DR. KALYAN RADHAKRISHNAN

One of the main worries of the nighttime astronomers who want to exploit the full capabilities of large optical, infrared telescopes is the sky coverage. Atmospheric turbulence degrades the performance of the telescope. Adaptive optics can overcome this limitation in real-time. However, only with natural stars, the sky coverage where you can achieve diffraction limited capabilities is limited. With the laser guide stars (LGS), the sky coverage increases substantially. Commonly used LGS is the Sodium-LGS (Na-LGS), created at an altitude of ~90km above the mean sea level by firing a laser at the sky. The sodium layer at the sky has a finite thickness. Also, the Sodium ion density varies both temporally and spatially. In short, the Na-LGS is not a point-like object but an extended source. To date, wavefront sensing using the Na-LGS treats it as a point-like object (like the natural star), which is not the optimum way to do it. Ingot wavefront sensor (I-WFS) was introduced to account for the extended nature of the Na-LGS. The speaker will present the Ingot wavefront sensor and its features from the perspective of extremely large telescopes.