the system noise temperature of HSTDM, which is determined by measurement， with unit in Kelvin (K)
the spectral resolution of the HSTDM spectrometer which is 1.2GHz/16384=73.2421875kHz
the required sensitivity of HSTDM in K (unit)
the spectrometer efficiency, which is determined through orbit calibration, with default value 1.0
the number of on source position for one offposition
total number of lines of the obervation