Telescope control system

So-called ``building crashes'' occur when the building stops (e.g., because the safety system is triggered or if the drive system fails) and the telescope will (after some time) drive in to a safety switch and its power will be cut. This requires the telescope to be powered-on which takes several minutes. Often, the safety system is triggered by accident and to avoid the unnecessary loss of time the system has been upgraded in two ways. When the telescope is slewing and the power is cut to the building now also the telescope will ramp down its speed in the same way and no crash should occur and only a reset of the safety system is needed. In case when the telescope is tracking and it will not crash immediately in to the building if it stops, the telescope will continue tracking as before but now it will stop if it reaches a given distance from the center position with respect to the building, or when it gets to within a given distance to the limit switch that would cut the telescope power. If the safety system is reset before the telescope reaches this limit, the tracking will just continue. Otherwise the telescope will stop in idle mode until the observer resets the safety system, but no powering-on of the telescope is needed. In all cases, the TCS provides information about what is happening and suggest what should be done to avoid confusion.

With the possibility to operate most of our (observing) systems at the mountain remotely there is a safety issue. In principle people can use the web cams and call the control room to see if anybody is working with the telescope or instrument, but when running (especially automated) observing scripts somebody might not be aware of that and get his/her hands in while a filter wheel rotates or a pick-off mirror is moved. The general idea is to provide commands that can be issued at the telescope and would prevent the use of the telescope or instrument remotely. There is the possibility that this might affect some remote (test) observations and people should use these commands with care, but safety is more important.

As the TCS is a closed system it is in principle simple to isolate and exclude commands issued remotely. Specifically, we will implemented, e.g., called `Inhibit-Remote-Commands' and `Permit-Remote-Commands' that can only be issued from the TCS user interface in the control room. For the instruments controlled through the observing system this is a bit more complicated (see below).

Some test were made to move the User Interface, which runs on a rather ancient computer screen to a big colour screen by using a regular PC to act as front end to the TCS.