Bridge to the stars: A mission concept to an interstellar object

Exoplanet discoveries since the mid-1990’s have revealed an astounding diversity of planetary systems. Studying these systems is essential to understanding planetary formation processes, as well as the development of life in the universe. Unfortunately, humanity can only observe limited aspects of exoplanetary systems by telescope, and the significant distances between stars presents a barrier to in situ exploration. In this study, we propose an alternative path to gain insight into exoplanetary systems: Bridge, a mission concept design to fly by an interstellar object as it passes through our solar system. Designed as a New Frontiers-class mission during the National Aeronautics and Space Administration (NASA) Planetary Science Summer School, Bridge would provide a unique opportunity to gain insight into potential physical, chemical, and biological differences between solar systems as well as the possible exchange of planetary materials between them. Bridge employs ultraviolet/visible, near-infrared, and mid-infrared point spectrometers, a visible camera, and a guided impactor. We also provide a quantitative Monte Carlo analysis that estimates wait times for a suitable target, and examines key trades between ground storage and a parking orbit, power sources, inner versus outer solar system encounters, and launch criteria. Due to the fleeting nature of interstellar objects, reaching an interstellar object may require an extended ground storage phase for the spacecraft until a suitable ISO is discovered, followed by a rapid response launch strategy. To enable rapid response missions designed to intercept such unique targets, language would need to be added to future NASA announcements of opportunity such that ground storage and rapid response would be allowable components of a proposed mission

Rotation Period of 584 Semiramis

Rotation periods were obtained for ten minor planets based on near-IR CCD observations made in 2014 at the urban Burleith Observatory, Washington, DC. (The link provided is to the entire bulletin. Scroll to page 4 for Dr. French\u27s article.

Improved ultraviolet dust aerosol properties derived from MAVEN/IUVS measurements of the Mars year 34 global dust storm

International audienceThe Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian surface and atmosphere. From these apoapse images, information about dust aerosols can be retrieved and comprise the only MAVEN observations of airborne dust. Measuring local time variability of large-scale recurring features is made possible with MAVENs nearly-global imaging combined with its ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. The Mars year 34 (2018) global dust storm provided a unique opportunity to improve measurements of aerosol properties. The presence of a thick layer of dust allowed us to sample the single scattering albedo (SSA) at a range of UV wavelengths unmeasured by previous missions. Having an optically thick atmosphere in the UV minimizes retrieval errors due to imprecise knowledge of surface reflectance properties and reduced sensitivity of some radiative parameters. To do this we employed the DIScrete Ordinates Radiative Transfer (DISORT) code to derive a wavelength-dependent SSA from the measured reflectance spectra given atmospheric parameters obtained from a general circulation model. The SSA was converted into an imaginary index of refraction using a T-matrix-based set of optical properties (with the real part of the index of refraction calculated using a subtractive Kramers-Kronig analysis.) With the new refractive indices, the scattering properties for the SSA retrievals were recalculated and the SSA was retrieved again until convergence was reached. Our analysis should be particularly valuable at shorter mid-UV wavelengths (200250 nm) where the SSA has not been well-characterized, and thus beneficial for IUVS retrievals during lower dust-loading conditions. It may also be of particular benefit to retrievals from EMM/EXI. We discuss our retrieved SSA and show its implications for future IUVS retrievals of dust

A study of cloud and dust phenomenology in MAVEN/IUVS data

International audienceThe Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian surface and atmosphere. From these apoapse images, a variety of cloud morphologies and local time variability can be seen and comprise the only MAVEN observations of water ice aerosols. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN's 4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have examined two Martian years' worth of data and present an overview of IUVS cloud observations. Topographic clouds are one of the most visually striking types of clouds observed in our data, which are seen throughout northern hemisphere summer (Ls = 90°) and persist into northern fall (Ls = 180°). These clouds are generally localized to Tharsis volcanoes and show streaks, waves, and spirals. From northern spring into late summer we also see the presence of aphelion cloud belt (ACB) clouds, a longitudinally continuous band of clouds that forms near equatorial regions. Throughout the year we see the presence of polar hoods. Sometimes these clouds are simply an amorphous structure centered around the pole; other times we see the presence of single and double vortices as well as cyclonic features that appear and diminish on the timescale of several hours. Finally, we have observed clouds above the 2018 dust storm. Some clouds are wispy--reminiscent of cirrus clouds--while other times we see the presence of gravity waves in the clouds and a "terminator cloud band." We present observations of these cloud morphologies and preliminary retrievals of aerosol properties

Another one derives the dust: Ultraviolet dust aerosol properties retrieved from MAVEN/IUVS data

International audienceWe derived the ultraviolet complex refractive indices of Martian dust aerosols using data from the Mars year 34 global dust storm (GDS). We used data taken by the Imaging Ultraviolet Spectrograph (IUVS) instrument aboard the Mars Atmosphere and Volatile Evolution spacecraft and surface-based derivations of the column-integrated optical depth from the Mastcam instrument on Curiosity. We first created an explicit microphysical representation of dust to compute dust-scattering properties at wavelengths within IUVS’ spectral range for four dust particle-size distributions plausibly present during this GDS. We then used radiative-transfer techniques to iteratively retrieve the single-scattering albedo from IUVS data using the Mastcam-derived column-integrated optical depth as a constraint. We converted the dust single-scattering albedo into its refractive indices and report the refractive indices at the four particle-size distributions. We performed dust optical depth retrievals at another time period using several of these refractive indices and show that our preferred refractive indices produce optical depths which are consistent with optical depths derived from Mastcam data at similar times. These ultraviolet refractive indices will be particularly beneficial for future observational and theoretical studies of Martian dust

Updated dust scattering properties derived from the 2018 global dust storm

International audienceThe Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian surface and atmosphere. From these apoapse images, information about dust and ice aerosols can be retrieved and comprise the only MAVEN observations of clouds and airborne dust. Measuring local time variability of large-scale recurring features is made possible with MAVEN's ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits

A study of cloud and dust phenomenology in MAVEN/IUVS data

International audienceThe Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian surface and atmosphere. From these apoapse images, a variety of cloud morphologies and local time variability can be seen and comprise the only MAVEN observations of water ice aerosols. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN's 4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have examined two Martian years' worth of data and present an overview of IUVS cloud observations. Topographic clouds are one of the most visually striking types of clouds observed in our data, which are seen throughout northern hemisphere summer (Ls = 90°) and persist into northern fall (Ls = 180°). These clouds are generally localized to Tharsis volcanoes and show streaks, waves, and spirals. From northern spring into late summer we also see the presence of aphelion cloud belt (ACB) clouds, a longitudinally continuous band of clouds that forms near equatorial regions. Throughout the year we see the presence of polar hoods. Sometimes these clouds are simply an amorphous structure centered around the pole; other times we see the presence of single and double vortices as well as cyclonic features that appear and diminish on the timescale of several hours. Finally, we have observed clouds above the 2018 dust storm. Some clouds are wispy--reminiscent of cirrus clouds--while other times we see the presence of gravity waves in the clouds and a "terminator cloud band." We present observations of these cloud morphologies and preliminary retrievals of aerosol properties

Seasonal and Diurnal Variation in the Vertical Structure of the Martian Nitric Oxide Nightglow Layer

International audienc