KENNEDY SPACE CENTER, FL-- Launch of a Delta 2 rocket carrying two NASA science satellites to precisely map the moon's gravity was delayed Thursday because of high upper level winds. NASA managers initially recycled for a Friday launch try, but late Thursday the agency announced the flight would slip to Saturday to give engineers time to review propulsion system data.

Credit: NASA TV

It was not immediately clear what sort of issue was being assessed, but a brief statement said the review was ordered in the wake of de-tanking operations following Thursday's scrub.

Two one-second launch windows were available Thursday and despite a 60 percent "no-go" forecast, the sky was relatively clear and surface winds were calm as the first opportunity approached. But data from a weather balloon showed upper level winds were out of limits and NASA managers passed up the first launch opportunity at 8:37:06 a.m. EDT (GMT-4).

A second opportunity was available at 9:16:12 a.m., but the winds remained "red" and engineers reported they would not have enough time to launch an additional balloon. As a result, the launch attempt was called off and the NASA/United Launch Alliance Delta 2 team recycled for a 24-hour delay.

But during de-tanking operations after the scrub, propulsion system data prompted enough concern to require an additional delay to Saturday to make sure the rocket is healthy and ready for launch. Again, two one-second opportunities will be available, the first at 8:29:45 a.m. and the second at 9:08:52 a.m.

Forecasters are predicting a 60 percent chance of good weather Saturday and Sunday.

The $496 million Gravity Recovery and Interior Laboratory -- GRAIL -- mission is designed to map the moon's gravitational field by precisely measuring the distance between twin satellites as they fly around the moon. The gravitational effects will provide a direct indication of underlying mass concentrations, shedding light on the nature of the moon's core and its interior structure.