Software Defined Radio with Parallelized Software Architecture

This software implements software-defined radio procession over multi-core, multi-CPU systems in a way that maximizes the use of CPU resources in the system. The software treats each processing step in either a communications or navigation modulator or demodulator system as an independent, threaded block. Each threaded block is defined with a programmable number of input or output buffers; these buffers are implemented using POSIX pipes. In addition, each threaded block is assigned a unique thread upon block installation. A modulator or demodulator system is built by assembly of the threaded blocks into a flow graph, which assembles the processing blocks to accomplish the desired signal processing. This software architecture allows the software to scale effortlessly between single CPU/single-core computers or multi-CPU/multi-core computers without recompilation. NASA spaceflight and ground communications systems currently rely exclusively on ASICs or FPGAs. This software allows low- and medium-bandwidth (100 bps to .50 Mbps) software defined radios to be designed and implemented solely in C/C++ software, while lowering development costs and facilitating reuse and extensibility

SCAN Testbed, Overview and Opportunity for Experiments

No abstract availabl

A GPS Receiver for Lunar Missions

Beginning with the launch of the Lunar Reconnaissance Orbiter (LRO) in October of 2008, NASA will once again begin its quest to land humans on the Moon. This effort will require the development of new spacecraft which will safely transport people from the Earth to the Moon and back again, as well as robotic probes tagged with science, re-supply, and communication duties. In addition to the next-generation spacecraft currently under construction, including the Orion capsule, NASA is also investigating and developing cutting edge navigation sensors which will allow for autonomous state estimation in low Earth orbit (LEO) and cislunar space. Such instruments could provide an extra layer of redundancy in avionics systems and reduce the reliance on support and on the Deep Space Network (DSN). One such sensor is the weak-signal Global Positioning System (GPS) receiver "Navigator" being developed at NASA's Goddard Space Flight Center (GSFC). At the heart of the Navigator is a Field Programmable Gate Array (FPGA) based acquisition engine. This engine allows for the rapid acquisition/reacquisition of strong GPS signals, enabling the receiver to quickly recover from outages due to blocked satellites or atmospheric entry. Additionally, the acquisition algorithm provides significantly lower sensitivities than a conventional space-based GPS receiver, permitting it to acquire satellites well above the GPS constellation. This paper assesses the performance of the Navigator receiver based upon three of the major flight regimes of a manned lunar mission: Earth ascent, cislunar navigation, and entry. Representative trajectories for each of these segments were provided by NASA. The Navigator receiver was connected to a Spirent GPS signal generator, to allow for the collection of real-time, hardware-in-the-loop results for each phase of the flight. For each of the flight segments, the Navigator was tested on its ability to acquire and track GPS satellites under the dynamical environment unique to that trajectory

Enabling Communication and Navigation Technologies for Future Near Earth Science Missions

In 2015, the Earth Regimes Network Evolution Study (ERNESt) Team proposed a fundamentally new architectural concept, with enabling technologies, that defines an evolutionary pathway out to the 2040 timeframe in which an increasing user community comprised of more diverse space science and exploration missions can be supported. The architectural concept evolves the current instantiations of the Near Earth Network and Space Network through implementation of select technologies resulting in a global communication and navigation network that provides communication and navigation services to a wide range of space users in the Near Earth regime, defined as an Earth-centered sphere with radius of 2M Km. The enabling technologies include: High Rate Optical Communications, Optical Multiple Access (OMA), Delay Tolerant Networking (DTN), User Initiated Services (UIS), and advanced Position, Navigation, and Timing technology (PNT). This paper describes this new architecture, the key technologies that enable it and their current technology readiness levels. Examples of science missions that could be enabled by the technologies and the projected operational benefits of the architecture concept to missions are also described

Miniaturized Phonon Trap Timing Units for PNT of Cubesats

This research is directed towards development of a chip-scale timing unit (clock) to be used in new systems that aim to improve the quantity and quality of data transmittal from small spacecrafts. The quantity and quality of data transmission are directly influenced by the speed and accuracy of the on-board clock. NASA roadmap identifies major technical challenges for space clocks using current technologies (i.e., quartz resonators), namely sensitivity to on-board thermal environment conditions and susceptibility to g-force, and ionizing radiation effects. The timing units developed under this project will enhance the current Small Satellites capabilities. With this technology Small Sats can make big contributions and pioneer an industry for future military, civilian, and commercial missions. The proposed approach directly tackles the stated technical challenges by developing a chip-scale all silicon integrated clock that has 10x better frequency stability compared to quartz-based clocks and 100x lower acceleration sensitivity at 10x higher speed. It is based on a new generation of phonon traps/resonators that are both passively and actively compensated to reach unprecedented frequency accuracy and stability. The proposed timing unit is stable across a wide range of temperatures. Recent measurements from a CubeSat indicate a temperature variation of -40 to 120 degree C for solar panels in geo orbit. For the main instrument board, the temperature is controlled at -2 to -10 degree C using thermal insulation to maintain the thermal fluctuation at a minimum. Assuming the timing unit experiences a worst case temperature fluctuation of -40 to +40 degree C, the frequency output can be maintained stable to less than 2 ppb using a feedback control loop. To do so, the proposed system includes a single phonon trap that exhibits two modes with significantly different temperature coefficient of frequencies (TCFs). In the feedback control loop, the dual mode oscillator is phase-locked at a stable operating point, where the phonon trap resonator is heated to a desired oven-set temperature. The proposed performance cannot be obtained from any other current, or planned product, with a solution that offers high science value through a small-size ( The low SWaP of the proposed system makes it an ideal candidate for CubeSats of as small as one unit (1U) with size of 10x10x10cm3. The low weight of the proposed clocks is several orders of magnitude smaller than the total weight of 1U to 3U CubeSats (1kg up to 5kg total), and its power consumption is a negligible fraction of the total system power (1W up to 6W (3U))