Enabling process science with CubeSat intersections: An orbit resampling study inspired by PREFIRE

Abstract. The Polar Radiant Energy in the Far-InfraRed Experiment (PREFIRE) will use two 6U CubeSats to continuously measure spectral far-infrared (FIR) emissions for the first time in the modern satellite era. By strategically operating two CubeSats in separate sun-synchronous orbits, PREFIRE will achieve frequent orbit resampling ("intersections") that afford insights into the underlying polar processes that modulate FIR emissions. These orbit intersections are integral to PREFIRE science and will likely feature prominently in future CubeSat missions, motivating methods to characterize resampling distributions. In this study, we develop new methods to locate orbit intersections and extract co-located pixels within crossovers. Such methods are applied to simulated PREFIRE orbits to characterize the spatial and temporal distribution of hypothetical PREFIRE intersections and identify the subset with short revisit times that can be used to inter-calibrate the PREFIRE sensors. The analysis confirms that hundreds of intersections are anticipated each day, with the majority (> 75 %) occurring poleward of 66.5°. Inter-calibration intersections are concentrated between 72° and 78° N/S and will be used to monitor changes in spectral differences between PREFIRE sensors.

Generalizing the analysis to pairs of polar orbiting CubeSats with different equatorial crossing times, we conclude that the second CubeSat nearly quadruples the number of total intersections available for polar process studies. Spatial and temporal resampling coverage is clearly enhanced when more than one CubeSat is deployed, securing greater latitudinal representation and more diverse time differences between crossovers. The spatio-temporal profile of intersections between CubeSats varies with the relative offset in their equatorial crossing times. Further, when two CubeSats are placed at different altitudes, we find that their intersections exhibit time-varying, cyclic coverage, significantly increasing latitudinal coverage relative to two CubeSats placed at identical altitudes that resample each other in constant latitude bands. This study ultimately illustrates some factors to consider when designing future CubeSat science missions and outlines methods for conducting the associated trade studies.