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Non-planar sun sensors can determine solar orientation by existing photodiodes or by reusing solar panels, without increasing the size and mass of spacecraft. However, a limiting factor for the improvement of the accuracy of orientation lies in the lack of a detailed performance assessment on interference suppression. In this paper, a new method that determines solar orientation in the frequency domain is developed for regular pyramid sun sensors, which are formed by regular pyramid arrays. Furthermore, two formulations are established to evaluate the errors of the solar azimuth and elevation angle in solar orientation determination based on the newly proposed frequency-domain method. With these formulations of performance evaluation, we discover the mathematical relationship between the interference spectrum, array geometry, solar irradiance, solar azimuth or elevation angle, and the error in solar orientation determination for the first time. This reveals that the internal interference from the detection system can be completely suppressed in solar orientation determination, and the constant interference can be eliminated in the estimation of solar azimuth angle. Simulation and field experiments validated the effectiveness of the new orientation method, error formulations and performance of each interference source.

We present a novel sun sensor concept. It is the very first sun sensor built with an address event representation spiking pixel matrix. Its pixels spike with a frequency proportional to illumination. It offers remarkable advantages over conventional digital sun sensors based on active pixel sensor (APS) pixels. Its output data flow is quite reduced. It is possible to resolve the sun position just receiving one single event operating in time-to-first-spike mode. It operates with a latency in the order of milliseconds. It has higher dynamic range than APS image sensors (higher than 100 dB). A custom algorithm to compute the centroid of the illuminated pixels is presented. Experimental results are provided. [ABSTRACT FROM PUBLISHER]

The solar vector, which defines the angle between the satellite and the Sun, is an important parameter for attitude control of a nanosatellite. It is highly desirable to enable accurate attitude control of a nanosatellite without increasing size and mass. To solve this issue, this study presents a novel sun sensor based on solar panel time‐division multiplexing. The mathematical relationship between the short‐circuit current of the solar panel and the solar vector is derived, and a mathematical model of the time‐division multiplexing for the sensor is introduced. A sample of the sensor is built and an experiment is conducted to obtain the short‐circuit current data for different angles. The output of the sensor is included in the mathematical model to obtain the solar vector. The relevant measurement errors of the sensor is also derived. The results show that the sensor is capable of measuring across the 0–180° range with a maximum absolute error of measurement of 4.531° and a relative error of 2.517%. [ABSTRACT FROM AUTHOR]

Most satellites use an on-board attitude estimation system, based on available sensors. In the case of low-cost satellites, which are of increasing interest, it is usual to use magnetometers and Sun sensors. A Kalman filter is commonly recommended for the estimation, to simultaneously exploit the information from sensors and from a mathematical model of the satellite motion. It would be also convenient to adhere to a quaternion representation. This article focuses on some problems linked to this context. The state of the system should be represented in observable form. Singularities due to alignment of measured vectors cause estimation problems. Accommodation of the Kalman filter originates convergence difficulties. The article includes a new proposal that solves these problems, not needing changes in the Kalman filter algorithm. In addition, the article includes assessment of different errors, initialization values for the Kalman filter; and considers the influence of the magnetic dipole moment perturbation, showing how to handle it as part of the Kalman filter framework. [ABSTRACT FROM AUTHOR]

• Spacecraft solar panels are combined with Sun sensor to obtain the Sun pointing direction. • Description of the variation of the solar panel performance due to environmental conditions is included. • A method to derive the satellites attitude using magnetometer data in satellites with constrained attitude is explained. • Verification of the methodology with experimental data from the [authors' satellite] mission, and performance assessment. 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 well-known 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. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a theoretical approach for the development of low cost radiometers to measure photosynthetically active radiation (PAR). Two alternatives are considered: a) glass optical filters attached to a silicon sensor, and b) dielectric coating on a silicon sensor. The devices proposed are based on radiometers previously developed by the Argentine National Atomic Energy Commission. The objective of this work is to adapt these low cost radiometers to construct reliable instruments for measuring PAR. The transmittance of optical filters and sensor response have been analyzed for different dielectric materials, number of layers deposited, and incidence angles. Uncertainties in thickness of layer deposition were evaluated. [Copyright &y& Elsevier]

Abstract: This work reports on processing, analysis and characterization of copper indium gallium diselenide (CIGS) used as a photosensitive layer for sensors such as sun angle detectors in space applications. CIGS-based solar cell devices with different CIGS layer thicknesses and the pn-junction located on the opposite side of the incidence of light were illuminated through their ultra-thin transparent molybdenum back contacts. The results from the current density versus voltage and quantum efficiency measurement indicate that the CIGS absorber layer may not exceed 750 nm at backside illumination, due to the limited CIGS diffusion length. [Copyright &y& Elsevier]

In this paper, we use genetic algorithms (GAs) as a heuristic for optimizing the illumination pattern for a single-axis digital sun sensor. Previous work has demonstrated that parametric algorithms can be used to provide better estimates of sun position than conventional centroiding techniques. The performance of these algorithms depends, in part, on the illumination pattern on the detector. Using a linear-phase superresolution technique that is combined with GA, we alter the number, shape, and placement of illuminating features. The GA estimator discovered high-fitness solutions that offer threefold to fivefold improvements over the baseline sensor design. We contend that these multiple peak patterns can greatly improve the performance of the sun sensor when they are coupled with parametric methods for sun position estimation. The optimal illumination pattern can be implemented, at minimal cost, by fabricating a replacement aperture mask. [ABSTRACT FROM AUTHOR]

Non-planar sun sensors can determine solar orientation by existing photodiodes or by reusing solar panels, without increasing the size and mass of spacecraft. However, a limiting factor for the improvement of the accuracy of orientation lies in the lack of a detailed performance assessment on interference suppression. In this paper, a new method that determines solar orientation in the frequency domain is developed for regular pyramid sun sensors, which are formed by regular pyramid arrays. Furthermore, two formulations are established to evaluate the errors of the solar azimuth and elevation angle in solar orientation determination based on the newly proposed frequency-domain method. With these formulations of performance evaluation, we discover the mathematical relationship between the interference spectrum, array geometry, solar irradiance, solar azimuth or elevation angle, and the error in solar orientation determination for the first time. This reveals that the internal interference from the detection system can be completely suppressed in solar orientation determination, and the constant interference can be eliminated in the estimation of solar azimuth angle. Simulation and field experiments validated the effectiveness of the new orientation method, error formulations and performance of each interference source. [ABSTRACT FROM AUTHOR]