The schedule is shown here:
https://docs.google.com/spreadsheets/d/1OFTLiFHjkTnbrpdFJI_jUK75OGjMNMPgCXqTCxk3z6c/edit#gid=1099502040
To avoid the situation where a towpilot arrives at SOSA and waits all day while no glider pilots come out to fly, the daily flying planner in freeflight will be used. If no one has posted to the daily flying planner before 8 am on a given day, then the towpilot is relieved of duty for that day and will not be at SOSA to tow.