System Design of the Miniaturized Distributed Occulter/Telescope (mDOT) Science Mission

The miniaturized Distributed Occulter Telescope (mDOT) will provide unprecedented detection and direct measurements of brightness of extrasolar dust disks at short visible to ultraviolet wavelengths. The baseline mission will observe over 15 targets using a starshade for high-contrast imaging, blocking the target star with a specially shaped free-flying occulter to allow nearby objects to be detected. mDOT operates on a much smaller scale than flagship NASA missions, with an autonomous formation of two small satellites in sun-synchronous low Earth orbit. An occulter-smallsat (246kg, 192W) carries a precisely manufactured 3m-diameter starshade and a telescope-cubesat (6U, 12kg, 40W) carries a 10cm-diameter telescope. The satellites are launched combined as a secondary payload for a total mission lifetime of 1.1 years. After launch, the occulter-smallsat ejects the telescope-cubesat and maneuvers to establish the desired relative orbit, leaving the spacecraft at slightly different longitudes of ascending node. Relative eccentricity and inclination vector separation provides the baseline for scientific observations at the equator (500 km) and a minimum safe distance perpendicular to the flight direction at all times (\u3e1km). The starshade suppresses the light of the target star by 10-7 or more. During a science pass, high-ISP green propellant thrusters on the occulter-smallsat maintain the formation, while differential GNSS is used for cm-accurate relative navigation. Earth’s oblateness perturbations are used to precess the orbits and acquire the science targets over the mission lifetime at minimal propellant cost. The mission addresses key NASA science objectives and provide the unique opportunity to mature starshade techniques for future exoplanet missions

Coordinating Development of the SWARM-EX CubeSat Swarm Across Multiple Institutions

The Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX) is a National Science Foundation (NSF) sponsored CubeSat mission distributed across six colleges and universities in the United States. The project has three primary goals: (1) contributing to aeronomy and space weather knowledge, (2) demonstrating novel engineering technology, and (3) advancing higher education. The scientific focus of SWARM-EX is to study the spatial and temporal variability of ion-neutral interactions in the equatorial Ionosphere-Thermosphere (I-T) region. Since the mission consists of three spacecraft operating in a swarm, SWARM-EX will take in-situ measurements of the neutral and ion composition on timescales of less than an orbital period to study the persistence and correlation between different phenomena in the I-T region. The engineering objectives of SWARM-EX are focused on advancing the state of the art in spacecraft formation flying. In addition to being the first passively safe, autonomous formation of more than two spacecraft, SWARM-EX will demonstrate several other key innovations. These include a novel hybrid propulsive/differential drag control scheme and the realization of a distributed aeronomy sensor. Asa project selected by the NSF for its broader impacts as well as its intellectual merit, SWARM-EX aims to use CubeSat development as a vehicle for education. The six collaborating institutions have varying levels of CubeSat experience and involve students who range from first-year undergraduates to Ph.D. candidates. These differences in knowledge, as well as the distributed nature of the program, present a tremendous educational opportunity, but also raise challenges such as cross-institutional communication and coordination, document sharing and file management, and hardware development. By detailing its procedures for overcoming these challenges, the SWARM-EX team believes that it may serve as a case study for the coordination of a successful CubeSat program distributed across multiple institutions