How ascending and descending passes of Sentinel1 effects coherence

I am doing landslide hazard assessment and monitoring using sentinel 1 InSAR data (SLC IW mode). Can anyone explains me how ascending and descending passes effects coherence values. I didn’t get high coherence in ascending pairs, while in descending I get relatively high coherence. How satellite pass effects or relates to coherence?
Labeeqa Zaheer

There is the difference in the observation direction, which can affect coherence over slopes. The other difference is observation time, which can affect the state of the vegetation in the scene.

Thank you Marcus for your response.