Complex sentence: On November 22,2017 InSight completed testing in a thermal vacuum, also known as TVAC testing, where the spacecraft is put in simulated space conditions with reduced pressure and various thermal loads.
Split into simpler sentences: On November 22,2017 InSight completed testing in a thermal vacuum, also known as TVAC testing. Basically, the spacecraft is put in simulated space conditions with reduced pressure and various thermal loads.