2 research outputs found
Addressing the effects of background plasma and wake formation on nanosatellites with electric propulsion using a 3D Particle In Cell code
3D-PIC (Particle In Cell) simulations were performed to emulate the dynamics and collection of plasma particles onto the surface of the UWE-IV, a satellite of miniaturized dimensions (CubeSat) launched in 2018. We review the electrostatic potential, currents collected and plasma disturbances of the CubeSat and characterize them by numerical simulation over Low Earth Orbits (LEO), in two general cases: as a passive satellite and with active thrusters without regard of neutralization units. During one orbital period the passive CubeSat drives an isotropic impingement of plasma electrons, that (because their higher mobility regarding ions) govern a negative surface potential. However, by the time-evolution of the charge sheath, we relate that potential barriers may be forming around the satellite that can reduce the collection of electrons over spacecraft surfaces. When thrusters are fired, spacecraft becomes more negatively charged than for a passive satellite, and their potential energy Esc is about hundreds of times larger than the ambient ion flowing energies, Ei. In this case, ion density maps of ambient oxygen (O+), show particles fill in the ion void (wake) zone due to bare electrostatic attraction by a (growing) negative satellite potential. The experiment was repeated in different orbit altitudes with varying plasma densities, showing that in space zones with greater concentration of plasma ions, the satellite potential is less negative, ultimately linked to this near-wake ion-focusing collection. Thus, we conclude that if thrusters operate in LEO altitudes, where the relatively higher plasma concentrations are (equatorial orbits of 300–500 km), large negative potentials can be avoided due to the natural rule of ambient ion dynamics. This study can be important for operations of future miniaturized satellites using this type of thruster technologie
Modeling degraded performance metrics of optical amplifiers under radiation
Gain, noise figure (NF), and output power are considered the common performance metrics of an optical fiber
amplifier. With an increasing interest of space industry in developing technologies for satellite-ground and intersatellite
communication in the optical band, the EDFA (erbium doped fiber amplifier) is needed as power
amplifier in space to compensate attenuation and insertion losses between the building blocks of the architecture.
There is very little research on modeling the degradation mechanisms of typical commercial fibers,
specifically on the NF and output power metrics, that requires knownledge of the insertion losses at the entrance
of the fiber for both the pump and the signal wavelengths λp and λs. In this brief report we propose that the noise
figure and output power trends can be extrapolated from a semi-empirical model for the insertion losses proved
at high and low dose rates at two different temperatures. The results show reasonable trends that a common offthe
shelf EDFA can present in co-propagating configuration on the NF and output power under several doses at
low and high rates. The radiation losses using non-hardened fiber show sustainable attenuation levels in dB that
can possibly allow employing this off-the shelf fibers in CubeSats or small satellites without the need of special
radiation insulation. It is further supported with theoretical data that the temperature factor can affect more the
EDFA degradation in space than the radiation itself, imposing limits on the temperature control of commercial
satellites using this photonics