Space instrumentation

Abstract:

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

Abstract:

© 2019 Society of PhotoOptical Instrumentation Engineers (SPIE). Twinkle is an upcoming 0.45-m space-based telescope equipped with a visible and two near-infrared spectrometers covering the spectral range 0.4 to 4.5 μm with a resolving power R 250 (λ < 2.42 μm) and R 60 (λ > 2.42 μm). We explore Twinkle's capabilities for small bodies science and find that, given Twinkle's sensitivity, pointing stability, and spectral range, the mission can observe a large number of small bodies. The sensitivity of Twinkle is calculated and compared to the flux from an object of a given visible magnitude. The number, and brightness, of asteroids and comets that enter Twinkle's field of regard is studied over three time periods of up to a decade. We find that, over a decade, several thousand asteroids enter Twinkle's field of regard with a brightness and nonsidereal rate that will allow Twinkle to characterize them at the instrumentation's native resolution with SNR > 100. Hundreds of comets can also be observed. Therefore, Twinkle offers researchers the opportunity to contribute significantly to the field of Solar System small bodies research.

Abstract:

Motivated by the Kepler K2 time series of Titan, we present an aperture optimization technique for extracting photometry of saturated moving targets with high temporally and spatially varying backgrounds. Our approach uses k-means clustering to identify interleaved families of images with similar point-spread function and saturation properties, optimizes apertures for each family independently, then merges the time series through a normalization procedure. By applying k-means aperture optimization to the K2 Titan data, we achieve ≤0.33% photometric scatter in spite of background levels varying from 15% to 60% of the target's flux. We find no compelling evidence for signals attributable to atmospheric variation on the timescales sampled by these observations. We explore other potential applications of the k-means aperture optimization technique, including testing its performance on a saturated K2 eclipsing binary star. We conclude with a discussion of the potential for future continuous high-precision photometry campaigns for revealing the dynamical properties of Titan's atmosphere.