ALAMO -- More than 100 students sat on the playground of Rancho Romero Elementary School on Wednesday morning staring into the clear, blue sky, waiting for their 10-minute date with an astronaut.

Many watched in rapt anticipation for one of the two 14-foot antenna towers perched atop one of the school's buildings to tilt into motion. That, they were told, would be the first sign they had made direct contact with the International Space Station.

Flying some 250 miles above them, American astronaut Mike Hopkins was ready to take their call, and ready to be quizzed about his life in space.

"This is going to be the biggest science experiment we've done with the school -- and my career as principal," proclaimed Skye Larsh, principal of Rancho Romero.

Using a radio she built, Rebecca Rubsamen, center left, 16, of Alamo, lets Spencer Lang, 8, center right, ask a question of astronaut Mike Hopkins aboard
Using a radio she built, Rebecca Rubsamen, center left, 16, of Alamo, lets Spencer Lang, 8, center right, ask a question of astronaut Mike Hopkins aboard the International Space Station from Rancho Romero Elementary School in Alamo, Calif., on Wednesday, Nov. 13, 2013. Students were allowed to ask questions for short window of time that the space station was in radio range. Rubsamen is part of the Amateur Radio International Space Station program developed by NASA to promote STEM education. (Dan Honda/Bay Area News Group)

The lead engineer in the whole grand experiment: 16 year-old Rebecca Rubsamen of Alamo, a sophomore at Bentley School in Lafayette who built her own VHF radio and crafted two large antennas in her backyard with the help of her father Reid Rubsamen, who is also an amateur radio enthusiast.

A licensed amateur radio operator, Rebecca wanted to return to her elementary alma mater to let students talk to astronauts in space. She applied for permission to do the direct contact through NASA's Amateur Radio on the International Space Station program. Since 1983, the program has connected schools and universities with astronauts in space to encourage interest in math and science -- and youth to become future astronauts.

NASA grants about 50 such permissions a year for amateur radio enthusiasts to make contact with the International Space Station. This year, there have been about 68 granted internationally. Rancho Romero's is one of 20 in the United States this year and just the third in California, said Ashle Harris, a NASA spokeswoman.

Tim Bosma, a NASA volunteer who helps to mentor amateur radio buffs through the program, said Rebecca was among the youngest people to act as a lead operator for such a radio communication for a school.

"It's very impressive," he said, adding that it is something he hadn't seen in his 30 years or so as a mentor in the program.

It was no small deal to get the kids hooked up to space.

It took a flatbed truck and a forklift to put the radio system on the school's roof. And Rebecca and the school tested out the equipment numerous times to ensure it would work the day of the big flyover.

During the 8-minute radio transmission, most of the 15 students who were selected to talk to Hopkins, were able to fit in their questions. They asked what it was like to sleep on the space station, whether there were insects on board and how they keep track of what day of the week it is.

Hopkins told them he has a special contraption and scuba-type outfit that allows him to sleep wherever he wants onboard. He told them there are no insects on board for experiments at this time, but that a fly got stuck in the spacecraft and it took them some time to get out.

He told the students it is hard to tell whether it was morning, noon or night in space, because the spacecraft orbits Earth some 60 times a day, but that with the help of computers, they can figure it out.

Rebecca said that since she took up amateur radio as a hobby with her dad about two years ago, she has talked to folks all over.

"The beauty of ham radio is that it can connect people from around the world," she said.

And even beyond it, it turns out.

"It's the final frontier," she said. "And, no, I never imagined this would be possible."

For a video of the radio transmission, go to www.RebeccaRubsamen.com later this week.

Contact Joyce Tsai at 925-847-2123. Follow her at Twitter.com/JoyceTsaiNews.