader }{
Glenn E.\ Allen, SDS }{
Bias-parity error spec }{
1.1 }{
http://space.mit.edu/CXC/docs/docs.html\#berr }{
/nfs/inconceivable/d0/SDS/SPECS/BERR/bias\_parity\_error\_spec\_1.1.tex }
% 2. Tool name
\section{Bias-parity errors}
% 3. Description
\subsection{ Description }
Some observations are adversely affected by bias-parity errors. To explore
the properties of these errors, 16,304 bias-parity error files were obtained
from the archive for the interval from the beginning of the mission through
July 8, 2010. Figure~\ref{fig01} shows histograms of the total number and
the ``valid'' number (see sec.~\ref{proc}) of errors for each file. The
results for the valid errors are also listed in Table~1. The results below
the horizontal line in the middle of the table are the results for the
twelve files that contain errors associated with the ``FEP0 problem.'' The
number of errors, if any, per frame of data is typically very small
(Fig.~\ref{fig02} and Table~2). The only bias-parity error files that have
more than 10 errors per frame are the twelve files associated with the FEP0
problem. As shown in Figure~\ref{fig03}, the number of bias-parity errors
varies with time. There is a correlation between the number of errors and
the number of pixels on which the errors occur (Fig.~\ref{fig04}). Of the
16,304 files, there are only seven where the number of valid errors is not
equal to the number of pixels affected by the errors. Six of these seven
files are ones associated with FEP0 problem for which the number of errors
is comparable to or greater than 262,144, the maximum number of pixels that
can be affected by the problem. The seventh file is for {\tt OBS\_ID} 7649,
where all but one of the 7,439 errors are reported for the
pixel $( {\tt CCD\_ID}, {\tt CHIPX}, {\tt CHIPY} ) = ( 8, 786, 356 )$.%
%
\footnote{These errors are valid and are not associated with the FEP0
problem.}
%
The distribution of the valid errors in chip coordinates is shown in
Figure~\ref{fig05}. Inspection of this figure suggests that there is a
periodic pattern every 32 pixels in {\tt CHIPX}.%
%
\footnote{The FEP reads the bias-parity error data in 32-bit words.}\ \
%
Figures~\ref{fig06} and \ref{fig07} confirm the existence of a periodic
pattern. As shown in Figure~\ref{fig08}, there is a similar, but much less
pronounced, 32-pixel periodicity in the {\tt CHIPX} values of the errors
associated with the FEP0 problem. A much more prominent feature of the FEP0
errors is that they only occur in columns with odd values of {\tt CHIPX}
(Fig.~\ref{fig09}) and in rows with values of ${\tt CHIPY} \ge 513$
(Fig.~\ref{fig08}).
The remainder of this spec describes how the tool {\tt acis\_build\_badpix}
handles bias-parity error files.
% 4. Input
\subsection{ Input }
\begin{enumerate}
\item
One or more Level 0 bias-parity error file (acis*berr0.fits)
\item
A Level 0 parameter-block file (acis*pbk0.fits)
\end{enumerate}
% 5. Output
\subsection{ Output }
\begin{enumerate}
\item
A bad-pixel file that includes, among other things, a list of the pixels
with valid bias-parity errors (acis*bpix1.fits).
\end{enumerate}
% 6. Parameters
\subsection{ Parameters }
\begin{enumerate}
\item
{ \tt berrfile,f,a,"",,,"Name(s) of input bias-parity error file(s)" }
\item
{ \tt berrext,s,h,"BERR",,,"Name of bias-parity error extension" }
\item
{ \tt pbkfile,f,a,"",,,"Name of input parameter-block file" }
\item
{ \tt maxerr,i,h,10,0,100%
%
\footnote{A maximum value of 100 is large enough to be well above the
maximum number of valid errors per frame for files that are not
associated with the FEP0 problem (Fig.~\ref{fig02} and Table~2) and
small enough to be well below the number of errors per frame in the
first frame associated with the FEP0 problem for the twelve FEP0 {\tt
OBS\_ID}s in Table~1.}%
%
,"Maximum number of valid
bias-parity errors per frame" }
\item
{ \tt outfile,f,a"",,,"Name of output bad-pixel file" }
\end{enumerate}
% 7. Processing
\subsection{ Processing }
\label{proc}
Perform the following tests before processing begins.
%
\begin{itemize}
\item
Verify that each {\tt berrfile} exists and has an an extension where the
value of {\tt EXTNAME} is identical to the value specified by {\tt
berrext}. If one or both of these conditions is not true, then exit
with an error message.
\item
Verify that the {\tt pbkfile} exists. If it does not, then exit with an
error message.
\item
Verify that {\tt maxerr} is in the specified range.
\item
If {\tt clobber = no}, then verify that the {\tt outfile} does not
exist. If it does, then exit with an error message.
\end{itemize}
Perform the following steps, in sequence, for each bias-parity error file.
Note that each file corresponds to a single CCD for an observation.
\begin{enumerate}
\item
Ignore invalid bias-parity errors. Invalid errors are those for which
{\tt{DATAMODE = VFAINT}} and for which the coordinates%
%
\footnote{As defined here, all errors associated with the FEP0 problem,
except for those at $({\tt CCDX},{\tt CCDY}) = (0,{\tt ROWCNT})$, are
valid.}
%
\begin{itemize}
\item
$( {\tt CCDX}, {\tt CCDY} ) = ( 0, {\tt ROWCNT} )$ or
\item
$( {\tt CCDX}, {\tt CCDY} ) = ( 1, {\tt ROWCNT} )$ or
\item
$( {\tt CCDX}, {\tt CCDY} ) = ( 1022, 0 )$ or
\item
$( {\tt CCDX}, {\tt CCDY} ) = ( 1023, 0 )$.
\end{itemize}
%
Here {\tt DATAMODE} is a keyword in the {\tt berrfile}, {\tt CCDX} and
{\tt CCDY} are elements of columns with the same names in the {\tt
berrfile} and {\tt ROWCNT} is a keyword in the {\tt pbkfile}.
\item
If a {\tt berrfile} includes one or more valid bias-parity errors, then
set the {\tt FEP\_ID} equal to the value of the keyword of the same name
in the {\tt berrfile} and use the information in the binary table of the
{\tt pbkfile} to find the corresponding {\tt CCD\_ID}.
\item
{ \red
A FEP is identified as having suffered from the FEP0 problem if
%
\begin{itemize}
\item
the ${\tt FEP\_ID} = 0$,
\item
the errors have ${\tt CCDY} \ge 0$ (if the ${\tt DATAMODE} = {\tt
CC33\_FAINT}$ or {\tt CC33\_GRADED}) or have ${\tt CCDY} \ge 512$
(if the {\tt DATAMODE} is anything else), and
\item
the total number of valid errors per frame, in the appropriate {\tt
CCDY} range, is greater than {\tt maxerr} for any frame.
\end{itemize}
}
\item
If a {\tt berrfile} includes one or more valid bias-parity errors that
are not associated with the FEP0 problem, then the extension of the {\tt
outfile} that is associated with {\tt CCD\_ID} includes one or more
entries such that
%
\begin{itemize}
\item
{\tt SHAPE} is computed as usual,
\item
{\tt COMPONENT} is computed as usual,
\item
${\tt CHIPX} = {\tt CCDX} + 1$,
\item
${\tt CHIPY} = {\tt CCDY} + {\tt STARTROW} + 1$ \hspace*{0.25in} (if
${\tt DATAMODE} = {\tt FAINT}$, {\tt FAINT\_BIAS}, {\tt GRADED}, or
{\tt VFAINT}), or \\
%
$1 \le {\tt CHIPY} \le 1024$ \hspace*{1.0in} (if ${\tt DATAMODE} =
{\tt CC33\_FAINT}$ or {\tt CC33\_GRADED}),
\item
${\tt TIME} = {\tt TIME}_{\rm berr}$,
\item
${\tt TIME\_STOP} = {\tt TSTOP}$, and
\item
{\tt STATUS} has bit 2 (of 0-31) set to one.
\end{itemize}
%
Here, {\tt CCDX} and {\tt CCDY} are the coordinates of the bias-parity
error, ${\tt TIME}_{\rm berr}$ is the {\tt TIME} associated with the
error, and {\tt STARTROW} and {\tt TSTOP} are keywords in the {\tt
pbkfile}.
\item
If a {\tt berrfile} contains valid bias-parity errors associated with
the FEP0 problem, then the extension of the {\tt outfile} that is
associated with {\tt CCD\_ID} includes an entry such that%
%
\footnote{An examination of the twelve bias-parity error files that
include errors associated with the FEP0 problem (\ie\ ones for the {\tt
OBS\_ID}s that are below the line in Table~1), reveals that the only
errors reported are errors associated with the FEP0 problem. There is
no evidence that there are other valid errors in the files.} % Therefore,
% the only entries that should be included in the corresponding bad-pixel
% files are entries for the FEP0 problem.}
%
\begin{itemize}
\item
{\tt SHAPE} is determined as usual,
\item
{\tt COMPONENT} is computed as usual,
\item
$1 \le {\tt CHIPX} \le 1024$,
\item
$513 \le {\tt CHIPY} \le 1024$,
\item
${\tt TIME} = {\tt TIME}_{\rm berr}$,
\item
${\tt TIME\_STOP} = {\tt TSTOP}$,
and
\item
{\tt STATUS} has bit 13 (of 0-31) set to one.
\end{itemize}
%
Here, ${\tt TIME}_{\rm berr}$ is the {\tt TIME} associated with the
first frame in which there are more than {\tt maxerr} valid bias-parity
errors and {\tt TSTOP} is a keyword in the {\tt pbkfile}.
\end{enumerate}
% 8. Caveats
\subsection{ Caveats }
\begin{enumerate}
\item
The values of {\tt TIME} in the bias-parity error files appear to be the
{\tt TIME}s of the mid points of the frames. Therefore, perhaps the
values of {\tt TIME} in the output file should be ${\tt TIME}_{\rm stat}
- {\tt TIMEPIXR}_{\rm stat} \times {\tt TIMEDEL}_{\rm stat}$ instead of
${\tt TIME}_{\rm berr}$, where ${\tt TIME}_{\rm stat}$ is the time
associated with the relevant {\tt EXPNO}.
\end{enumerate}
% 9. Figures and table
% 9.1. Table 1
\begin{center}
\begin{tabular}{ccl}
\multicolumn{3}{c}{Table 1. Histogram of the number of valid bias-parity
errors} \\
\hline \hline
No.\ valid errors & No.\ files & {\tt OBS\_ID}(s) \\
\hline
0 & 14079 & {\ldots} \\
1 & 2055 & {\ldots} \\
2 & 124 & {\ldots} \\
3 & 23 & {\ldots} \\
4 & 6 & 2977, 5771, 9581, 10052, 10806, 11011 \\
5 & 1 & 4195 \\
6 & 2 & 9893, 11058 \\
7 & 1 & 9924 \\
7439 & 1 & 7649 \\
\hline
127003 [3550]\ \ \ \ & 1 & 62340 \\
136481 [625]\ \ \ \ \ & 1 & 62338 \\
139559 [139522] & 1 & 965 \\
139756 [139744] & 1 & 510 \\
149668 [149668] & 1 & 62502 \\
186595 [186383] & 1 & 62333 \\
200635 [4827]\ \ \ \ & 1 & 62327 \\
238050 [146756] & 1 & 62353 \\
265784 [118226] & 1 & 18 \\
336595 [79091]\ \ & 1 & 62363 \\
1043209 [139813]\ \ & 1 & 1383 \\
3286241 [101649]\ \ & 1 & 333 \\
\hline
Total & 16304 & {\ldots} \\
\hline \hline
%
\multicolumn{3}{l}{\parbox{5.0in}{The numbers inside the square brackets
in the first column are the number of errors in the first frame that has
an error. These values are well above the maximum allowed value for
{\tt maxerr}.}}
%
\end{tabular}
\end{center}
% 9.2. Table 2
\vspace*{1.0\baselineskip}
\begin{center}
\begin{tabular}{ccl}
\multicolumn{3}{c}{Table 2. Histogram of the number of valid bias-parity
errors per frame} \\
\hline \hline
No.\ valid errors per frame & No.\ frames & {\tt OBS\_ID}(s) \\
\hline
1 & 9613 & {\ldots} \\
2 & 90 & {\ldots} \\
3 & 13 & {\ldots} \\
4 & 1 & 5771 \\
5 & 1 & 4195 \\
6 & 2 & 9893, 11058 \\
7 & 1 & 9924 \\
\hline
Total & 9721 & {\ldots} \\
\hline \hline
%
\multicolumn{3}{l}{\parbox{5.0in}{The very large number of frames with
no valid errors is omitted. The data in the files that are associated
with the FEP0 problem are also omitted. Therefore, the values for the
number of frames are the differences between the red and green
histograms in Figure~\ref{fig02}. }}
%
\end{tabular}
\end{center}
% 9.3. Fig 1
\begin{figure}
\hbox{\psfig{file=FIGS/n_errs_hist.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of bias-parity errors in the bias-parity
error files. The black histogram includes all telemetered bias-parity
errors. The red histogram includes only the valid errors (see
sec.~{\ref{proc}}). The bin at the right-hand side of the plot
indicates the number of files that have at least 200 errors.
%
\label{fig01}}
\end{figure}
% 9.4. Fig 2
\begin{figure}
\hbox{\psfig{file=FIGS/err_rate_hist.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of bias-parity errors per frame of data.
The black histogram includes all telemetered bias-parity errors. The
red histogram includes only the valid errors (see sec.~\ref{proc}). The
green histogram includes only the valid errors that are associated with
the FEP0 problem. The bin at the right-hand side of the plot indicates
the number for frames that have at least 30 errors. All twelve of the
files associated with the FEP0 problem have at least one frame with 30
or more errors (Table~1). The dotted, vertical line is the default value for {\tt
maxerr}.
%
\label{fig02}}
\end{figure}
% 9.5. Fig 3
\begin{figure}
\hbox{\psfig{file=FIGS/n_errs_v_time.ps,angle=-90,width=6.5in}}
%
\caption{The number of valid bias-parity errors as a function of time.
Each data point is the sum over a 365-day interval. The day is the
mission elapsed time (\ie\ is relative to 1998-01-01T00:00:00). The
data associated with the FEP0 problem and with {\tt OBS\_ID} 7649 are
excluded. As noted by Peter Ford, there is a correlation between the
number of bias-parity errors and the number of threshold crossings.
%
\label{fig03}}
\end{figure}
% 9.6. Fig 4
\begin{figure}
\hbox{\psfig{file=FIGS/n_errs_v_n_pix.ps,angle=-90,width=6.5in}}
%
\caption{The number of pixels on which valid bias-parity errors occur v.\
the number of valid errors. The dashed line is the line along which the
number of pixels equals the number of errors. It is not possible for a
data point to lie above this line (\ie\ to have more pixels with
bias-parity errors than errors). The cluster of points near the upper,
right-hand corner are those associated with the FEP0 problem. The
dotted, horizontal line at 262,144 represents the maximum number of
pixels that can be affected by the FEP0 problem. The point near the
middle of the lower edge is for {\tt OBS\_ID} 7649. A bias-parity error
file for this observation had 7,439 errors, all but one of which
occurred at the location $( {\tt CCD\_ID}, {\tt CHIPX}, {\tt CHIPY} ) =
( 8, 786, 356 )$.
%
\label{fig04}}
\end{figure}
% 9.7. Fig 5
\begin{figure}
\hbox{\psfig{file=FIGS/valid_coords.ps,angle=-90,width=6.5in}}
%
\caption{A plot of the chip coordinates at which valid bias-parity errors
occur. Note that all CCDs are included. The data in the files that are
associated with the FEP0 problem are excluded. A periodic pattern in
{\tt CHIPX} is evident.
%
\label{fig05}}
\end{figure}
% 9.8. Fig 6
\begin{figure}
\hbox{\psfig{file=FIGS/n_valid_v_coords_1024.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of valid bias-parity errors as a
function of {\tt CHIPX} (black) and {\tt CHIPY} (red). Note that all
CCDs are included. The data in the files that are associated with the
FEP0 problem are excluded. The spikes at ${\tt CHIPX} = 786$ and ${\tt
CHIPY} = 356$ are associated with the 7,438 errors at this location for
{\tt OBS\_ID} 7649. A periodic pattern in {\tt CHIPX} is evident.
%
\label{fig06}}
\end{figure}
% 9.9. Fig 7
\begin{figure}
\hbox{\psfig{file=FIGS/n_valid_v_coords_32.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of valid bias-parity errors as a
function of {\tt CHIPX} (black) and {\tt CHIPY} (red). The coordinates
are modulo 32. Note that all CCDs are included. The data in the files
that are associated with the FEP0 problem are excluded. The spikes at
coordinates of 18 and 2 are associated with the 7,438 errors at ${\tt
CHIPX} = 786$ and ${\tt CHIPY} = 356$ for {\tt OBS\_ID} 7649. Errors
occur almost exclusively on one of the last four columns in each set of
32 columns.
%
\label{fig07}}
\end{figure}
% 9.10. Fig 8
\begin{figure}
\hbox{\psfig{file=FIGS/n_fep0_v_coords_1024.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of bias-parity errors as a function of
{\tt CHIPX} (black) and {\tt CHIPY} (red) for the errors associated with
the FEP0 problem. Note that all CCDs are included. A periodic pattern
in {\tt CHIPX} is evident. No errors are reported for pixels that have
${\tt CHIPY} < 513$.
%
\label{fig08}}
\end{figure}
% 9.11. Fig 9
\begin{figure}
\hbox{\psfig{file=FIGS/n_fep0_v_coords_32.ps,angle=-90,width=6.5in}}
%
\caption{Histograms of the number of bias-parity errors as a function of
{\tt CHIPX} (black) and {\tt CHIPY} (red) for the errors associated with
the FEP0 problem. The coordinates are modulo 32. Note that all CCDs
are included. No errors are reported for pixels that have even values
of {\tt CHIPX}.
%
\label{fig09}}
\end{figure}
% 10. Finish
\end{document}