Can We Estimate Air Density of the Thermosphere with CubeSats?

The measurement of air density in the Earth’s thermosphere has a wide range of scientific applications from space weather to upper atmosphere dynamics, but also technical applications from satellite control to predictions of atmospheric reentry of space debris. This study models the torques applying on a three-unit CubeSat in low Earth orbit to infer the capability of such platforms to measure the air density along their orbit. Realistic noise levels of available CubeSat components are used, and sensitivity to the various noise sources is presented. The precise knowledge of the spacecraft attitude, angular acceleration, residual magnetic dipole, and center of gravity is critical to allow proper air density retrieval. Winds in the thermosphere also have a significant impact on the thermosphere density retrieval, suggesting that this parameter can also be constrained. Attitude control is not necessary if the attitude itself is properly known. The application to the EntrySat CubeSat predicts that such retrieval is possible at altitudes lower than 200 km with errors lower than 30%. The air density retrieval from CubeSat platforms will open new capabilities to infer upper atmosphere dynamics

ARM: Asteroid Reflection Model: The implementation of an asteroid polarimetry model and its application to interpret asteroid (3200) Phaethon observations

Asteroid Reflection Model (ARM) is a newly developed model that simulates reflected radiation and polarization on an asteroid's surface. The working principle behind the model is radiative transfer using Fourier series expansions of reflection matrices. Input models and parameters are: a triangle polyhedron shape model of an asteroid, a surface scattering model, and the desired asteroid location and orientation and the phase angle. Output parameters are the reflected Stokes vector and the degree and direction of polarization, for each individual surface facet and disk-integrated. ARM is fully verified. Generated phase-polarization curves are validated using polarimetric data of four asteroids, including (3200) Phaethon, for which various surface scattering models are deployed. These phase-polarization curves are fit to the Phaethon data, but this did not result in a good match for any of the surface scattering models, since they fail to simulate the opposition effect. However, the effect of the shape, orientation and the rotational motion is clearly visible in the results, as is the relation between wavelength and polarization. Finally, it was concluded that the polarization is favored over the flux when determining an asteroid's surface characteristics and shape, and that both flux and polarization can be used together when determining its size.Section 3.4 is left out due to publication reasons.Aerospace Engineerin