Software infrastructure for the visible tunable filter

The Visible Tunable Filter Instrument (VTF) is a 2D imaging spectropolarimeter for high spatial and spectral resolution solar observations in the visible light. Integration into the world largest solar telescope, the 4m aperture Daniel K. Inouye Solar Telescope (DKIST) started in January 2024. In this paper we present an overview over the complete software infrastructure designed and developed for this instrument. In particular the Instrument Control Software (ICS), the Instrument Performance Calculator (IPC) which is a graphical tool enabling scientist to explore instrument performance and create executable observing configurations. Furthermore, real-time monitoring plugins were implemented to verify data acquisition and instrument performance. The main part of the infrastructure is the ICS package which provides the interface between the operator, the instrument and the observatory. It is based on the Common Services Framework (CSF) provided by DKIST and is based on an object-oriented design and written in JAVA. The interface to the operator is given by the engineering GUI that allows the user to monitor and control all system drives and sensors. All observation and calibration tasks can be configured and started from this GUI. The interface to the instrument is realized by a DKIST framework compatible OPC/UA layer developed for this instrument which interfaces to a Beckhoff Programmable Logic Controller (PLC) that manages the real-time requirements of the instrument. All real-time and synchronization requirements are implemented using the DKIST timing and synchronization system (TRADS) based on the precision time protocol (PTP) that allows timing accuracy well below microseconds. Furthermore, the ICS interfaces to the Camera System Software (CSS) and Data Handling System (DHS), where VTF delivers up to 2400 MB/s or roughly 9 TB/hour when used in spectropolarimetric imaging mode.