SNTP client not working behind satellite?

Hi, I placed 8 RouterBoards (RB750) behind 8 satellite modems.
I correctly set IP addresses of NTP servers, but I can’t synchronize time.
I suppose due to the latency of satellite connection.

Is there a way to solve the problem, even if so not accurate timing?
Thanks.

Are the satellite modems using satellite TCP?

I suppose yes, I mean I use the satellite modem like as a common ADSL modem (provider is SkyWay).