 to burn up in the atmosphere, they won't have the opportunity to test these thrusters or further study them if they were to come home now and before these ground tests were done. And so they are performing ground tests of similar thrusters, and then if those tests show that there's a merit to do so, they may perform additional tests while at the space station before they're given a date to undock, jettison the service module, and return to Earth.