1. Update on Target Engagement
Graham Flint June 21, 2005

2. Poisson-Spot-Based Target Tracking System
Equivalent to “pessimistic assumption” from last HAPL meeting

3. Transverse Target Tracking Along Injection Axis
Theoretical Poisson spot cross section (z = 7 m)
Measured data at z=10 meters

4. Poisson Spot Centroiding Precision
Target/sensor offset: 10 m
NI Vision Assistant
12-point radial profile
Computational time: 0.71 ms
RMS precision (single axis): 4.6 m (~5x10-7)
LLNL Free Electron Laser ±25 m over 300 m (~8x10-8)

5. Illumination for Target Tracking/Beamlet Fine Pointing
Far-field reflected intensity from specular sphere uniform over 4 steradians (geometric)
Dual wavelength provides ~5 m per fringe
Power required: few 10’s of milliwatts
Successful demonstration with commercial rangefinder at 17 meters

6. Target Engagement Assumptions
Target injection velocity ~100 ms-1
Chamber gas affects target trajectory
Target injection accuracy ±5 mm
Shot-to-shot beamlet drift exceeds target engagement error budget
Beamlet-to-beamlet image rotation
Leads to a robust approach in “worst case” scenario…

7. Beamlet Steering Concept
Misalignment between each outgoing beamlet and target determined 1-2 msec before shot
Individual beamlets directed via fast-steering mirrors

8. Target Illumination via Common Footprint on Grazing Incidence Mirror (GIM)
Combines pre-selectable lead time with large target offset
Fast steering mirror speed matched to beamlet drift rate

9. Summary and Conclusions
Demonstrated Poisson centroiding with 4.6 m precision at 10 m
Reliably ranged on target “glint” at 17 m
Identified technique for “on target” beamlet alignment at cm target offset
Developed robust target engagement strategy for “worst case” scenario:
Injection accuracy ±5 mm
In-chamber trajectory influenced by residual gas
Shot-to-shot beamlet drift exceeds engagement error budget
Differential beamlet-to-beamlet image rotation
Engagement strategy calls for ~3000 steering mirrors
Coarse adjustment commences at approx. t = -100 ms
Fine adjust commences at approx. t = -2 ms
Precision at target ~ ± 5 m