ASHI: The All Sky Heliospheric Imager: August 22-26, 2022, NASA Balloon Flight and Image Data Reduction Analysis

Abstract We have conceived, designed, and evaluated components for an All-Sky Heliospheric Imager (ASHI), suitable for flight on future space missions both in Earth orbit and in deep space. ASHI was tested in the summer of 2022 on a NASA-sponsored topside balloon flight; in this article we highlight the images taken and the current state of the data reduction from this instrument’s successful overnight flight. The data reduction involves the removal of atmospheric glow, starlight, and zodiacal light in order to enable the measurements of the outward flow of heliospheric structures. As a simple, light weight (~ 8kg) and relatively inexpensive spaceflight instrument, ASHI has the principal objective of providing a minute-by-minute and day-by-day near real time acquisition of precision Thomson-scattering photometric maps of the inner heliosphere. The instrument's unique optical system is designed to view a hemisphere of sky starting a few degrees from the Sun. A key photometric specification for ASHI is better than 0.05% differential photometry in one-degree sky bins at 90 degrees elongation that enables the three-dimensional reconstruction of heliospheric density extending outward from the Sun along with the ability to measure velocity outflows in the imagery. The ASHI system, unlike coronagraphs or other currently-planned or in-flight heliospheric imagers, will directly enhance our analysis capabilities of the remotely-sensed heliospheric structures that pass the spacecraft and hence if near Earth, that pass Earth, too. This has large potential benefits for improving space-weather forecast and nowcast capabilities.