The Black Jack (BJ) receiver is the revolutionary flight Global Positioning System (GPS) receiver developed by NASA to fill future needs for orbit-based GPS science. These range from a receiver to determine precise (1-cm radial accuracy goal for JASON-1) orbits, to missions using the GPS signals for remote sensing of the Earth's atmosphere. The BJ receiver follows the TurboRogue space receiver, which was successfully used in collaboration with engineers and scientists at JPL on five satellite missions. While the TurboRogue was initially designed as a high-accuracy ground receiver, the BJ was designed from the start as an instrument for use from orbit. The BJ contains many innovations to better suit it to this application. In order to simplify the analog electronics, it directly samples the amplified and filtered RF (radio-frequency) signal. This sampling produces two sample streams in quadrature for improved SNR (signal-to-noise ratio). The BJ semicustom Application Specific Integrated Circuit (ASIC) uses a full matrix switch so that inputs from multiple antennas can be directed to any of 48 tracking channels. Other ASIC capabilities are telemetry reception, tone tracking, and precise time tagging of external events. Although the receiver is designed as a science instrument rather than for mission-critical operation, it does contain innovative features such as the capability to operate in a bit-grab mode. In the event the highly-redundant digital processing fails, the main processor stops, or the spacecraft can no longer power the GPS receiver, the BJ can turn on for less than a second every hour, and still transmit data to the ground allowing sub-100-m orbit determination. The BJ receiver is designed with excess processor capacity to allow it to perform non-GPS functions; for example, on the GRACE mission, the BJ controls an intersatellite K-band link and also processes the output of a star camera to determine spacecraft attitude.
This work was done by Thomas Meehan, Jeffrey Srinivasan, Jeffrey Tien, Garth Franklin, Donovan Spitzmesser, Timothy Munson, and Charles Dunn of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Black Jack GPS Receiver," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronics & Computers category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
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Refer to NPO-20891, volume and number of this NASA Tech Briefs issue, and the page number.
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Blackjack GPS Receiver
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Overview
The document is a technical support package prepared under the sponsorship of the National Aeronautics and Space Administration (NASA) and outlines the development and capabilities of the TurboRogue Space Receiver (TRSR) subsystem. The TRSR is designed for use with Earth-orbiting satellites and is a 48-channel Global Positioning System (GPS) receiver, which includes dual-frequency capabilities for enhanced performance.
The document begins with a disclaimer stating that references to specific commercial products or services do not imply endorsement by the U.S. Government or the Jet Propulsion Laboratory (JPL). It emphasizes that the work was conducted at JPL under a NASA contract.
The TRSR subsystem is detailed in terms of its components, which include a downconverter assembly, dual-frequency antennas, and interconnecting RF cables. The system is designed to down-convert dual-frequency L-band signals, which are then digitized and processed by a dual-redundant processor section, ensuring reliability by allowing only one processor to be powered at a time.
The introduction highlights the motivation behind the TRSR's development, which was the need for an affordable flight GPS receiver capable of generating scientific results. The document outlines the innovative design approach, which utilizes semi-custom Application-Specific Integrated Circuits (ASICs) and a powerful general-purpose microprocessor. This design incorporates multiple novel features aimed at enhancing performance while keeping costs low.
Key features of the TRSR include low-multipath helibowl antennas, a baseband sampler, and a matrix input switch that allows dynamic reconfiguration of inputs across the 48 tracking channels. The receiver is capable of extracting telemetry from non-GPS signals and determining precise timing of external events. Additionally, it can generate and track codes from GLONASS, the Russian equivalent of GPS, and employs three-level digitization for superior accuracy.
Overall, the document serves as a comprehensive overview of the TRSR subsystem, detailing its technical specifications, innovative design, and the significant advancements it brings to GPS technology for space applications. The TRSR is positioned as a critical tool for future scientific missions, enhancing the ability to conduct precise orbit determination and atmospheric remote sensing.
