https://techcrunch.com/2020/01/19/watch-spacex-launch-its-crew-dragon-astronaut-spacecraft-for-a-key-safety-test/

SpaceX is looking to launch its Crew Dragon spacecraft using a Falcon 9 rocket today, in a crucial test of the human-rated spacecraft’s In-Flight Abort (IFA) system. This safety feature will separate the Crew Dragon from the Falcon 9 rocket early, propelling the spacecraft (and any astronauts who would be on board, during a real mission) to a safe distance at extremely high speed.

The test was originally scheduled for Saturday, but weather prevented that from being a workable option. Now, SpaceX’s launch window opens today at 8 AM EST (5 AM PST) and lasts for six hours. SpaceX and NASA are currently aiming for a 10 AM EST (7 AM PST) liftoff time during that window, in order to ensure that weather both for launch and for recovery of the Crew Dragon spacecraft in the Atlantic Ocean are optimal. Depending on conditions, that time could slip again, or if they exceed the launch window, push to a backup date on Monday.