Master Control Station Research Articles

Hardware-in-the-loop simulation test platform for UAV flight control system

The flight control system is the integrated command center and core component of the UAV system. Aiming at the problems of poor accuracy and low efficiency in the field measurement of flight control system parameters, combined with the configuration of the flight attitude sensor-vertical gyroscope, hardware-in-the-loop simulation technology, and integrated automatic test methods are adopted. The hardware-in-the-loop simulation test platform for the UAV flight control system composed of a low-cost, high-precision miniaturized UAV attitude calibration platform and a control piston deflection angle test device is designed. The main controller replaces the ground master control station of the UAV and directly sends remote control commands to the aircraft. By changing the attitude of the aircraft, and measuring the voltage of the control signal, the feedback signal, and the rudder angle, the comprehensive performance test of the parameters of the flight control system is realized. The performance test of the platform shows that the platform can meet the test requirements of angular position, system voltage, and control piston deflection angle.

Research on Primary Frequency Modulation Online Monitoring and Assessment Management System Under “Master–Sub” Control Station Model

In a modern power system, to realize the safe operation of units and maintain the frequency stability of the power network, various means of frequency modulation can be adopted. However, there are some deficiencies in the real-time monitoring and assessment management of primary frequency modulation (PFM). To solve these problems, a PFM online monitoring and management method based on the “master–sub” control station model in a wide area measurement system (WAMS) is proposed as a control strategy to support frequency modulation of units and assist power network assessment. In the hybrid monitoring system strategy of the master control station and sub control station, the sub control station is built locally in the power plant to monitor the operational status of the unit in real-time and calculate the PFM assessment index. The master control station is built in the dispatching center, receiving the assessment data uploaded by the sub control station and sending the PFM simulation test instruction. This strategy can effectively improve the real-time performance of dynamic monitoring and parameter calculation, and reduce the probability of frame loss and communication instability in long-distance data transmission. The experimental results show that the PFM online monitoring management control strategy based on the “master–sub” control station model can effectively monitor the unit and provide data support for PFM assessment.

Battery Management System for Unmanned Electric Vehicles with CAN BUS and Internet of Things

In recent decades, the trend of using zero-emission vehicles has been constantly evolving. This trend brings about not only the pressure to develop electric vehicles (EVs) or hybrid electric vehicles (HEVs) but also the demand for further developments in battery technologies and safe use of battery systems. Concerning the safe usage of battery systems, Battery Management Systems (BMS) play one of the most important roles. A BMS is used to monitor operating temperature and State of Charge (SoC), as well as protect the battery system against cell imbalance. The paper aims to present hardware and software designs of a BMS for unmanned EVs, which use Lithium multi-cell battery packs. For higher modularity, the designed BMS uses a distributed topology and contains a master module with more slave modules. Each slave module is in charge of monitoring and protecting a multi-cell battery pack. All information about the state of each battery pack is sent to the master module which saves and sends all data to the control station if required. Controlled Area Network (CAN) bus and Internet of Things technologies are designed for requirements from different applications for communications between slave modules and the master module, and between the master module and control station.

Towards the Quantum Internet: Satellite Control Plane Architectures and Protocol Design

The creation of the future quantum Internet requires the development of new systems, architectures, and communications protocols. As a matter of fact, the optical fiber technology is affected by extremely high losses; thus, the deployment of a quantum satellite network (QSN) composed of quantum satellite repeaters (QSRs) in low Earth orbit would make it possible to overcome these attenuation problems. For these reasons, we consider the design of an ad hoc quantum satellite backbone based on the Software-Defined Networking (SDN) paradigm with a modular two-tier Control Plane (CP). The first tier of the CP is embedded into a Master Control Station (MCS) on the ground, which coordinates the entire constellation and performs the management of the CP integrated into the constellation itself. This second tier is responsible for entanglement generation and management on the selected path. In addition to defining the SDN architecture in all its components, we present a possible protocol to generate entanglement on the end-to-end (E2E) path. Furthermore, we evaluate the performance of the developed protocol in terms of the latency required to establish entanglement between two ground stations connected via the quantum satellite backbone.

The space\u2013time references of BeiDou Navigation Satellite System

The BeiDou Navigation Satellite System (BDS) is essentially a precise time measurement and time synchronization system for a large-scale space near the Earth. General relativity is the basic theoretical framework for the information processing in the master control station of BDS. Having introduced the basic conceptions of relativistic space–time reference systems, the space–time references of BDS are analyzed and the function and acquisition method of the Earth Orientation Parameters (EOP) are briefly discussed. The basic space reference of BDS is BeiDou Coordinate System (BDCS), and the time standard is the BDS Time (BDT). BDCS and BDT are the realizations of the Geocentric Terrestrial Reference System (GTRS) and the Terrestrial Time (TT) for BDS, respectively. The station coordinates in the BDCS are consistent with those in International Terrestrial Reference Frame (ITRF)2014 at the cm–level and the difference in scale is about 1.1 times 10^{ - 8}. The time deviation of BDT relative to International Atomic Time (TAI) is less than 50 ns and the frequency deviation is less than 2 times 10^{ - 14}. The Geocentric Celestial Reference System (GCRS) and the solar Barycentric Celestial Reference System (BCRS) are also involved in the operation of BDS. The observation models for time synchronization and precise orbit determination are established within the GCRS framework. The coordinate transformation between BDCS and GCRS is consistent with the International Earth Rotation and Reference Systems Service (IERS). In the autonomous operation mode without the support of the ground master control station, Earth Orientation Parameters (EOP) is obtained by means of long-term prediction and on-board observation. The observation models for the on-board astrometry should be established within the BCRS framework.

Orbit determination and prediction for Beidou GEO satellites at the time of the spring/autumn equinox

Geostationary (GEO) satellites form an indispensable component of the constellation of Beidou navigation system (BDS). The ephemerides, or predicted orbits of these GEO satellites(GEOs), are broadcast to positioning, navigation, and timing users. User equivalent ranging error (UERE) based on broadcast message is better than 1.5 m (root formal errors: RMS) for GEO satellites. However, monitoring of UERE indicates that the orbital prediction precision is significantly degraded when the Sun is close to the Earth's equatorial plane (or near spring or autumn Equinox). Error source analysis shows that the complicated solar radiation pressure on satellite buses and the simple box-wing model maybe the major contributor to the deterioration of orbital precision. With the aid of BDS' two-way frequency and time transfer between the GEOs and Beidou time (BDT, that is maintained at the master control station), we propose a new orbit determination strategy, namely three-step approach of the multi-satellite precise orbit determination (MPOD). Pseudo-range (carrier phase) data are transformed to geometric range (biased geometric range) data without clock offsets; and reasonable empirical acceleration parameters are estimated along with orbital elements to account for the error in solar radiation pressure modeling. Experiments with Beidou data show that using the proposed approach, the GEOs' UERE when near the autumn Equinox of 2012 can be improved to 1.3 m from 2.5 m (RMS), and the probability of user equivalent range error (UERE)<2.0 m can be improved from 50% to above 85%.

DirMove: direction of movement based routing in DTN architecture for post-disaster scenario

Network architecture based on opportunistic Delay Tolerant Network (DTN) is best applicable for post-disaster scenarios, where the controlling point of relief work is any fixed point like a local school building or a hospital, whose location is known to everyone. In this work, 4-tier network architecture for post-disaster relief and situation analysis is proposed. The disaster struck area has been divided into clusters known as Shelter Points (SP). The architecture consists of mobile Relief Workers (RW) at tier 1, Throw boxes (TB) at tier 2 placed at fixed locations within SPs. Data Mules (DM) like vehicles, boats, etc. operate at tier 3 that provide inter-SP connectivity. Master Control Station (MCS) is placed at tier 4. The RWs are provided with smart-phones that act as mobile nodes. The mobile nodes collect information from the disaster incident area and send that information to the TB of its SP, using DTN as the communication technology. The messages are then forwarded to the MCS via the DMs. Based on this architecture, a novel DTN routing protocol is proposed. The routing strategy works by tracking recent direction of movement of mobile nodes by measuring their consecutive distances from the destination at two different instants. If any node moves away from the destination, then it is very unlikely to carry its messages towards the destination. For a node, the fittest node among all its neighbours is selected as the next hop. The fittest node is selected using parameters like past history of successful delivery and delivery latency, current direction of movement and node's recent proximity to the destination. Issues related to routing such as fitness of a node for message delivery, buffer management, packet drop and node energy have been considered. The routing protocol has been implemented in the Opportunistic Networks Environment (ONE) simulator with customized mobility models. It is compared with existing standard DTN routing protocols for efficiency. It is found to reduce message delivery latency and improve message delivery ratio by incurring a small overhead .

The Design of an Miniature Underwater Robot for Hazardous Environment

An miniature underwater robotic system for hazardous environment has been developed. The system consists of an underwater robot, a robot control station and a cameral control station. The underwater robot is installed two cameras for inspection, one is a camera of radiation resistant with two-freedom PTZ in the front of the robot, and the other is a fixed camera in the back of the robot. A miniature manipulator is equipped under the fore-camera to catch the small parts like bolts and nuts in the pools. The movement of the underwater robot is controlled by the master control station and the cameral control station controls the rotation and focus of the fore-camera. Besides, the underwater robot is equipped with the sensors, as MEMS inertial measurement unit, magnetometers, side scan sonar, water-depth gauges, which are integrated to determine the orientation and location of the robot. Meanwhile the navigation information is displayed in the virtual environment, which is modeled upon the real pools of the nuclear power plant. The underwater robotic system is easy to operate and will be applied to the hazardous environment like nuclear environment in future.

Chinese Area Positioning System With Wide Area Augmentation

The Chinese Area Positioning System (CAPS) is a regional satellite navigation system; its space segment consists of some Geostationary Earth Orbit (GEO) satellites and 2∼3 Inclined Geo-Synchronous Orbit (IGSO) satellites. Only a few satellites are needed to provide good area coverage and hence it is an ideal space segment for a regional navigation system. A time transfer mode is used to transmit navigation signals, so no high-precision atomic clocks are required onboard the satellites; all of the transferred navigation signals are generated by the same atomic clock at the master control station on the ground. By using virtual clock technology, the time of emission of signals from the ground control station is transformed to the time of transfer of signals at the phase centre of the satellite antenna; thus the impact of ephemeris errors of satellite on positioning accuracy is greatly decreased, enabling the CAPS to have the capability of wide area augmentation. A novel technology of orbit determination, called Paired Observation Combination for Both Stations (POCBS), proposed by the National Time Service Centre, is used in CAPS. The generation and measurement of ranging signals for the orbit survey are carried out in the ground station and the instrument errors are corrected in real-time. The determination of the clock offset is completely independent of the determination of satellite orbit, so the error of the clock offset has no impact on orbit determination. Therefore, a very high precision of satellite orbits, better than 4·2 cm (1 drms) can be obtained by the stations under regional distribution.

Intelligent Surveillance and Image Transmission Based on Wireless Video Sensor Network

Design and implement an energy-efficient smart camera mote architecture to be used as surveillance device for assisted living. Add the Passive Infrared Sensor (PIR) to WVSN, PIR detect the human or animal’s moving, then it triggers the camera to wake up. The image captured will be grayscale processing by the central processing unit. Camera sensor nodes transmit a grayscale image over wireless channel to master control station. It offers reduced complexity, response time, and power consumption over conventional solutions. By experimental results from the test illustrate that performance of the designed wireless image sensor is better than the exiting ones in the market in terms of received signal strength intensity (RSSI) and packet rate ratio (PRR) with respect to the distance. This scheme is less complicated than other wireless video sensor surveillance techniques, allowing resource-constrained video sensors to operate more reliably and longer.

Intelligent Surveillance and Image Transmission Based on Wireless Video Sensor Network

Design and implement an energy-efficient smart camera mote architecture to be used as surveillance device for assisted living. Add the Passive Infrared Sensor (PIR) to WVSN, PIR detect the human or animal’s moving, then it triggers the camera to wake up. The image captured will be grayscale processing by the central processing unit. Camera sensor nodes transmit a grayscale image over wireless channel to master control station. It offers reduced complexity, response time, and power consumption over conventional solutions. By experimental results from the test illustrate that performance of the designed wireless image sensor is better than the exiting ones in the market in terms of received signal strength intensity (RSSI) and packet rate ratio (PRR) with respect to the distance. This scheme is less complicated than other wireless video sensor surveillance techniques, allowing resource-constrained video sensors to operate more reliably and longer.

English

&nbsp; &nbsp; The concept of Real Time Kinematic (RTK) Network has become popular throughout the world since the beginning of 2000s. The RTK Network server collects satellite observations from the RTK Network, performs calculations and sends RTK corrections to the rover. Thus, these RTK Networks eliminates the need for post-processing GPS observations; instead the users in the field instantaneously obtain the receiver antenna&rsquo;s three dimensional coordinates with cm accuracy. This paper details the infrastructure of the Turkish RTK CORS Network called TUSAGA-Aktif established by Istanbul Kultur University in association with the General Directorate of Land Registration and Cadastre and the General Command of Mapping and sponsored by the Turkish Scientific and Technical Research Agency (TUBITAK). The network constitutes 146 Continuously Operating Reference Stations controlled by the two control stations, the Master Control Station at the Photogrammetry and Geodesy Administration of the General Directorate of Land Registration and Cadastre and the Auxiliary Control Station at the Headquarters of the General Command of Mapping both in Ankara, the capital city of Turkey. &nbsp; Key words:&nbsp;Continuously operating reference stations, real time kinematic network, control stations. &nbsp

Research of Ambiguity Solution in CEI-based Orbit Determination

相位干涉测量是一种被动测角跟踪方法, 其中的中短基线相位干涉测量(CEI)具有测角精度高、基线短、布网灵活、实时性好等特点. 分析采用CEI对GEO卫星定轨时初始整周模糊度解算的可行性, 由于中继卫星的初始轨道精度较低, 对其定轨时必须首先解决模糊度问题. 主控站具有测距功能时, 利用精度较高的距离观测量来计算整周模糊度; 主控站没有测距功能时, 提出了固定模糊度参数的参数估计方法. 仿真计算表明, 系统误差小于1.0 m时该方法效果较好. 给出了该方法对星下点在中国上空一定经度带上的GEO卫星网的整体定轨能力, 当系统误差为0.1 m时, 110°E卫星的迹向精度达到25 m, 对于80°E, 140°E卫星, 迹向精度分别达82 m, 34 m.

Tahiti-Project System Qualification

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 19859, "Tahiti- Project Subsea System Design/Qualification," by Chris Hey, SPE, and James Rasmussen, Chevron, and Steve Tattersall, SPE, Cameron, originally prepared for the 2009 Offshore Technology Conference, Houston, 4-7 May. The paper has not been peer reviewed. The design requirements of the Tahiti subsea facilities, while not dependent on the qualification of new or "enabling" technology, did depend on extending or "enhancing" the limits of existing technology. The full-length paper briefly describes some of the key design requirements, the approach to determine the then current level of equipment qualification relative to these design requirements, the qualification process, and the subsequent lessons learned. Subsea Overview The Tahiti project was the first high-pressure subsea development for Chevron. The Tahiti subsea facilities consist of an eight-well production drill center in the south and a six-well production drill center in the north of the field. There is a single-well, mid-flowline tie-in midway between the north drill center and the host facility. The drill centers are approximately 3 miles from the host facility, and each is served by a 2-×9-in.-nominal-outside-diameter (OD) production flowline and a 1-×6-in.-nominal-OD test flowline. Each drill center is served by two electrohydraulic steel-tube umbilicals. Each manifold has 2-×9.625-in.-nominal-OD production headers and a 1-×6.625-in.-nominal-OD test header. All headers are rated to 12,900-psi operating pressure. Round-trip pigging of the production and test flowlines is achieved by means of removable pigging loops and a Y-spool. The Y-spool allows the smaller test pig to drop into the larger production header where it will be swept back to the host using a production-flowline pig. The manifold configuration enables production from any well to be directed into any header. Each of the manifolds is supported by a single suction pile, 18 ft in diameter and 77 ft long. The wells are connected to the manifolds by means of rigid production-well jumpers that are as much as 120 ft long and 3.50 in. inside diameter. Eight production trees were purchased, with the latter two of these configured for smart well completions. The trees are 5 1/8×2 1/16 in. and are rated to 15,000 psi and 0 to 250°F with HH-rated production trim and EE-rated annulus trim. Each tree has its own subsea control module (SCM) that also controls the manifold branch-isolation valves. The control system is fully redundant, from the master control station to the SCM hydraulic control valves. Each manifold has its own SCM that controls the pigging-loop isolation valves and the methanol-injection isolation valves and monitors the pressure, temperature, and corrosion sensors. The corrosion sensors are located on each of the flowline jumpers connected to the manifold headers. The development requires equipment to be rated for 5,000-ft water depth, 15,000 psi, and 0 to 250°F, with high-pressure/high-temperature flowlines and steel catenary risers.

The transmission link of CAPS navigation and communication system

The Chinese Area Positioning System (CAPS) is based on communication satellites with integrated capability, which is different from the Global Positioning System (GPS), the International Maritime Satellite Organization (Inmarsat) and so on. CAPS works at C-band, and its navigation information is not directly generated from the satellite, but from the master control station on the ground and transmitted to users via the satellite. The slightly inclined geostationary-satellite orbit (SIGSO) satellites are adopted in CAPS. All of these increase the difficulty in the design of the system and terminals. In this paper, the authors study the CAPS configuration parameters of the navigation master control station, information transmission capability, and the selection of the antenna aperture of the communication center station, as well as the impact of satellite parameters on the whole communication system from the perspective of the transmission link budget. The conclusion of availability of the CAPS navigation system is achieved. The results show that the CAPS inbound communication system forms a new low-data-rate satellite communication system, which can accommodate mass communication terminals with the transmission rate of no more than 1 kbps for every terminal. The communication center station should be configured with a large-aperture antenna (about 10–15 m); spread spectrum communication technology should be used with the spreading gain as high as about 40 dB; reduction of the satellite transponder gain attenuation is beneficial to improving the signal-to-noise ratio of the system, with the attenuation value of 0 or 2 dB as the best choice. The fact that the CAPS navigation system has been checked and accepted by the experts and the operation is stable till now clarifies the rationality of the analysis results. The fact that a variety of experiments and applications of the satellite communication system designed according to the findings in this paper have been successfully carried out confirms the correctness of the study results.

The solutions of navigation observation equations for CAPS

Chinese scientists invent the navigation and positioning system based on commercial communications satellites and develop them successfully into China Area Positioning System (CAPS). In principle, this system is different from the GPS broadcasting satellite navigation class, where the propagation epoch of original navigation signals for pseudo-range measurement is from a ground master control station rather than from satellite transponders. This paper addresses the establishment of the three observation equation models for the navigation and positioning system based on communications satellites, and expresses them identically to operator equations and optimized models. Furthermore, both algorithms of the linear solution for the observable characteristic equation and the least-squares solution for the condition number more than 4 are discussed, with several methods for the exact solution, such as improving the behavior of coefficient matrices, right estimation for the weighted right hand side and selection of iteration forms of solutions, and the influence of the condition number on improving navigation and positioning accuracy is also analyzed carefully. Hopefully, all the works would be contributive to further development of the navigation and positioning system based on communications satellites, and be potentially valuable to other satellite navigation and positioning systems.

Autonomous Navigation Environment with Self-Calibrating Transceivers

An operable navigation system which demonstrates successful self-calibration and precise local navigation has been developed by EADS Astrium. This paper presents the architecture of the autonomous navigation environment with the ability to calibrate itself as well as the results of field tests. The Self-calibrating autonomous Navigation Environment (SekaN) can be used as stand-alone navigation system for applications where satellite signals are not available or where autonomy and high precision is required. Cargo drop, navigation in canyons and open pit mines, indoor navigation and extraterrestrial navigation are just examples of possible applications. The self-calibrating feature of SekaN is of special interest in conflict areas where a temporary autonomous navigation environment has to be installed quickly and where it is not possible to calibrate the locations of the pseudolites a priori. Furthermore, the system can be operated as augmentation system to classical satellite navigation systems. Therefore a mixed mode has been introduced which allows for simultaneous tracking of both satellite signals and pseudolite signals. Referencing of the local coordinate system to e.g. WGS84 becomes possible. The SekaN system comprises the following HW units developed by EADS Astrium: at least 4 Transceivers (TCs), a Rover receiver (ROV) and a Master Control Station (MCS). A WLAN data link is used between the units. Each TC comprises a GNSS signal generator NSG 5100 which supports both GPS and Galileo signals and an Astriumspecific GPS/PSL receiver. The number of TCs in the network is scalable and dependent on the specific application of the SekaN. Various TC-array sizes are supported as the output power of the pseudolites can be varied in a wide range. The rover receiver positioning takes place at the MCS. However, several receivers may be registered at the MCS. The TCs are operated unsynchronized and differential concepts are applied to eliminate the clock errors. Presently the pulsed signals with pseudolite spreading codes at the GPS L1 and dummy navigation messages are used as navigation signals. As soon as low-cost Galileo receivers are available the system can be switched to any Galileo frequency band. In a batch process the exact locations of the TC TX-antennas are determined without any a priori knowledge of the geometric array configuration. The general idea behind the self-calibration algorithms is based on the solution algorithm for self-calibrating pseudolite arrays presented in (LeMaster and Rock, 2002). However, several modifications were necessary to adapt the algorithms to the SekaN system requirements. The rover which is used for data collection during the self-calibration process is designed as a Receiver-only module instead of a TC module. This makes the rover hardware less complex, smaller and lighter, but also complicates the self-calibration process. Self-differencing between the stationary TCs and the rover TC can no longer be applied. The ranges between the rover RX and the TCs are therefore not directly observable. The selfcalibration and navigation algorithms developed for the SekaN work in both 2-D and 3-D scenarios. Although multipath effects, non-linearities and the near-far-effect are inherent in these kinds of ground-based navigation systems, precise user positioning at the sub-meter level becomes possible even with low-cost receivers within the self-calibrated navigation environment.

Development of the EGNOS Pseudolite System

In order to access the Satellite Based Augmentation System (SBAS) service, the end user needs to have a direct line of sight to at least one of the Geostationary Earth Orbit (GEO) satellites transmitting the augmentation messages. This requirement is critical for users in environments such as city canyons, valleys and fjords since high buildings and mountains in the vicinity of the end user can easily block the lines of sight to the GEO satellites. The situation becomes worse at high latitudes because of the low elevation angles to the GEO satellites. Even a very low obstacle can block the lines of sight to the GEO satellites. This limitation reduces SBAS Signal in Space (SIS) availability significantly at high latitude especially for land applications. This paper presents a solution of transmitting the European Geostationary Navigation Overlay Service (EGNOS) SIS using a pseudolite. The EGNOS pseudolite functions in a similar way as a GEO satellite. It will provide not only a terrestrial-based solution for transmitting the EGNOS SIS, but also a ranging measurement for the navigation solution. The EGNOS pseudolite system mainly consists of a Master Control Station, an EGNOS Data Server, EGNOS pseudolites and the user terminal. A preliminary test on a surveyed site has been carried out to verify the functionalities of the system. The data set collected from the test has been processed with two scenarios: one with four GPS satellites, while the other with three GPS satellites plus an EGNOS pseudolite. Both data processing scenarios have similar satellite geometries. The test result shows that the positioning accuracies are similar for both scenarios.

KeproVt : underwater robotic system for visual inspection of nuclear reactor internals

An underwater robotic system for visual inspection of reactor vessel internals has been developed. The Korea Electric Power Robot for Visual Test (KeproVt) consists of an underwater robot, a vision processor based measuring unit, a master control station and a servo control station. The vision processor based measuring unit employs a first-of-a-kind engineering technology in nuclear robotics. The vision processor makes use of a camera located at the top of the water level referenced to the reactor center line to get an image of the robot, and computes the location and orientation of the robot. The robot guided by the control station with the measuring unit can be controlled to have any motion at any position in the reactor vessel with ±1 cm positioning and ±2° heading accuracies with enough precision to inspect reactor internals. A simple and fast installation process is emphasized in the developed system. The installation process consists of hooking a vision camera on the guide rail of the refueling machine and putting a small robot (14.5 kg in weight) in the reactor cavity pool. The easy installation and automatic operation meet the demand of shortening the reactor outage and reducing the number of inspection personnel. The developed robotic system was successfully deployed at the Yonggwang Nuclear Unit 1 for the visual inspection of reactor internals.

Welcome to the Machine: An Overview of GPS Master Control Station Anomaly Detection and Resolution Techniques

The mission of the GPS Master Control Station (MCS) is to maximize the accuracy, reliability, integrity, and continuity of GPS services provided to the worldwide user community. A significant part of this mission involves the detection, prevention, and resolution of a host of satellite vehicle anomalies. Over the last several years, MCS Air Force and contractor personnel have amassed a considerable number of techniques for handling problems quickly, and in many cases preventing them altogether. This paper describes many of these tools in an attempt to impart a better understanding of behind-the-scenes operations to the GPS community at large. Included are examples of actual satellite problems and the analysis that resulted in their ultimate resolution.