A Baseline Correction Algorithm for FAST

• Published in: Research in astronomy and astrophysics Vol. 22; no. 8; pp. 81001 - 81005
• Main Authors: Liu, De-Jian, Xu, Ye, Li, Ying-Jie, Lin, Ze-Hao, Bian, Shuai-Bo, Hao, Chao-Jie
• Format: Journal Article
• Language: English
• Published: Beijing National Astromonical Observatories, CAS and IOP Publishing 01.08.2022; IOP Publishing
• Subjects: Algorithms; Envelope curves; Fast Fourier transformations; Fourier transforms; methods: observational; Noise levels; Radio telescopes; Sensitivity; Spectra; Standing waves; techniques: spectroscopic; telescopes
• ISSN: 1674-4527; 2397-6209
• DOI: 10.1088/1674-4527/ac7d43

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most sensitive ground-based, single-dish radio telescope on Earth. However, the original H i spectra produced by FAST are affected by standing waves. To maximize the power of FAST for high-sensitivity observations, we proposed an algorithm that combines fast Fourier transforms and extreme envelope curves to automatically correct the baselines of FAST H i spectra and remove standing waves from the baselines. This algorithm can reduce the amplified noise level caused by standing waves to a near-ideal level without losing signals or introducing false signals. The root mean square of the average baseline reaches ∼8 mK, approaching the theoretical sensitivity of an H i spectrum produced by FAST for an integration time of 335 minutes, i.e., ∼6 mK.