Field scanner design for MUSTANG of the Green Bank Telescope

MUSTANG (Multiplex SQUID TES Array at Ninety GHz) is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz.The detector has a field of view of 40 arcsec.To cancel out random emission change from atmosphere and other sources,requires a fast scanning reflecting system with a few arcminute ranges.In this paper,the aberrations of an off-axis system are reviewed.The condition for an optimized system is provided.In an optimized system,as additional image transfer mirrors are introduced,new aberrations of the off-axis system may be reintroduced,resulting in a limited field of view.In this paper,different scanning mirror arrangements for the GBT system are analyzed through the ray tracing analysis.These include using the subreflector as the scanning mirror,chopping a flat mirror and transferring image with an ellipse mirror,and chopping a flat mirror and transferring image with a pair of face-to-face paraboloid mirrors.The system analysis shows that chopping a flat mirror and using a well aligned pair of paraboloids can generate the required field of view for the MUSTANG detector system,while other systems all suffer from larger off-axis aberrations added by the system modification.The spot diagrams of the well aligned pair of paraboloids produced are only about one Airy disk size within a scanning angle of about 3 arcmin.

Central visual function and inner retinal structure in primary open-angle glaucoma

To investigate associations between central visual function and inner retinal structure in primary open-angle glaucoma(POAG). This study enrolled 78 POAG patients and 58 healthy controls. POAG was classified into early glaucoma and moderate to advanced glaucoma. The following tests were performed on all participants: isolated-check visual evoked potential(ic VEP) testing, 24-2 standard automated perimetry(SAP), and Cirrus optical coherence tomography(OCT) examinations. Signal-to-noise ratio(SNR) measures obtained from ic VEP responses to isolated checks presented at four depths of modulation(DOMs;8%, 14%, 22%, and 32%) were explored. Mean macular sensitivity(mMS) was assessed by calculating the mean sensitivities of central 12 SAP points. Ganglion cell layer+ inner plexiform layer thickness(GCL+IPLT) and peripapillary retinal nerve fiber layer thickness(pRNFLT) were measured by OCT scanning. For each group of subjects, linear relationships among the following measures were analyzed: SNR, mMS, GCL+IPLT, and pRNFLT. SNR, mMS, GCL+IPLT, and pRNFLT were all more significantly decreased in glaucoma than in controls(P<0.001). A significant positive association was found between SNR at 14% DOM and GCL+IPLT at the inferior sector in early glaucoma(r=0.465, P=0.004). In moderate to advanced glaucoma, significant correlations were found between SNR at 32% DOM and mean GCL+IPLT(r=0.364, P=0.023), superior GCL+IPLT(r=0.358, P=0.025), and mean p RNFLT(r=0.396, P=0.025). In addition, in moderate to advanced glaucoma, there were significant correlations between mMS and all relevant measures of retinal thickness(r=0.330–0.663, P< 0.010). In early glaucoma, significant correlations were found between mean mMS and minimum GCL+IPLT(r=0.373, P=0.023), and between inferior mMS and superior GCL+IPLT(r=0.470, P=0.003). Linear models provided a good explanation for the relationship between SNR and inner retinal thickness(IRT), whereas nonlinear models better explained the relationship between mMS and IRT. In early glaucoma, both SNR and mMS were related moderately and significantly to IRT, whereas in moderate to advanced glaucoma, mMS was more strongly correlated with IRT than SNR.