Transcripts of YOUTUBE_HQ_G2015-039_Driving_A_Lunar_Spacecraft_MASTER_youtube_hq

[ sound effects ] The Lunar Reconnaissance Orbiter has been orbiting the Moon since 2009, and during this time, NASA videos have explored numerous aspects of the spacecraft. But one question keeps popping up . . . How do you drive that thing? Well, first imagine a souped-up racecar. Picture revving up that engine, wind flowing over its streamlined body, turning the wheel around sharp hairpin turns . . . Got that image? Great! It's nothing like that. Now picture playing an arcade game, using your controls to fly a spacecraft around at crazy warp speeds. Yeah, it's nothing like that either. Flying LRO involves computer science, satellite technology, and a great deal of teamwork. Not as cool as what you might have imagined, but it's still an impressive and sophisticated technological operation. For starters, LRO is controlled by a group of engineers - the Mission Operations Team. They work out of a control room, called the Mission Operations Center. All commands to the spacecraft originate from this control room and are sent through antennas around the globe. And here's where we reveal the big secret. Most spacecraft operations are actually handled using preprogrammed commands. Every day a team member builds a "command load" using specialized computer software. This is essentially a time-sensitive schedule of commands, such as thruster maneuvers, starting and stopping its cameras, and pointing the spacecraft to a selected target. These command loads are then activated on board by the "Single Board Computer," which talks to the electronics and microprocessors in LRO's instruments. Many operations require real-time monitoring. In some cases, team members simply observe as the preprogrammed commands execute. At other times, the team must initiate a specific command for an action to occur on board. One event requiring real-time monitoring is a lunar eclipse. A lunar eclipse could mean trouble for LRO since it's solar-powered. To prevent damage from the frigid temperatures, prior to the eclipse, the spacecraft will spend about fourteen hours heating up. Nearly all instruments will be turned off as well to preserve battery power. Once out of the darkness, commands are given to reconfigure the spacecraft. If an emergency occurs during spaceflight, the Single Board Computer can put LRO into a "safe mode." This maintains safe temperatures and electricity until the team can contact the satellite and determine the problem. One final aspect to operating this spacecraft involves its reaction wheels. And no, these don't have spinners or flashy rims. Reaction wheels help orient a spacecraft through managing angular momentum. An easy way to think about this concept is how it's easier for a bicycle to stay upright when the wheels are turning. On LRO there are four reaction wheels constantly spinning. By making very small changes in their speeds, the satellite is kept pointed toward the moon. Larger changes in the wheel speeds can get the spacecraft to point in different directions - perhaps toward Earth to take a picture or the stars for instrument calibration. Over time, the reaction wheels spin faster and faster as they keep the instruments pointing at the moon, causing the angular momentum to steadily increase. As a result, every few weeks, a decrease in the angular momentum is needed. This is done by firing thrusters, as that gets the reaction wheels to compensate and spin more slowly. This process is called a momentum unload maneuver. So as you can see, operating a lunar spacecraft is a different sort of driving experience. You may have been thinking this . . . but it actually involves this.