Measurement of limb radiance and Trace Gases in UV over Tropical region by Balloon-Borne Instruments – Flight Validation and Initial Results

Abstract

Abstract.We describe a method to measure the solar scattered UV radiance and trace gases in the upper troposphere and stratosphere using a spectrograph carried by high-altitude balloons. The flights have been conducted over tropical regions near urban areas.The instrumentation was developed using off-the-shelf components and can be easily reproduced. We describe the design of the instrument, its operation in flight and discuss some flight result. Observations of the scattered solar radiance were performed 5 by looking towards the Earth's limb at Sun angles of more than 90 degrees at altitudes of 10 to 29 km. This method allows us to estimate the variation of the scattered UV solar radiance with height. It also can be used to measure the column densities in the upper atmosphere.

Balloon UV Experiments for Astronomical and Atmospheric Observations

“…Balloons can provide remote sensing and in-situ measurements of trace gases in upper troposphere and stratosphere. 6 The UV window of 200-400 nm includes the lines from several important species in atmospheric chemistry, such as S0 2 , O 3 , BrO, HCHO. Spectroscopic observations at these wavelengths allow simultaneous measurement of multiple gas species, and thus avoid the need for separate electrochemical systems for each gas.…”

“…With a telescope placed on the high-altitude balloon payload, one of the major factor in the design of the pointing system is the transfer of oscillations from the flight train, with this constrain more important if the required stability for observation is within one degree of accuracy. In our first experiments of atmospheric lines (Sreejith et al, 2016), the pointing accuracy was not of a great concern, but we plan to observe astronomical sources for which we require pointing and stabilization of the order of arcseconds.…”

“…The reference spectrum for trace gas analysis will be obtained at float, and the measurements will continue during descent. 6 In this flight we also plan to supplement the observational instruments with the detachable pre-sterilized sampling chamber SAMPLE (Stratospheric Altitude Microbiology Probe for Life Existence) 15 designed to collect and contain the dust stratospheric samples and get them back without contamination. November is the peak time for the Leonid meteor shower, and we plan to collect cometary dust particles, where further study will be conducted to establish the possibility of microbial life in the upper atmosphere.…”

Pointing system for the balloon-borne astronomical payloads

“…1 We are limited to payloads under 6 kg for regulatory reasons and this constrains our payload size. Our first experiments were of atmospheric lines 2 where the pointing stability is less important, but we do plan to observe astronomical sources for which a pointing mechanism is required. Light balloons are an exceptionally challenging platform for accurate pointing because the platform itself is in constant motion, sometimes with violent jerks and rotations.…”

“…1, Left). Each frame is controlled by a servomotor: the inner frame uses a noncontinuous servomotor and the outer uses a continuous servomotor 2 . The shaft of these motors can be moved accurately to the desired angle using an internal electronic circuit, which identifies the current angle of the motor shaft from a reference point and then moves the shaft to the desired position.…”