Tunable Multi-Tone, Multi-Band, High-Frequency Synthesizer
Glenn's revolutionary new multi-tone, high-frequency synthesizer can enable a major upgrade in the design of high data rate, wide-band satellite communications links, in addition to the study of atmospheric effects. Conventional single-frequency beacon transmitters have a major limitation: they must assume that atmospheric attenuation and group delay effects are constant at all frequencies across the band of interest. Glenn's synthesizer overcomes this limitation by enabling measurements to be made at multiple frequencies across the entire multi-GHz wide frequency, providing much more accurate and actionable readings. This novel synthesizer consists of a solid-state frequency comb or harmonic generator that uses step-recovery semiconductor diodes to generate a broad range of evenly spaced harmonic frequencies, which are coherent and tunable over a wide frequency range. These harmonics are then filtered by a tunable bandpass filter and amplified to the necessary power level by a tunable millimeter-wave power amplifier. Next, the amplified signals are transmitted as beacon signals from a satellite to a ground receiving station. By measuring the relative signal strength and phase at ground sites the atmospheric induced effects can be determined, enabling scientists to gather essential climate data on hurricanes and climate change. In addition, the synthesizer can serve as a wideband source in place of a satellite transponder, making it easier to downlink high volumes of collected data to the scientific community. Glenn's synthesizer enables a beacon transmitter that, from the economical CubeSat platform, offers simultaneous, fast, and more accurate wideband transmission from space through the Earth's atmosphere than has ever been possible before.
information technology and software
Highly distributed next-generation computer-based systems require self-managing environments that feature a range of autonomic computing techniques. This functionality is provided by collaborating agents, and includes an apoptotic (self-destruct) mechanism, autonomic quiescence (self-sleep), and others. The apoptotic feature is necessary to maintain system security and integrity when a component endangers the overall operation and viability of the entire system. However, the self-destruction of an agent/component may remove a key piece of functionality. The novel autopoietic functionality provides the capability to duplicate or substitute a new agent that provides the functionality of the self-destructed component.
The Navigator GPS Receiver
To enable it to acquire GPS signals very quickly and also track weak signals, the radiation-hardened Navigator receiver utilizes a bank of hardware correlators, a ColdFire microprocessor, and a specialized fast acquisition module (see figure 1). The hardware is implemented in VHSIC Hardware Description Language (VHDL) to target radiation-hardened Field Programmable Gate Arrays (FPGA) rather than Application-Specific Integrated Circuits (ASIC), in order to maintain flexibility for growth and design modifications. The Navigator was designed to operate autonomously to enable the use of GPS for onboard navigation in high altitude space missions. With the exception of GPS signals, Navigator requires no external data (e.g., current time estimate, recent GPS almanac, or converged navigation filter estimate of the receiver dynamics). By double buffering data up front in 1ms blocks, data can be processed as it is acquired. A discrete Fourier transform (DFT) is used to calculate the 1ms correlations, significantly reducing computing time. Computational efficiency is optimized and tradeoffs among sampling rate, data format, and data-path bit rate are carefully weighed in order to increase performance of the algorithm. In addition, the Navigators hardware-independent receiver software includes both a hardware interface to perform low-level functions as well as basic navigation. Onboard orbit determination and accurate state estimation/propagation during periods with no GPS access are accomplished by integration with the GPS Enhanced Onboard Navigation System (GEONS). Exploiting the properties of Fourier transform in a massively parallel search for the GSP signal, the Navigator has been tested and proven capable of acquiring signals at 25dB-Hz and below.
CubeSat Compatible High Resolution Thermal Infrared Imager
This dual band infrared imaging system is capable of spatial resolution of 60 m from orbit and earth observing expected NEDT less than 0.2o C. It is designed to fit within the top two-thirds of a 3U CubeSat envelope, installed on the International Space Station, or deployed on other orbiting or airborne platforms. This infrared imaging system will utilize a newly conceived strained-layer superlattice GaSb/InAs broadband detector array cooled to 60 K by a miniature mechanical cryocooler. The camera is controlled by a sensor chip assembly consisting of a newly developed 25 m pitch, 640 x 512 pixel.
High-Speed, Low-Cost Telemetry Access from Space
NASA's SDR uses Field-Programmable Gate Array (FPGA) technology to enable flexible performance on orbit. A first-generation FM-modulated transceiver is capable of operating at up to 1 Mbps downlink and 50 kbps uplink, full duplex. An FPGA performs Reed-Solomon (255,223) encoding, decoding, and bit synchronization, providing Consultative Committee for Space Data Systems (CCSDS) and Near Earth Network (NEN) telemetry protocol compatibility. The transceiver accepts data from the onboard flight computer via a source synchronous RS422 interface. NASA's second-generation full duplex SDR, known as PULSAR (programmable ultra-lightweight system-adaptable radio, Figures 1 and 2 below) incorporates command receiver and telemetry transmitters, as well as updated processing and power capabilities. An S-band command receiver offers a max uplink data rate of 300 Kbps and built-in QPSK demodulation. X- and S-Band telemetry transmitters offer a max downlink data rate of 150 Mbps and flexible forward-error correction (FEC) using Reed-Solomon encoding (LDPC rate 7/8 and 1/2 convolution in development), and it uses QPSK modulation. The use of FEC adds an order of magnitude increase in telemetry throughput due to an improved coding gain. An onboard FPGA uses high-speed logic for uplink/downlink and encoding/decoding processes. Balloon flight testing has been conducted and is ongoing for PULSAR.
Diminutive Assembly for Nanosatellite deploYables (DANY)
SmallSat designers seek to employ restraints and release mechanisms of minimal size and weight, often placing each on the outside of the SmallSat structure. Surprisingly, "fishing line" (released via burn through) is often used to secure and release deployables. Vibrations and forces generated during launch can stretch the fishing line, thus allowing these precious deployables to become damaged or otherwise not release properly later on. While these small sats are less expensive than their larger counterparts, satellite owners must minimize the chance that deployables are damaged or that deployment is unsuccessful. Five years ago, engineers at NASA GSFC faced these SmallSat deployment challenges and knew a better way must exist to prevent equipment damage and ensure successful release. Investigating a host of designs to minimize size, weight, and cost while maximizing communication and mechanical reliability, NASA's engineers created DANY (the Diminutive Assembly for Nanosatellite deploYables). NASA's DANY technology uses spring-loaded metal pins, a reliable burn-through mechanism, efficient bracketing, and a circuit board - all within a 3.0" x 1.3" x 0.2" volume (smaller than a stack of 10 business cards) - to reliably stow and release deployables on command. Using DANY, stowed deployables are securely fastened using the spring-loaded locking pins. Upon receiving a deployment signal, a plastic restraining link is burned through which allows the spring-loaded pins to release the deployable and simultaneously trigger a switch to signal a successful deployment event.
CubeSat Form Factor Thermal Control Louvers
Thermal control of small spacecraft, including CubeSats, is a challenge for the next era of NASA spaceflight. Science objectives and components will still require strict thermal control while smaller volumes will inherently absorb and shed heat more quickly than a larger body. Thus, game-changing technologies must be developed to stabilize the thermal environment inside of small spacecraft. The CubeSat louver assembly of the present invention is based upon the proven designs of full-sized louvers for large spacecraft. Internal spacecraft components are thermally coupled to the side of the spacecraft. Bimetallic springs serve as a passive control mechanism for opening and closing flaps. As the spacecraft heats up the springs expand due to the difference in thermal expansion rates of their two fused metals (hence bimetallic). This opens the flaps, changing the thermal radiation properties of the exterior surface. As the spacecraft cools the flaps close and return the exterior surface to the previous emissivity. These temperature-driven adjustments create a more stable thermal environment for components. The power dissipated via the thermal louvers shows a substantial difference between fully closed and fully open louvers at the high temperatures significant for electrical components.
Dellingr 6U CubeSat
A NASA team gave itself just one year to develop, test and integrate a CubeSat that could reliably and easily accommodate agency-class science investigations and technology demonstrations at a lower cost. The CubeSat known as Dellingr, a name derived from the god of the dawn in Norse mythology will carry three heliophysics-related payloads. It doubles the payload capability of the ubiquitous and proven three-unit, or 3U, CubeSat pioneered by the California Polytechnic Institute in 1999 primarily for the university community. The need for such a platform, which measures about 12 inches long, nearly 8 inches wide and 4 inches high, was for more cost-effective approaches to achieve compelling Earth and space science. Disadvantages of the 3U size include more constraints on volume and power. Furthermore, some studies suggest that previous CubeSats failed 40 percent of the time. By doubling the platform's girth, increasing its power capacity, and employing novel processes to increase its on-orbit reliability, the team believes it will have created a platform capable of carrying out more robust missions for science. Once successfully demonstrated, the team says it will make the platform's design implemented with low-cost, commercial off-the-shelf parts available to any U.S. organization interested in using it.
information technology and software
Automata Learning in Generation of Scenario-Based Requirements in System Development
In addition, the higher the level of abstraction that developers can work from, as is afforded through the use of scenarios to describe system behavior, the less likely that a mismatch will occur between requirements and implementation and the more likely that the system can be validated. Working from a higher level of abstraction also provides that errors in the system are more easily caught, since developers can more easily see the big picture of the system. This technology is a technique for fully tractable code generation from requirements, which has an application in other areas such as generation and verification of scripts and procedures, generation and verification of policies for autonomic systems, and may have future applications in the areas of security and software safety. The approach accepts requirements expressed as a set of scenarios and converts them to a process based description. The more complete the set of scenarios, the better the quality of the process based description that is generated. The proposed technology using automata learning to generate possible additional scenarios can be useful in completing the description of the requirements.
mechanical and fluid systems
Nitinol-Actuated Normally Open Valve Assembly (NOVA)
The nitinol-actuated Normally Open Valve Assembly (NOVA) is a type of zero-leak permanent isolation valve designed for liquid propellant service on in-space propulsion systems with operating pressures less than or equal to 500 psia. The NOVA is a drop-in replacement for the currently used pyrovalve. Prior to actuation, the valve allows propellant flow with a pressure drop of < 3 psi at a flow rate of 0.15 kg/s. A compressed piece of nitinol inside the valve is heated once actuation is desired, causing the nitinol to recover to its origin shape. This recovery closes the valve, creating a leak-tight seal. The valve is compatible with all storable propellants.