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XMM-Newton Science Analysis System


hkgtigen (hkgtigen-1.14.2) [xmmsas_20070708_1801-7.1.0]

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Detailed Description

For each instrument standard HK parameter validity ranges are stored in the corresponding CCF constituent HKParmInt [2]. The ranges are expressed in terms of boolean selection expressions as defined by the selectlib package. Each expression is indexed by a unique keyword which is the HK parameter name to which the expression applies. It can contain one or more occurrences of the character '@' which must be replaced with the parameter name to form a complete syntactically correct selection expression. As an example, the HKParmInt entry:

    PYRO_DOOR_RELEASE_MECHANISM_T:   (@ in [120, 273])

defines the valid range of the HK parameter PYRO_DOOR_RELEASE_MECHANISM_T to be 120 to 273 K. Different entries are combined by hkgtigen via the logical and operator (&&) to form a single boolean expression according to the syntax rules defined in package selectlib.

The HK parameter names are defined by the names of the corresponding columns in the periodic HK parameter tables of the ODF [1,3]. Depending on the instrument, there is either one or two types of periodic HK files for each exposure. hkgtigen generates a single GTI set which is applicable to the entire observation period, i.e., it must first construct a number of individual GTI sets (one per type of periodic HK file per exposure period) and subsequently merge all sets into one. For the construction of an actual GTI set from a given periodic ODF HK file the task tabgtigen is used. The merging of the individual GTI sets is done in task hkgtigen itself.

In more detail, when invoked for a particular instrument (see parameter instrument), hkgtigen performs the following operations to construct the single GTI data set:

1. Retrieve all applicable validity intervals for that instrument from the CCF via the Calibration Access Layer (CAL) and replace all '@'-references with the actual HK parameter names.
2. For each instrument exposure in the given ODF and each type of periodic HK file the following steps are carried out:
   1. Construct a boolean expression containing validity ranges only for those HK parameters present in the current HK file
   2. Invoke the task tabgtigen with the constructed expression and the name of the current HK file. This generates a new GTI data set.
3. Merge all GTI sets constructed in step 2 into a single GTI data set which is applicable to the entire observation period.

hkgtigen provides a number of parameters to influence this algorithm. For instance, the parameter parameters can contain the explicit list of HK parameter names on which the CAL should be queried for validity ranges. It is also possible to augment the list of validity ranges retrieved from the CAL with additional ones. For more information on this and other command line options see below.