NASA might have to cease operations on the Endeavour launch, pictured here, because of the government shutdown. NASA

NASA has outlined what will happen to their operations in the event of a government shutdown.

NASA chief financial officer Elizabeth Robinson wrote a letter to program associate director Sally Ericsson, which was posted on the space agency's website. It details what will happen if the government shuts down.

Only a few exceptions will be made. NASA will only allow the bare minimum amount of employees that remain critical due to the hazardous nature of various operations.

Essentially, Robinson says who will still be working and excepted from the furlough will be left up to various center directors. NASA has published guidelines for Center Directors to follow in determining the minimum number of persons who may excepted from a furlough. Specifically, the Center Directors are instructed to narrowly construe the available exceptions and except from the furlough only those employees who contribute directly to activities are permitted to continue, Robinson wrote.

The agency's two major programs; the International Space Station and the Space Shuttle, were discussed. The ISS is a good example of an operation where various employees would remain in place, since there is a crew of six currently up there.

To protect the life of the crew as well as the assets themselves, we would continue to support planned operations of the ISS during any funding hiatus, NASA said on its web site.

However, the Space Shuttle program, which is expected to conclude after the next two launches. NASA said if the space shuttle has commenced countdown (four days or closer) or is in flight then it will go on as planned. If the government shutdown happens before that, then it will cease operations on that mission.

Cost won't play a role. Even if a project costs more to shut down than do work on it, it will get axed. The exceptions will be those that are involved in jobs related to hazardous missions or activities. Other employees might be on call for emergency services. Workers also cannot volunteer to do work during the shutdown if they are not excepted employees, says NASA.

In addition, certain projects that begin before the shutdown, might need to be completed, Robinson says, for example to fulfill contractual obligations. Depending on when a shutdown occurs, certain specific activities, for example equipment tests and research that may be underway at the time of a hiatus, may require longer to conduct an orderly shutdown that eliminates the risk to personnel and preserves the government property involved, she writes.

NASA was not specific about how many employees would be affected.