Two rockets were fired into the sky within the space of a few hours, one carrying a commercial satellite and the other as part of a test of the U.S. missile defense system.

The Department of Defense rocket was successfully launched from Vandenberg Air Force Base on California's Central Coast, military officials said Wednesday.

The rocket, a Chimera target launch vehicle, took off from an underground silo at 11:57 p.m. Tuesday as part of an experiment designed to help the military track missiles more closely.

The rocket was programmed to fly near a research satellite sent up last year. The hope was to collect images of the rocket to help the military study how its body can be distinguished from its exhaust plume. The test did not include plans to shoot it down.

In the other launch, a rocket carrying a communications satellite for Intelsat lifted off from an oceangoing launch pad floating in the equatorial Pacific.

Long Beach-based Sea Launch Co.'s Zenit-3SL rocket blasted off at 2:28 a.m. PDT Wednesday, carrying the Galaxy 19 satellite toward orbit. The satellite is intended to serve Intelsat customers in the United States, Canada, Mexico and the Caribbean.

• Click here to visit FOXNews.com's Space Center.