Simulated CTA view of LS 5039 orbital variations above 1 TeV energy for 0.5 and 5 h long snapshots as observed from the southern CTA site. Upper panel: integral flux above 1 TeV, and middle and lower panels: estimated uncertainty of the measured spectral index and cut-off energy, correspondingly. The data points corresponding to T_obs = 5 h are shifted to the right by 0.01 phase for clarity.