Global Positioning System Satellites Research Articles

Single point positioning using full and fractional pseudorange measurements from GPS and BDS

In conventional global navigation satellite system (GNSS) receivers, full pseudorange measurements are usually required to complete a single point position fix, which takes longer time than obtaining fractional pseudorange measurements. In order to shorten the time to first fix and improve the position accuracy during cold or warm start of a dual-constellation GNSS receiver, we propose a positioning algorithm using at least four full pseudorange measurements from one constellation and fractional measurements from either or both constellations. Theoretical rapid position results can be obtained with an identical accuracy to that of the conventional method using full measurements. Tests with simulated and real Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) data validate the performance of the proposed approach.

Robust Static Vehicle Detection Method Based on the Fusion of GPS SNR and Magnetic Signal

The wireless vehicle detectors (WVDs) based on the magnetic sensor for outdoor parking spaces have been studied in many papers. However, the magnetic signal has a blind zone between the front and rear wheels of vehicles, thus it is difficult for the WVDs to judge whether the magnetic signal is affected by the vehicle on the current or adjacent parking space. This paper proposes a robust vehicle detection method, which combines the data feature of global positioning system (GPS) satellites’ signal-to-noise ratios (SNRs) and magnetic signals to achieve vehicle detection. Since the high energy consumption of GPS receivers, the reference background of GPS-based method is calculated in the wireless access point (WAP), and the WVDs spend no energy on the background calculation in the proposed method. Moreover, the GPS receiver is activated to assist in the vehicle detection, when the data feature of magnetic signals is insufficient for the WVDs to make an accurate decision on the vehicle status, which improves the vehicle detection accuracy and reduces the average energy consumption of WVDs. Experiments show that the vehicle detection accuracy of our proposed method is up to 99.83%, when the sampling rate of magnetic sensor is 1 Hz, and it has a strong practical significance for the battery-powered WVDs.

Design and packaging of multi-polarized triple-band antenna for automotive applications

This paper proposes a novel design and packaging of single-fed asymmetric slot loaded triple band antenna with left-hand circular polarization (LHCP) at SDARS, right-hand circular polarization (RHCP) at GPS L5 band, and linear polarization at GSM-1900 that be able to deploy at hand-held device for geo-informatics and surveying applications. Triple-band operation and multi-polarization are obtained by inculcation of asymmetric slots in the patch. The all-inclusive dimensions of the designed antenna is only 51 × 52 × 1.6 mm3, rendering it attractive for the user market. A archetype of the proposed model is fabricated, and its performance is substantiate through measurement. Measured results shows that the antenna exhibits multiple independent polarized radiations, i.e. RHCP and LHCP radiation at two distinct bands namely Global Positioning System (GPS) L5 (1.17645 GHz) and Satellite Digital Audio Radio Service (SDARS) (2.320–2.345 GHz) bands, respectively and linear Polarized radiation at GSM-1900 band. The proposed antenna display good radiation performance when installed on car housing and various other type of housing.

Estimation of Ionospheric Total Electron Content From a Multi-GNSS Station in China

Ionospheric total electron content (TEC) is an important parameter in ionospheric researches and applications. However, the determination of the absolute value of TEC can be greatly influenced by the differential code biases (DCBs) estimation. Nowadays, there are more and more Global Navigation Satellite System (GNSS) signals available all over the world, which allow us to solve TEC and DCBs with the hypothesis of local spherical symmetry (LSS) imposed on the dual-frequency observations from only one individual station. For comparison, the results based on the global ionospheric map (GIM) act as a reference in this article. On the one hand, different combinations of Global Positioning System (GPS), GLONASS, and BeiDou Navigation Satellite System (BDS) are considered to illustrate the significance of multi-GNSS observations, with the mixed GPS, GLONASS, and BDS combination performing best when compared to the referenced results. On the other hand, different parameters in LSS condition are taken into account to investigate the suitable geometric constraint of LSS, with the differential longitude, latitude, and epoch suggested to be 3.0°, 0.6°, and 4 min, respectively. Moreover, a group of detailed comparisons from several different stations also show that the combined DCBs and ionospheric TEC derived from our method are compatible with those from the GIM-aided method, especially in the low-latitude area. In summary, with the advantage of the multi-GNSS signals from an individual station, our method can estimate the ionospheric TEC and DCBs independently, which could provide a potential tool in the future real-time applications.

Arduino Based Radioactive Tracking System

There is a clear need to enhance security action to prevent any malicious use or inadvertent abuse of radiation sources. Some of these radioactive sources are consistently transferred beyond the office or laboratory grounds for work and consulting reasons. This paper presents the early development of the radioactive citation tracking, which combined the Arduino microcontroller, Global Positioning System (GPS) and Global Mobile Communication System (GSM) systems. The monitoring scheme will assist the proprietor track the motion of irradiated sources. The system is completely capable of monitoring the motion of the toxic substance through GPS satellite signals. The GPS position could either be transferred to the headquarters at a set intervalShort Messaging Service (SMS) enables real-time surveillance or storage on a flash drive for offline surveillance and information capturing.

Performance Analysis of Positioning Solution Using Low-Cost Single-Frequency U-Blox Receiver Based on Baseline Length Constraint.

With the rapid development of the satellite navigation industry, low-cost and high-precision Global Navigation Satellite System (GNSS) positioning has recently become a research hotspot. The traditional application of GNSS may be further extended thanks to the low cost of measuring instruments, but effective methods are also desperately needed due to the low quality of the data obtained using these instruments. Thus, in this paper, we propose the analysis and evaluation of the ambiguity fixed-rate and positioning accuracy of single-frequency Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) data, collected from a low-cost u-blox receiver, based on the Constrained LAMBDA (CLAMBDA) method with a baseline length constraint, instead of the classical LAMBDA method. Three sets of experiments in different observation environments, including two sets of static short-baseline experiments and a set of dynamic vehicle experiments, are adopted in this paper. The experiment results show that, compared to classical LAMBDA method, the CLAMBDA method can significantly improve the success rate of the GNSS ambiguity resolution. When the ambiguity is fixed correctly, the baseline solution accuracy reaches 0.5 and 1 cm in a static scenario, and 1 and 2 cm on a dynamic platform.

Improving the GRACE Kinematic Precise Orbit Determination Through Modified Clock Estimating.

Utilizing global positioning system (GPS) to determine the precise kinematic orbits for the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) plays a very important role in the earth’s gravitational and other scientific fields. However, the orbit quality is highly depended on the geometry of observed GPS satellites. In this study, we propose a kinematic orbit determination method for improving the GRACE orbit quality especially when the geometry of observed GPS satellites is weak, where an appropriate random walk clock constraint between adjacent epochs is recommended according to the stability of on-board GPS receiver clocks. GRACE data over one month were adopted in the experimental validation. Results show that the proposed method could improve the root mean square (RMS) by 20–40% in radial component and 5–20% in along and cross components. For those epochs with position dilution of precision (PDOP) larger than 4, the orbits were improved by 50–70% in radial component and 17–50% in along and cross components. Meanwhile, the Allan deviation of clock estimates in the proposed method was much closer to the reported Allan deviation of GRACE on-board oscillator. All the results confirmed the improvement of the proposed method.

Red de transporte de datos en formato RTCM, vía protocolo de Internet (Ntrip). Implementación en la región y proyección futura a través de SIRGAS

Las CORS (Estaciones de Referencia de Observación Continua), utilizan los GNSS (Sistemas Satelitales de Posicionamiento Global), para determinar con alta preci- sión una posición, mediante la observación de los satélites de las constelaciones disponibles (GPS, GLONNAS, próximamente Galileo y Compass/BeiDou). 
 Empleando la técnica llamada de Corrección Diferencial, es posible eliminar casi totalmente la influencia de los errores inducidos voluntariamente o producidos por la señal GNSS. El método DGNSS, tanto en modo Post Proceso como en Tiempo Real, son las modalidades más utilizadas. Actualmente están disponibles tam- bién soluciones PPP (Precise Point Positioning - Posicionamiento Puntual Preciso), a partir de desarrollos generados en varias agencias de investigación. Últimamente se han presentado ciertos avances sobre PPP (Posicionamiento de Punto Preciso), particularmente en tiempo real: PPP-RTK. 
 Las Correcciones Diferenciales pueden ser obtenidas directamente a partir de un receptor GNSS, de una CORS o de una red CORS, conectadas a un Servidor-Cáster a través de Internet. 
 El cliente o usuario móvil utilizando tecnología de telefonía móvil (GSM, GPRS, EDGE, UMTS) y un programa Cliente, puede acceder a la dirección IP del Cáster, a través de protocolo Ntrip (Red de Transporte de datos en formato RTCM a través Protocolo de Internet), a fin de obtener los datos de corrección diferencial para el receptor GNSS que está utilizando. 
 Ntrip se basa en HTTP (HyperText Transfer Protocol - Protocolo de Transferencia de Hipertexto), siendo capaz de trasmitir cualquier tipo de datos GNSS a través de mensajes RTCM (Radio Technical Commission for Maritime Services) o datos en formato propietario (raw data). El usuario puede elegir entre una serie de produc- tos, como por ejemplo correcciones de una sola CORS, o corrección de una red CORS. Existen diversas soluciones de red, como ser: VRS (Estación de Referencia Virtual), FKP (Parámetros de Corrección de Planos), MAX (Máster-Auxiliar), iMAX (individual Máster-Auxiliar

Rain Monitoring with Polarimetric GNSS Signals: Ground-Based Experimental Research

In recent years, there has been a preliminary research on monitoring rainfall information based on polarimetric Global Navigation Satellite System (GNSS) signals, which is a quite novel concept. After previous theoretical research on monitoring rain based on polarimetric phase shift of GNSS signals, the paper aims to detect rain using polarimetric GNSS signals from a ground-based experiment. Firstly, a conical horn antenna specially designed for receiving dual-polarized (H, horizontal, and V, vertical) GNSS signals was developed, and an experimental system for polarimetric GNSS rain detection was built. Then, taking Global Positioning System (GPS) satellites as signal source, a ground-based experiment was carried out at a mountain in Nanjing, where heavy rain tends to occur frequently in rainy season. Additionally, a data processing algorithm mainly following Padullés et al. (2016) to solve the problems of quality control, unlocking, hardware effect, phase ambiguity, multipath effect was applied independently to this ground-based data from the polarimetric GNSS rain detection system. Also, the multi-source data from nearby weather radar and weather stations was used for verification. Results from 14 GPS satellites show that the obtained phase shift is zero in all no-rain days while it is not zero during rainy days, which is in accordance with the actual situation. Compared with weather radar and rain gauges’ data, the results verify that the phase shift is caused by rain. Besides, when individual cases are examined, many show that their tendencies of accumulated phase shift are quite similar to that of a weather station’s rainfall data, even some correlation coefficients are up to 0.99. These demonstrate the reliability of our experimental system and the feasibility of the data processing algorithm. This study will provide technical support for future spaceborne experiment, which has promising applications in global rain monitoring.

Accuracy analysis of GPS broadcast ephemeris in the 2036th GPS week

Satellite orbit error is one of main sources in Global Positioning System (GPS) receiver positioning error. Using broadcast ephemeris in navigation message, the receiver can calculate spatial position of GPS satellites, then combine pseudorange measurements and achieve positioning solution. In this work, taking broadcast ephemeris in the 2036th GPS week as an example, orbital position of the satellite with the pseudo-random-noise (PRN) code 4 is calculated. Furthermore, using GPS precision ephemeris as a reference, orbital error of the broadcast ephemeris for the PRN 4 satellite is investigated. The results show that the maximum difference of the satellite in three directions is 36 meters, 57 meters and 39 meters, respectively. The three-dimension distance deviating from precision ephemeris is at most 61 meters. The maximum deviation occurs only during certain time periods in the whole GPS week.

Covariance Analysis of Real-Time Precise GPS Orbit Estimated from Double-Differenced Carrier Phase Observations

The covariance of real-time global positioning system (GPS) orbits has been drawing attention in various fields such as user integrity, navigation performance improvement, and fault detection. The international global navigation satellite system (GNSS) service (IGS) provides real-time orbit standard deviations without correlations between the axes. However, without correlation information, the provided covariance cannot assure the performance of the orbit product, which would, in turn, causes significant problems in fault detection and user integrity. Therefore, we studied real-time GPS orbit covariance characteristics along various coordinates to effectively provide conservative covariance. To this end, the covariance and precise orbits are estimated by means of an extended Kalman filter using double-differenced carrier phase observations of 61 IGS reference stations. Furthermore, we propose a new method for providing covariance to minimize loss of correlation. The method adopted by the IGS, which neglects correlation, requires 4.5 times the size of the covariance to bind orbit errors. By comparison, our proposed method reduces this size from 4.5 to 1.3 using only one additional parameter. In conclusion, the proposed method effectively provides covariance to users.

Target moving trajectory estimation by multiple receivers based on GPS forward scattering radar

The estimation of target moving trajectory by the multiple receivers based on global positioning system (GPS) forward scattering radar has been first presented in the study, which cannot be obtained by the traditional method. A new estimation approach has been considered using the following information. First, the starting and ending time at which the target pass through the baseline of GPS transmitter–receiver can be obtained. Second, the azimuth and elevation angles of GPS satellites are extracted in combination with the satellite sky map at the recording time. On the basis, the target moving trajectory can be obtained by the established model. In order to validate its feasibility, the experiment has been completed in the open area of Beihang University, which regards the human as the target. Four GPS receivers have been employed to record the data. The experimental results show that the estimation of target trajectory is consistent with the real situation, which proves the practical applicability of the proposed technique.

Improving Accuracy of the Alpha-Beta Filter Algorithm Using an ANN-Based Learning Mechanism in Indoor Navigation System.

The navigation system has been around for the last several years. Recently, the emergence of miniaturized sensors has made it easy to navigate the object in an indoor environment. These sensors give away a great deal of information about the user (location, posture, communication patterns, etc.), which helps in capturing the user’s context. Such information can be utilized to create smarter apps from which the user can benefit. A challenging new area that is receiving a lot of attention is Indoor Localization, whereas interest in location-based services is also rising. While numerous inertial measurement unit-based indoor localization techniques have been proposed, these techniques have many shortcomings related to accuracy and consistency. In this article, we present a novel solution for improving the accuracy of indoor navigation using a learning to perdition model. The design system tracks the location of the object in an indoor environment where the global positioning system and other satellites will not work properly. Moreover, in order to improve the accuracy of indoor navigation, we proposed a learning to prediction model-based artificial neural network to improve the prediction accuracy of the prediction algorithm. For experimental analysis, we use the next generation inertial measurement unit (IMU) in order to acquired sensing data. The next generation IMU is a compact IMU and data acquisition platform that combines onboard triple-axis sensors like accelerometers, gyroscopes, and magnetometers. Furthermore, we consider a scenario where the prediction algorithm is used to predict the actual sensor reading from the noisy sensor reading. Additionally, we have developed an artificial neural network-based learning module to tune the parameter of alpha and beta in the alpha–beta filter algorithm to minimize the amount of error in the current sensor readings. In order to evaluate the accuracy of the system, we carried out a number of experiments through which we observed that the alpha–beta filter with a learning module performed better than the traditional alpha–beta filter algorithm in terms of RMSE.

Diurnal, seasonal and solar cycle variation in total electron content and comparison with IRI-2016 model at Birnin Kebbi

Abstract. The ionosphere is the major error source for the signals of global positioning system (GPS) satellites. In the analysis of GPS measurements, ionospheric error is assumed to be somewhat of a nuisance. The error induced by the ionosphere is proportional to the number of electrons along the line of sight (LOS) from the satellite to receiver and can be determined in order to study the diurnal, seasonal, solar cycle and spatial variations in the ionosphere during quiet and disturbed conditions. In this study, we characterize the diurnal, seasonal and solar cycle variation in observed total electron content (OBS-TEC) and compare the results with the International Reference Ionosphere (IRI-2016) model. We obtained TEC from a dual-frequency GPS receiver located at Birnin Kebbi Federal Polytechnic (BKFP) in northern Nigeria (geographic location: 12.64∘ N, 4.22∘ E; 2.68∘ N dip) for the period 2011–2014. We observed differences between the diurnal variation in OBS-TEC and the IRI-2016 model for all hours of the day except during the post-midnight hours. Slight post-noon peaks in the daytime maximum and post-sunset decrease and enhancement are observed in the diurnal variation in OBS-TEC during the equinoxes. On a seasonal scale, we observed that OBS-TEC values were higher in the equinoxes than the solstices only in 2012. However, in 2011, the September equinox and December solstice recorded a higher magnitude, followed by the March equinox, and the magnitude was lowest in the June solstice. In 2013, the December solstice magnitude was highest, followed by the equinoxes, and it was lowest in the June solstice. In 2014, the March equinox and December solstice magnitudes were higher than the September equinox and June solstice magnitude. The June solstice consistently recorded the lowest values for all the years. OBS-TEC is found to increase from 2011 to 2014, thus revealing solar cycle dependence.

Efficient jamming signal against civilian GPS receivers

Civilian Global Positioning System (GPS) receivers are subjected to different types of jamming/interference impacts, which degrade its accuracy and reliability.It is well known that GPS signals are considered weak signals; thus, it can be efficiently jammed by using a GPS jammer.One of the paper goals is to increase the interference effectiveness in such a way being able to jam multiple satellites simultaneously, causing continues loss of lock for the GPS receiver tracking loop and decreasing the mitigation probability; a novel jamming signal is proposed which increases the interference influence zone and affects more than one satellite simultaneously. The proposed jamming signal has the ability to generate continuous loss of lock for the GPS receiver-tracking loop and to decrease the mitigation probability. The proposed jamming signal affects all GPS satellites with nearly small interference tolerance value and causes continuous loss of lock to the carrier-tracking loop of the GPS receiver.

Performance Assessment for Combined GPS and BDS Real-time Precise Point Positioning in the Coastal Region of Bohai Gulf, China

Qu, L.; Huang, H.; Du, M., and Acharya, T.D., 2019. Performance assessment for combined GPS and BDS real-time precise point positioning in the coastal region of Bohai Gulf, China. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 271-275. Coconut Creek (Florida), ISSN 0749-0208.In this study, we focus on the performance assessment of combined Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) real-time Precise Point Positioning (PPP) in the coastal region of Bohai Gulf, China. Firstly, 120 Global Navigation Satellite System (GNSS) stations from Multi-GNSS Experiment (MGEX) network of the International GNSS Service (IGS) were processed to generate ultra-rapid precise orbit of both GPS and BDS satellites, updated with the interval of three hours. Secondly, real-time precise satellite clock errors were estimated to compensate the orbit error with 24 regional stations from Crustal Monitor of Network of China (CMONOC) and MGEX networks. Finally, with those products, the performances of GPS-only, BDS-only and combined GPS and BDS real-time PPP were compared and evaluated. The experimental result illustrated that the ultra-rapid orbit accuracy of BDS-2 satellites was still worse than that of GPS satellites which was sub-decimeter level. Among three types of orbital satellites of BDS-2, the orbital accuracy of medium Earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites were at decimeter level while for geostationary Earth orbit (GEO) satellites was at meter-level. The MEO satellites had the best accuracy while the GEO satellites performed the worst. In addition, the 3D accuracy of BDS-only real-time PPP was 10 cm better. Although the accuracy of BDS-2 real-time PPP was still worse than that of GPS and more time was taken for convergence. By adding BDS on top of GPS, the accuracy in the east, north and up components improved 40.0%, 33.3% and 18.5%, respectively, and the convergence time reduced 36.3%, 15.4% and 58.3%, respectively compared to the GPS only.

Precise Orbit Determination for GNSS Maneuvering Satellite with the Constraint of a Predicted Clock

Precise orbit products are essential and a prerequisite for global navigation satellite system (GNSS) applications, which, however, are unavailable or unusable when satellites are undertaking maneuvers. We propose a clock-constrained reverse precise point positioning (RPPP) method to generate the rather precise orbits for GNSS maneuvering satellites. In this method, the precise clock estimates generated by the dynamic precise orbit determination (POD) processing before maneuvering are modeled and predicted to the maneuvering periods and they constrain the RPPP POD during maneuvering. The prediction model is developed according to different clock types, of which the 2-h prediction error is 0.31 ns and 1.07 ns for global positioning system (GPS) Rubidium (Rb) and Cesium (Cs) clocks, and 0.45 ns and 0.60 ns for the Beidou navigation satellite system (BDS) geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO)/Median Earth orbit (MEO) satellite clocks, respectively. The performance of this proposed method is first evaluated using the normal observations without maneuvers. Experiment results show that, without clock-constraint, the average root mean square (RMS) of RPPP orbit solutions in the radial, cross-track and along-track directions is 69.3 cm, 5.4 cm and 5.7 cm for GPS satellites and 153.9 cm, 12.8 cm and 10.0 cm for BDS satellites. When the constraint of predicted satellite clocks is introduced, the average RMS is dramatically reduced in the radial direction by a factor of 7–11, with the value of 9.7 cm and 13.4 cm for GPS and BDS satellites. At last, the proposed method is further tested on the actual GPS and BDS maneuver events. The clock-constrained RPPP POD solution is compared to the forward and backward integration orbits of the dynamic POD solution. The resulting orbit differences are less than 20 cm in all three directions for GPS satellite, and less than 30 cm in the radial and cross-track directions and up to 100 cm in the along-track direction for BDS satellites. From the orbit differences, the maneuver start and end time is detected, which reveals that the maneuver duration of GPS satellites is less than 2 min, and the maneuver events last from 22.5 min to 107 min for different BDS satellites.

Assessment of L5 frequency on real-time GPS orbit and clock estimation

Real-time precise Global Navigation Satellite System (GNSS) satellite orbit and clock products are the prerequisite of real-time GNSS-based applications. With the modernization of Global Positioning System (GPS) constellation and construction of other GNSS constellations, the number of GNSS satellites transmitting multi-frequency signals is increasing rapidly. While the benefit of multi-frequency to Precise Point Positioning (PPP) and Precise Clock Estimation (PCE) has been evaluated by many researchers, the impact of multi-frequency on orbit and clock estimation is still limited, especially in real-time mode. Different from the dual-frequency model, the Inter-Frequency Clock Bias (IFCB) must be treated carefully in the triple-frequency model. In this contribution, the triple-frequency model for real-time GPS satellite orbit and clock estimation is derived and the influence of L5 frequency observations on real-time GPS satellite orbit and clock are analyzed. With observation data from globally distributed stations spanning January 1 to 14 of 2018, real-time GPS orbit and clock are estimated with both dual-frequency and triple-frequency observations. Numerical experiments indicate that, compared to the International GNSS Service (IGS) final orbit, the L5 frequency observations improve the consistency of the normal component with about 0.2 cm, however lead to a decrease of consistency in the radial component with about 0.6 cm; the influence on the tangential direction varies with different number of stations. The potential reason for this phenomenon may partly be attributed to the absence of accurate antenna information for L5 frequency. However, due to the tight constraint of dynamic force model on orbit, the overall differences for each component is less than 1.0 cm, which means the contribution of the third frequency observation on the orbit is limited.

The Case for Global Positioning System Arcing and High Satellite Arc Rates

The Global Positioning System (GPS) satellites arc into the space environment. Evidence for this consists of undispersed impulsive radio frequency signals are shown in the dual-frequency RF receivers, that are on-board all GPS satellites, with high rates that track the charging electron environment, detection of appropriate amplitude short-timescale pulses from GPS satellites at 327 and 430 MHz with the Arecibo 305-m Gordon radiotelescope that do not appear in off-source scans, and arcing on laboratory GPS-like solar arrays at voltages similar to those inferred from GPS arc thresholds. In addition, GPS satellites (up to the Block IIRM) have power degradation (in excess of that expected from radiation) of about 1.5% per year. This degradation is primarily in the short-circuit current, consistent with contamination on the solar array cover glasses, which was detected by a thermal monitor on one GPS satellite solar array, and to be consistent with the power degradation observed on a highly arced GPS-like laboratory solar array if extrapolated to GPS undispersed event rates. The GPS arc rates required for solar array contamination and consistent with the onboard observed event rates are very high, in fact, higher than the rates measured previously on SCATHA, CTS, and other satellites. It is conjectured that the effects of these arcs on satellite power systems have been routinely prevented by highly filtering the power system and antenna response, that most satellites have had no way to detect arcing, and that most power losses up to the present time have been ascribed to radiation damage. Results of new optical and radio-frequency radio frequency observations of satellite arcing are discussed, as well as laboratory measurements confirming the high arc rates and their consequences.

XPS Investigation of the Source of GPS Arc Contamination

Global positioning system (GPS) satellites are strongly suspected to arc into the space environment. Arcing on spacecraft due to differential charging can be blamed for a host of operational anomalies resulting in the loss of billions of dollars and productivity. In addition to anomalous behavior on spacecraft, arcing can be accused of an otherwise unexplained degradation in solar power production of GPS satellites while on orbit. In the study presented here, it will be shown that arcs on a GPS-representative solar array coupon under representative medium earth orbit/geosynchronous earth orbit (MEO/GEO)-like conditions result in contamination of solar panel coverglasses. This finding supports the argument that arc-induced contamination is a prime suspect in explaining the mysterious excess power loss of GPS satellites on orbit. Further, optical mapping suggests that this arcing occurs primarily at the edges of the sample panel where silicone adhesive with glass microspheres was exposed. X-ray photoelectron spectroscopy (XPS) reveals that the concentration of Si near the arc sites is increased, suggesting that the adhesive is ionized during the electrostatic discharge and coats the surface of the solar panel, resulting in reduced optical transmission through the coverglass and therefore reducing power production. X-ray depth profiling suggests that the silicon detected is due to surface contamination, and electrostatic simulations indicate that glass microspheres intended to reduce adhesive mass and produce a uniform bond-line may be exacerbating the arcing problem.