Abstract Details
| Name: Varun Kumar Affiliation: Indian Institute of Astrophysics Conference ID: ASI2015_732 Title : Edge Sensor for Segmented Mirror Telescope Authors and Co-Authors : Sreekanth Reddy V., Padmakar Parihar, Sachin Bhat (Indian Institute of Astrophysics, Bangalore 560034) Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : Segmented mirror technology is becoming natural choice for any telescope larger than 8 meter in size. Performance of a segmented mirror telescope primarily depend on its edge sensors, actuators, primary mirror control and alignment-phasing system. Edge sensor plays a very vital role in segmented mirror telescope and it precisely detect any relative displacement between mirror segment, induced by either gravity or wind loading. Edge sensor is expected to not only measure relatively large displacement with nano-meter precision but also should have ability to simultaneously measure more than one dimensions, should not get affected over varying environmental conditions and should have temporal stability extended over period of a month. Various groups are working to develop edge sensor which can meet these stringent requirements and most of them are private companies. It has been found that performance of a capacitance based edge sensor is limited by their sensitivity towards excessive humidity, dust and condensation, whereas, inductive sensor is expected to be free from all these problems. Inductive edge sensor uses principle of mutual inductance measurement between two planner coils, placed on each sides of mirror segments. The mutual inductance of these sensor varies with overlapping area of the coils as well as gap between them. Whereas, capacitive edge sensor which can meet all required technical specifications can be a simple parallel plate capacitor crafted on a very stable base usually made of same material used to make the mirror segment. Both the sensors have transmitter and receiver half mounted on sides of two segments facing each other. The transmitter half of both inductive and capacitive sensors are excited with sinusoidal signal and the change in the signal at the receiver end is demodulated by applying different methods. In the ITCC laboratory of IIA we have been working on a project to develop inductive and capacitive edge sensors, which should not only full-fill all technical requirements, but also be very cost effective. Here we report the progress made in developing edge-sensors and related electronics as well as preliminary test results obtained in the lab. |