Once the target was ten kilometres or so away, laser beaming experiments would be performed. (Figure 5.2-4) Data from the target would be relayed directly to Astro-SPAS and recorded. This could be continued for many orbits with the beam operating continuously throughout In addition, the laser optics should demonstrate the ability to focus the beam evenly on the target surface and maintain fine pointing control as the two continue to separate a distance in excess of several hundred kilometres. Adaptive optic systems would probably be required to achieve this where a precision of less than 0.1 arcseconds would need to be demonstrated. This first test programme of the experiment could last for one or two days. The SILEX activities would be valuable in understanding critical beam pointing issues. When the two spacecraft had drifted to a separation of around 1,000 km or more the second test programme could begin. The target spacecraft would fire a small solid rocket motor against its velocity vector. This would cause the target to initially move further away from Astro-SPAS, but at the same time lower its perigee by around 50-100 km, depending on the thrust level used. The low perigee would mean that the target would quickly catch-up to Astro-SPAS. When it was within several hundred kilometres of Astro-SPAS, beaming experiments would begin and continue as the target passes underneath and in front of the demonstrator. (Figure 5.2-5) This second experiment would demonstrate the ability to continually track the target in a representation of the Laser Solution described in PART I. This experiment could probably also be conducted just once as it could be many days before the orbits would rephase sufficiently for a second attempt The power level and pointing characteristics of the laser Astro-SPAS advanced demonstrator may also enable a third test programme involving beaming power to the Earth. Considerable mission and safety analysis would need to be done to understand the feasibility of this space-to-ground experiment. Schematically, it is possible to envisage an experiment where
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