With no ability to enter orbit at Mars, the MarCO spacecraft will shoot on past, remaining in solar orbit. I assume their Earth controllers will remain in contact for as long as possible.

Launch day

Check out my preview of the InSight launch for a detailed launch timeline. The MarCO satellites ride to space at the aft end of the Centaur inside a CubeSat dispenser attached to an aft bulkhead carrier. Following the separation of InSight, at about 90 minutes after launch, the dispenser will release MarCO-A. The Centaur will roll 180 degrees and then release MarCO-B about a minute later.

The MarCO satellites have to "detumble" after their release, then deploy their solar arrays, then initiate communications. Their first signals should arrive on Earth within 45 minutes of separation. The two spacecraft will be navigated separately to Mars and have five trajectory correction maneuver opportunities. They use reaction wheels to control their orientation and cold-gas thrusters to maneuver and desaturate the reaction wheels.

A major challenge for smallsats operating at great distances from Earth is deep-space communications, which usually requires bulky dish antennas and significant power. The MarCO spacecraft have flat "reflectarray" X-band antennas that operate at lower power.

Each MarCO has a wide-field camera and a narrow-field camera, each producing 752 by 480 pixel images. The wide-field camera is primarily intended to confirm high-gain antenna deployment. It has a 138-degree diagonal field of view. The narrow-field camera has a 6.8-degree diagonal field of view. It is boresighted opposite the high-gain antenna. I don't know the details of imaging plans.