Bottom-up laboratory testing of the DKIST Visible Broadband Imager (VBI)

Abstract

The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter solar observatory under construction at Haleakala, Hawaii [1]. The Visible Broadband Imager (VBI) is a first light instrument that will record images at the highest possible spatial and temporal resolution of the DKIST at a number of scientifically important wavelengths [2]. The VBI is a pathfinder for DKIST instrumentation and a bed for developing processes and procedures in the areas of unit, systems integration, and user acceptance testing. These procedures have been developed and repeatedly executed during VBI construction in the lab as part of a test early and often philosophy aimed at identifying and resolving issues early thus saving cost during integration and commissioning on summit. The VBI team recently completed a bottom up end-to-end system of the instrument in the lab that allowed the instrument’s functionality, performance, and usability to be validated against documented system requirements. The bottom up testing approach includes four levels of testing, each introducing another layer in the control hierarchy that is tested before moving to the next level. First the instrument mechanisms are tested for positioning accuracy and repeatability using a laboratory position-sensing detector (PSD). Second the real-time motion controls are used to drive the mechanisms to verify speed and timing synchronization requirements are being met. Next the high-level software is introduced and the instrument is driven through a series of end-to-end tests that exercise the mechanisms, cameras, and simulated data processing. Finally, user acceptance testing is performed on operational and engineering use cases through the use of the instrument engineering graphical user interface (GUI). In this paper we present the VBI bottom up plan, procedures, example cases and tools used, as well as results from execution in the laboratory. We will also discuss the benefits realized through completion of this testing, and share lessons learned from the bottoms up testing process.