Scientific Cubesats: The SORTIE Mission

There is a great deal of interest in using small satellites, often known as Cubesats, for scientific research missions. The "Cubesat revolution" has seen Cubesats evolve from undergraduate or hobbyist projects, into full-fledged satellite missions using professional engineers. We have also seen increases in the number and availability of Commercial Off The Shelf Cubesat components, and the number of sensors for use on small satellites, and in turn the reliability of small satellite missions has increased. Whereas the early pioneers hoped to simply launch their satellite, or perhaps hear it sending out a beacon signal, today's expectations are set much higher and one expects to obtain scientific quality data from a mission that lasts 1-2 years.   The benefits of small satellites include significantly reduced cost and shorter development lifetimes prior to launch.  On the other hand, small satellites usually do not carry as many instruments as classical missions, but that is also beginning to change.  ASTRA has been centrally involved in the Cubesat revolution, and we will describe some of the missions and sensors we have been involved with. The presentation will describe the NASA-funded SORTIE mission that will launch in late 2017. SORTIE (Scintillation Observations and Response of The Ionosphere to Electrodynamics) will address the following science questions: (Q1) Discover the sources of wave-like plasma perturbations in the F-region ionosphere and; (Q2) Determine the relative role of dynamo action versus direct mechanical forcing in the formation of wave-like plasma perturbations. To address these questions we plan to fly a CubeSat with novel sensors that measure key plasma parameters in a circular, low to middle inclination orbit near 350-400 km altitude. The sensors include an ion velocity meter (built by UTD) and a Planar Langmuir Probe (built by AFRL). The SORTIE mission plan is to describe the distribution of wave-like structures in the plasma density of the ionospheric F-region. In doing so, the SORTIE team will determine the possible role of these perturbations in aiding the growth of plasma instabilities. SORTIE will provide (1) the initial spectrum of wave perturbations which are the starting point for plasma instabilities; (2) measured electric fields which determine the magnitude of the instability growth rate near the region where plasma bubbles are generated; (3) initial observations of irregularities in plasma density which result from plasma instability growth. In this presentation, we will review the science objectives, and provide an overview of the spacecraft and instruments.