Differential Drag Maneuvers for 6U CubeSat Separation: Enabling Space Based Radio Interferometry Observation from Small Satellite Platforms

The Auroral Emission Radio Observer (AERO) and Vector Interferometry Space Technology using AERO (VISTA) are two low polar Earth orbit CubeSat missions jointly scheduled for flight in 2022. These missions are led by a multi-institution team and supported by NASA's Heliophysics Technology and Instrument Development for Science (H-TiDES) and Heliophysics Flight Opportunities for Research and Technology (H-FORT) programs. In order to achieve the science objectives outlined in the mission requirements and to explore auroral processes in Earth's dynamic high latitude region, AERO and VISTA must be capable of maintaining spacecraft separation between 1 km and 100 km for 30 days of operation to successfully act as a two-element interferometer. However, as is the case with many small satellite missions, there is limited attitude and orbit control and no propulsion system on-board. Therefore, the spacecraft will rely on differential drag to manage separation. Since aerodynamic drag force is dependent on a satellite's geometry and orientation at a specified orbit, this study explores mission scenarios and parameters capable of controlling spacecraft separation in order to achieve science goals. AERO and VISTA will fly simultaneously in a high-inclination sun synchronous orbit and will each carry an electromagnetic vector sensor to study auroral radio emissions; six orthogonal dipole and loop antennas provide wave angle of arrival and polarization information. The differential drag and satellite separation analysis was done by producing a high-fidelity numerical model employing both AGI's Systems Tool Kit (STK) and MATLAB. We will discuss analysis results, further comparing and confirming them with a simplified analytical model. We will also discuss the impacts of our study on mission planning operations, addressing such questions as: 1) how often does daily application of drag control need to be performed; 2) how long does it take to bring the spacecraft back together due to anomalies; 3) how much power can the spacecraft produce in their drag configurations; 4) how to balance drag with other daily tasks; 5) what are the density fluctuations in the upper atmosphere and how will that affect the drag on the spacecraft; and finally 6) what is an ideal differential deployment velocity of the two CubeSats.