Telescope control system

The way the TCS is rebooted has been significantly simplified and is now limited to a single command and a single press on the `Reset' button without having to power cycle anything. Not only does this reduce the total time for a full reboot from 8-10 min to less than 3 minutes, it also reduces wear on power supplies etc. In principle this also allows in an emergency to let an observer performed this task.

Work has continued on integrate the TCS more in to the general observing system as for status information and operation through sequencer commands and scripts. A main part of this is communication between the TCS and the general data base which has significantly expanded. After this upgrade a major problem was encountered where the network connection to the TCS would get blocked ones every few days where a reboot was needed. The cause of this was identified as being a problem in the OS-9 operating system of the TCS computer system itself. By sub-dividing the data that is being send in smaller chunks which does not cause a clogging-up of the network connection while still allowing to send the full set of information in a reasonable time (a full set of the data is still sent about 2 times per second).

Some new commands have been added, some have been modified and simplifications were made for sequencer use. Practically all documentation has now been updated and revised to reflect the current TCS implementation in all details.

A log interface for handling TCS logs in an easier way is being developed. As it is now it is cumbersome to extract info from them, and the idea is that anyone should be able to get info about selected areas of interest with a web interface. Preliminary specifications and tests were made.

The temperature monitoring system that supplies TCS with the structure temperature measurements used to calculate and correct the telescope focus is rather slowly and only updates once per minute. These measurements have noise (in the measurements and on the line) or can be faulty (e.g., due to failure of one of the various sensors used), which has let to wrongly calculated telescope focus values. To avoid this causing unphysical changes in the telescope focus the TCS has been changed to ignore sudden, steep temperature changes and only follow more steady variations. This protection system is only operative when the dome is open, starting only 20 min after opening as during that time fairly steep temperature changes are normal and hard to separate from noise related changes. In case there are persistent changes that are considered unphysical by the system the observer is warned to check if the changes are real. If there truly is a steep change in temperature, the value can be accepted. Otherwise, the cage can be ignored and the cause of the wrong reported value can be investigated without directly causing large errors in focussing of the telescope.

Some additions and modifications have been made to the set of standard catalogues provided to the users. Some more improvements are currently being prepared.

Thomas Augusteijn 2010-02-09