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Javier Cubas

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Javier Pérez Álvarez

Universidad Politécnica de Madrid

Universidad Politécnica de Madrid

Rocío Jado Puente

Universidad Politécnica de Madrid

Carlos de Manuel

Sabastine Ezike

Ata sattarzadeh

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Papers by Javier Cubas

Use of spacecraft solar panels and Sun sensors for estimation of the Sun-pointing direction in the UPMSat-2 mission

Measurement

Solar panels are a key component for most spacecraft as they provide energy to the vehicle. Howev... more Solar panels are a key component for most spacecraft as they provide energy to the vehicle. However, their possible use is not limited only to power generation, as they can also be used as solar sensors for attitude determination. To calculate the direction of the Sun, photovoltaic models (two of them explicit, and the wellknown 1-D/2-R equivalent circuit) that simulate the performance of the solar panel (including environmental conditions such as temperature, irradiance and Earth's albedo, to obtain accurate results) are described in this paper. These models are used to estimate the Sun incidence angle in relation to a spacecraft based on solar panel generation data. This methodology is checked with data from the UPMSat-2 mission and compared with independent measurements derived from this satellite magnetometer data. The Sun direction results are finally compared to the results obtained from the low-cost solar sensors on board the UPMSat-2. The results included in this paper hint at the possibility of using spacecraft solar panels as an additional attitude determination instrument to improve the accuracy of the estimation of the sun direction.

To expand beyond LiteBIRD full success scientific goals

Trabajo presentado al LiteBIRD Global Face to Face Meeting, celebrado en Sagamihara (Japón) del 3... more

Design and calibration process of solar sensors for small satellite missions

4th Symposium on Space Educational Activities

In combination with magnetometers, solar sensors are one of the most used instruments for determi... more In combination with magnetometers, solar sensors are one of the most used instruments for determining the attitude of small satellites. These devices use the photoelectric effect to produce an electrical current. This electrical current, or the voltage associated with the electrical circuit of the solar sensor, is measured in order to compute the angle of incident of the sun with the normal direction of the sensor. Then, together with the computed angles of other solar sensors on different faces of the satellite, the sun's direction in relation to a spacecraft can be calculated. Solar sensors are simple devices whose low-cost design based on photodiodes can be developed by students. During the design and fabrication process of a solar sensor, one of the most important tasks is the accurate estimation of the sensor response in the space radiative environment. It is possible to simulate the Sun’s radiation spectrum, but the equipment and facilities needed are costly for a universi...

UPMSat-2 Micro-Satellite: In-orbit Technological Demonstration for Education and Science

Ranking de revistas de impacto en la investigación de sistemas fotovoltaicos

El trabajo de un investigador, sea en el campo o en la materia que sea, no se limita únicamente a... more El trabajo de un investigador, sea en el campo o en la materia que sea, no se limita únicamente a la realización de nuevos estudios o a la generación de tablas de resultados. Uno de los aspectos fundamentales de la investigación consiste en la divulgación de los resultados a la comunidad científica, no sólo por la comunicación de resultados en sí sino también por el propio avance en la carrera científica, reflejado muchas veces, como es el caso de la investigación docente, en la promoción por medio de méritos. Sin embargo, la divulgación y publicación en revistas científicas requiere de una búsqueda y conocimiento en este campo que recoge aspectos tan importantes como la búsqueda de posibles publicaciones, del impacto de las revistas en las cuales se publique, de los índices de relevancia de estas, etc. En este trabajo se realiza un análisis de las principales revistas en el ámbito de la energía solar y los paneles fotovoltaicos, así como de sus categorías, análisis de los diferentes criterios de calidad, y de su evolución en dichos criterios a lo largo de los años 2015 a 2018. Por último, se aportan un conjunto de variables estadísticas que permitan a los investigadores un estudio de decisión y de comparación a la hora de seleccionar una revista en la que publicar

Nanosatellite Development Methodology and Preliminary Design Guides for the NANOSTAR Project

The objective of the NANOSTAR project is to promote the development of small satellites in South-... more The objective of the NANOSTAR project is to promote the development of small satellites in South-Western Europe by creating collaborations between the partners, developing new tools and facilities and testing them through student challenges. In this paper is presented the nanosatellite development methodology and the collaboration methodology for the first phase of the student challenges. The documentation for the students was prepared based on a survey on nanosatellite development methodologies, and is divided in preliminary design guides, management methodologies and overviews of ECSS standards, collaborative tools and concurrent engineering. Finally, some conclusions are drawn from the Student Challenge.

Analytical models for Li-ion batteries developed at the IDR/UPM Institute

The present document summarizes the work carried out by the IDR/UPM Institute in relation to the ... more The present document summarizes the work carried out by the IDR/UPM Institute in relation to the development of Analytical models of Li-ion batteries. The proposed models are based on the energy discharge level (in relation to full capacity). This represents a new approach in relation to battery assessment with applications at the design phases of the power subsystem of satellites.

Analysis of the Trends in Air Traffic and CO2 Emissions Within the European Union

The rebound of air traffic after the economic crisis and the development of the emerging countrie... more The rebound of air traffic after the economic crisis and the development of the emerging countries have led an increase in the CO2 emissions that the technological improvements have not been able to restrain so far. And although these emissions are reduced in comparison with the global total, if the projected growth estimates are met, air traffic would become one of the most polluting sectors in the next few years. That is why several organizations have proposed and implemented measures to counteract and reduce emissions, such as the European Union 2008/101/EC directive, the CORSIA program from ICAO or the commitment of the IATA member airlines of stabilizing the CO2 emissions from 2020. The purpose of this study, which is a continuation of previous work from the Department of Aerospace Systems, Air Transport and Airports from the ETSIAE, is to analyse the evolution of the air traffic in the European Union and its emissions, trying to evaluate the impact of the new technologies, reg...

On the UPMSat-2 Attitude, Control and Determination Subsystems design

In the present paper the work carried out in relation to the Attitude, Control and Determination ... more In the present paper the work carried out in relation to the Attitude, Control and Determination Subsystem (ACDS) of the UPMSat-2 is summarized. This engineering project is integrated within the UPMSat-2 mission framework. This 50-kg satellite has been designed and manufactured by the Polytechnic University of Madrid (Universidad Politecnica de Madrid). The development of this ACDS comprises the selection of the different parts, sensors (magnetometers) and actuators (magnetorquers), the design of the control law, the testing campaigns of the different subsystem\'s parts, and its verification. The magnetometers and magnetorquers were tested in the IDR/UPM Institute facilities at Montegancedo campus, in order to check its accuracy. Besides, the effect of their uncertainty levels on the satellite\'s stabilization process once its normal attitude has been perturbed, were studied. The control law is based on B-dot, being thoroughly simulated by using Monte Carlo analysis. Finally...

Development of a Calibration Satellite for a CMB Telescope Flying in Formation about L2 Libration Point

The new generation of cosmic microwave background (CMB) telescopes have reached unprecedented lev... more The new generation of cosmic microwave background (CMB) telescopes have reached unprecedented levels of sensitivity. These telescopes measure several cosmological parameters with different levels of accuracy. In particular, considerable effort has been made to measure the B-mode polarization, which is related to the inflationary process of the universe. The power spectrum of this signal is about four orders of magnitude fainter than the CMB temperature power spectrum. Due to the signal weakness, the instruments must be subjected to calibration processes before and after launching. Additionally, data from the same sky area is gathered repeatedly to mitigate during data analysis the systematic errors induced by instruments. Celestial sources are often used as an external reference for calibration after launch, but these sources are not perfectly characterized. In this paper we study the concept of using a calibration satellite (CalSat) flying in formation with a CMB telescope in an or...

Implementation of Concurrent Engineering approach in MUSE (Master in Space Systems) Master's degree in space engineering

The UPMSat-2 Attıtude Control Subsystem

Lambert W-function simplified expressions for photovoltaic current-voltage modelling

2020 IEEE International Conference on Environment and Electrical Engineering and 2020 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2020

In this paper, the first work carried out at the IDR/UPM Institute within the frame of the educat... more In this paper, the first work carried out at the IDR/UPM Institute within the frame of the educational innovation project PIRAMIDE is presented. This work is related to photovoltaic behavior modeling simplification. The aim is to derive simplified and easy-to-work-with equations for the Lambert W-function. This mathematical function represents a quite useful tool when modeling solar cells/panels performance (that is, the current-voltage curve) by analytical approaches. However, the Lambert W-function has a complex solving process which might represent an unaffordable mathematical challenge for a great number of professionals/technicians from the photovoltaic industrial sector. Simple approximations for the Lambert W-function on both of its branches (positive and negative), are proposed in this work. The results of the present work show a simple but accurate way of photovoltaic systems modeling, even when working with the implicit equation of the 1-Diode/2-Resistor equivalent circuit model (whose solution is given in the present work by an explicit equation).

Overview of the medium and high frequency telescopes of the LiteBIRD space mission

Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, 2020

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the ... more LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Mediumand High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224 GHz) and the High-Frequency Telescope (166-448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.

Article Explicit Expressions for Solar Panel Equivalent Circuit Parameters Based on Analytical Formulation and the

Due to the high dependence of photovoltaic energy efficiency on environmental conditions (tempera... more Due to the high dependence of photovoltaic energy efficiency on environmental conditions (temperature, irradiation...), it is quite important to perform some analysis focusing on the characteristics of photovoltaic devices in order to optimize energy production, even for small-scale users. The use of equivalent circuits is the preferred option to analyze solar cells/panels performance. However, the aforementioned small-scale users rarely have the equipment or expertise to perform large testing/calculation campaigns, the only information available for them being the manufacturer datasheet. The solution to this problem is the development of new and simple methods to define equivalent circuits able to reproduce the behavior of the panel for any working condition, from a very small amount of information. In the present work a direct and completely explicit method to extract solar cell parameters from the manufacturer datasheet is presented and tested. This method is based on analytical formulation which includes the use of the Lambert W-function to turn the series resistor equation explicit. The presented method is used to analyze commercial solar panel performance (i.e., the current-voltage-I-V-curve) at different levels OPEN ACCESS Energies 2014, 7 4099 of irradiation and temperature. The analysis performed is based only on the information included in the manufacturer's datasheet.

Review The Cup Anemometer, a Fundamental Meteorological Instrument for the Wind Energy Industry. Research at the

The results of several research campaigns investigating cup anemometer performance carried out si... more The results of several research campaigns investigating cup anemometer performance carried out since 2008 at the IDR/UPM Institute are included in the present paper. Several analysis of large series of calibrations were done by studying the effect of the rotor's geometry, climatic conditions during calibration, and anemometers' ageing. More specific testing campaigns were done regarding the cup anemometer rotor aerodynamics, and the anemometer signals. The effect of the rotor's geometry on the cup anemometer transfer function has been investigated experimentally and analytically. The analysis of the anemometer's output signal as a way of monitoring the anemometer status is revealed as a promising procedure for detecting anomalies.

Design, Ground Testing and On-Orbit Performance of a Sun Sensor Based on COTS Photodiodes for the UPMSat-2 Satellite

Sensors, 2021

This paper presents the development of the UPMSat-2 sun sensor, from the design to on-orbit opera... more This paper presents the development of the UPMSat-2 sun sensor, from the design to on-orbit operation. It also includes the testing of the instrument, one of the most important tasks that needs to be performed to operate a sensor with precision. The UPMSat-2 solar sensor has been designed, tested, and manufactured at the Universidad Politécnica de Madrid (UPM) using 3D printing and COTS (photodiodes). The work described in this paper was carried out by students and teachers of the Master in Space Systems (Máster Universitario en Sistemas Espaciales—MUSE). The solar sensor is composed of six photodiodes that are divided into two sets; each set is held and oriented on the satellite by its corresponding support printed in Delrin. The paper describes the choice of components, the electrical diagram, and the manufacture of the supports. The methodology followed to obtain the response curve of each photodiode is simple and inexpensive, as it requires a limited number of instruments and to...

Concept design of low frequency telescope for CMB B-mode polarization satellite LiteBIRD

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, 2020

LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic ... more LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of −56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34-161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view (18 • × 9 •) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90 • are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.

On the satellite attitude determination using simple environmental models and sensor data

Journal of Physics: Conference Series, 2021

Attitude determination represents a fundamental task for most of the spacecrafts. It relies on th... more Attitude determination represents a fundamental task for most of the spacecrafts. It relies on three basic aspects: 1) sensors selection, 2) relevant environmental conditions estimation, and 3) algorithms that relate the sensor measurements to the expected conditions in the reference frame. Each one has its own impact on the accuracy that the system can achieve. Besides, two factors stand out above the others in terms of accuracy: 1) sensor quality (calibration, range, etc), and 2) precision of the environmental models. The computation of the satellite attitude needs at least two independent measurements (magnetometers, solar sensors...), whit their corresponding simulated measurements in the reference frame. Nevertheless, the number of measurements can be reduced to one if the satellite attitude is constrained. This paper describes a procedure to calculate satellites’ attitude and the main environmental models used (Earth magnetic model, Sun position model, Albedo model), including...

On the UPMSat-2 Attitude Determination and Control Subsystem’s magnetometers integration

Journal of Physics: Conference Series, 2021

In the present work, a method for magnetometer calibration through least squares fitting is prese... more In the present work, a method for magnetometer calibration through least squares fitting is presented. This method has been applied over the magnetometer’s data set obtained during the integration tests of the Attitude Determination and Control Subsystem (ADCS) of UPMSat-2. The UPMSat-2 mission is a 50-kg satellite designed and manufactured by the Technical University of Madrid (Universidad Politécnica de Madrid), and finally launched in September 2020. The satellite has three fluxgate magnetometers (one of them experimental) whose calibration is critical to obtain correct measurements to be used by the ADCS. Among several mathematical methods suitable to obtain the calibration parameters, an ordinary least squares fitting algorithm is selected as a first step of the calibration process. The surface estimated is an ellipsoid, surface represented by the magnetometer’s measures of the Earth magnetic field in a point of the space. The calibration elements of the magnetometers are relat...

Use of spacecraft solar panels and Sun sensors for estimation of the Sun-pointing direction in the UPMSat-2 mission

Measurement

Solar panels are a key component for most spacecraft as they provide energy to the vehicle. Howev... more Solar panels are a key component for most spacecraft as they provide energy to the vehicle. However, their possible use is not limited only to power generation, as they can also be used as solar sensors for attitude determination. To calculate the direction of the Sun, photovoltaic models (two of them explicit, and the wellknown 1-D/2-R equivalent circuit) that simulate the performance of the solar panel (including environmental conditions such as temperature, irradiance and Earth's albedo, to obtain accurate results) are described in this paper. These models are used to estimate the Sun incidence angle in relation to a spacecraft based on solar panel generation data. This methodology is checked with data from the UPMSat-2 mission and compared with independent measurements derived from this satellite magnetometer data. The Sun direction results are finally compared to the results obtained from the low-cost solar sensors on board the UPMSat-2. The results included in this paper hint at the possibility of using spacecraft solar panels as an additional attitude determination instrument to improve the accuracy of the estimation of the sun direction.

To expand beyond LiteBIRD full success scientific goals

Trabajo presentado al LiteBIRD Global Face to Face Meeting, celebrado en Sagamihara (Japón) del 3... more

Design and calibration process of solar sensors for small satellite missions

4th Symposium on Space Educational Activities

In combination with magnetometers, solar sensors are one of the most used instruments for determi... more In combination with magnetometers, solar sensors are one of the most used instruments for determining the attitude of small satellites. These devices use the photoelectric effect to produce an electrical current. This electrical current, or the voltage associated with the electrical circuit of the solar sensor, is measured in order to compute the angle of incident of the sun with the normal direction of the sensor. Then, together with the computed angles of other solar sensors on different faces of the satellite, the sun's direction in relation to a spacecraft can be calculated. Solar sensors are simple devices whose low-cost design based on photodiodes can be developed by students. During the design and fabrication process of a solar sensor, one of the most important tasks is the accurate estimation of the sensor response in the space radiative environment. It is possible to simulate the Sun’s radiation spectrum, but the equipment and facilities needed are costly for a universi...

UPMSat-2 Micro-Satellite: In-orbit Technological Demonstration for Education and Science

Ranking de revistas de impacto en la investigación de sistemas fotovoltaicos

El trabajo de un investigador, sea en el campo o en la materia que sea, no se limita únicamente a... more El trabajo de un investigador, sea en el campo o en la materia que sea, no se limita únicamente a la realización de nuevos estudios o a la generación de tablas de resultados. Uno de los aspectos fundamentales de la investigación consiste en la divulgación de los resultados a la comunidad científica, no sólo por la comunicación de resultados en sí sino también por el propio avance en la carrera científica, reflejado muchas veces, como es el caso de la investigación docente, en la promoción por medio de méritos. Sin embargo, la divulgación y publicación en revistas científicas requiere de una búsqueda y conocimiento en este campo que recoge aspectos tan importantes como la búsqueda de posibles publicaciones, del impacto de las revistas en las cuales se publique, de los índices de relevancia de estas, etc. En este trabajo se realiza un análisis de las principales revistas en el ámbito de la energía solar y los paneles fotovoltaicos, así como de sus categorías, análisis de los diferentes criterios de calidad, y de su evolución en dichos criterios a lo largo de los años 2015 a 2018. Por último, se aportan un conjunto de variables estadísticas que permitan a los investigadores un estudio de decisión y de comparación a la hora de seleccionar una revista en la que publicar

Nanosatellite Development Methodology and Preliminary Design Guides for the NANOSTAR Project

The objective of the NANOSTAR project is to promote the development of small satellites in South-... more The objective of the NANOSTAR project is to promote the development of small satellites in South-Western Europe by creating collaborations between the partners, developing new tools and facilities and testing them through student challenges. In this paper is presented the nanosatellite development methodology and the collaboration methodology for the first phase of the student challenges. The documentation for the students was prepared based on a survey on nanosatellite development methodologies, and is divided in preliminary design guides, management methodologies and overviews of ECSS standards, collaborative tools and concurrent engineering. Finally, some conclusions are drawn from the Student Challenge.

Analytical models for Li-ion batteries developed at the IDR/UPM Institute

The present document summarizes the work carried out by the IDR/UPM Institute in relation to the ... more The present document summarizes the work carried out by the IDR/UPM Institute in relation to the development of Analytical models of Li-ion batteries. The proposed models are based on the energy discharge level (in relation to full capacity). This represents a new approach in relation to battery assessment with applications at the design phases of the power subsystem of satellites.

Analysis of the Trends in Air Traffic and CO2 Emissions Within the European Union

The rebound of air traffic after the economic crisis and the development of the emerging countrie... more The rebound of air traffic after the economic crisis and the development of the emerging countries have led an increase in the CO2 emissions that the technological improvements have not been able to restrain so far. And although these emissions are reduced in comparison with the global total, if the projected growth estimates are met, air traffic would become one of the most polluting sectors in the next few years. That is why several organizations have proposed and implemented measures to counteract and reduce emissions, such as the European Union 2008/101/EC directive, the CORSIA program from ICAO or the commitment of the IATA member airlines of stabilizing the CO2 emissions from 2020. The purpose of this study, which is a continuation of previous work from the Department of Aerospace Systems, Air Transport and Airports from the ETSIAE, is to analyse the evolution of the air traffic in the European Union and its emissions, trying to evaluate the impact of the new technologies, reg...

On the UPMSat-2 Attitude, Control and Determination Subsystems design

In the present paper the work carried out in relation to the Attitude, Control and Determination ... more In the present paper the work carried out in relation to the Attitude, Control and Determination Subsystem (ACDS) of the UPMSat-2 is summarized. This engineering project is integrated within the UPMSat-2 mission framework. This 50-kg satellite has been designed and manufactured by the Polytechnic University of Madrid (Universidad Politecnica de Madrid). The development of this ACDS comprises the selection of the different parts, sensors (magnetometers) and actuators (magnetorquers), the design of the control law, the testing campaigns of the different subsystem\'s parts, and its verification. The magnetometers and magnetorquers were tested in the IDR/UPM Institute facilities at Montegancedo campus, in order to check its accuracy. Besides, the effect of their uncertainty levels on the satellite\'s stabilization process once its normal attitude has been perturbed, were studied. The control law is based on B-dot, being thoroughly simulated by using Monte Carlo analysis. Finally...

Development of a Calibration Satellite for a CMB Telescope Flying in Formation about L2 Libration Point

The new generation of cosmic microwave background (CMB) telescopes have reached unprecedented lev... more The new generation of cosmic microwave background (CMB) telescopes have reached unprecedented levels of sensitivity. These telescopes measure several cosmological parameters with different levels of accuracy. In particular, considerable effort has been made to measure the B-mode polarization, which is related to the inflationary process of the universe. The power spectrum of this signal is about four orders of magnitude fainter than the CMB temperature power spectrum. Due to the signal weakness, the instruments must be subjected to calibration processes before and after launching. Additionally, data from the same sky area is gathered repeatedly to mitigate during data analysis the systematic errors induced by instruments. Celestial sources are often used as an external reference for calibration after launch, but these sources are not perfectly characterized. In this paper we study the concept of using a calibration satellite (CalSat) flying in formation with a CMB telescope in an or...

Implementation of Concurrent Engineering approach in MUSE (Master in Space Systems) Master's degree in space engineering

The UPMSat-2 Attıtude Control Subsystem

Lambert W-function simplified expressions for photovoltaic current-voltage modelling

2020 IEEE International Conference on Environment and Electrical Engineering and 2020 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2020

In this paper, the first work carried out at the IDR/UPM Institute within the frame of the educat... more In this paper, the first work carried out at the IDR/UPM Institute within the frame of the educational innovation project PIRAMIDE is presented. This work is related to photovoltaic behavior modeling simplification. The aim is to derive simplified and easy-to-work-with equations for the Lambert W-function. This mathematical function represents a quite useful tool when modeling solar cells/panels performance (that is, the current-voltage curve) by analytical approaches. However, the Lambert W-function has a complex solving process which might represent an unaffordable mathematical challenge for a great number of professionals/technicians from the photovoltaic industrial sector. Simple approximations for the Lambert W-function on both of its branches (positive and negative), are proposed in this work. The results of the present work show a simple but accurate way of photovoltaic systems modeling, even when working with the implicit equation of the 1-Diode/2-Resistor equivalent circuit model (whose solution is given in the present work by an explicit equation).

Overview of the medium and high frequency telescopes of the LiteBIRD space mission

Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, 2020

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the ... more LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Mediumand High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224 GHz) and the High-Frequency Telescope (166-448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.

Article Explicit Expressions for Solar Panel Equivalent Circuit Parameters Based on Analytical Formulation and the

Due to the high dependence of photovoltaic energy efficiency on environmental conditions (tempera... more Due to the high dependence of photovoltaic energy efficiency on environmental conditions (temperature, irradiation...), it is quite important to perform some analysis focusing on the characteristics of photovoltaic devices in order to optimize energy production, even for small-scale users. The use of equivalent circuits is the preferred option to analyze solar cells/panels performance. However, the aforementioned small-scale users rarely have the equipment or expertise to perform large testing/calculation campaigns, the only information available for them being the manufacturer datasheet. The solution to this problem is the development of new and simple methods to define equivalent circuits able to reproduce the behavior of the panel for any working condition, from a very small amount of information. In the present work a direct and completely explicit method to extract solar cell parameters from the manufacturer datasheet is presented and tested. This method is based on analytical formulation which includes the use of the Lambert W-function to turn the series resistor equation explicit. The presented method is used to analyze commercial solar panel performance (i.e., the current-voltage-I-V-curve) at different levels OPEN ACCESS Energies 2014, 7 4099 of irradiation and temperature. The analysis performed is based only on the information included in the manufacturer's datasheet.

Review The Cup Anemometer, a Fundamental Meteorological Instrument for the Wind Energy Industry. Research at the

The results of several research campaigns investigating cup anemometer performance carried out si... more The results of several research campaigns investigating cup anemometer performance carried out since 2008 at the IDR/UPM Institute are included in the present paper. Several analysis of large series of calibrations were done by studying the effect of the rotor's geometry, climatic conditions during calibration, and anemometers' ageing. More specific testing campaigns were done regarding the cup anemometer rotor aerodynamics, and the anemometer signals. The effect of the rotor's geometry on the cup anemometer transfer function has been investigated experimentally and analytically. The analysis of the anemometer's output signal as a way of monitoring the anemometer status is revealed as a promising procedure for detecting anomalies.

Design, Ground Testing and On-Orbit Performance of a Sun Sensor Based on COTS Photodiodes for the UPMSat-2 Satellite

Sensors, 2021

This paper presents the development of the UPMSat-2 sun sensor, from the design to on-orbit opera... more This paper presents the development of the UPMSat-2 sun sensor, from the design to on-orbit operation. It also includes the testing of the instrument, one of the most important tasks that needs to be performed to operate a sensor with precision. The UPMSat-2 solar sensor has been designed, tested, and manufactured at the Universidad Politécnica de Madrid (UPM) using 3D printing and COTS (photodiodes). The work described in this paper was carried out by students and teachers of the Master in Space Systems (Máster Universitario en Sistemas Espaciales—MUSE). The solar sensor is composed of six photodiodes that are divided into two sets; each set is held and oriented on the satellite by its corresponding support printed in Delrin. The paper describes the choice of components, the electrical diagram, and the manufacture of the supports. The methodology followed to obtain the response curve of each photodiode is simple and inexpensive, as it requires a limited number of instruments and to...

Concept design of low frequency telescope for CMB B-mode polarization satellite LiteBIRD

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, 2020

LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic ... more LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of −56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34-161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view (18 • × 9 •) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90 • are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.

On the satellite attitude determination using simple environmental models and sensor data

Journal of Physics: Conference Series, 2021

Attitude determination represents a fundamental task for most of the spacecrafts. It relies on th... more Attitude determination represents a fundamental task for most of the spacecrafts. It relies on three basic aspects: 1) sensors selection, 2) relevant environmental conditions estimation, and 3) algorithms that relate the sensor measurements to the expected conditions in the reference frame. Each one has its own impact on the accuracy that the system can achieve. Besides, two factors stand out above the others in terms of accuracy: 1) sensor quality (calibration, range, etc), and 2) precision of the environmental models. The computation of the satellite attitude needs at least two independent measurements (magnetometers, solar sensors...), whit their corresponding simulated measurements in the reference frame. Nevertheless, the number of measurements can be reduced to one if the satellite attitude is constrained. This paper describes a procedure to calculate satellites’ attitude and the main environmental models used (Earth magnetic model, Sun position model, Albedo model), including...

On the UPMSat-2 Attitude Determination and Control Subsystem’s magnetometers integration

Journal of Physics: Conference Series, 2021

In the present work, a method for magnetometer calibration through least squares fitting is prese... more In the present work, a method for magnetometer calibration through least squares fitting is presented. This method has been applied over the magnetometer’s data set obtained during the integration tests of the Attitude Determination and Control Subsystem (ADCS) of UPMSat-2. The UPMSat-2 mission is a 50-kg satellite designed and manufactured by the Technical University of Madrid (Universidad Politécnica de Madrid), and finally launched in September 2020. The satellite has three fluxgate magnetometers (one of them experimental) whose calibration is critical to obtain correct measurements to be used by the ADCS. Among several mathematical methods suitable to obtain the calibration parameters, an ordinary least squares fitting algorithm is selected as a first step of the calibration process. The surface estimated is an ellipsoid, surface represented by the magnetometer’s measures of the Earth magnetic field in a point of the space. The calibration elements of the magnetometers are relat...