Rayleigh Laser Guide Star Returns to the WHT
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ING Newsletter No. 7, December 2003

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Rayleigh Laser Guide Star Returns to the WHT

Tim Morris (Durham Univ.)

On the nights of November 7th to 10th, a team from the University of Durham Astronomical Instrumentation Group, together with colleagues from MPIA Heidelberg, had a highly successful second run with the prototype laser guide star on the WHT. Representing the completion of Phase B of the Durham experimental Rayleigh Laser Guide Star (LGS) programme, the two teams were able to collect simultaneous natural and laser guide star wavefront data.

Figure 1 Figure 2 Figure 3
Figure 1 (left). The laser launch coincided with a Lunar eclipse [ JPEG | TIFF ]. Figure 2 (middle). Laser launch telescope mounted at the top of the WHT, behind the telescope secondary mirror [ JPEG | TIFF ]. Figure 3 (right). The laser beam seen projected against the night sky above the WHT [ JPEG | TIFF ].

3.5W of 523nm laser light was projected onto the sky using a custom- made 30cm launch telescope mounted behind WHT secondary. The laser itself was installed in GRACE and the beam relayed to the launch telescope via enclosed fold mirrors attached to the WHT structure.

A novel, focus-insensitive, wavefront sensor was utilised by the MPIA team to observe the LGS return in GHRIL. Early analysis of the collected data indicates that the focussed spot size at 4.5km was approximately 2×4 arcseconds in seeing of 1 arcsecond, the spot elongation being due to the ellipticity of the laser output itself.

Reduction of the collected data is underway. The laser operated reliably over the 3.5 nights with no technical downtime. This development work indicates that the proposed 20W common-user Rayleigh laser guide star system for NAOMI can be implemented with confidence.

The assistance and support provided by ING, without which the trial would not have been possible, is gratefully acknowledged.¤

Email contact: Tim Morris (t.j.morris@durham.ac.uk)

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Last modified: 13 December 2010