How to process radio occultation data: 1. From time series of frequency residuals to vertical profiles of atmospheric and ionospheric properties

Expertise in processing radio occultation observations, which provide vertical profiles of atmospheric and ionospheric properties from measurements of the frequency of radio signals, is not widespread amongst the planetary science community. In order to increase the population of radio occultation processing experts, which will have positive consequences for this field, here we provide detailed instructions for one critical aspect of radio occultation data processing: how to obtain a series of bending angles as a function of the ray impact parameter from a time series of frequency residuals. As developed, this tool is valid only for one-way, single frequency occultations at spherically symmetric objects, and is thus not immediately applicable to either two-way occultations, such as those of Mars Express, or occultations at oblate objects, such as Jupiter or Saturn. This tool is demonstrated successfully on frequency residuals from a Mars Global Surveyor occultation at Mars, and the resultant set of bending angles and impact parameters are used to obtain vertical profiles of ionospheric electron density, neutral atmospheric number density, mass density, pressure, and temperature via the usual Abel transform. The root-mean-square difference between electron densities in the ionospheric profile derived herein and archived electron densities is 7×10[superscript 8] m[superscript −3]. At the lowest altitudes, temperatures in the neutral atmospheric profile derived herein differ from archived neutral temperatures by less than 0.1 K. Software programs that implement these procedures accompany this paper and may be used to extract scientifically useful data products from lower-level data sets

SPICES: Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems

SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450 - 900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/22, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5-10 AU) from nearby stars ($<$25 pc) with masses ranging from a few Jupiter masses to Super Earths ($\sim$2 Earth radii, $\sim$10 M$_{\oplus}$) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System

Modeling dispersions in initial conditions for air-launched rockets and their effect on vehicle performance

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 157-159).Growing interest in air-launched rockets as a method for lofting satellites into orbit motivates the need to investigate the unique challenges that air launch presents. This thesis explores how uncertainties in an air-launched rocket's state at ignition can affect system performance and investigates a reference trajectory strategy to mitigate performance loss. First, representative vehicle configurations for a generic air-launch system are presented. Mass properties, propulsion characteristics, and vehicle aerodynamics are estimated for the generic rocket configuration. A six-degree-of-freedom (6-DOF) simulation models the vehicle's behavior during the uncontrolled drop phase prior to rocket ignition. The results of 1000 Monte Carlo runs with various initial conditions produce a statistical representation of the expected dispersions in vehicle state at ignition. A 6-DOF Simulink simulation of the rocket's first stage bum is used to quantify the vehicle's performance. The simulation is run for a variety of ignition states, reference trajectories, and constraints on the rocket's control system. The results indicate that for a highly responsive thrust vector control (TVC) system, the rocket experiences negligible performance losses due to dispersions in ignition conditions. However, for a rocket with a less responsive TVC system, dispersions will result in significant performance loss by the end of first stage burn. Finally, the thesis illustrates how selection of a reference trajectory that is optimized for a given dispersed ignition state can significantly reduce the system's performance loss due to dispersions..by Ingrid Mary Beerer.S.M

Direct imaging of exoEarths embedded in clumpy debris disks

The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths, this dust cloud is in fact the most luminous component in the solar system after the Sun itself and the Earth may appear similar to a clump of zodiacal dust to an external observer. Hence, the presence of large amounts of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of exoEarths with future dedicated space-based telescopes. In that context, we address in this paper the detectability of exoEarths embedded in structured debris disks with future space-based visible coronagraphs and mid-infrared interferometers. Using a collisional grooming algorithm, we produce models of dust clouds that simultaneously and self-consistently handle dust grain dynamics, including resonant interactions with planets, and grain-grain collisions. Considering various viewing geometries, we also derive limiting dust densities that can be tolerated around nearby main-sequence stars in order to ensure the characterization of exoEarths with future direct imaging missions