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Planet is a vertically integrated aerospace and data analytics company that operates the world's 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's 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.

We present deep CCS and HC_7N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the K-band focal plane array on the 100 m Green Bank Telescope. We observed the L1495-B218 filaments in CCS J_N = 2_1–1_0 and HC_7N J = 21−20 with a spectral resolution of 0.038 km s^(−1) and an angular resolution of 31''. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC_7N emission is observed only in L1495A-N and L1521D. We find that CCS and HC_7N intensity peaks do not coincide with NH_3 or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC_7N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH_3, HC_7N, CCS, CO, HCN, and HCO^+, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).

Planet's mission is to monitor global change by imaging the entire Earth every day. To achieve this objective, Planet has launched over 250 satellites and built the mission control and ground station infrastructure to autonomously monitor and control the satellites and download their data. Historically, CubeSat radios have been downlink limited because of size, weight, and power (SWaP) constraints. Planet has overcome the downlink data rate limitation by optimizing every part of the radio communication system to achieve over 220 Mbps peak and 160 Mbps average data throughput. This paper presents an overview of the latest generation compact, low-mass, and low-power High Speed Downlink (HSD) radio that was built and deployed on over 100 3U form-factor Dove satellites that form Planet's Mission 1 constellation. The HSD operates at X-band and is built using commercial-o-the-shelf (COTS) parts with a high-gain spacecraft antenna and reasonably sized ground station antennas (4.5m - 7.6m diameter reflector). Planet's X-band ground station network includes 22 active dishes across 8 sites located around the world. Commercial standards, such as the DVB-S2 modulation and coding suite, have been used where appropriate. The latest generation HSD system is capable of providing downlink volumes of 12-15 GB during a single ground station pass, which has a duration of 7 to 10 minutes. Some lessons learned along the way are presented as Planet transitioned from building and operating a few prototypes to a production constellation of over 100 satellites and 22 active ground stations.