MILESTONES ACCOMPLISHED Scenario 5

Update 06/17/07 -- After a four-week hiatus in unmated operations that was used to analyze flight data and determine fixes for some of the problems experienced in Scenario 3-1, Orbital Express successfully completed Scenario 5-1, another industry first demonstrating a fully autonomous fly-around and capture of the NextSat client spacecraft on Saturday, June 16.

Using only the onboard cameras and advanced video guidance system, ASTRO separated from the NextSat, backed away to a distance of 120 meters, flew around the NextSat, and then approached along the minus Rbar, and captured NextSat with its capture mechanism.

This marks the first time that a fly-around of another spacecraft was performed using primarily passive sensors, and with no active exchange of relative navigation information, and no intervention or control from the ground. This was also our first unmated operation since the 3-1 Scenario in mid-May where we had an anomaly during the unmated portion of the operations. This scenario was important for several reasons. For future scenarios, we verified that many of the issues that we experienced in the 3-1 scenario anomaly recovery operations had been fixed. For satellite servicing in general, we demonstrated that one could successfully perform an autonomous fly-around inspection of the client using passive sensors and without exchanging relative navigation information. We also demonstrated that a minus Rbar approach is practical. This type of approach is desired by many potential clients because it allows the servicing spacecraft to approach the client without needing the client to slew away from the earth, which would cause a loss of service because the antennas would no longer be pointed properly.

As in previous scenarios, ASTRO and NextSat began the scenario in Mated Nominal mode. At roughly 3:50 AM MDT on 6/16, ASTRO's autonomous systems performed all the operations required to separate from NextSat to a range of up to 120 meters. ASTRO then flew around NextSat using the ARCSS sensors to continuously track the NextSat during the fly-around. If sensor or navigation systems limits had been violated, an autonomous abort would have been performed to maneuver to a safe location, as happened when the sensor computer experienced a problem in Scenario 3-1.

After completing the fly-around, ASTRO station kept with NextSat at 120 meters for 17 minutes, then maneuvered to the minus Rbar "above" NextSat and performed a corridor approach to within the NextSat capture box. The capture mechanism then grasped NextSat and performed a standard direct capture. The demonstrations occurred at full spacecraft autonomy requiring no ground-based "approval to proceed" confirmations. Our next major unmated operation will be Scenario 7-1, currently scheduled for 6/22, where ASTRO will depart NextSat to a range of 4 kilometers on the minus Vbar, then approach and perform a free flyer capture, using the robotic arm to grapple and berth NextSat.

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