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DART Webcast: Spacecraft Presentation
 
Tiffany Nail: Now, let's go to Tim Rumford for an overview of the DART spacecraft. Tim works for Orbital Sciences Corporation and is their program manager for the DART spacecraft. Tim?

Tim Rumford: My name is Tim Rumford, I've been the program manager on DART since it started back in June of 2001. Prior to working on DART, I was chief engineer on Pegasus. The synergy on DART and Pegasus is really important there. What's really unique about the DART spacecraft is the fact that it's half launch vehicle, half spacecraft. This is an efficiency from the standpoint of volume, weight, cost, development time. A lot of DART is heritage Pegasus hardware and essentially that was available to us off the shelf. The remainder of it had to be developed as mission-specific, but at least we had a head start. NASA awarded us a contract to develop the hardware and software necessary for autonomous rendezvous.

We started in June of 2001 as part of Space Exploration Initiative, which is a larger program whose goal was to create a successor to the space shuttle. NASA developed a strategy to develop and buy down some of the risk items that were currently just not available for that next-generation shuttle. One of those was autonomous rendezvous. Right now we have a space station, the only way for servicing of that space station is the shuttle. We are hoping that autonomous rendezvous technology will enable that next-generation shuttle to service that space station autonomously. We're also looking at applications where other satellites in orbit can be robotically serviced (for example, the Hubble space telescope). We also know there are applications for DART technology in some of the DoD applications. And finally, NASA's got very high goals for space exploration. We know that the next generation crew exploration vehicles will be large and will need to be manufactured on the ground and assembled in orbit.

After the Pegasus portion is complete, there's an initial on-orbit checkout. We then rendezvous with the target spacecraft we call MUBLCOM and that takes between two and eight hours. Once you get close enough to get a visual guidance link with the target spacecraft, we'll perform a series of maneuvers along different approaches/corridors along the target... in some cases, along the velocity vector of the target, in other cases below the vehicle, in what we call the radial vector. We'll also perform a series of circumnavigation maneuvers, and all of this will be completed and then repeated a series of times within 24 hours. At the completion of that 24-hour period, we'll do a completion burn, where we safely put the vehicle in a low enough orbit so it won't interfere with future missions. The point of closest approach will be the point of five meters. Once we're that close, we'll slave the attitude of the chase vehicle -- the DART vehicle, to the target vehicle. This is what we call a docking approach. It's a precursor to an actual docking maneuver which we cannot do on this mission but will be done on subsequent missions.

There's several instruments required for autonomous rendezvous. Probably the most important one for this mission is the advanced video guidance sensor, simply called the AVGS. It is probably the main instrument for this mission. It uses a video guidance sensor to interrogate the target and determine precise relative range in relative attitude data between the two orbiting spacecraft. This is inherently a challenging mission. The U.S. simply has not done this before, so this will be the first for the United States. I find that very exciting. To be able to do something like this that is a real enabling technology for the U.S, is important, it energizes the entire team. We all feel a real sense of commitment.

Nail: Thanks for the great introduction to DART, Tim.