arXiv subjects

Alberto Carrasco-Casado

Publications and source records attributed to Alberto Carrasco-Casado.

At least 19 recordsLinked to original sources

arXiv2022

Development and Space-Qualification of a Miniaturized CubeSat's 2-W EDFA for Space Laser Communications

The Japanese National Institute of Information and Communications Technology (NICT) is currently developing a high-performance laser-communication terminal for CubeSats aiming at providing a high-datarate communication solution for LEO satellites requiring to transmit large volumes of data from the orbit. A key part of the communication system is a high-power optical amplifier capable of providing enough gain to the transmitted signals to be able to close the link on its counterpart's receiver with the smallest impact in terms of energy and power on the CubeSat's platform. This manuscript describes the development of a miniaturized 2-W space-grade 2-stage Erbium-Doped Fiber Amplifier (EDFA) compatible with the CubeSat form factor, showing the best power-to-size ratio for a spaced-qualified EDFA to the best of the authors' knowledge. Performance results under realistic conditions as well as full space qualification and test are presented, proving that this module can support short-duration LEO-ground downlinks as well as long-duration inter-satellite links.

physics.ins-det↗

arXiv2022

NICT's versatile miniaturized lasercom terminals for moving platforms

With the goal of meeting the diverse requirements of many different types of platforms, ranging from small drones to big satellites, and being applied in a variety of diverse scenarios, ranging from fixed terrestrial links to moving platforms in general, and operating within a wide range of conditions and distances, the Japanese National Institute of Information and Communications Technology (NICT) is currently working towards the development of a series of versatile miniaturized free-space laser-communication terminals. By choosing the appropriate terminal configuration for any given scenario, the basic conditions of operations can be satisfied without the need of customization, and the adaptive design of the terminals can close the gap to achieve an optimum solution that meets the communication requirements. This paper presents NICT's current efforts regarding the development of this series of lasercom terminals and introduces the first prototypes developed for validation and test purposes.

cs.NI↗

arXiv2022

Prototype Development and Validation of a Beam-Divergence Control System for Free-Space Laser Communications

Being able to dynamically control the transmitted-beam divergence can bring important advantages in free-space optical communications. Specifically, this technique can help to optimize the overall communications performance when the optimum laser-beam divergence is not fixed or known. This is the case in most realistic space laser communication systems, since the optimum beam divergence depends on multiple factors that can vary with time, such as the link distance, or cannot be accurately known, such as the actual pointing accuracy. A dynamic beam-divergence control allows to optimize the link performance for every platform, scenario, and condition. NICT is currently working towards the development of a series of versatile lasercom terminals that can fit a variety of conditions, for which the adaptive element of the transmitted beam divergence is a key element. This manuscript presents a prototype of a beam-divergence control system designed and developed by NICT and Tamron to evaluate this technique and to be later integrated within the lasercom terminals. The basic design of the prototype is introduced as well as the first validation tests that demonstrate its performance.

eess.SY↗

arXiv2021

Development of a miniaturized laser-communication terminal for small satellites

Free-space optical communication is becoming a mature technology that has been demonstrated in space a number of times in the last few years. The Japanese National Institute of Information and Communications Technology (NICT) has carried out some of the most-significant in-orbit demonstrations over the last three decades. However, this technology has not reached a wide commercial adoption yet. For this reason, NICT is currently working towards the development of a miniaturized laser-communication terminal that can be installed in very-small satellites, while also compatible with a variety of other different platforms, meeting a wide span of bandwidth requirements. The strategy adopted in this design has been to create a versatile lasercom terminal that can operate in multiple scenarios and platforms without the need of extensive customization. This manuscript describes the current efforts in NICT towards the development of this terminal, and it shows the prototype that has been already developed for the preliminary tests, which are described as well. These tests will include the performance verification using drones first with the goal of installing the prototype on High-Altitude Platform Systems (HAPS) to carry out communication links between HAPS and ground, and later with the Geostationary (GEO) orbit, covering this way a wide range of operating conditions. For these tests, in the former case the counter terminal is a simple transmitter in the case of the drone, and a transportable ground station in the case of the HAPS; and in the latter case the counter terminal is the GEO satellite ETS-IX, foreseen to be launched by NICT in 2023.

eess.SP↗

arXiv2020

Free-space optical links for space communication networks

Future spacecraft will require a paradigm shift in the way the information is transmitted due to the continuous increase in the amount of data requiring space links. Current radiofrequency-based communication systems impose a bottleneck in the volume of data that can be transmitted back to Earth due to technological as well as regulatory reasons. Free-space optical communication has finally emerged as a key technology for solving the increasing bandwidth limitations for space communication while reducing the size, weight and power of satellite communication systems, and taking advantage of a license-free spectrum. In the last few years, many missions have demonstrated in orbit the fundamental principles of this technology proving to be ready for operational deployment, and we are now witnessing the emergence of an increasing number of projects oriented to exploit space laser communication (lasercom) in scientific and commercial applications. This chapter describes the basic principles and current trends of this new technology.

astro-ph.IM↗

arXiv2020

Intersatellite-link demonstration mission between CubeSOTA (LEO CubeSat) and ETS9-HICALI (GEO satellite)

LEO-to-GEO intersatellite links using laser communications bring important benefits to greatly enhance applications such as downloading big amounts of data from LEO satellites by using the GEO satellite as a relay. By using this strategy, the total availability of the LEO satellite increases from less than 1% if the data is downloaded directly to the ground up to about 60% if the data is relayed through GEO. The main drawback of using a GEO relay is that link budget is much more difficult to close due to the much larger distance. However, this can be partially compensated by transmitting at a lower data rate, and still benefiting from the much-higher link availability when compared to LEO-to-ground downlinks, which additionally are more limited by the clouds than the relay option. After carrying out a feasibility study, NICT and the University of Tokyo started preparing a mission to demonstrate the technologies needed to perform these challenging lasercom links. Furthermore, to demonstrate the feasibility of this technique, an extremely-small satellite, i.e. a 6U CubeSat, will be used to achieve data rates as high as 10 Gbit/s between LEO and GEO. Some of the biggest challenges of this mission are the extremely low size, weight and power available in the CubeSat, the accurate pointing precision required for the lasercom link, and the difficulties of closing the link at such a high speed as 10 Gbit/s.

physics.ins-det↗

arXiv2018

LEO-to-ground optical communications using SOTA (Small Optical TrAnsponder) - Payload verification results and experiments on space quantum communications

Free-space optical communications have held the promise of revolutionizing space communications for a long time. The benefits of increasing the bitrate while reducing the volume, mass and energy of the space terminals have attracted the attention of many researchers for a long time. In the last few years, more and more technology demonstrations have been taking place with participants from both the public and the private sector. The National Institute of Information and Communications Technology (NICT) in Japan has a long experience in this field. SOTA (Small Optical TrAnsponder) was the last NICT space lasercom mission, designed to demonstrate the potential of this technology applied to microsatellites. Since the beginning of SOTA mission in 2014, NICT regularly established communication using the Optical Ground Stations (OGS) located in the Headquarters at Koganei (Tokyo) to receive the SOTA signals, with over one hundred successful links. All the goals of the SOTA mission were fulfilled, including up to 10-Mbit/s downlinks using two different wavelengths and apertures, coarse and fine tracking of the OGS beacon, space-to-ground transmission of the on-board-camera images, experiments with different error correcting codes, interoperability with other international OGS, and experiments on quantum communications. The SOTA mission ended on November 2016, more than doubling the designed lifetime of 1-year. In this paper, the SOTA characteristics and basic operation are explained, along with the most relevant technological demonstrations.

physics.space-ph↗

arXiv2018

Optical communication on CubeSats - Enabling the next era in space science

CubeSats are excellent platforms to rapidly perform simple space experiments. Several hundreds of CubeSats have already been successfully launched in the past few years and the number of announced launches grows every year. These platforms provide an easy access to space for universities and organizations which otherwise could not afford it. However, these spacecraft still rely on RF communications, where the spectrum is already crowded and cannot support the growing demand for data transmission to the ground. Lasercom holds the promise to be the solution to this problem, with a potential improvement of several orders of magnitude in the transmission capacity, while keeping a low size, weight and power. Between 2016 and 2017, The Keck Institute for Space Studies (KISS), a joint institute of the California Institute of Technology and the Jet Propulsion Laboratory, brought together a group of space scientists and lasercom engineers to address the current challenges that this technology faces, in order to enable it to compete with RF and eventually replace it when high-data rate is needed. After two one-week workshops, the working group started developing a report addressing three study cases: low Earth orbit, crosslinks and deep space. This paper presents the main points and conclusions of these KISS workshops.

astro-ph.IM↗

arXiv2018

QKD from a microsatellite: the SOTA experience

The transmission and reception of polarized quantum-limited signals from space is of capital interest for a variety of fundamental-physics experiments and quantum-communication protocols. Specifically, Quantum Key Distribution (QKD) deals with the problem of distributing unconditionally-secure cryptographic keys between two parties. Enabling this technology from space is a critical step for developing a truly-secure global communication network. The National Institute of Information and Communications Technology (NICT, Japan) performed the first successful measurement on the ground of a quantum-limited signal from a satellite in experiments carried out on early August in 2016. The SOTA (Small Optical TrAnsponder) lasercom terminal onboard the LEO satellite SOCRATES (Space Optical Communications Research Advanced Technology Satellite) was utilized for this purpose. Two non-orthogonally polarized signals in the ~800-nm band and modulated at 10 MHz were transmitted by SOTA and received in the single-photon regime by using a 1-m Cassegrain telescope on a ground station located in an urban area of Tokyo (Japan). In these experiments, after compensating the Doppler effect induced by the fast motion of the satellite, a QKD-enabling QBER (Quantum Bit Error Rate) below 5% was measured with estimated key rates in the order of several Kbit/s, proving the feasibility of quantum communications in a real scenario from space for the first time.

quant-ph↗

arXiv2018

Space QUEST mission proposal: Experimentally testing decoherence due to gravity

Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum properties, such as entanglement, may exhibit entirely different behavior to purely classical systems. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance, as predicted by Ralph and coworkers [T C Ralph, G J Milburn, and T Downes, Phys. Rev. A, 79(2):22121, 2009, T C Ralph and J Pienaar, New Journal of Physics, 16(8):85008, 2014], a bipartite entangled system could decohere if each particle traversed through a different gravitational field gradient. We propose to study this effect in a ground to space uplink scenario. We extend the above theoretical predictions of Ralph and coworkers and discuss the scientific consequences of detecting/failing to detect the predicted gravitational decoherence. We present a detailed mission design of the European Space Agency's (ESA) Space QUEST (Space - Quantum Entanglement Space Test) mission, and study the feasibility of the mission schema.

quant-ph↗

arXiv2017

Satellite-to-ground quantum communication using a 50-kg-class micro-satellite

Recent rapid growth in the number of satellite-constellation programs for remote sensing and communications, thanks to the availability of small-size and low-cost satellites, provides impetus for high capacity laser communication (lasercom) in space. Quantum communication can enhance the overall performance of lasercom, and also enables intrinsically hack-proof secure communication known as Quantum Key Distribution (QKD). Here, we report a quantum communication experiment between a micro-satellite (48 kg and 50 cm cube) in a low earth orbit and a ground station with single-photon counters. Non-orthogonal polarization states were transmitted from the satellite at a 10-MHz repetition rate. On the ground, by post-processing the received quantum states at an average of 0.14 photons/pulse, clock data recovery and polarization reference-frame synchronization were successfully done even under remarkable Doppler shifts. A quantum bit error rate below 5% was measured, demonstrating the feasibility of quantum communication in a real scenario from space.

physics.optics↗

arXiv2016

Free-Space Quantum Key Distribution

Based on the firm laws of physics rather than unproven foundations of mathematical complexity, quantum cryptography provides a radically different solution for encryption and promises unconditional security. Quantum cryptography systems are typically built between two nodes connected to each other through fiber optic. This chapter focuses on quantum cryptography systems operating over free-space optical channels as a cost-effective and license-free alternative to fiber optic counterparts. It provides an overview of the different parts of an experimental free-space quantum communication link developed in the Spanish National Research Council (Madrid, Spain).

physics.optics↗

arXiv2016

Contributions to free-space optical communications: feasibility of utilizing Cherenkov telescopes as receivers and beam-wander correction in quantum communications

This thesis focuses on the two main applications where free-space optical communication (FSOC) can bring the most significant impact: interplanetary communications and quantum communications. Consequently, the dissertation is structured in two sections. In the first one, a novel proposal is suggested regarding to using Cherenkov telescopes as ground-station receivers. A feasibility study addresses the posibility of using the technology developed for the gamma-ray telescopes that will make up the Cherenkov Telescope Array (CTA) in the implementation of a new kind of ground station. Among the main advantages that these telescopes provide are the much larger apertures needed to overcome the power limitation that ground-based gamma-ray astronomy and deep-space optical communication both have. Also, the large number of big telescopes that will be built for CTA will make it possible to reduce unitary costs by economy-scale production. The second section of the thesis is framed in the field of free-space Quantum Key Distribution (QKD), which has become a new paradigm in the discipline of information security. This technique offers a theoretically-secure way to communicate over an insecure channel since the presence of an eventual eavesdropper can be detected. The main challenge of Free-space QKD is the need to operate both under strong atmospheric turbulence and daylight background noise. To mitigate these effects, a trade-off is usually required when designing the receiver's optics, since a narrow field-of-view improves background noise rejection, but increases turbulence-related losses and a wide field-of-view produces the opposite effect. A correction system for atmospheric turbulence is proposed to overcome both limitations at the same time, and different strategies are analyzed and experimented to carry out the implementation and integration within the QKD system.

astro-ph.IM↗

arXiv2016

Design of an optical-communication link with Mars

The possibility of using optical communications in free-space as an improvement of current RF communication systems was analyzed in this Project. The particular case of a link Mars-Earth was studied and a link based in the future NASA's MLCD project, which is currently being developed, was designed. For this, an orbit simulator was programmed, evaluating the transfer orbit, analyzing the losses that occur in the transmission channel, using several atmospheric models, selecting the most adequate elements for the transmitter and the receiver, calculating the Doppler effect during the mission, and performing a budget link for the different orbit positions. From these results, the maximum bitrate through the MLCD mission was evaluated for the different astronomical observatories chosen as optical ground stations.

astro-ph.IM↗

arXiv2016

Ground-based gamma-ray telescopes as ground stations in deep-space lasercom

As the amount of information to be transmitted from deep-space rapidly increases, the radiofrequency technology has become a bottleneck in space communications. RF is already limiting the scientific outcome of deep-space missions and could be a significant obstacle in the developing of manned missions. Lasercom holds the promise to solve this problem, as it will considerably increase the data rate while decreasing the energy, mass and volume of onboard communication systems. In RF deep-space communications, where the received power is the main limitation, the traditional approach to boost the data throughput has been increasing the receiver's aperture, e.g. the 70-m antennas in the NASA's Deep Space Network. Optical communications also can benefit from this strategy, thus 10-m class telescopes have typically been suggested to support future deep-space links. However, the cost of big telescopes increase exponentially with their aperture, and new ideas are needed to optimize this ratio. Here, the use of ground-based gamma-ray telescopes, known as Cherenkov telescopes, is suggested. These are optical telescopes designed to maximize the receiver's aperture at a minimum cost with some relaxed requirements. As they are used in an array configuration and multiple identical units need to be built, each element of the telescope is designed to minimize its cost. Furthermore, the native array configuration would facilitate the joint operation of Cherenkov and lasercom telescopes. These telescopes offer very big apertures, ranging from several meters to almost 30 meters, which could greatly improve the performance of optical ground stations. The key elements of these telescopes have been studied applied to lasercom, reaching the conclusion that it could be an interesting strategy to include them in the future development of an optical deep-space network.

astro-ph.IM↗

arXiv2016

Chromatic effects in beam wander correction for free-space quantum communications

Beam wander caused by atmospheric turbulence can significantly degrade the performance of horizontal free-space quantum communication links. Classical beam wander correction techniques cannot be applied due to the stronger requirements of transmitting single photons. One strategy to overcome this limitation consists in using a separate wavelength from that of the quantum signal to analyze the beam wander and use this information for its correction. For this strategy to work adequately, both wavelengths should be affected equally by atmospheric turbulence, i.e. no chromatic effects should be originated from beam wander. In this letter, a series of experiments are performed to prove that this is the case for λ ~ 850 nm as the quantum signal and λ ~ 1550 nm as the tracking signal of a quantum communication system.

physics.ins-det↗

arXiv2015

CTA telescopes as deep-space lasercom ground receivers

The amount of scientific data to be transmitted from deep-space probes is very limited due to RF-communications constraints. Free-space optical communication can alleviate this bottleneck, increasing data rate while reducing weight, mass and power of communication onboard equipment. Nevertheless, optimizing the power delivery from spacecraft to Earth is needed. In RF communications, the strategy has been to increase the aperture of ground terminals. Free-space optical communications can also follow it, as they share the limitation of low power received on Earth. As the cost of big telescopes increases exponentially with aperture, new ideas are required to maximize the aperture-to-cost ratio. This work explores the feasibility of using telescopes of the future Cherenkov Telescope Array as optical-communication ground stations. Ground-based gamma-ray astronomy has the same power limitation, hence Cherenkov telescopes are designed to maximize receiver's aperture with minimum cost and some relaxed requirements. Both critical issues of the reutilization and possible adaptations of the telescopes to optimize them for communications, and telescopes simulations and numerical computations of several link budgets applied to worst-case scenarios are discussed, concluding that the proposal is technically feasible and would bring important cost reductions and performance improvements compared to current designs for deepspace optical ground stations.

astro-ph.IM↗

arXiv2015

Low-Impact Air-to-Ground Free-Space Optical Communication System Design and First Results

An air-to-ground free-space optical communication system has been designed and partially developed. The design covers both the communications between the airborne and the ground station, and the acquisition, tracking and pointing. A strong effort has been made in order to achieve the minimum payload power, size and weight, for which a MEMS modulating retroreflector has been chosen. In the ground station, a new technique for fine pointing, based on a liquid crystal device, is proposed and will be demonstrated, as well as other improvements with the aim of optimizing the ground station performance.

astro-ph.IM↗