Peggy Whitson, commander of the 16th mission for the International Space Station, gestures just before the launch of the Russian Soyuz rocket Oct. 10 at the Baikonur cosmodrome, Kazakhstan. When space shuttle Discovery blasts off, with Pamela Melroy on board, it will be the first time in the 50-year history of spaceflight that two women are in charge of two spacecraft at the same time.

Cape Canaveral, Fla. ? A giant leap is about to be made for womankind.

When space shuttle Discovery blasts off Tuesday, a woman will be sitting in the commander’s seat. And up at the international space station, a female skipper will be waiting to greet her.

It will be the first time in the 50-year history of spaceflight that two women are in charge of two spacecraft at the same time.

This is no public relations gimmick cooked up by NASA. It’s coincidence, which pleases shuttle commander Pamela Melroy and station commander Peggy Whitson.

“To me, that’s one of the best parts about it,” said Melroy, a retired Air Force colonel who will be only the second woman to command a space shuttle flight. “This is not something that was planned or orchestrated in any way.”

Indeed, Melroy’s two-week space station construction mission was originally supposed to be done before Whitson’s six-month expedition.

“This is a really special event for us,” Melroy said. “… There are enough women in the program that coincidentally this can happen, and that is a wonderful thing. It says a lot about the first 50 years of spaceflight that this is where we’re at.”

Whitson – the first woman to be in charge of a space station – arrived at the orbital outpost on a Russian Soyuz spacecraft on Oct. 12. She flew there with two men, one a Russian cosmonaut who will spend the entire six months with her.

Before the launch, an official presented her with a traditional Kazakh whip to take with her. It’s a symbol of power, Whitson explained, because of all the horseback and camel riding in Kazakhstan.

Smiling, she said she took the gift as a compliment and added: “I did think it was interesting though, that they talked a lot about the fact that they don’t typically let women have these.”

At least it wasn’t a mop. The whip stayed behind on Earth.

Eleven years ago, just before Shannon Lucid rocketed to the Russian space station Mir, a Russian space official said during a live prime-time news conference that he was pleased she was going up because “we know that women love to clean.”

“I really haven’t heard very much like that at all from the Russian perspective,” Whitson said in an interview with The Associated Press last week. “Russian cosmonauts are very professional and having worked and trained with them for years before we get to this point, I think makes it better because then it doesn’t seem unusual to them either.”

“So I think I’m luckier. Shannon was probably breaking more barriers in that way than I have been,” added Whitson, who spent six months aboard the space station in 2002.

Melroy, 46, a former test pilot from Rochester, N.Y., and Whitson, 47, a biochemist with a Ph.D. who grew up on a hog farm near Beaconsfield, Iowa, are among 18 female astronauts at NASA. Seventy-three astronauts are men.

The countdown started Saturday for Discovery’s launch. There was concern about rain on Tuesday morning, but meteorologists put the odds of acceptable weather at liftoff time at 60 percent. No major technical problems were being tracked.