Planet High Speed Radio: Crossing Gbps from a 3U CubeSat

Planet is a vertically integrated aerospace and data analytics company that operates the world\u27s largest commercial fleet of remote sensing satellites. Our mission is to image the whole world everyday, and make change visible, accessible, and actionable. We have launched over 350 satellites and built up an automated mission control and ground station infrastructure to monitor and control the satellites, and download the imagery data. Historically, small satellite radios have been downlink limited because of tight size, weight, and power (SWaP) constraints. Rapid prototyping, iteration, and adaptation of the latest commercial-o_-the-shelf (COTS) technology has allowed for continuous improvements in data throughput on our high speed radio from a very low-cost cubesat platform. In this talk, we will report on our latest X-band radio and antenna solution which has achieved a data rate over 1.6 Gbps from a 3U CubeSat on-orbit. Planet\u27s High Speed Downlink 2 (HSD2) is the latest generation compact, low-mass, and low-power radio that was built and deployed on 3U form-factor imaging CubeSats in December 2018. This system operates at X- band and is built using COTS parts with a dual polarization antenna. The two physical channels represent the two polarization modes, right hand circular polarization (RHCP) and left hand circular polarization (LHCP) and each physical channel utilizes 300 MHz of total bandwidth. Within each physical channel, there are three logical channels spaced 100 MHz apart center-to-center frequency. The individual channel symbol rate is 76.8 Msps. Each physical channel has 1 W RF output power and 15 dBi antenna gain. The total DC power consumption of the radio including the processor and the FPGA is 50Wand the total volume occupied by the radio and antenna, including the mechanical deployment structure for the antenna is 0.25U. The commercial digital television broadcasting standard DVB-S2 is used for modulation and coding. An adaptive coding and modulation (ACM) scheme is used to dynamically change the modulation and coding for each channel individually based on the available link margin. Our ground station network includes 15 dishes (29 dB/K gain-to-noise-temperature) across 5 sites located around the world. The HSD2 is capable of providing downlink volume of over 80 GB during a single ground station pass

Correlation of cycles in Lava Lake motion and degassing at Erebus Volcano, Antarctica

Several studies at Erebus volcano have recorded pulsatory behaviour in many of the observable properties of its active lava lake. A strong correlation between the variations in surface speed of the lake and the composition of gas emitted has previously been noted. While previous studies have shown that the SO2 flux and the surface elevation exhibit pulsatory behaviour with a similar period to that of the surface speed and gas composition, suggesting they are linked, a lack of overlap between the di erent measurements has prevented direct comparisons from being made. Using high time-resolution measurements of surface elevation, surface speed, gas composition and SO2 flux we demonstrate for the rst time an unambiguous link between the cyclic behaviour in each of these properties. We also show that the variation in gas composition may be explained by a subtle change in oxygen fugacity. The cycles are found to be in-phase with each other, with a small but consistent lag of 1-3 min between the peaks in surface elevation and surface speed. Explosive events are found to have no observable e ffect on the pulsatory behaviour beyond the ~5 min period required for lake refi ll. The close correspondences between the varying lake surface motion, gas flux and composition, and modelled oxygen fugacity suggest strong links between magma degassing, redox change and the fluid dynamics of the shallow magmatic system.This is the final version of the article. It was originally published by Wiley on behalf of the American Geophysical Union in Geochemistry, Geophysics, Geosystems here: http://onlinelibrary.wiley.com/doi/10.1002/2014GC005399/abstract. It will be embargoed until 19/1/15

Normal Human Pluripotent Stem Cell Lines Exhibit Pervasive Mosaic Aneuploidy

Human pluripotent stem cell (hPSC) lines have been considered to be homogeneously euploid. Here we report that normal hPSC – including induced pluripotent - lines are karyotypic mosaics of euploid cells intermixed with many cells showing non-clonal aneuploidies as identified by chromosome counting, spectral karyotyping (SKY) and fluorescent in situ hybridization (FISH) of interphase/non-mitotic cells. This mosaic aneuploidy resembles that observed in progenitor cells of the developing brain and preimplantation embryos, suggesting that it is a normal, rather than pathological, feature of stem cell lines. The karyotypic heterogeneity generated by mosaic aneuploidy may contribute to the reported functional and phenotypic heterogeneity of hPSCs lines, as well as their therapeutic efficacy and safety following transplantation

Decadal persistence of cycles in lava lake motion at Erebus volcano, Antarctica

Studies of Erebus volcano's active lava lake have shown that many of its observable properties (gas composition, surface motion and radiant heat output) exhibit cyclic behaviour with a period of ~10 min. We investigate the multi-year progression of the cycles in surface motion of the lake using an extended (but intermittent) dataset of thermal infrared images collected by the Mount Erebus Volcano Observatory between 2004 and 2011. Cycles with a period of ~5-18 min are found to be a persistent feature of the lake's behaviour and no obvious long-term change is observed despite variations in lake level and surface area. The times at which gas bubbles arrive at the lake's surface are found to be random with respect to the phase of the motion cycles, suggesting that the remarkable behaviour of the lake is governed by magma exchange rather than an intermittent flux of gases from the underlying magma reservoir. © 2014 The Authors