The environment of a balloon based telescope puts opto-mechanical stability demands that wavefront sensing and focus control are important features to consider. The GHAPS telescope is designed to correct for rigid body motion of the secondary mirror based upon wavefront sensing from reference stars. In order to support the concept of operations of this approach, the precision of wavefront sensing with candidate reference stars needs to be addressed. Precision is expected to degrade with reduction in irradiance. To confirm this, a study was conducted to determine the relationship between broadband and narrow spectral irradiance and wavefront measurement precision. The results of the study demonstrate that a precision of 5 nm RMS can be achieved with a 20 x 20 sampling of the wavefront with an irradiance of a visual magnitude 5 star on 1 meter aperture with an exposure of 30 msec.
For the first time, a gold coated single mode optical fiber has been used to detect a liquid sodium leakage on a pipe of secondary circuit pipe mock-up of nuclear fast reactor (Gen IV) by means of Optical Frequency Domain Reflectometry-based on Rayleigh backscattering. During 150 min of the experiment we were able to detect and monitor the evolution of a liquid sodium leakage on the surface of the pipe.