Big Test Coming up for Tiny Satellites Trailing Mars Lander

This illustration made available by NASA in March 2018 shows the twin Mars Cube One project (MarCO) spacecrafts flying over Mars with Earth and the sun in the distance. NASA/JPL-Caltech via AP

CAPE CANAVERAL, Fla.—A pair of tiny experimental satellites trailing NASA’s InSight spacecraft all the way to Mars face their biggest test yet.

Their mission: Broadcast immediate news, good or bad, of InSight’s plunge through the Martian atmosphere on Monday.