Transcripts of G2014-003_PlayingTagWAsteroid_youtube_hq

Most of us can remember playing tag as a kid. It was an easy game to learn: identify your target, run around, touch, and get out of there. Pretty simple, if you're on Earth. Now, how would you play this game in space, with little gravity, and with an asteroid? That's actually part of the mission of OSIRIS-REx; a NASA spacecraft that will study the asteroid Bennu in 2018. As leftover debris from the solar system formation process that began over four billion years ago, asteroids can teach us a lot about the history of the Sun and planets. This is why OSIRIS-REx plans on collecting a sample of Bennu for us to analyze. And to do that, it will play a more sophisticated version of tag, with an instrument on board called the Touch-and-Go Sample Acquisition Mechanism, or TAGSAM. The TAGSAM system consists of a robotic arm with an attached sampler head. Think of this as the spacecraft's arm and hand. But unlike the game we played as kids, where speed was a goal, the spacecraft needs to approach Bennu carefully to avoid damage; moving about 10 centimeters a second - slower than a human's walking pace. When TAGSAM touches the surface of Bennu, it will release a burst of nitrogen gas, causing loose rocks and soil to be stirred up and directed into a collector on the sampler head. The entire process will take about five seconds. There's enough nitrogen on board to support up to three sampling attempts if necessary, but hopefully, the first time's a charm. As a backup, special contact pads on the bottom side of the sampler head are designed to trap fine-grained, dust-like material, up to a few millimeters across. After the spacecraft measures the mass of the sample, the TAGSAM head will then be stowed in a Sample Return Capsule for the journey home. Just before reaching our planet, OSIRIS-Rex will release the capsule for collection on Earth, where scientists will be able to study the sample of Bennu for decades to come. The TAGSAM feature was chosen, in part, to avoid some of the difficulties that landing on an asteroid would present. Since the gravitational force at the surface of Bennu is only a fraction of what we experience on Earth, an astronaut trying to dig with a shovel there could easily wind up launching himself into space. OSIRIS-Rex would have the same challenge. Anchoring the entire spacecraft to Bennu wouldn't be any easier, and would add more technological complexity to OSIRIS-Rex's design. Plus, the asteroid's surface is hot, and extended exposure could cause instruments on the spacecraft to overheat. So, playing tag with Bennu is actually one of the simplest and safest ways to get a sample. It's not child's play, but when scientists considered their options, they said, "TAGSAM . . . you're it."