Missions to Titan are severely limited in available mass and power because spacecraft have to travel over a billion miles to get there, consuming large masses of propellants. Thus low-mass, low-power instruments are a high priority need for Titan missions. A miniature, liquid-phase, high-resolution, pulsed proton-NMR (1H-NMR) spectrometer was developed with low mass (1.5 kg), requiring low power, that can be operated cryogenically on the surface of Titan. This work focuses on new pulsed electronic circuits, optimized for a nuclear magnetic resonance (NMR) spectrometer for analysis of hydrocarbon liquids on Titan.
From this experience, a new, pulsed NMR circuit was developed with all low- temperature-compatible components. The NMR circuit is powered by a USB interface and consumes less than 0.5 W total electrical power during normal operation. Central to the operation of the circuit, a direct digital synthesizer generates the main frequency source, which is coupled through a transformer, followed by a four-pole, low-pass filter to allow generation of any frequency up to 50 MHz. A clock source was used to set the frequency of the output drive and input frequency of the receiver.
Since bipolar transistors failed below –150 °C due to a carrier freeze-out phenomenon in silicon, they were replaced with CMOS (complementary metal-oxide semiconductor) operational amplifiers and a voltage regulator. To maintain a constant input voltage to the NMR circuit at all temperatures, a temperature-compensated voltage regulator was constructed by inserting a thermistor (resistance temperature detector) and an adjustable voltage divider into the circuit. The new NMR circuit with all low-temperature-compatible components performed properly down to 77 K.
The low-temperature-compatibility of the NMR system is critical for chemical characterization of hydrocarbons in their natural liquid state in the Titan environment. Such an instrument will facilitate simplified spacecraft design because it will not require a warm electronics box. The NMR will provide non-destructive, first-hand identification of organic molecules, their functional groups, and relative abundances, thus allowing complex chemical analyses to be accomplished by a low-mass, low-power instrument.
This work was carried out by Soon Sam Kim, Shannon P. Jackson, and Mohammad Mojarradi of Caltech; and Christopher T. Ulmer for NASA’s Jet Propulsion Laboratory. NPO-49367
This Brief includes a Technical Support Package (TSP).
Low-Temperature-Compatible Electronics for a Miniature Nuclear Magnetic Resonance Spectrometer
(reference NPO49367) is currently available for download from the TSP library.
Don't have an account?
Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing advancements in low-temperature-compatible electronics for a miniature Nuclear Magnetic Resonance (NMR) spectrometer. This technology is particularly relevant for in situ chemical analysis on celestial bodies, such as Titan, Saturn's largest moon, where extreme environmental conditions necessitate specialized instrumentation.
Key components of the document include the development of a sample acquisition and distribution system designed for flight capability. This system incorporates low mass, volume, and power cryogenic actuators and valves, achieving a compact design with a volume of 0.004 m³, mass under 1 kg, and power consumption below 5 W. The system has been tested successfully in a bench-top configuration, demonstrating various fluid transfer functions essential for sampling.
A significant focus of the research is on solid phase micro-extraction (SPME) probes, which have been refined for sampling complex organic species from Titan's lakes. The document reports a detection limit of 2 mg/L for benzene in liquid ethane, showcasing the sensitivity and effectiveness of the sampling technology.
The document outlines the objectives for FY2013, which include strengthening the overall system design by integrating the sample acquisition subsystem with three primary instruments, building and testing prototype instruments, and completing the design of the sample acquisition system. Specific tasks involve developing an ion trap control system for ion manipulation, testing NMR electronics at low temperatures, and utilizing SPME fibers for extracting minor lake species.
Results from FY2013 highlight the progress made in developing the Orbitrap mass spectrometer, including the successful demonstration of a digital ion trap capable of generating necessary waveforms for mass analysis. Additionally, advancements in the cryogenic liquid phase NMR spectrometer are noted, with the design and testing of low-temperature compatible components and a new pulsed NMR control circuit.
The document emphasizes the potential benefits of these technologies for NASA and JPL, including the development of advanced instruments for structural analysis and in situ chemical analysis on Titan and other planetary bodies. Overall, the research aims to position JPL at the forefront of low mass, low power instrument development for extreme environments, enabling future exploration missions.
