Motivation-Why Study the Upper Atmosphere
The Earth’s upper atmosphere, which includes the Mesosphere and Lower Thermosphere, together with the Ionosphere (MLTI) is a complex dynamical system, sensitive to effects both from above and bellow. From above, the sun produces dramatic effects and significantly alters its energetics, dynamics and chemistry in a way that is not entirely understood; and from below, atmospheric motions are dominated by poorly understood gravity waves and tides that both propagate through and dissipate in this region. The response of the upper atmosphere to global warming in the lower atmosphere is also not well known: whereas the increase in CO2 is expected to result in a global rise in temperature, model simulations predict that the thermosphere might actually show a cooling trend and a thermal shrinking of the upper atmosphere, and might play a role in energy balance processes. However, despite its significance, the MLTI region is the least measured and least understood of all atmospheric regions: Situated at altitudes from 50 to ~300 km the MLTI region is too high for balloon experiments and too low
for orbital vehicles, due to significant atmospheric drag. Even with the new advances from remotesensing measurements from missions at higher altitudes, this remains an under-sampled region with many remaining open questions. Thus it is not surprising that among scientists the MLTI region is often called (quite appropriately) the “Agnostosphere” (or the Ignorosphere) . The continuous and ever- increasing presence of mankind in space,and the importance of the behavior of this region to multiple issues related to aerospace technology, such as orbital calculations, vehicle re-entry, space debris lifetime etc., make its extensive study a pressing need. The QB50 mission targets to perform measurements in exactly this region, and, though instrumentation will be limited due to spacecraft size and power, the combination of the large number of in-situ measurements from all 50 CubeSats will be able to provide answers to some of the questions on the sequence of events that lead to MLTI heating and expansion, as well as its composition.
Upper Atmosphere Electrodynamics Modeling
DUTH/SRL has extensive expertise in modelling and data analysis in the Mesosphere-Lower Thermosphere-Ionosphere (MLTI); DUTH/SRL has undertaken and has recently successfully completed an ESA project titled “Electrodynamics Simulations in support to Future MLTI Missions”, aiming to investigate the range of variability of key variables in the MLTI. Through this project a number of key MLTI models were run for a range of input conditions (solar, geomagnetic, seasonal) and the results from the models were intercompared and also compared against measurements.
a) Electron Density and Neutral Temperature vs. latitude and longitude and DUTHSat ground track
b) Electron density (Ne) over one orbit at three altitudes, for quiet and disturbed conditions;
The models and corresponding variables investigated are listed below:
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• TIE-GCM(Tn,Ti,Te,U,W,O,O2,NO, N(4S),N(2D),O+,O2+,N2+,NO+,N+,Ne,G-Potential,E-Pot)
• GUMICS-4 (N,P,U,T,MF,EF,ΣPedersen,ΣHall, E-Potential, PP power, Joule heating, FAC)
• IRI-07 (Ne, Te, Ti, H+, He+, NO+, O+,O2+, ion drifts, TEC, F1 and spread-F-probability)
• NRLMSISE-00 (Tn, He, O, O2, N2,Ar, H, N, Density, collision frequency)
• CHAMP Currents Model (Horizontal and Field Aligned Currents)
• Alpha parameter Model (Pedersen/Hall conductivity ratio)
• HWM-07 (Zonal and Meridional winds )
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In the list above we mark in red the MLTI variables that will be sampled by the QB50 CubeSats. The analysis performed at DUTH/SRL will allow for the optimal calibration of the QB50 Science Units and will play a key role in the data analysis, through comparisons of the measurements of all 50 QB50 sensors with current state-of-the-art models.
Model temperature vs. altitude at high latitudes together with a sample QB50 orbit. The location of the ground station at the Democritus University ofThrace is also shown.
The analysis performed at DUTH/SRL will allow for the optimal calibration of the QB50 Science Units and will play a key role in the data analysis, through comparisons of the measurements of all 50 QB50 sensors with current state-of-the-art models.
Educational Aspects of the QB50 Cubesat Initiative
Graduate students of the Department of Electrical and Computer Engineering of the
Democritus University of Thrace are working on the assembly of DUTHSat in a Controlled
Environment area of the Laboratory of Electromagnetism and Space Research
Together with its scientific impact, the QB50 initiative has an important educational aspect: the QB50 CubeSats are being designed and built by a large number of young engineers, supervised by experienced university staff and guided by the QB50 project through formal reviews and feedback. At the same time, space mission analysis and design procedures and standards are followed, introducing in the optimal way young engineers in a broad variety of aspects of space projects. These engineers will not only learn about space engineering in theory but will leave their universities with handson experience. At the Democritus University of Thrace, the design and construction of the satellite is accompanied by a series of classes on Space Systems, Space Applications and Space Electrodynamics; furthermore, multiple undergraduate and graduate diploma theses are focused on Satellite Subsystems. The students that participate in this project have a unique opportunity to follow all phases of a space mission, from design to spacecraft development, integration with instruments, testing, launch, tracking and finally to receiving and analysing valuable scientific data.