摘要
Accurate flux density calibration is essential for precise analysis and interpretation of observations across different observation modes and instruments.In this research,we first introduce the flux calibration model that incorporated in Hi FAST pipeline,and designed for processing HⅠ21 cm spectra.Furthermore,we investigate different calibration techniques and assess the dependence of the gain parameter on the time and environmental factors.A comparison is carried out in various observation modes(e.g.,tracking and scanning modes)to determine the flux density gain(G),revealing insignificant discrepancies in G among different methods.Long-term monitoring data shows a linear correlation between G and atmospheric temperature.After subtracting the G-Temperature dependence,the dispersion of G is reduced to<3%over a one-year timescale.The stability of the receiver response of Five-hundred-meter Aperture Spherical radio Telescope(FAST)is considered sufficient to facilitate HⅠobservations that can accommodate a moderate error in flux calibration(e.g.,>~5%)when utilizing a constant G for calibration purposes.Our study will serve as a useful addition to the results provided by Jiang et al.Detailed measurement of G for the 19 beams of FAST,covering the frequency range 1000-1500 MHz,can be found on the Hi FAST homepage:https://hifast.readthedocs.io/fluxgain.
基金
the support of the China National Key Program for Science and Technology Research and Development of China(2022YFA1602901,2023YFA1608204)
the National Natural Science Foundation of China(Nos.11988101,11873051,12125302,12373011,12041305,12173016)
the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)。
