scholarly journals The Miniature Optical Communication Transceiver—A Compact, Power-Efficient Lasercom System for Deep Space Nanosatellites

Aerospace ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 2 ◽  
Author(s):  
Nathan Barnwell ◽  
Tyler Ritz ◽  
Samantha Parry ◽  
Myles Clark ◽  
Paul Serra ◽  
...  
Keyword(s):  
Optical Communication ◽  
Peak Power ◽  
Optical Amplifier ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Power Efficient ◽  
Optical Links ◽  
Simulated Performance ◽  
Bit Error Ratio ◽  
Amplifier Design

Optical communication is becoming more prevalent in orbit due to the need for increased data throughput. Nanosatellites, which are satellites that typically weigh less than 10 kg, are also becoming more common due to lower launch costs that enable the rapid testing of technology in a space environment. Nanosatellites are cheaper to launch than their larger counterparts and may be a viable option for communicating beyond Earth’s orbit, but have strict Size,Weight, and Power (SWaP) requirements. The Miniature Optical Communication Transceiver (MOCT) is a compact optical transceiver designed to provide modest data rates to SWaP constrained platforms, like nanosatellites. This paper will cover the optical amplifier characterization and simulated performance of the MOCT amplifier design that produces 1 kW peak power pulses and closes three optical links which include Low Earth Orbit (LEO) to Earth, LEO to LEO, and Moon to Earth. Additionally, a benchtop version of the amplifier design was constructed and was able to produce amplified pulses with 1.37 W peak power, including a 35.7% transmit optics loss, at a pump power of 500 mW. Finally, the modulator, seed laser, amplifier, receiver, and time-to-digital converter were all used together to measure the Bit Error Ratio (BER), which was 0.00257 for a received optical peak power of 176 nW.

scholarly journals The Effect of Low Earth Orbit Atomic Oxygen Exposure on Phenylphosphine Oxide-Containing Polymers

2000 ◽  
Vol 12 (1) ◽  
pp. 43-52 ◽  
Author(s):  
John W Connell
Keyword(s):  
Thin Film ◽  
Atomic Oxygen ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Earth Orbit ◽  
Cooperative Effort ◽  
Flight Experiment ◽  
Oxygen Exposure ◽  
Atomic Oxygen Exposure ◽  
Phenylphosphine Oxide

Thin films of phenylphosphine oxide-containing polymers were exposed to low Earth orbit aboard a space shuttle flight (STS-85) as part of flight experiment designated Evaluation of Space Environment and Effects on Materials (ESEM). This flight experiment was a cooperative effort between the NASA Langley Research Center (LaRC) and the National Space Development Agency of Japan (NASDA). The thin-film samples described herein were part of an atomic oxygen exposure (AOE) experiment and were exposed to primarily atomic oxygen (∼1×1019 atoms cm−2). The thin-film samples consisted of three phosphine oxide-containing polymers (arylene ether, benzimidazole and imide). Based on post-flight analyses using atomic force microscopy, x-ray photo-electron spectroscopy and weight loss data, it was found that the exposure of these materials to atomic oxygen (AO) produces a phosphorus oxide layer on the surface of the samples. Earlier work has shown that this layer provides a barrier towards further attack by AO. Consequently, these materials do not exhibit linear erosion rates which is in contrast with most organic polymers. Qualitatively, the results obtained from these analyses compare favourably with those obtained from samples exposed to AO and/or an oxygen plasma in ground-based exposure experiments. The results of the low Earth orbit AO exposure on these materials will be compared with those of ground-based exposure to AO.

scholarly journals The affect of the space environment on the survival ofHalorubrum chaoviatorandSynechococcus(Nägeli): data from the Space Experiment OSMO on EXPOSE-R

2014 ◽  
Vol 14 (1) ◽  
pp. 123-128 ◽  
Author(s):  
R. L. Mancinelli
Keyword(s):  
Survival Rate ◽  
Uv Radiation ◽  
Molecular Probes ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Dust Particles ◽  
Most Probable Number ◽  
Earth Orbit ◽  
Probable Number ◽  
Space Vacuum

AbstractWe have shown using ESA's Biopan facility flown in Earth orbit that when exposed to the space environment for 2 weeks the survival rate ofSynechococcus(Nägeli), a halophilic cyanobacterium isolated from the evaporitic gypsum–halite crusts that form along the marine intertidal, andHalorubrum chaoviatora member of the Halobacteriaceae isolated from an evaporitic NaCl crystal obtained from a salt evaporation pond, were higher than all other test organisms exceptBacillusspores. These results led to the EXPOSE-R mission to extend and refine these experiments as part of the experimental package for the external platform space exposure facility on the ISS. The experiment was flown in February 2009 and the organisms were exposed to low-Earth orbit for nearly 2 years. Samples were either exposed to solar ultraviolet (UV)-radiation (λ > 110 nm or λ > 200 nm, cosmic radiation (dosage range 225–320 mGy), or kept in darkness shielded from solar UV-radiation. Half of each of the UV-radiation exposed samples and dark samples were exposed to space vacuum and half kept at 105pascals in argon. Duplicate samples were kept in the laboratory to serve as unexposed controls. Ground simulation control experiments were also performed. After retrieval, organism viability was tested using Molecular Probes Live–Dead Bac-Lite stain and by their reproduction capability. Samples kept in the dark, but exposed to space vacuum had a 90 ± 5% survival rate compared to the ground controls. Samples exposed to full UV-radiation for over a year were bleached and although results from Molecular Probes Live–Dead stain suggested ~10% survival, the data indicate that no survival was detected using cell growth and division using the most probable number method. Those samples exposed to attenuated UV-radiation exhibited limited survival. Results from of this study are relevant to understanding adaptation and evolution of life, the future of life beyond earth, the potential for interplanetary transfer of viable microbes via meteorites and dust particles as well as spacecraft, and the physiology of halophiles.

scholarly journals Modern radar techniques and the hazard of meteoroids to space platforms

1998 ◽  
Vol 41 (5-6) ◽  
Author(s):  
G. Cevolani
Keyword(s):  
Parent Body ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Meteoroid Streams ◽  
Storm Activity ◽  
Plasma Generation ◽  
Near Earth Space ◽  
Space Objects ◽  
Very High ◽  
Perihelion Passage

Modern radar techniques, and in particular ground based radars, are a powerful tool to observe space objects (natural meteoroids and artificial space debris) on account of their all-weather and day-and-night performance. Natural meteoroids are an important component of the near-Earth space environment and represent a potential risk for all Earth-orbiting space platforms, which could significantly increase in coincidence of enhanced (outburst or storm) activity of meteoroid streams. A review of the currently active meteoroid streams suggests that a few streams have shown a quasi-periodic outburst activity in the two last centuries and may even undergo a storm activity in the next few years. The Leonids, the most intense of meteor showers, present a potentially serious damage to spacecraft in November of 1998 and 1999, after the perihelion passage of the parent body. Impact probability values of storm meteoroids on space platforms in Low Earth Orbit (LEO) were calculated using the data recorded during systematic observational campaigns carried out by the FS radar facility Bologna-Lecce in Italy. Meteoroid flux predictions and directionality, and investigation on impact parameters at very high velocities (up to 71 km/s) for penetration, charge production and plasma generation, are relevant aspects to develop strategies for safe deployment of the near Earrth-orbiting space platforms.

scholarly journals Improvement of Multipath Channel Performance for Optical MIMO-OFDM in LED Modulation with Fully Generalized Spatial-Frequency

2021 ◽  
Author(s):  
Nandhini Devi R ◽  
Leones Sherwin VimalrajS ◽  
Lydia J
Keyword(s):  
Optical Communication ◽  
Spatial Multiplexing ◽  
Modulation Scheme ◽  
New Concepts ◽  
Data Rates ◽  
Error Ratio ◽  
Bit Error Ratio ◽  
Mimo Ofdm ◽  
Transmission Diversity ◽  
Ofdm Signals

This paper suggests a scheme to generalize the idea of LED index modulation concept by using the spatial multiplexing principle to relay complex OFDM signals through various channels such as AWGN, Rayleigh and Rician by splitting these signals into their real-imaginary and positive-negative components. In order to combat ISI as well as to increase the channel capacity. The MIMO-OFDM efficiency analysis, taking into account the constraint of the forward current of the LED is extracted. The accuracy of the theoretical results is verified by comparing the Bit Error Ratio (BER) reduction and improvement to the (SNR) results under varying condition of the channel. Using MIMO-OFDM as next-generation techniques, along with QAM aims to provide development of new concepts that will lead to the growth of future optical communication. Simulation results validate data rates gained over optical communication using LED modulation scheme and the pure transmission diversity method.

Quasi real-time monitoring of the ionosphere plasma irregularities by the records of the Swarm mission

2021 ◽  
Author(s):  
Peter Kovacs ◽  
Balazs Heilig
Keyword(s):  
Magnetic Field ◽  
Temporal Distribution ◽  
Typical Feature ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Signal Loss ◽  
Plasma Bubble ◽  
Plasma Irregularities ◽  
Ionosphere Plasma ◽  
Swarm Mission

<p>The magnetic and plasma observations of Low-Earth orbit (LEO) space missions represent not only the dynamical state of the ionosphere but also the physical variations of its electromagnetically connected surroundings, i.e. of the plasmasphere and magnetosphere, as well as of their driver, the solar wind. The monitoring of the ionosphere plasma variables is therefore a big asset for the study of our space environment in broad spatial region. Within the framework of the EPHEMERIS project supported by ESA, we aim at investigating two ionosphere phenomena that exhibit close relationship to global physical processes and space weather activity. We use the magnetic and plasma records of the LEO Swarm mission. First, we investigate the temporal and spatial occurrences of the mid-latitude ionosphere trough (MIT), a typical feature of the topside sub-auroral ionosphere appearing as a few degree wide depleted zone, where electron density (Ne) drops by orders of magnitude. It is shown that the locations of MITs are excellent proxies for the detection of the plasmapause position as well as of the equatorward edge of the auroral oval. Secondly, we monitor the irregular fluctuations of the magnetic field along the Swarm orbits via their intermittent behaviour. A new index called intermittency index (IMI) is introduced for the quantitative exemplification of the spatial and temporal distribution of irregular variations at the Swarm spacecraft altitudes. The paper focuses on the introduction of the methodology of IMI time-series compilation. Since IMIs are deduced via a statistical approach, we use the 50 Hz sampling frequency magnetic field records of the mission. We show that most frequently, the ionosphere magnetic field irregularities occur at low-latitudes, about the dip equator and at high latitudes, around the auroral region. It is conjectured that the equatorial events are the results of equatorial spread F (ESF) or equatorial plasma bubble (EPB) phenomena, while the auroral irregularities are related to field-aligned currents (FAC). The ionosphere plasma irregularities may result in the distortion or loss of GPS signals. Therefore our analysis also concerns the investigation of the correlation between observed intermittent events in the ionosphere and contemporary GPS signal loss events and scintillations detected both by on-board Swarm GPS receivers and ground GNSS stations.</p>

A peak power efficient cooperative diversity using star-QAM

2011 ◽  
Author(s):  
Koji Ishibashi ◽  
Won-Yong Shin ◽  
Hyo Seok Yi ◽  
Hideki Ochiai
Keyword(s):  
Peak Power ◽  
Cooperative Diversity ◽  
Power Efficient
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