## 5 Conclusions  
The THz Atmospheric Limb Sounder (TALIS) is the first microwave limb sounder being developed in China, and will contribute to atmosphere observation in the future. In this study, the impact of errors on the retrieval induced by three sources including instrument, calibration and external errors, are discussed. Sideband weight, local oscillator offset, measurement noise (NEDT) and pointing angle offset are considered as instrument uncertainties. Calibration errors contain hot target offset, nonlinearity of the two-point calibration, R-J approximation and the antenna pattern. The a priori profiles of temperature, pressure and species are the main external errors, since the model error could not be estimated. It should be noted that simulations from atmospheric profiles under different conditions could have led to different retrieval errors and usable vertical ranges. This simulation only represents a typical atmospheric condition. Local oscillator offset is quite important in the mesosphere and causes as large as a 5 K error above 50 km. Retrieval error due to the antenna pattern can be as large as 20 K in the troposphere, but less than 3 K at the other altitudes. NEDT, sideband weight and R-J approximation lead to errors of around 1-2 K, respectively. The effect of nonlinearity, hot target offset, pointing offset, pressure and a priori profile are relatively small (\(<\)1 K) in the main observation region. NEDT is the largest error source in 190 GHz H\({}_{2}\)O retrieval which leads to an error of 10%-40% above 60 km. Local oscillator offset causes as large as a 15% retrieval error at 70 km, but can be neglected below 60 km. R-J approximation is quite important in this frequency band and leads to an error of around 7%. The antenna pattern causes an error of less than 5%, but becomes large in the troposphere. Error due to sideband weight, nonlinearity and hot target offset is less than 1% in the main region, respectively. The effect of pointing offset and a priori profile is quite small. The results of 240 GHz O\({}_{3}\) retrieval are similar to that of 190 GHz. Error induced by NEDT dominates the retrieval in the middle and upper atmosphere. It can lead to the largest error of 50% at 80 km. The error due to R-J approximation is around 10% below 70 km. The impact of the local oscillator is important above 60 km, and this is around 10%. Hot target and nonlinearity are less than 1% below 70 km, respectively. The effect of the antenna pattern is similar to that of 190 GHz. The effect of sideband weight, pointing offset and a priori can be neglected in the main observation region. The results of 643 GHz have some difference. R-J approximation becomes the largest error source in 643 GHz HCl retrieval. An error of 10%-100% is caused by using R-J approximation in calibration. NEDT causes an error of 10%-50% in the middle and upper atmosphere. Retrieval error induced by the local oscillator is 3%-10% above 60 km, which is similar to other radiometers. Errors due to sideband weight, hot target offset and nonlinearity are less than 1%, respectively. Antenna pattern, pointing offset and a priori are quite small in the main observation region, but become large in the troposphere, since the measurement response is small. From the simulation above, instrument uncertainties are the most important error sources. The calibration residual errors will affect the retrieval in the troposphere and lower stratosphere. R-J approximation should not be used in calibration unless an additional correction can be done. The a priori uncertainties have little influence. Moreover, it is necessary to use an entire antenna pattern in calibration. [PERSON] performed the simulation and analyzed the results; [PERSON] and [PERSON] analyzed the error sources; [PERSON] wrote the manuscript; [PERSON] edited the article. All authors have read and agreed to the published version of the manuscript. This research received no external funding.