Abstract
We report on a comprehensive signal processing procedure for very low signal levels for the measurement of neutral deuterium in the local interstellar medium from a spacecraft in Earth orbit. The deuterium measurements were performed with the IBEX-Lo camera on NASA’s Interstellar Boundary Explorer (IBEX) satellite. Our analysis technique for these data consists of creating a mass relation in three-dimensional time of flight space to accurately determine the position of the predicted D events, to precisely model the tail of the H events in the region where the H tail events are near the expected D events, and then to separate the H tail from the observations to extract the very faint D signal. This interstellar D signal, which is expected to be a few counts per year, is extracted from a strong terrestrial background signal, consisting of sputter products from the sensor’s conversion surface. As reference we accurately measure the terrestrial D/H ratio in these sputtered products and then discriminate this terrestrial background source. During the three years of the mission time when the deuterium signal was visible to IBEX, the observation geometry and orbit allowed for a total observation time of 115.3 days. Because of the spinning of the spacecraft and the stepping through eight energy channels the actual observing time of the interstellar wind was only 1.44 days. With the optimised data analysis we found three counts that could be attributed to interstellar deuterium. These results update our earlier work.
Highlights
Measurements of the interstellar wind by the Interstellar Boundary Explorer (IBEX) satellite [1] inEarth orbit provide a supplementary means to observe the D/H ratio in the local interstellar medium for telescopic observations
We report on a comprehensive signal processing procedure for very low signal levels for the measurement of neutral species in the local interstellar medium from a spacecraft in Earth orbit
In to our earlier work [8], the 3D-TOF method demonstrated that deuterium from the local interstellar medium can be measured in the interstellar wind with IBEX-Lo at Earth orbit at a low signal level of counts-per-year
Summary
Measurements of the interstellar wind by the Interstellar Boundary Explorer (IBEX) satellite [1] inEarth orbit provide a supplementary means to observe the D/H ratio in the local interstellar medium for telescopic observations. According to the standard cosmological model, deuterium was produced in significant amounts only during primordial nucleosynthesis within the first 100–1,000 s of the universe. It is destroyed in the interiors of stars much faster than it is produced by the other natural processes that produce insignificant amounts. Baryonic matter is processed in stars where deuterium is destroyed by nuclear reactions (astration). Deuterium-poor and metal-rich material is returned to the interstellar medium in supernova explosions and stellar winds. Measurements of the D abundance in different locations of the galaxy provide important tests for models of primordial nucleosynthesis and for the chemical evolution of the galaxy and intergalactic medium
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