This will count as one of your downloads.
You will have access to both the presentation and article (if available).
The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) has made the transition from construction to science operations. It is currently operating with a “classical” single-conjugate Adaptive Optics (AO) system, which will be upgraded to a multi-conjugate AO (MCAO) system within the next few years. One of the key challenges for the DKIST MCAO system will be procuring a suitable Deformable Mirror (DM) to replace the current M7 flat, which is conjugate to 11.2 km.
The DM must be large in size with an elliptical clear aperture 884 by 625 mm. It must also have a high actuator density, with actuator spacings smaller than 11 mm. Additionally, it must have an actuator rise time of 100 µs and an update rate greater than 2 kHz. We have identified the surface-parallel actuated silicon carbide DMs made by Northrop Grumman’s AOA Xinetics (AOX) as a likely candidate to meet our requirements. However, there are some challenges that come with using this technology for the DKIST MCAO system. We must design our controller to avoid exciting resonant modes in the mirror. We also must minimize actuator saturation or it will become the dominant error term in our wavefront fitting error.
We discuss the advantages and disadvantages of this deformable mirror technology for astronomical imaging through the turbulent atmosphere. We use NSO’s Blur adaptive optics simulation software and the KAOS Evo 2 control software to simulate the performance of a large aperture silicon carbide DM. We also present simulation results that model the temporal error incurred by reducing the control bandwidth of the mirror’s resonant modes.
At the start of operations, five instruments will be deployed: a visible broadband imager (VTF), a visible spectropolarimeter (ViSP), a visible tunable filter (VTF), a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of 2017, the project finished its fifth year of construction and eighth year overall. Major milestones included delivery of the commissioning blank, the completed primary mirror (M1), and its cell. Commissioning and testing of the coudé rotator is complete and the installation of the coudé cleanroom is underway; likewise, commissioning of the telescope mount assembly (TMA) has also begun. Various other systems and equipment are also being installed and tested. Finally, the observatory integration, testing, and commissioning (IT&C) activities have begun, including the first coating of the M1 commissioning blank and its integration within its cell assembly. Science mirror coating and initial on-sky activities are both anticipated in 2018.
As of mid-2016, the project construction is in its 4th year of site construction and 7th year overall. Major milestones in the off-site development include the conclusion of the polishing of the M1 mirror by University of Arizona, College of Optical Sciences, the delivery of the Top End Optical Assembly (L3), the acceptance of the Deformable Mirror System (Xinetics); all optical systems have been contracted and are either accepted or in fabrication. The Enclosure and Telescope Mount Assembly passed through their factory acceptance in 2014 and 2015, respectively. The enclosure site construction is currently concluding while the Telescope Mount Assembly site erection is underway. The facility buildings (Utility and Support and Operations) have been completed with ongoing work on the thermal systems to support the challenging imaging requirements needed for the solar research.
Finally, we present the construction phase performance (schedule, budget) with projections for the start of early operations.
The VBI team recently completed a bottom up end-to-end system test 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 test plan, procedures, example test cases and tools used, as well as results from test 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.
The DKIST wavefront correction system will provide active alignment control and jitter compensation for all six of the DKIST science instruments. Five of the instruments will also be fed by a conventional adaptive optics (AO) system, which corrects for high frequency jitter and atmospheric wavefront disturbances. The AO system is built around an extended-source correlating Shack-Hartmann wavefront sensor, a Physik Instrumente fast tip-tilt mirror (FTTM) and a Xinetics 1600-actuator deformable mirror (DM), which are controlled by an FPGA-based real-time system running at 1975 Hz. It is designed to achieve on-axis Strehl of 0.3 at 500 nm in median seeing (r0 = 7 cm) and Strehl of 0.6 at 630 nm in excellent seeing (r0 = 20 cm).
The DKIST wavefront correction team has completed the design phase and is well into the fabrication phase. The FTTM and DM have both been delivered to the DKIST laboratory in Boulder, CO. The real-time controller has been completed and is able to read out the camera and deliver commands to the DM with a total latency of approximately 750 μs. All optics and optomechanics, including many high-precision custom optics, mounts, and stages, are completed or nearing the end of the fabrication process and will soon undergo rigorous acceptance testing.
Before installing the wavefront correction system at the telescope, it will be assembled as a testbed in the laboratory. In the lab, performance tests beginning with component-level testing and continuing to full system testing will ensure that the wavefront correction system meets all performance requirements. Further work in the lab will focus on fine-tuning our alignment and calibration procedures so that installation and alignment on the summit will proceed as efficiently as possible.
View contact details
No SPIE Account? Create one
