Many tasks astronauts perform on the international space station (ISS) are tedious, long and too complicated to do from memory. Often an astronaut needs to be read instructions by another person, or constantly switch his or her attention from the task at hand to a laptop computer displaying the instructions, then back to whatever is being worked on.

Both of those current methods have their disadvantages. The first requires two people where only one is necessary; the other involves a floating laptop and the potential to lose the pieces of whatever is being worked on.

Engineers at NASA’s Ames Research Center felt they had a solution to this problem: a speech-powered virtual assistant with the ability to follow several dozen spoken commands. Using suggestions from astronauts, they developed Clarissa, the first spoken dialogue system in space, to provide crew members a hands-free means of getting technical instructions.

Clarissa’s parents believe that she will greatly improve the efficiency of some of the longer tasks performed by crewmembers, including analyzing potable water and routine check-ups of the space suits.

At present, the program understands about 500 words, said John Dowding, a senior scientist on the project. Clarissa understands about 75 vocal commands — such as “go forward” or “go back” — related to reading procedures. Should she recommend the wrong step or misrecognize a command, astronauts can correct her by saying “undo” or “no, I said go to …” and then say the step they wish to hear.

Clarissa is included in the standard software package included in each of the ISS client laptops, Dowding said. Astronauts only need to connect a noise-canceling headset to the laptop to use the program. There has been work done in the past to incorporate speech-recognition software like Clarissa into a proposed Personal Satellite Assistant , an orb-shaped robot that would hover aboard the station, working with the astronauts like a personal roving laptop.

Manny Rayner, a senior consultant on the project, is not optimistic about Clarissa’s future as an add-on to a Personal Satellite Assistant . “In principle, it would be easy to make Clarissa accessible through the [Personal Satellite Assistant], but my feeling is that it will never happen,” he said.

Clarissa was delivered to the ISS Dec. 25, 2004, onboard the Progress 16 supply ship and installed shortly after. However, the program has not been tested yet in space, and the test date was pushed back due in part to the current crew spending time on station repairs and preparing for spacewalks.

Although the system hasn’t been tested in space, its developers are confident it will work based on successful test runs on Earth. Three quarters of the astronauts who have tried out Clarissa liked the technology, according to Rayner.

Since Clarissa’s developers planned to set her up on the ISS , the team “went looking for names for the system that contained the letters ‘ISS,’” said Dowding.

“There aren’t many of those. Clarissa won out,” Rayner said, adding that the team thought a woman’s name would make the system sound friendly.

Clarissa gets her voice from one of her developers, Beth Ann Hockey, another reason for giving the system a feminine name. Hockey recorded sound files of all the words Clarissa would need to say. While the intonation of individual words strung together does not always sound natural, Clarissa speaks quite smoothly, Rayner said.

The system is not perfect, though. When in “open mike” mode, Clarissa gets confused about 10 percent of the time trying to distinguish between direct voice commands and words not directed at her, such as those times when an astronaut is speaking to other astronauts or mission control.

The team is currently modifying her software so she does a better job making these distinctions. By listening to thousands of examples of people talking to her and people talking to other people, Clarissa will “learn to recognize artifacts and determine whether [she] is being spoken to by listening to subtle nuances,” said Rayner.

Also, she is currently only fluent in English — a problem since half the ISS crew speaks primarily Russian. However, she has been programmed to understand a variety of English dialects, including Russian-accented English, said Dowding.

“It understands Russian-accented English, but not as well as American English,” said Rayner. Teaching her Russian is “only a matter of recording enough Russian data and entering it into her programming.”

As Clarissa grows more as a talker, scientists expect her to aid astronauts in many more procedures related to life support systems, medical exams and equipment check-out.

“We look forward to increasing [Clarissa’s capacity] to include all of the ISS procedures, about 10,000 in all,” said Dowding, who has a long-term goal to “build computerized systems that can participate as equal partners in otherwise human-human conversations.”