The target - GW170817 - is being observed by ACIS-S for 8 hours and 20 minutes. The observation started 3 hours ago and ends in 6 hours, and is part of the proposal A SENSITIVE BROAD-BAND SEARCH FOR THE AFTERGLOW FROM THE KILONOVA OF GW170817. The target - also called GrW 170817 - is located in the constellation Hydra and is a Gravitational Wave Event. More information on the target can be found at SIMBAD. See related observations: 23870, 24923.
This is a joint observation with National Radio Astronomy Observatory (NRAO) (for 4 hours and 26 minutes). However, it does not necessarily mean that the observations will be done at the same time! This is a time-critical observation.