A Method to Estimate the Observable Time of X-ray Sources

The observation constraints for astronomical satellite are always restricted by space environment, such as Sun angle constraint, the time occulted by the Earth and the time passing through South Atlantic Anomaly. There are also some time periods, such as the time in high background region, the time when satellite between the Sun and the Earth, and the time when field of view of the satellite is close to the surface of the Earth, which can't be used for scientific analysis since the background level is very high or the background model is of great uncertainties. In this work, we establish an interface for these variations to estimate observable time of X-ray sources, and use orbitTools library to generate orbital data and HEAsoft's attitude library to calculate these variations. Compared with the actual observation, the predicted time of this work is consistent well with the time of observed data.