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, even 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/EMT has extensive expertise in modelling and data analysis in the Mesosphere-Lower Thermosphere-Ionosphere (MLTI): for example, DUTH/EMT 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 inter-compared and also compared against measurements.


Figure: 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. In the following plots from the IRI-07 and NRLMSISE-00 models we show sample runs that have been performed at DUTH/EMT, in which the models are sampled along DUTHSat orbits; this aims to demonstrate the measurements that will be performed by DUTHSat and the rest of the QB50 satellites. Through such comparisons of actual data to existing models, significant improvements are expected to arise through extensive model-data comparisons.

 Figure:  Electron Density and Neutral Temperature vs. latitude and longitude and DUTHSat ground track (left) and Electron density (Ne) over one orbit at three altitudes, for quiet and disturbed conditions (right)

The analysis performed at DUTH/EMT 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

Together with its scientific impact, the development of the DUTHSat satellite has an important educational aspect: the satellite has been designed and built with the participation of a large number of young engineers, supervised by experienced university staff. At the same time, common space mission analysis and design procedures and standards have been followed, introducing in the optimal way young engineers in a broad variety of aspects of space projects. These engineering students will thus leave their university with hands-on experience that can be applied to a range of fields. At the Democritus University of Thrace, the design and construction of the satellite has been accompanied by a series of classes on Space Systems, Space Applications and Space Electrodynamics; furthermore, multiple undergraduate and graduate diploma theses have been completed that are focused on Space Electrodynamics and Satellite Subsystems. More importantly, the students that participate in this project have had 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 analyzing valuable scientific data.


Picture: Graduate students Ilias Vasileiou and Ioannis Nissopoulos 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 Electromagnetic Theory (EMT lab)