In 2004, the X Prize Foundation celebrated the culmination of its first prize competition, awarding $10 million for successful flights of SpaceShipOne, the first privately financed reusable spacecraft to take a pilot to space, defined as 62 miles above the Earth’s surface.

Three years later, the foundation announced a more ambitious prize to spur private endeavors farther out. The Google Lunar X Prize would award $20 million to the first team that could land on the moon an unmanned spacecraft that would then move at least 1,640 feet across the lunar surface and send back photographs and videos. The second team to accomplish the tasks would receive $5 million.

The prizes were to have been won more than two years ago, by the end of 2012.

But the technology and financing hurdles proved higher than prize organizers had anticipated. In 2010, the deadline was pushed to the end of this year; last year, it was extended to Dec. 31, 2016.

The foundation also rejiggered how the money would be paid. Instead of waiting for a successful completion of the feat, it decided to offer partial payments to teams for their efforts. On Monday, it announced what it called the Milestone Prizes, accompanied by $5.25 million, to five teams for progress in three categories: landing, moving on the lunar surface and imaging.