Integration and Testing of the Nanosatellite Optical Downlink Experiment

CubeSat sensor performance continues to improve despite the limited size, weight, and power (SWaP) available on the platform. Missions are evolving into sensor constellations, demanding power-efficient high rate data downlink to compact and cost-effective ground terminals. SWaP constraints onboard nanosatellites limit the ability to accommodate large high gain antennas or higher power radio systems along with high duty cycle sensors. With the growing numbers of satellites in upcoming scientific, defense, and commercial constellations, it is difficult to place the high-gain burden solely on the ground stations, given the cost to acquire, maintain, and continuously operate facilities with dish diameters from 5 meters to 20 meters. In addition to the space and ground terminal hardware challenges, it is also increasingly difficult and sometimes not possible to obtain radio frequency licenses for CubeSats that require significant bandwidth. Free space optical communications (lasercom) can cost-effectively support data rates higher than 10 Mbps for similar space terminal SWaP as current RF solutions and with more compact ground terminals by leveraging components available for terrestrial fiber optic communication systems, and by using commercial amateur-astronomy telescopes as ground stations. We present results from the flight unit development, integration, and test of the Nanosatellite Optical Downlink Experiment (NODE) space terminal and ground station, scheduled for completion by summer of 2017. NODE’s objective is to demonstrate an end-to-end solution based on commercial telecommunications components and amateur telescope hardware that can initially compete with RF solutions at \u3e10 Mbps and ultimately scale to Gbps. The 1550 nm NODE transmitter is designed to accommodate platform pointing errors \u3c 3 degrees. The system uses an uplink beacon from the ground station and an onboard MEMS fine steering mirror to precisely point the 0.12 degree (2.1 mrad) 200 mW transmit laser beam toward the ground telescope. We plan to downlink to an estalblished ground terminal at the Jet Propulsion Laboratory (JPL) Optical Communications Telescope Laboratory (OCTL) ground station as well as the new low-cost 30 cm amateur telescope ground station design to reduce overall mission risk. Moving beyond our initial laboratory prototyping captured in Clements et al. 2016 we discuss recent progress developing and testing the flight electronics, opto-mechanical structures, and controls algorithms, including demonstration of a hardware-in-the-loop test of the fine pointing system, for both the space and ground terminals. We present results of over-the-air testing of the NODE system, as we advance from benchtop to hallway to rooftop demonstrations. We will present thermal and environmental test plans and discuss experimental as well as expected results

Nanosatellite optical downlink experiment: design, simulation, and prototyping

The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10  Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.United States. National Aeronautics and Space Administration. Research Fellowship ProgramLincoln Laboratory (Lincoln Scholars)Lincoln Laboratory (Military Fellowship Program)Fundación Obra Social de La Caixa (Fellowship)Samsung FellowshipUnited States. Air Force (Assistant Secretary of Defense for Research & Engineering. Contract FAs872105C0002

Разработка техники трансплантации 3D-клетонных сфероидов ретинального пигментного эпителия в опыте на животных

Aim. This research is aimed to devise the technique for transplantation of 3D spheroids retinal pigment epithelium (RPE) in the experimental animal’s eyes (rabbits).Materials and methods. 3D spheroids of RPE for subsequent transplantation were created using agarose tablets (3D Petri Dishes, Microtissue, USA). The phenotype of the obtained cell cultures was studied by immunocytochemical tests (laser scanning confocal microscope “Fluo View FV10i”, Olympus, Japan). Vitrectomy - 2500 cuts per minute, vacuum 600 mm Hg (Alcon, Accurus, USA) was performed on all rabbits (n = 10). Then, we made retinotomy and injected spheroids in subretinal space (MicroDose injection kit 1 ml, Med One, USA). The following methods of control: ultrasound B-scan (Ultrasonic UD-6000, Tomey, Japan) and optical coherence tomography (OCT), (Askin Spectralis, Heidelberg engineering, Germany). Eyes were enucleated for histological examination on 7, 10, 14 and 20 days.Results. Immunocytochemical tests revealed preservation of the RPE epithelial phenotype in 3D spheroids. Clinical map was similar in all experimental animals - during the first 7 days after surgery we saw cystic edema and flat retinal detachment in the surgery area. As we observed, the retina was adjoining and retinal edema was decreasing. Also, on day 3, 7 and 10 on OCT we saw subretinal round conglomerates with a diameter of 60 to 80 µm - presumably RPE 3D spheroids. According to histological findings, there was observed adhesion of the RPE spheroids to the choroid with subsequent spreading and formation of new cell layer with the increase of observation periods.Conclusion. The proposed technology of cultivation of rabbit RPE with subsequent construction of 3D spheroids allows to preserve the epithelial phenotype of cells. The developed surgical technique of RPE transplantation is acceptable and can be used for further experimental studies to be implemented in clinical practice.Цель исследования. Разработка техники трансплантации SD-клеточных сфероидов ретинального пигментного эпителия (РПЭ) на глазах экспериментальных животных (кролики).Материалы и методы. SD-сфероиды РПЭ для последующей трансплантации создавали с использованием агарозных планшетов (3D Petri Dishes, Microtissue, США). Фенотип полученных клеточных культур исследовали с помощью иммуноцитохимического анализа (лазерный сканирующий конфокальный микроскоп «Fluo View FV10i», Olympus, Япония). Всем экспериментальным животным (кролики породы шиншилла, n = 10) выполняли витрэктомию - 2500 резов в минуту, вакуум 600 мм рт. ст. (Alcon, Accurus, США), ретинотомию и субретинально вводили сфероиды РПЭ (MicroDose injection kit 1 ml, Med One, США). Методы послеоперационного контроля: ультразвуковое В-сканирование глаза (Ultrasonic UD-6000, Tomey, Япония) и оптическая когерентная томография - ОКТ (Askin Spectralis, Heidelberg engineering, Германия). Глазные яблоки энуклеировали на 7, 10, 14, 20-е сутки для последующего гистологического исследования.Результаты. Иммуноцитохимическое окрашивание выявило сохранение фенотипа РПЭ в форме 3D-сфе-роидов. В послеоперационном периоде у всех экспериментальных животных по данным ультразвукового В-сканирования и ОКТ отмечалась схожая клиническая картина: отек и плоская отслойка сетчатки в зоне оперативного вмешательства. По мере наблюдения сетчатка прилегала и отек сетчатки уменьшался. Также, по данным ОКТ, субретинально обнаруживались округлые конгломераты диаметром от 60 до 80 мкм - предположительно 3D-сфероиды РПЭ. По данным гистологического исследования отмечалась адгезия сфероидов РПЭ к сосудистой оболочке с последующим распластыванием и образованием нового клеточного слоя по мере увеличения сроков наблюдения.Заключение. Предложенная технология культивирования кроличьего РПЭ с последующим конструированием 3D-сфероидов позволяет сохранить эпителиальный фенотип клеток. Разработанная хирургическая техника трансплантации РПЭ является приемлемой и может использоваться для дальнейших экспериментальных исследований с целью внедрения в клиническую практику

Rotary SMA actuator for CubeSat deployable structures

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 155-158).Over a decade of continuing CubeSat technology improvements are driving the wide adoption of CubeSats for research and commercial missions. Resource constraints onboard CubeSats still limit their ability to support multi-use actuators, but there is a need for a rotary CubeSat actuator that can be actively commanded to different angles. This type of actuator can be implemented in a CubeSat mechanism for differential drag management, increased power generation, and reconfigurable deployable structures. We propose using a shape memory alloy (SMA) actuator to meet this need. A SMA can be annealed at high temperatures to remember a trained shape. Upon cool down, the SMA element transforms to the martensite phase and is easily deformed. When the element is heated above the transformation temperature it transforms to the stiff austenite phase and assumes its remembered shape, driving the mechanism. Two SMA actuators are trained to different shapes and provide bidirectional rotary motion for use as a space mechanism. The actuators are designed by implementing kinematic, thermal, and bending models to size the SMA element. The models also predict the performance, size, weight, and power of the actuator and ensure it can operate in the CubeSat environment. Then, a prototype of the proposed actuator is manufactured, assembled, and ground tested. Testing is used to validate the models and verify the requirements necessary to operate onboard a CubeSat. The prototype meets all requirements and offers a reduced mass, volume, and complexity alternative to current CubeSat electromagnetic actuators. Future work is necessary to improve the mechanical performance and positional control of the SMA actuator.by Maxim O. Khatsenko.S.M