\documentclass[a4paper,12pt]{article}

\title{            STEREO -- IMPACT -- SEP
\\         Solar Electron Proton Telescope (SEPT)
\\                 Ground Test Procedures
}
\author{             Stephan B\"ottcher
\and              Reinhold M\"uller-Mellin
}
\date{v\,\rcs       $Revision: 1.7 $, 
      \rcs          $Date: 2005/05/12 09:26:18 $
}
\def\rcs$#1: #2 #3${#2}
\newcommand\units{\,\mathrm} 
\newcommand\tc[1]{{\let\<\tcmeta\texttt{#1}}}
\def\tcmeta#1>{$\langle$\textrm{\textit{#1}}$\rangle$}
\newenvironment{dtc}
  {\ttfamily\let\<\tcmeta\quote\obeylines}
  {\endquote}
\def\Co60{\ensuremath{{}^{60}\mathrm{Co}}}


\begin{document}
\maketitle

\section{Scope}

This note describes the procedures to test the SEPT instruments after
integration with the SEP suite, up to, and including integration on
the spacecraft.

\section{Requirements}

To perform these tests, SEPT must be hooked up to a SEP-Central unit,
and a communication channel must be set up to send commands to
SEP-Central and to receive telemetry packets from SEP-Central.

The gamma source aliveness test requires a radioactive source, like
\Co60, with an activity in the order of $1\units{\mu Ci}$.

\section{Tests}

Four tests are defined to verify the health of the instrument:
\begin{itemize}
\item Quiet run.
\item Inflight test pulse generator run.
\item \Co60 source run.
\item Cosmics run.
\end{itemize}

\subsection{Quiet Run}
\label{sec:Quiet}

To run this test, the SEPT instruments are configured for nominal
mission data acquisition, and collect data for at least ten minutes.

Ten minutes of data are required to make sure that each detector's
individual count rate is observed at least once during a one minute
observation cycle.  Three further minutes are required for the
instrument to reach nominal mode after receiving the command to do
so. 

When the SEP-Central unit is not configured with the connected SEPT
instrument's nominal thresholds, sensible detection thresholds must be
uploaded before this test.

\subsubsection{Procedure}\label{sec:quiet}

The command to turn the instruments to nominal mode after power up is: 
\begin{dtc}
  SPFM\<n>-GO
\end{dtc}
where \tc{\<n>} is either \tc{1}, or \tc{2}, for flight model 1 (S/C
ahead) and 2 (S/C behind).  This command loads the preconfigured
detection thresholds for the appropriate flight instruments.

That command is part of the command
\begin{dtc}
  ALLON\<n>
\end{dtc}
which also boots the other instruments of the SEP suite, if that is
desirable. 

To turn on SEPT into nominal mode without loading thresholds, the
distinction between 1 and 2 is not needed, use the
command 
\begin{dtc}
  SP-GO
\end{dtc}

If the SEP-Central unit is not known to be configured with proper
thresholds for the connected instruments, some sensible values
should be loaded for main threshold levels
\begin{dtc}
  15 MLEV-E!  
  15 MLEV-N!
\end{dtc}
and guard (coincidence) threshold levels:
\begin{dtc}
  17 CLEV-E!
  17 CLEV-N!
\end{dtc}

Collect data for 10 minutes, to make sure that all commands became
effective and eight successive accumulation periods worth of data
were recorded.

\subsubsection{Results}

In the SEP housekeeping packets (APID 577, 0x241 hex), verify that the
values returned by the SEP-Central power supply voltage monitors are
within range.

In the SEP housekeeping packets, verify that the SEPT temperatures are
within range.  (Subtract 166 from the raw readings to get degree
Celsius.)  A raw temperature reading of zero indicates that SEPT is
not (yet) sending data.  A valid reading confirms that SEPT is
responding to commands.

In the SEP housekeeping packets, verify that the raw leakage current
readings do not overflow to the value 255.  A reading different from
255 indicates that the bias voltage is present.  Raw readings between
50 and 150 are expected.

In the SEPT science packets for SEPT-NS (APID 600, 0x258 hex) and
SEPT-E (APID 601, 0x259 hex), verify that the spectra contain only
noise counts in the lower five energy bins, and only a few sporadic
counts in the higher bins of the 32-bin histogram.  Excess noise may
be caused by disturbances from the environment.

\subsection{Inflight Test Pulse Generator}
\label{sec:Itpg}

The SEPT instruments have simple inflight test pulse generators to
test the analog electronics and the coincidence logic.  Serious
detector noise problems will also show up.

Pulses of four different amplitudes can be injected into the charge
sensitive amplifiers. A 4-bit mask defines the set of inputs subjected
to the pulses.

SEP-Central keeps a table of test configurations (amplitude, mask,
coincidence mode) to be performed.  The first ten entries in the table
are preloaded with a set of tests that reasonably covers all detector
channels and coincidence conditions, with a single pulse amplitude.
The remaining 30 entries repeat these tests with different amplitudes.

A short test would run through 10 entries, a full test runs through
all 40 entries.  Each test requires a one minute accumulation cycle.

\subsubsection{Procedure}

Make sure that SEPT is up and running, with reasonable thresholds.
This test is usually run after the \emph{quiet mode run}, so that no
further action is required.  To run a test for \tc{\<n>} minutes
(usually 10 or 40), do
\begin{dtc}
  \<n> \ SPETEST
  \<n> \ SPNTEST
\end{dtc}
After \tc{\<n>} minutes, the instruments will automatically return to
nominal mode.

\begin{table}[!b]
  \centering
  \belowcaptionskip\abovecaptionskip
  \caption{Inflight test pulse generator mode table}
  \label{tab:itpg}
  \let\bf\bfseries
  \small
  \begin{tabular}{cllllc}
    \bf seq  & \bf pdfe & \bf filter  & \bf counter & \bf pulse & \bf peak \\[5pt]
    0   & anti & nominal & (0) Main 0  & (0x28) Main even                 & even \\
    1   & anti & nominal & (1) Main 1  & (0x22) Main odd                  & odd  \\
    2   & anti & nominal & (2) Main 2  & (0x2A) Main even/odd             & none \\
    3   & anti & nominal & (4) Guard 0 & (0x2C) Main/Guard even           & none \\
    4   & anti & nominal & (5) Guard 1 & (0x23) Main/Guard odd            & none \\
    5   & anti & nominal & (7) Guard 3 & (0x29) Main even, Guard odd      & none \\
    6   & anti & nominal & (6) Guard 2 & (0x26) Main odd, Guard even      & none \\
    7   & coinc & test   & (3) Main 3  & (0x2A) Main even/odd             & all  \\
    8   & coinc & test   & (4) Guard 0 & (0x2E) Main/Guard even, Main odd & all  \\
    9   & coinc & test   & (7) Guard 3 & (0x2B) Main even, Main/Guard odd & all  \\
  \end{tabular}
  \vspace{\abovecaptionskip}
  \footnotesize
  \begin{description}
  \item[pdfe:]
    PDFE operation mode, external coincidence (mode~5) or
    anti-coincidence (mode~4).
  \item[filter:] External coincidence filter mode. \emph{nominal}: all other
    signals contribute (0xAA), or \emph{test}: only the other Main channel
    contributes (0xFF).
  \item[counter:] 
    Single detector counter number.  Main channels: 0--3, Guard
    channels 4--7.
  \item[pulse:] Which PDFE inputs the generated pulse is applied to.
    The pulser configuration specifies the amplitude in bits 5:4. The
    value 0 is the highest, 3 the lowest amplitude.  For a short run
    the amplitude is 2, as shown in the table.  The bits 3:0 indicate
    which detector inputs to stimulate.  Bit~3: even main,
    bit~2: even guard, bit~1: odd main, bit~0: odd guard.  The A and B
    sides of the telescopes receive the same stimulation.
  \item[peak:]
    Which spectra must show the pulser peak.
  \end{description}
\end{table}

\subsubsection{Results}

Identify the SEPT science packets with non-zero test-pulser
configuration.  (Current versions of the flight software keep the
pulser configuration unchanged when the pulse generator run finished.
In that case, the previous data packet must show the value 0x4f hex in
the mode flags byte.)

All test pulser packets must show about 1\,047\,000 counts in the
single detector counter.  

The sixth column in Table~\ref{tab:itpg} tells which spectra should
show a corresponding peak.  The peaks should be mostly contained in a
single energy bin of the spectra.

\subsection{\Co60 Source Test}
\label{sec:Source}

A quick test to certify that all detectors are alive is achieved with
a radioactive gamma ray source.

\subsubsection{Procedure}

The instruments are setup in nominal mode just like for a quiet run in
section~\ref{sec:quiet}.  

The source, preferably \Co60 with an activity in the
order of $1\units{\mu Ci}$, is placed as closely as permitted to the
sensor head of the SEPT instrument.  When the instrument is standing,
it is easy to just lay the source on top of the sensor housing.  A
small plastic transport container need not be removed from the source.
The source should be bagged, to prevent contamination of the
instrument.  The instrument doors should remain closed.

When the instruments are running in nominal quiet mode, the source is
placed for 10~minutes next to each instrument.

\subsubsection{Results}

After placing the source, wait a few minutes until SEPT science
packets arrive with the source present during the full acquisition
period.

When the source is present, significant activity should be recorded in
higher energy bins in the spectra of all channels.

In eight consecutive acquisition periods, the single detector counter
readings should show increased activity compared to quiet run without
source. 

\subsection{Cosmics Run}
\label{sec:Cosmics}

The SEPT instrument's response to cosmic muons can certify aliveness
of the main detector channels, and give a coarse indication that the
energy scale is correct.

About two hours of accumulation is necessary to see the peaks of
minimum ionizing particles in the spectra.

\subsubsection{Procedure}

The discriminator thresholds must be raised well above their nominal
values to prevent coherent digital noise from triggering the readout.
After bringing the instruments up (section~\ref{sec:quiet}), issue:
\begin{dtc}
  30 MLEV-E!  
  30 MLEV-N!
  30 CLEV-E!
  30 CLEV-N!
\end{dtc}
To start a cosmics run for \tc{\<n>} minutes, do
\begin{dtc}
  \<n> SPECALM
  \<n> SPNCALM
\end{dtc}
The instruments will return to nominal mode after \tc{\<n>} minutes.
To abort a cosmics run and return to nominal mode earlier, issue
\begin{dtc}
  SPENORM
  SPNNORM
\end{dtc}

\subsubsection{Results}

The spectra in the SEPT science packets should be very quiet, mostly
no counts at all.  Beyond that, any activity is a sign of
environmental noise or a problem with the instrument.

To see the minimum ionizing particles peak, the spectra of the whole
run must be added, for each channel separately, omitting noisy
accumulations with more than, say, three counts.

\begin{table}[!b]
  \belowcaptionskip\abovecaptionskip
  \caption{Test sequences}
  \label{tab:seq}
  \centering
  \let\bf\bfseries
  \begin{tabular}{lcccc}
\bf Test             & \bf LPT & \bf CPT & \bf CPT+\Co60 & \bf Cosmics \\[5pt]
Quiet run                         & 11 min & 11 min & 11 min & \\
Inflight test pulse generator run & 12 min & 42 min & 42 min & \\
\Co60 source run (SEPT-E)         &        &        & 11 min & \\
\Co60 source run (SEPT-NS)        &        &        & 11 min & \\
Cosmics Test                      &        &        &        & 123 min \\[5pt]
Total                             & 23 min & 53 min & 75 min & 123 min \\
  \end{tabular}
\end{table}

\section{Test sequences}

This section defines four test sequences: a \emph{Limited Performance
  Test} (LPT, 20~minutes), a \emph{Comprehensive Performance Test}
(CPT) with (70~minutes) and without \Co60 source test (50~minutes),
and a cosmics test (120~minutes).  See Table~\ref{tab:seq} for a
summary.

\begin{table}[!b]
  \centering
  \belowcaptionskip\abovecaptionskip
  \caption{LPT command sequence}
  \label{tab:lpt}
  \begin{tabular}{l|lr}
                    & power on                     &  1 min \\
    \tc{SP-GO}      & start SEPT software          &  0 min \\
    \tc{15 MLEV-E!} & load main thresholds SEPT-E  &  0 min \\
    \tc{15 MLEV-N!} & load main thresholds SEPT-NS &  0 min \\
    \tc{17 CLEV-E!} & load guard thresholds SEPT-E &  0 min \\
    \tc{17 CLEV-N!} & load guard thresholds SEPT-NS&  0 min \\
                    & record 10 acquisition cycles & 10 min \\
    \tc{10 SPETEST} & start itpg run SEPT-E        &  0 min \\
    \tc{10 SPNTEST} & start itpg run SEPT-NS       &  0 min \\
                    & wait for mode change         &  2 min \\
                    & record 10 acquisition cycles & 10 min \\
\hline              & \hfill           Total time: & 23 min \\
  \end{tabular}
\end{table}

\begin{table}[!b]
  \centering
  \belowcaptionskip\abovecaptionskip
  \caption{CPT command sequence}
  \label{tab:cpt}
  \begin{tabular}{l|lr}
                    & power on                     &  1 min \\
    \tc{SP-GO}      & start SEPT software          &  0 min \\
    \tc{15 MLEV-E!} & load main thresholds SEPT-E  &  0 min \\
    \tc{15 MLEV-N!} & load main thresholds SEPT-NS &  0 min \\
    \tc{17 CLEV-E!} & load guard thresholds SEPT-E &  0 min \\
    \tc{17 CLEV-N!} & load guard thresholds SEPT-NS&  0 min \\
                    & record 10 acquisition cycles & 10 min \\
    \tc{40 SPETEST} & start itpg run SEPT-E        &  0 min \\
    \tc{40 SPNTEST} & start itpg run SEPT-NS       &  0 min \\
                    & wait for mode change         &  2 min \\
                    & record 40 acquisition cycles & 40 min \\
\hline              & \hfill           Total time: & 53 min \\
  \end{tabular}
\end{table}

\begin{table}[!b]
  \centering
  \belowcaptionskip\abovecaptionskip
  \caption{CPT+\Co60 command sequence}
  \label{tab:cpt+co60}
  \begin{tabular}{l|lr}
                    & power on SEP-Central         &  1 min \\
    \tc{SP-GO}      & start SEPT software          &  0 min \\
    \tc{15 MLEV-E!} & load main thresholds SEPT-E  &  0 min \\
    \tc{15 MLEV-N!} & load main thresholds SEPT-NS &  0 min \\
    \tc{17 CLEV-E!} & load guard thresholds SEPT-E &  0 min \\
    \tc{17 CLEV-N!} & load guard thresholds SEPT-NS&  0 min \\
                    & record 10 acquisition cycles & 10 min \\
    \tc{40 SPETEST} & start itpg run SEPT-E        &  0 min \\
    \tc{40 SPNTEST} & start itpg run SEPT-NS       &  0 min \\
                    & wait for mode change         &  2 min \\
                    & record 40 acquisition cycles & 40 min \\
                    & place source next to SEPT-E  &  1 min \\
                    & record 10 acquisition cycles & 10 min \\
                    & place source next to SEPT-NS &  1 min \\
                    & record 10 acquisition cycles & 10 min \\
\hline              & \hfill           Total time: & 75 min \\
  \end{tabular}
\end{table}

\begin{table}[!b]
  \centering
  \belowcaptionskip\abovecaptionskip
  \caption{Cosmics Test command sequence}
  \label{tab:cosmics}
  \begin{tabular}{l|lr}
                    & power on SEP-Central         &  1 min \\
    \tc{SP-GO}      & start SEPT software          &  0 min \\
    \tc{30 MLEV-E!} & load main thresholds SEPT-E  &  0 min \\
    \tc{30 MLEV-N!} & load main thresholds SEPT-NS &  0 min \\
    \tc{30 CLEV-E!} & load guard thresholds SEPT-E &  0 min \\
    \tc{30 CLEV-N!} & load guard thresholds SEPT-NS&  0 min \\
    \tc{120 SPECALM}& start cosmics run SEPT-E     &  0 min \\
    \tc{120 SPNCALM}& start cosmics run SEPT-NS    &  0 min \\
                    & wait for mode change         &  2 min \\
                    & record 120 acquisition cycles&120 min \\
\hline              & \hfill           Total time: &123 min \\
  \end{tabular}
\end{table}

\subsection{Limited Performance Test}

The limited performance test is a quick test to confirm
that the instruments basic functions are working.  During a
\emph{quiet run} (section~\ref{sec:Quiet}), the basic housekeeping
numbers are checked, and a short \emph{inflight test pulse generator
  run} (section~\ref{sec:Itpg}) tells wether the analog electronics are
alive.  

See Table~\ref{tab:lpt} for the complete command sequence.  This test
can be completed in 23~minutes.

\subsection{Comprehensive Performance Test}

The comprehensive performance test differs from the LPT only by
extending the inflight test pulse generator run to the full
40~minutes, thus providing a more comprehensive test of the analog
electronic.  

See Table~\ref{tab:cpt} for the complete command sequence.  This test
can be completed in 53~minutes.

\subsection{Comprehensive Performance Test + \Co60}

The simple CPT does not test wether the detectors are alive.  A \Co60
source test is required to confirm that all detectors are connected to
the electronics and provide a signal.

See Table~\ref{tab:cpt+co60} for the complete command sequence.  This
test can be completed in 75~minutes.

\subsection{Cosmics Test}

The cosmics test can replace or complement the \Co60 source test, in
cases when bringing a source is difficult, and enough time in a low
noise environment is available.

This test requires at least two hours to provide meaningful data, but
no operator attention nor telecommanding is necessary during the run.
The instruments operate in a very quiet configuration.  Therefore,
this test can run in the background while other SEP-suite instruments
are undergoing tests.

See Table~\ref{tab:cosmics} for the complete command sequence.

\end{document}
