 This is how the world saw the deployment of the TDRS, or Tracking and Data Relay Satellite, during the most recent mission of discovery. What most people didn't realize was that the bottom half of this satellite assembly, the lighter-colored area, is a space transfer vehicle called the Inertial Upper Stage, or IUS. Now NASA is gearing up to use this IUS to help launch another TDRS satellite during the next shuttle flight, and they're aiming for a carbon copy of that previous mission. I would like to see it just like that again. That was just letter perfect. Parker Counts oversees the Upper Stage Projects Office at the Marshall Space Flight Center. He explains that the IUS was developed by the Air Force for use aboard the shuttle and expendable launch vehicles. Marshall Center officials purchased the transfer vehicle from the Air Force for use aboard NASA missions. It bridges an important orbital gap between the altitude of the shuttle and what you might call the parking orbit for satellites that's nearly 150 times higher. Roughly we're looking at an orbit of 160 miles where we start with the shuttle. Then we take it from there with a two-stage inertial upper stage to 22,300 miles. So that's what we call the geostationary orbit, where that orbit is in sync with the rotation of the Earth. That's important because it means that satellite dishes on the Earth can remain pointed in one direction. But the IUS is powerful enough to do much more than just boost satellites. The shuttle mission after next, for example, will use an IUS to send the unmanned Magellan space probe on its journey to map the surface of Venus. At least two other planetary probes will also be propelled by IUS vehicles. Later this year, Galileo is slated to begin a mission to explore Jupiter. Ulysses is scheduled to begin a voyage to the Sun about a year later. As NASA continues to probe the frontiers of space, the inertial upper stage remains a powerful way to extend our reach. At the Marshall Space Flight Center, this is Mike Errington reporting. Roughly we're looking at an orbit of 160 miles where we start with the shuttle. Then we take it from there with a two-stage inertial upper stage to 22,300 miles. That's what we call the geostationary orbit, where that orbit is in sync with the rotation of the Earth. And we were able to do that with a very good accuracy last mission.