The launch of NASA’s Dawn spacecraft has been rescheduled to September, NASA announced July 7.

The primary reasons for the delay are a combination of limited launch opportunities in July and the potential impact to launch preparations for the upcoming Phoenix Mars Lander mission, which is set for early August.

The next launch window for Dawn opens in September and will not affect mission goals, though the delay adds an additional $25 million to the mission’s $449 million cost, according to NASA spokesman Dwayne Brown.