SPACE CENTER, Houston (CNN) -- On the day John Glenn and his fellow astronauts on the shuttle Discovery took a break, NASA officials praised the crew's performance and said that in some instances the crew is actually ahead of schedule.

"The crew has been performing in an excellent manner," said Dr. Dave Williams, director of Space and Life Sciences, at an afternoon briefing. "They actually have been able to get ahead of the time-line in a number of situations ... All in all, they have been doing a stellar job."

"Across the board, the orbiter, the experiments, the crew ... everything is performing very well," said flight director Paul Hill.


Aboard Discovery, a rose plant is part of a study that looks at the effects of microgravity on the production of essential oils

As the officials spoke, the crew was enjoying its first extended time off since the launch last Thursday.

Williams said that customarily on such breaks, the crew spends a lot of time looking out the windows -- "Something they don't always have time to do" -- taking crew photographs, getting organized and even writing e-mails.

NASA officials said a mid-mission work break is scheduled on all shuttle missions to prevent crew fatigue. "It's a break in a very, very tight timeline," said Williams.

Earlier in the day, each member of the crew had an opportunity for private 15-minute video linkups with family members on Earth.

Astronauts sleep tethered

The officials also said Glenn, who is on his first space mission since his history-making Earth orbit in 1962, told them he is sleeping about six-and-a-half hours a night.

According to Dr. Charles Czeisler, a sleep investigator from the Brigham and Women's Hospital in Boston, "That is consistent with prior, much younger crew members who have indicated that that is the average for both U.S. crew members as well as crew members from other countries in terms of the sleep they get in the space environment."

Glenn and fellow payload specialist Dr. Chiaki Mukai are participating in a sleep experiment that requires them to sleep wearing a webbed headgear studded with electrodes to monitor their brain waves. They must also wear black tank tops that are wired to measure their other vital signs.

Officials said it took the pair an hour Sunday night to put on all the gear before sleep. The astronauts sleep suspended in mid-air but use Velcro to tether themselves to the walls of the spacecraft so, in Czeisler's words, "they don't float around."

Williams, himself a former astronaut, noted during a question-and-answer period that while microphones are also used in sleep experiments to monitor for sound, "It really is quite evident who snores in space and who doesn't."

Mukai and Glenn also took a test Monday designed to help measure how their reaction times and performance are affected by their stay in space.


In an image captured by the Spartan satellite, the sun's corona surrounds a disk on the satellite used to block the full glare of the sun. The bright object to the left is Venus

Spartan performing flawlessly

Among Monday's accomplishments, officials said, were the completion of a blood experiment and the reception of 300 images from the Spartan satellite deployed Sunday.

This is the satellite's fifth trip into space to study the sun's corona. On its last mission aboard the shuttle Columbia in November 1997, it pinwheeled out of control and had to be recaptured. As a result, it was unable to gather any data.

"We have a healthy spacecraft, a perfect deployment and images on par or better than any previous mission," said Spartan mission manager Craig Tooley.

20 laptops on board

Glenn spent part of the day doing a round of interviews with national television networks, including one with Pedro Duque in a program for schoolchildren in Spain. Duque, the first Spaniard in space, Glenn and Cmdr. Curt Brown chatted briefly with Esperanza Aguirre, Spain's education minister in Madrid.


Glenn stands next to shuttle commander Curt Brown during a briefing Sunday

Aguirre called Glenn "one of the great American living legends" and an "example for everybody."

The astronauts awakened Monday to the strains of Andy Williams' "Moon River," a song that won an Academy Award in 1962 -- the same year Glenn made his first venture into space aboard the Mercury capsule Friendship 7. Williams is a friend of Glenn's and gave him music to listen to on Discovery.

"That was great, couldn't do any better than that wake-up this morning," Glenn radioed from orbit.

The crew has 83 separate research projects to undertake during the mission, so many that NASA officials had to trim the original length of the flight by a day because of demands on the shuttle power system. There are 20 laptop computers on board, the most in shuttle history.

On Tuesday, one of their main concerns will be retrieving the $9 million, 3,000-pound Spartan.

Reuters contributed to this report.