Monitoring Space Weather with a Sensitive 1 U CubeSat Mass Spectrometer

The chemical composition of Earth's upper atmosphere provides key insights into the status and evolution of the space weather. Earth's exosphere extends from hundreds of kilometers to ten thousands of kilometers. Characteristic measures of the exosphere include the altitude of the exobase, where the transition between the two flow regimes namely continuum flow and free-molecular flow occurs, the number density of species at given altitudes and their dynamics. The chemical composition can be measured, and the vertical structure can be converted into exospheric temperatures for each compound. Although major species dominate, the abundance of minor species, radicals and even traces of species might be underestimated, as they might represent more sensitive tracers of both the space weather influence on the atmosphere and the pollution of the outer atmosphere by decomposing space debris. Considering the complex sequence of chemical reactions, detailed mass spectrometric investigations are necessary. Despite some chemical species being measured during the latest measurements in the 1980s, the abundances of minor components, radicals and trace gasses remain unassessed until today, as previous instrumentation lacked both sensitivity and mass range. As these measures are of dynamic nature, constant monitoring with sensitive instrumentation and high cadence is demanded to derive data for meaningful investigations of the atmosphere composition in response to the exogenous and anthropogenic drivers. Here we report on the development of a novel mass spectrometer that provides sensitive in situ measurements of both the neutral gas and ions in Earth's upper atmosphere. The time-of-flight ion-optical system together with its detector provides a sensitivity that is comparable to full-scale mass spectrometers on board major deep space missions. In addition, this mass spectrometer directly measures species without contact with a wall, preventing on one hand complex species from hypervelocity impact induced bond- dissociation and on the other hand radicals from recombining before measuring at the usual orbital velocities exceeding 7 km/s. These unique instrument capabilities together with its performance empowers the instrument to measure the exosphere close to the exobase to determine scale heights of species reliably, identify and quantify the drivers of the exosphere, and derive almost real-time exospheric temperatures from the exosphere. Thanks to its size of 1 U, establishing a network consisting of several satellites for real-time space weather monitoring and its related forecasting becomes feasible, soon.