how large are these two satellites?
On May 5, 2018, NASA launched a stationary lander called InSight to Mars. Riding along with InSight were two CubeSats — the first of this kind of spacecraft to fly to deep space. If this flyby demonstration is successful, the technology onboard each CubeSat will provide NASA the ability to quickly transmit status information about InSight as it lands on Mars.
The twin communications-relay CubeSats, built by NASA’s Jet Propulsion Laboratory, Pasadena, California, constitute a technology demonstration called Mars Cube One (MarCO). CubeSats are a class of spacecraft based on a standardized small size and modular use of off-the-shelf technologies. Many have been made by university students, and dozens have been launched into Earth orbit using extra payload mass available on launches of larger spacecraft.
The basic CubeSat unit is a box roughly 4 inches (10 centimeters) square. Larger CubeSats are multiples of that unit. MarCO’s design is a six-unit CubeSat - about the size of a briefcase — with a stowed size of about 14.4 inches (36.6 centimeters) by 9.5 inches (24.3 centimeters) by 4.6 inches (11.8 centimeters).