Which of the following is one of NASA's space shuttles?

Challenger is one of NASA's space shuttles that played a significant role in the agency's human spaceflight program. It was the second operational space shuttle, making its first flight in 1983 and completing a total of nine missions before tragedy struck on January 28, 1986, during its tenth flight, STS-51-L, leading to a catastrophic explosion shortly after launch.

The other options do not refer to space shuttles. Voyager refers to a pair of unmanned spacecraft launched in the 1970s to explore the outer planets and now continuing their journey into interstellar space. Pioneer is also a series of unmanned spacecraft designed for planetary exploration, including missions to Jupiter and Saturn. Curiosity, on the other hand, is a rover that was sent to Mars to explore the planet's surface and gather data, but it is not a shuttle.

Thus, Challenger's identity as a part of the NASA space shuttle program distinguishes it as the correct answer in this context.