2 The MAJORDOME

The MAJORDOME is the software that enables TAROT to optimally schedules observations, as well as alert observations. In the routine mode, The MAJORDOME implements several algorithms in order to ensure a maximum efficiency of the observations. Objects should be observed at minimal airmass (unless they have other constraints), and the number of possible observations should be maximized, according to various parameters such as the Moon, user constraints, observations types (periodic, single, etc.) and priorities. Whenever an alert occurs, the routine program is interrupted, and its program is activated. A forthcoming paper will focus on the MAJORDOME algorithm.

2.1 The MAJORDOME in routine mode

In a routine mode, the scheduling program is divided in 2 parts:

- The selection procedure.

- The run procedure.

The selection procedure selects from the request database all the visible objects for the next night. The requests may be entered at any time (thanks to the OBSERVATION REQUESTOR) and have a lifetime of 1 year. Hence, we have a list of all the possible observations for the next night at our disposal that goes through the run procedure. The core of the run procedure relies on a sequencing algorithm performing pairwise interchanges ([Baker 1979]) between observation tasks, in order to minimize an evaluation function taking into account parameters such as airmass, proximity of the Moon, etc. The first observations to be scheduled are the strongly constrained requests in reverse priority order. The MAJORDOME then schedules periodic requests and finally the non constrained requests. Their actual date of execution depends on the parameters described above (air mass, moon, etc.). We then have a time table optimized for the night. In case of an interruption due to an alert or bad weather conditions, the run program is reactivated, and a new schedule recomputed for the remaining of the night, taking eventually into account follow up observations if an alert occurs.

2.2 The MAJORDOME in alert mode

Whenever a GCN/BACODINE ([Barthelemy et al. 1999]) alert occurs, the MAJORDOME quits its routine program and instantly starts imaging the GRB position. This takes 3 seconds at most. We have decided to follow the alert types shown in Tab. 1 in descending priority order.

 

Figure 2: Mosaic for large error box

  

Table 1: TAROT follow up observations with priorities (1 being the highest priority level) and error boxes radii

For a large error box as BATSE provides, the MAJORDOME will generate a mosaic of 25 frames covering 25 sq deg for the present camera and 100 sq deg for the next camera available in May 1999. TAROT will image the mosaic until the MAJORDOME receives a higher priority alert.

We have decided to start our mosaic at the bottom left for our $1^{\circ}\times 1^{\circ}$ field of view camera because it is better to image first the setting objects. For a bigger field of view, it is better to start from the center because, 50% of the BATSE/LOCBURST GRB sources are found in a 1.$6^{\circ}$ radius error box. Today with the commercial camera, TAROT needs 25 minutes to image the whole mosaic. When the next camera will be operational, it will take 5 minutes to produce the mosaic, and only 1.8 minutes to image 50% of the BATSE alert error box.