Studies of Earth's Atmosphere from Space and near Space

Abstract

"We are conducting high-altitude balloon experiments at Indian Institute of Astrophysics using small scientific payloads for atmospheric and astronomical studies. The ultraviolet (UV) window has been largely unexplored through balloons for astronomical observations. This thesis describes the basic instrumentation developed for the balloon experiments including the tracking, telemetry, and flight termination. The current observations are of atmospheric trace gases, as they provide valuable information about the state of the Earth's upper atmosphere. The trace gas retrieval is carried out using DOAS (Differential Optical Absorption Spectroscopy) technique from scattered solar light observations. We have developed a lightweight compact portable unit for measurement of trace gas strengths from ground and airborne platforms. It is essential to understand the orientation of the payload and the direction of observation for any scientific study. To achieve this, we have developed a lightweight low-cost attitude sensor, based on a Raspberry Pi, built with readily available commercial components which can provide an accuracy of ±0:240. It can be used in experiments where weight and power are constrained, such as in light-weight high-altitude balloons. We are using the attitude sensor as the major building block in a closed-loop control system with driver motors, to stabilize and point cameras and telescopes for observations from a balloon-borne payload. The thesis also describes the details of other instruments developed for balloon experiments, one of which is a near UV spectrograph. The spectrograph is a modified Czerny-Turner design in the wavelength band of 250 nm to 400 nm. The system uses an image intensified CMOS as the detector and is designed to be portable and scalable for different telescopes. It is important to simulate the ultraviolet sky for future ultraviolet space missions and for this, we have developed a sky simulator tool. The software is available as a downloadable package and as a web-based tool. The thesis also contains a description of the time series analysis of airglow observations from FUSE (Far Ultraviolet Spectroscopic Explorer)."