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Membership of the Current Calibration File

Here we address the issue of how to determine what calibration files make up the current calibration file for a given observation time.

Each calibration file has a validity start date and a validity end date. These are indicated by the FITS keywords VALDATE and EVALDATE. A missing EVALDATE is taken to mean no end of validity.

Given the naming convention above, a calibration file can be labeled with a quadruplet of the form $\{Fname, Issue, T_{start}, T_{end}\}$, where $Fname \equiv \textrm{ \textbf{scope}\_\textbf{calname}}$, and $T_{end}$ is optional.

New issues of a calibration file can enter the archive with any $T_{start}$, any $T_{end}$, and increasing issue numbers.

In the simplest case (no end of validity date), a new version of the calibration file — call it $\{Fname, Issue^\prime,
T_{start}^\prime\}$, will have $T_{start} < T_{start}^\prime$ and $Issue < Issue^\prime$ (figure 1).

\begin{figure}
% latex2html id marker 326
\begin{center}
\leavevmode
\epsfig{...
...ne\_0001.ccf} and
\textit{xmm\_ExampleTwo\_0002.ccf}}
\end{center}\end{figure}

A more complex situation is illustrated in figure 2. Here new versions are introduced to improve on past calibrations.

\begin{figure}
% latex2html id marker 335
\begin{center}
\leavevmode
\epsfig{...
...ne\_0001.ccf} and
\textit{xmm\_ExampleTwo\_0005.ccf}}
\end{center}\end{figure}

In figure 3 we show an example where a CCF constituent has an end of validity date. In this case at the time $T$ the situation is the same as shown in figure 2, whereas at the time $T1$ the constituent xmm_ExampleTwo_005.ccf is no longer applicable.

\begin{figure}
% latex2html id marker 346
\begin{center}
\leavevmode
\epsfig{...
...e\_0001.ccf} and
\textit{xmm\_ExampleTwo\_0003.ccf}.}
\end{center}\end{figure}

Within this scheme, at any time $T$ the applicable issue of the calibration file $Fname$ is obtained by selecting among all files $\{Fname, Issue, T_{start} \le T, T_{end} \ge T\}$ the one with the higher issue number.

Should it become necessary, a new $Fname$ can be introduced in the archive, as illustrated in figure 4.

\begin{figure}
% latex2html id marker 359
\begin{center}
\leavevmode
\epsfig{...
...\_0003.ccf} and
\textit{xmm\_ExampleThree\_0002.ccf}}
\end{center}\end{figure}

With this scheme the number of constituents in the current calibration file is not fixed, and can be determined only when the time $T$ is specified.

XMM-Newton SOC -- 2021-03-17