COMPTEL interface

Overview

The COMPTEL module provides an instrument interface for the COMPTEL telescope that has been operated on the Compton Gamma-Ray Observatory (CGRO) from 1991 to 2000.

The following figure presents an overview over the classes of the COMPTEL module and their relations.

COMPTEL module

The central object is a COMPTEL observation, implemented by the GCOMObservation class. The class either holds a COMPTEL event cube, implemented by the GCOMEventCube class, or an event list, implemented by the GCOMEventList class. A single bin of the event cube is implemented by the GCOMEventBin class, a single event by the GCOMEventAtom class.

The GCOMEventCube class uses the general GCOMDri class to store the data. GCOMDri implements a general three-dimensional data-space of COMPTEL, spanned by the scatter direction \(\chi\) and \(\Psi\) and the scatter angle \(\bar{\varphi}\). This three-dimensional coordinate is implemented by the GCOMInstDir class. The GCOMDri class further stores the selection sets, implemented by the GCOMSelection class.

The GCOMObservation class further holds COMPTEL Good Time Intervals, implemented by the GCOMTim class, and Orbit Aspect Data, implemented by the GCOMOads container class that holds records of GCOMOad. Optionally, the data may also hold information needed for barycentre correction of event arrival times, implemented by the GCOMBvcs container class that holds records of GCOMBvc. If this information is not provided, the barycentre correction information is computed on the fly, using JPL DE200 ephemerides that are provided by the GEphemerides class.

The module also provides a GCOMIaq class that enables computation of instrument response functions. The computation is based on the D1 and D2 detector response functions, that are accessed via the GCOMD1Response and GCOMD2Response classes. Instrument characteristics that are also required for the computation are access via the GCOMInstChars class.

So far two COMPTEL background model exists, that performs fitting of the \(\bar{\varphi}\) layers of a DRI model cube. While the GCOMModelDRBPhibarBins class fits each \(\bar{\varphi}\) layer with a separate scaling factor, the GCOMModelDRBPhibarNodes class specifies a scaling factor for a number of \(\bar{\varphi}\) values and interpolates the results linearly for \(\bar{\varphi}\) values that are not represented by the nodes. In addition, the GCOMModelDRM class implements the fitting of a data space model with a single scaling factor, and may be used either for source or background model fitting.

Finally, the GCOMStatus class holds instrument status information.