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Title: Inertial stabilization platform and pointing system for balloon borne telescope
Authors: Nirmal, K
Issue Date: Aug-2014
Publisher: Indian Institute of Astrophysics
Citation: M. Tech. Thesis, University of Calcutta, Calcutta
Abstract: We have begun a new programme with lightweight and low-cost balloons to observe in the near-UV window from 200 to 400 nm that has been yet largely unexplored by the balloon community. This window includes the spectroscopic lines from several key players in atmospheric chemistry. It also allows us to observe spectroscopic lines in astronomical sources, for example, in comets and meteors. To observe any astronomical source in UV using high altitude balloon we will have one small telescope as a part of the payload. And it is important to know the telescopes pointing direction each time so that we can apply correction to make the telescope pointing in the right direction. We have already developed an altitude sensor using Inertial measurement unit,magnetometer and GPS unit. This will give us the pointing direction.Since our payload movement is random and motion of the balloon is completely unpredictable,controlling a balloon borne telescope is a stringent and difficult process. So first step is to stabilize the platform. We made a stabilization platform by using the principle of gyroscopic stabilization.We also constructed a robotic alt-azi mount.The controller in the mount converts the desired stellar object’s RA and Dec into altitude and azimuth.Controller utilizes GPS to get current time and location which is used for the conversion. The inertial measurement unit and magnetometer provides the current inertial frame of payload.Error signal is calculated subtracting current position from required position.Control signal is applied based on the error signal to altitude and azimuth servo. This feedback loop allow us to point and track astronomical sources. This checking and correction is done once in every tenth of a second.By using this system we could able to achieve a pointing accuracy of one degree.This drawback comes into picture because of our sensor’s limitations. Although our stabilization platform is designed for airborne telescope this can be used for image stabilization in moving vehicle in ground or water. In this report we discuss the design ,calibration ,implementation and testing of our Inertial Stabilization Platform (ISP) and pointing mechanism.
Description: Restricted Access
Thesis Supervisor Prof. Jayant Murthy
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Appears in Collections:Integrated M.Tech-Ph.D (Tech.)

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