Global Position System in the Role of Microprocessor - Term Paper Example

Content Introduction Technology detail Autonomous operation Motivation and theoretical background Navigator Design Principles Strong Signal Mode Weak Signal Mode Tracking Navigator hardware design Simulation Studies Acquisition HW Navigator software References Introduction To control the operation of a GPS receiver, a microprocessor is essential for acquiring the signals, processing the signal and decoding of broadcasted messages. This gives additional facility of computation of on-line position and velocity, convert into given local data or determine point the way information that are also required. In future mere and mere user connected with software will be resident on miniaturized memory chip. Processing means, including a standard software operating system and an application program for processing global positioning system location information to application program and providing navigation information based upon application program. The word Navigator is an autonomous, real time, fully space-qualified GPS receiver with exceptional capabilities for fast signal acquisition and weak signal tracking. Features of GPS enable the use of GPS navigation in high Earth orbit (HEO), geostationary orbit and other applications. This GPS Navigator receiver can quickly track GPS signals. For determine positioning with the help of GPS, a receiver must first obtain the GPS signals and then track those signals continuously. When we track the signal receiver can holds and remove data, making range measurement from every satellite. Following measurements are used to determine the position of each satellite and then guess the receiver’s position. For enable and acquire GPS signals very quickly and also trace weak signals, the radiation-hardened Navigator receiver uses the bank of hardware correlates, a ColdFire microprocessor, and a specialized fast acquisition module (as indicate in figure) . This hardware is indicated in VHSIC Hardware Description Language (VHDL) to target radiation-hardened Field Programmable Gate Arrays (FPGA) in very small amount of Application-specific Integrated Circuits (ASIC), for maintaining flexibility for growth and design modification. Technology Details Signals of GPS from above the ground level the GPS constellation are 10 to 100 times weaker and less densely populated, GPS receivers haven’t been able to use this LEC. Navigator is a radiation-hardened GPS receiver specially designed for use in high earth orbits. It is capable for trace both strong and weak signals. It required no external data, and properties enable it to be powered down in any orbit whenever needed. NASA Goddard Flight Center is currently try to patent protection for the Navigator GPS Receiver. Autonomous operation Navigator is designed to operate autonomously to enable the use of GPS as navigator in high space mission. Except GPS signals, Navigator doesn’t require any external data (e.g., current time estimate, recent GPS almanac or converged navigation filter estimate the receiver dimensions) Introduction There are many application found in GPS for precision spacecraft navigation and formation flying application in low Earth orbit (LEO) and these features of GPS receiver design and signal processing capabilities now make it able to consider using GPS provide autonomous, onboard navigation capabilities for geostationary (GEO) or other high altitude space mission. There is one program Geostationary Operational Environmental Satellite (GOES) that would derive significant benefits from a GPS receiver this is capable of autonomously detect satellite position to 100 meters or less in a GEO orbit and options are limited for procuring a receiver that could provide both the performance and reliability required to meet the 10+ year life time of the GOES satellite. From some last years, many organization have contributed to advancing capabilities for applying GPS to high altitude orbits through analytical studies, flight experiments, and GPS receiver development efforts. TRW (now Northrop Grumman) developed a highly successful GPS based system. This system used to perform operational orbit determination for a US military GEO satellite. Alcatel and CNES are jointly develop a GPS receiver for the geostationary STENTOR satellite that employed a tightly coupled navigation filter or tracking loop design to enable weak signal tracking. Large number of other commercial manufactures of space capable GPS receiver includes General Dynamics and surrey Satellite Technology have recently consider plans to market space receivers for high altitude applications. . The Mission Engineering and Systems Analysis Division at Goddard Space Flight Center (GSFC) developed a GPS receiver called PiVoT (shown in figure) based on the commercially available GPS development system marketed by Zarlink (formerly Mitel and before that GEC Plessey). The PiVoT receiver was originally developed for LEO applications; The PiVoT GPS Receiver PiVot receiver incorporates a number of software modification that enable its operation above the GPS constellation and it used extensively at GSFC for hardware in the loop testing in high altitude orbit. PiVot can we use as a high quality, temperature compensated crystal oscillator that integrates with the GPS Enhanced Orbit Navigation System (GEONS) software. These papers make easy to understand a project at GSFC to develop a new, fully space qualified GPS receiver for high altitude applications. Navigator receiver project prepared on the base of GSFC’s that covers large quantity experience in high altitude GPS applications, and all configuration developed in following design specifications: To make a fully flight qualified GPS receiver with the help of radiation-hardened (red-hard) parts Plan the algorithm in FPGAs to make possible for easy modification, upgrading and customization Get the required signal and trace the signal at Carrier to noise Density Ratio, C/NO=25 dB-Hz To get GPS signals (with no a priori knowledge) within one second for strong signals (>40 dB-Hz) and one minute for weak signals ( Read More