[Artist's impression of MAVEN: image courtesy Lockheed Martin]

The MAVEN spacecraft will explore the upper atmosphere of Mars.

Launch preparations were put on hold Tuesday as NASA workers went on furlough.

Project leader Bruce Jakosky says the Anti-deficiency Act only allows activities which protect lives and property.

He says NASA decided Thursday the mission could proceed.

“The property that we’re protecting is the two Mars rovers that are operating on the surface of Mars," says Jakosky.

"We’ll be acting as a communications relay and if we didn’t launch at this opportunity, it would be much more difficult for us to fill that role.”

Jakosky says a couple of hundred people are involved in the project. They were back at work Friday morning.

He says he's relieved NASA was able to restart preparations for the mission.

"What I was thinking about the government was unprintable, but I was very concerned for what this meant for MAVEN launch," he says. 

"At the same time I know we had margin built into our schedule and could accomodate a brief shutdown."

MAVEN’s three week launch window begins November 18th.

The next launch opportunity after that isn’t until 2016.