The fifth Sloan Digital Sky Survey Local Volume Mapper (LVM) is a wide-field integral field unit survey that uses an array of four 160 mm fixed telescopes with siderostats to minimize the number of moving parts. An individual telescope observes the science or calibration field independently and is synchronized with the science exposure. We developed the LVM Acquisition and Guiding Package (LVMAGP)-optimized telescope control software program for LVM observations, which can simultaneously control four focusers, three K-mirrors, one fiber selector, four mounts (siderostats), and seven guide cameras. This software is built on a hierarchical architecture and the SDSS framework and provides three key sequences: autofocus, field acquisition, and autoguide. We designed and fabricated a proto-model siderostat to test the telescope pointing model and LVMAGP software. The mirrors of the proto-model were designed as an isogrid open-back type, which reduced the weight by 46% and enabled reaching thermal equilibrium quickly. In addition, deflection due to bolting torque, self-gravity, and thermal deformation was simulated, and the maximum scatter of the pointing model induced by the tilt of optomechanics was predicted to be 4′.4, which can be compensated for by the field acquisition sequence. We performed a real sky test of LVMAGP with the proto-model siderostat and obtained field acquisition and autoguide accuracies of 0″.38 and 1″.5, respectively. It met all requirements except for the autoguide specification, which will be resolved by more precise alignment among the hardware components at Las Campanas Observatory.
KEYWORDS: Spectrographs, Control software, Software development, Charge-coupled devices, Camera shutters, Design and modelling, Control systems, Computer architecture, Data acquisition, Switches
Local Volume Mapper Spectrograph Control Package (LVMSCP) is the software that controls three spectrographs to acquire science spectral data cubes automatically. The software architecture design based on Python 3.9 follows a hierarchical structure of Actors, the unit that controls each piece of hardware. We used the software framework Codified Likeness Utility to implement each Actor. The Actors communicate with each other through RabbitMQ, which implements the Advanced Message Queuing Protocol. The Actor applies asynchronous programming with non-blocking procedures as the three spectrographs should operate simultaneously. For the requirement of incremental code change and management in the collaboration of the developers, we adopted the SDSS Github Action, which supports continuous integration/continuous deployment. As a result, unit testing with Pytest tested the individual components of the software, respectively, and lab testing with LVMSCP provided the spectra data for the spectrograph calibration. The LVMSCP provides the application programming interface to the Robotic Observation Package to fulfill the required scientific survey execution for the spectrographs.
The Local Volume Mapper (LVM) project in the fifth iteration of the Sloan Digital Sky Survey (SDSS-Ⅴ) will produce large integral-field spectroscopic survey data to understand the physical conditions of the interstellar medium in the Milky Way, the Magellanic Clouds, and other local-volume galaxies. We developed the Local Volume Mapper Spectrograph Control Package (LVMSCP) which controls the instruments for the operation of the spectrograph. We use the new SDSS message passing protocol CLU (Codified Likeness Utility) for the interaction, based on the RabbitMQ that implemented the Advanced Message Queuing Protocol (AMQP). Also, asynchronous programming with non-blocking procedures is applied for the package since three spectrographs should be operated simultaneously. The software is implemented based on Python 3.9, and will provide the Application Programming Interface (API) to the Robotic Observation Package (ROP) for the integrated observation.
Sloan Digital Sky Survey fifth-generation (SDSS-V) Local Volume Mapper (LVM) is a wide-field IFU survey that uses an array of four 160 mm telescopes. It provides IFU spectra over the optical range with R ∼ 4,000 to reveal the inner components of galaxies and the evolution of the universe. Each telescope observes the science field or the calibration field independently, but all of them should be simultaneously synchronized with the science exposure. To minimize the moving parts, the LVM adopted the siderostat design with a field derotator. We designed the optimized control software for our LVM observation, lvmagp, which controls four focusers, three K-mirror derotators, one fiber selector, four mounts (siderostats), and seven guide cameras. It was built on its owen user interface and messaging protocol called actor and clu based on asynchronous programming. The lvmagp provides three key sequences: autofocus sequence, field acquisition sequence, and autoguide sequence. Also, we designed and fabricated the proto-model siderostat for the software test. The real sky test was made with proto-model siderostat, and the lvmagp showed arcsecond-level field acquisition and autoguide accuracy.
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