We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

[1] Energy spectra of electron microbursts in the energy range 170-360 keV have been measured in the outer radiation zone by the low-altitude (680 km), polarorbiting Korean satellite STSAT-1. These electrons are the lower energy population of relativistic microbursts. Our observations show microburst energy spectra of precipitated electrons inside the loss cone (precipitated) have higher e-folding energies during disturbed times than quiet times. The loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast pitch angle diffusion requires diffusion coefficients larger than $3.5 Â 10 À2 rad 2 /sec, while $1.5 Â 10 À5 rad 2 /sec was proposed by a wave particle interaction theory. The source of microbursts remains unknown as our observations are not adequately explained by wave and particle resonant interaction models.

No abstract

No abstract

We quantify the performance of aerosol and ocean remote sensing products from the PolCube instrument using a previously developed polarimeter retrieval algorithm based on optimal estimation. PolCube is a modified version of the PolCam lunar instrument on the Korea Pathfinder Lunar Orbiter that has been optimized for Earth-Science observations of aerosol, ocean, and thin cloud optical properties. The objective of the PolCube instrument is to retrieve detailed fine-mode (pollution and smoke) and coarse-mode (sea-salt and dust) aerosol properties over the ocean for a range of light to heavy aerosol loadings using its polarimetric-imaging capability at multiple angles and wavelengths from 410−865 nm. An additional objective is to discriminate aerosols from thin clouds. PolCube’s retrieval performance of aerosol optical and microphysical properties and ocean products is quantitatively assessed. We estimate that PolCube can retrieve total aerosol optical depth at 555 nm (AOD555) within ±0.068, fine-mode AOD555 within ±0.078, and fine-mode single-scattering albedo within ±0.036, where all uncertainties are expressed as one standard deviation (1σ). PolCube’s accurate and high-resolution aerosol-retrieval products will provide unique spatial and temporal coverage of the Earth that can be used synergistically with other instruments, such as the Geostationary Environmental Monitoring Spectrometer to improve air-quality forecasting.