Subjects: Astronomy submitted time 2023-12-15 Cooperative journals: 《天文学报》
Abstract： The Square Kilometre Array (SKA) project is an international collaboration to build the world's largest radio telescope, whose sensitivity and measurement speed will be an order of magnitude higher than those of all current radio telescopes. Radio continuum survey is one of the main observation mode of the SKA, and the establishment of a standard map of the survey area based on continuum imaging will provide an important foundation for subsequent astronomical science. The GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) is a project of the SKA pilot telescope Murchison Widefield Array (MWA) in 2018---2020. GLEAM-X is a new radio continuum survey project to be carried out with the MWA Phase II expansion array in 2018---2020. The experience of optimizing the imaging pipeline based on the distributed execution framework will help to solve the problem of massive data processing. In this paper, we describe the process steps of GLEAM-X imaging pipeline, integrate and improve it, and realize parallel processing of multiple pipelines on the China SKA Regional Centre Prototype (CSRC-P), and verify the deployment and test the correctness of the imaging pipeline system using GLEAM-X observation data. The GLEAM-X observations were used to validate the deployment of the imaging pipeline system and test its correctness. Then, to optimize the pipelines and improve the processing efficiency, the Data Activated Liu Graph Engine (DALiuGE) was used to integrate the imaging pipelines into the DALiuGE execution framework to automate the distributed parallel processing of the pipelines. Performance tests and results analysis show that the optimized imaging pipeline based on the DALiuGE execution framework has better performance, more flexible adaptability and scalability than the traditional parallel approach, and can support future large-scale continuum imaging experiments during the first phase of SKA commissioning.
Subjects: Astronomy submitted time 2023-08-02 Cooperative journals: 《天文学报》
Abstract： This paper describes the method of using the optical telescope to assist the Tianma 13\;m radio telescope for pointing measurement and establishing the pointing error correction model. For small-aperture telescopes, there are few target sources for pointing and calibration, and it is difficult to establish a pointing model by radio method to cover the whole sky area. The Tianma 13\;m radio telescope of Shanghai Astronomical Observatory is used to conduct optical-assisted pointing measurement research. A set of optical pointing system was installed on the back frame of Tianma 13\;m antenna, which obtained a repeatable measurement accuracy better than 3$''$. In addition, through the analysis of the factors affecting the antenna pointing, a pointing error correction model containing 8 error terms, as well as the optical axis and electrical axis deviation models were established. The pointing model was brought into the antenna servo control system to cross-scan the calibration target radio source, and a pointing error of about 5$''$ was obtained. This research can provide a reference method for high-precision pointing modeling.
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