The MAss Spectrometer for Planetary EXploration (MASPEX) is a high-mass-resolution, high-sensitivity, multi-bounce time-of-flight mass spectrometer (MBTOF) capable of measuring minor species with abundances of sub-parts-per-million in Europa’s sputter-produced and radiolytically modified exosphere and in its oceanic plumes. The goal of the MASPEX-Europa investigation is to determine, through in-situ measurement of the exosphere and plume composition, whether the conditions for habitability exist or have existed on Europa. As conventionally defined, based on our knowledge of Earth life, the three fundamental conditions for habitability are: (1) the presence of liquid water; (2) the presence of organic compounds and the biogenic elements CHNOPS; and (3) a source of energy available for metabolic processes, which for Europa will most probably be chemosynthetic rather than photosynthetic. Condition (1) is already established by previous indirect (magnetic field) measurements, while MASPEX will contribute directly to the evaluation of condition (2) through highly specific compositional measurements in the Europan exosphere and plumes. The composition measurements will also contribute to the test of condition (3) through disequilibrium states of chemical reactions. Thus, the primary goal of MASPEX for Europa Clipper is to assess the habitability of Europa and specifically of its interior ocean. MASPEX has been developed successfully, and its calibration has demonstrated that it meets its specified requirements for sensitivity, dynamic range, and mass resolution. This paper reports the development of the MASPEX scientific investigation, the instrument, its performance, and calibration.

Magnetosheath plasma usually determines properties of asymmetric magnetic reconnection at the subsolar region of Earth's magnetopause. However, cold plasma that originated from the ionosphere can also reach the magnetopause and modify the kinetic physics of asymmetric reconnection. We present a magnetopause crossing with high‐density (10–60 cm−3) cold ions and ongoing reconnection from the observation of the Magnetospheric Multiscale (MMS) spacecraft. The magnetopause crossing is estimated to be 300 ion inertial lengths south of the X line. Two distinct ion populations are observed on the magnetosheath edge of the ion jet. One population with high parallel velocities (200–300 km/s) is identified to be cold ion beams, and the other population is the magnetosheath ions. In the deHoffman‐Teller frame, the field‐aligned magnetosheath ions are Alfvénic and move toward the jet region, while the field‐aligned cold ion beams move toward the magnetosheath boundary layer, with much lower speeds. These cold ion beams are suggested to be from the cold ions entering the jet close to the X line. This is the first observation of the cold ionospheric ions in the reconnection outflow region, including the reconnection jet and the magnetosheath boundary layer.

The dusk flank magnetopause was surveyed with instruments on board the Magnetospheric Multiscale (MMS) spacecraft on 28 August 2015 between 13: 55 UT and 14: 15 UT during a period of persistent southward interplanetary magnetic field (IMF) with varying dawn-dusk component. Plasma measurements (500 eV electrons, > 2 keV ions) revealed the existence of at least one active reconnection region that persisted throughout the interval. The reconnection region convected equatorward despite the poleward and tailward magnetosheath flow, which ranged from slightly sub-Alfvenic to slightly super-Alfvenic throughout the interval. These results suggest that magnetic reconnection moved in response to changes in the IMF clock angle rather than the magnetosheath flow, which is corroborated using predictions of the maximum magnetic shear model.

This paper describes the science motivation, measurement objectives, performance requirements, detailed design, approach and implementation, and calibration of the four Hot Plasma Composition Analyzers (HPCA) for the Magnetospheric Multiscale mission. The HPCA is based entirely on electrostatic optics combining an electrostatic energy analyzer with a carbon-foil based time-of-flight analyzer. In order to fulfill mission requirements, the HPCA incorporates three unique technologies that give it very wide dynamic range capabilities essential to measuring minor ion species in the presence of extremely high proton fluxes found in the region of magnetopause reconnection. Dynamic range is controlled primarily by a novel radio frequency system analogous to an RF mass spectrometer. The RF, in combination with capabilities for high TOF event processing rates and high current micro-channel plates, ensures the dynamic range and sensitivity needed for accurate measurements of ion fluxes between ∼1 eV and 40 keV that are expected in the region of reconnection events. A third technology enhances mass resolution in the presence of high proton flux. In order to calibrate the four HPCA instruments we have developed a unique ion calibration system. The system delivers a multi-species beam resolved to M /Δ M ∼100 and current densities between 0.05 and 200 pA/cm 2 with a stability of ±5 %. The entire system is controlled by a dedicated computer synchronized with the HPCA ground support equipment. This approach results not only in accurate calibration but also in a comprehensive set of coordinated instrument and auxiliary data that makes analysis straightforward and ensures archival of all relevant data.

AbstractReconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy, mass, and momentum to flow into the magnetosphere. It is the primary science goal of the recently launched MMS mission to unlock the mechanism of magnetic reconnection with a novel suite of plasma and field instruments. This study investigates several magnetopause crossings in the vicinity of the X‐line on 19 September 2015 and compares the observed X‐line location with predictions from the Maximum Magnetic Shear model. Rotations of the interplanetary magnetic field (IMF) during the magnetopause crossings together with the close proximity of the four MMS satellites are used to determine the response time of the reconnection X‐line location to changes in the IMF. The reconnection location exhibits a continuous motion during slow changes in the IMF but a delayed response to sudden changes in the IMF.

Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

Magnetic reconnection at the Earth's magnetopause is the primary process by which solar wind plasma and energy gains access to the magnetosphere. One indication that magnetic reconnection is occurring is the observation of accelerated plasma as a jet tangential to the magnetopause. The direction of ion jets along the magnetopause surface as observed by the Fast Plasma Instrument (FPI) and the Hot Plasma Composition Analyzer (HPCA) instrument on board the recently launched Magnetospheric Multiscale (MMS) set of spacecraft is examined. For those cases where ion jets are clearly discerned, the direction of origin compares well statistically with the predicted location of magnetic reconnection using convected solar wind observations in conjunction with the Maximum Magnetic Shear model.

Cassini Ion Neutral Mass Spectrometer (INMS) measurements from roughly a hundred Titan encounters over the Cassini mission yield neutral and ion densities systematically lower, by factors approximately 2 to 3, than estimates from several other spacecraft systems, including the Attitude and Articulation Control System, and Navigation system. In this paper we present a new INMS instrument sensitivity model, obtained by re-analyzing (1) the capture and transmission of neutral gas through the instrument, and (2) the detector gain reduction during pre-launch testing. By correcting for an under-estimation of gas leakage out of the instrument into space by the original calibration model, and adjusting for the gain change, the new model brings INMS densities into much closer agreement with the other Cassini systems. Accordingly, the INMS ion densities are revised upward by a constant detector sensitivity correction factor of 1.55±21 %, while the neutral sensitivities have a complex instrument pointing direction dependence, due (mostly) to the effect of the INMS vent and antechamber-to-closed source tube. In the special case of on-ram pointing the neutral densities are revised upward by a constant factor of 2.2±23 %. The corrected neutral and ion sensitivities given here are applicable to all previously published INMS results at Titan, Enceladus and elsewhere in the Saturn system. The new model gives reliable densities at high ram angles, in some cases above 90 degrees, thereby expanding the list of Titan flybys from which INMS densities may be extracted. We apply the model to obtain accurate densities from several off-ram Titan flybys which gave unusual neutral density vs. altitude profiles, or unreasonably high densities, with the original calibration.

Time-of-flight (TOF) velocity filtering can be used in conjunction with electrostatic energy analysis to provide mass identification. This method has several advantages: all species are measured essentially instantaneously and good mass resolution is obtained over a wide energy range. For example, one can easily maintain sufficient mass resolution using the TOF technique to separate the major magnetospheric ion constituents (H +, He +, He 2+, O 2+, and O +) at energies per charge from roughly 1 eV/e to 50 keV/e. This energy range and mass resolution are required for many near-Earth plasma investigations, in particular for elements of the International Solar Terrestrial Physics program. The hot plasma composition analyzer (HPCA) is one example of an instrument that employs the TOF technique, incorporating a 360° field-of-view toroidal electrostatic analyzer and a linear TOF velocity filter. The geometry of the toroidal electrostatic analyzer results in a large geometric factor and allows for focusing within the TOF unit (Young et at., 1988), maximizing transmission and instrument sensitivity. The HPCA is capable of measuring masses from 1–32 amu and energies from 1 to 50,000 eV/e, with M/ΔM on the order of 5 and ΔE/E of 0.18. Results of ray tracing and instrument prototype studies are presented along with a discussion of the instrument optics.

The cost of space plasma sensors is high for several reasons: (1) Most are one-of-a-kind and state-of-the-art, (2) the cost of launch to orbit is high, (3) ruggedness and reliability requirements lead to costly development and test programs, and (4) overhead is added by overly elaborate or generalized spacecraft interface requirements. Possible approaches to reducing costs include development of small 'sensors' (defined as including all necessary optics, detectors, and related electronics) that will ultimately lead to cheaper missions by reducing (2), improving (3), and, through work with spacecraft designers, reducing (4). Despite this logical approach, there is no guarantee that smaller sensors are necessarily either better or cheaper. We have previously advocated applying analytical 'quality factors' to plasma sensors (and spacecraft) and have begun to develop miniaturized particle optical systems by applying quantitative optimization criteria. We are currently designing a Miniaturized Optimized Smart Sensor (MOSS) in which miniaturized electronics (e.g., employing new power supply topology and extensive us of gate arrays and hybrid circuits) are fully integrated with newly developed particle optics to give significant savings in volume and mass. The goal of the SwRI MOSS program is development of a fully self-contained and functional plasma sensor weighing 1 lb and requiring 1 W. MOSS will require only a typical spacecraft DC power source (e.g., 30 V) and command/data interfaces in order to be fully functional, and will provide measurement capabilities comparable in most ways to current sensors.

Attaining a satisfactory understanding of the origin and evolution of the solar system and life within it are among the primary scientific goals of current and future planetary missions. One important clue to understanding these questions is the chemical and isotopic composition of atmospheric and surface volatile materials. Sample-return missions may one day become the method of choice for carrying out detailed laboratory studies of these materials. Until then, however, high-quality in situ measurements of volatiles will be essential to improving our current knowledge and to providing context and support for future missions. Small (similar to1 kg), high-performance (M/DeltaM>10(3)), space-qualified mass spectrometers are the only known method for quantitative analysis that is capable of delivering the isotopic, atomic, and molecular composition of trace amounts (<10(-13) moles/gram) of sample materials. Of particular interest is the identification of biomarker molecules to roughly that level on Mars. These are very difficult performance goals in their own right, but they are more so when increasingly constrained mission resources are taken into account. The current state-of-the-art in space-borne mass spectrometry is examined by defining a quality metric proportional to (performance/resources). The metric suggests that future requirements and constraints represent significant technical challenges. This paper briefly examines historical progress in planetary mass spectrometry before moving to the principles of particle optics that govern spectrometer design and implementation. Several alternative methods are examined, but only four are examined in detail: quadrupole, ion trap, magnetic, and time-of-flight spectrometry. This choice reflects both past successes and the promise of the methodology for future adaptations.

Space Plasma Particle Instrumentation and the New Paradigm: Faster, Cheaper, Better David T. Young, David T. Young Southwest Research Institute, San Antonio, TXSearch for more papers by this author David T. Young, David T. Young Southwest Research Institute, San Antonio, TXSearch for more papers by this author Book Editor(s):Robert F. Pfaff, Robert F. PfaffSearch for more papers by this authorJoseph.E Borovsky, Joseph.E BorovskySearch for more papers by this authorDavid T. Young, David T. YoungSearch for more papers by this author First published: 01 January 1998 https://doi.org/10.1029/GM102p0001Citations: 12Book Series:Geophysical Monograph Series AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Introduction A Survey of Measurement Techniques Instrument Design Principles Tradeoffs Recent Advances Future Innovations Citing Literature Measurement Techniques in Space Plasmas: Particles, Volume 102 RelatedInformation

The Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) uses a unique electric field configuration coupled with precise sub-nanosecond timing to produce a high mass-resolution plasma analyzer with both broad energy an mass ranges. The IMS maintains a spectrographic mass resolution (m/Δm) of ≥50 over a mass range of 1 to 40amu for singly charged positive ions in the energy range of 0.001 to 15ke V. Ions having energies between 15 and 50keV are measured with a lower mass resolution of ∼7.5 as are ions below 15keV which are neutralized or negatively ionized by passage through thin carbon foils at the entrance to the mass analysis section. Bot high and medium mass resolution measurements are made simultaneously on incoming ions of all masses. The total angular acceptance is 11° × 160° and areal acceptance is ∼1cm 2 per pixel. An overview of the design and results of the laboratory testing of the IMS are presented here.

One of the major aims of the Cassini spacecraft is to characterize in detail the interaction of the solar wind with the Saturnian system. The Cassini Plasma Spectrometer (CAPS) addresses this aim by measuring the plasma particles, ions and electrons, with a suite of three complementary sensors. One of these, the Electron Spectrometer (ELS), will measure the energy and angular distributions of solar wind and magnetospheric electrons at Saturn with unprecedented accuracy.

The joint NASA/European Space Agency Cassini mission to Saturn will carry the Cassini Plasma Spectrometer (CAPS). This instrument consists of three sensors, including the Ion Mass Spectrometer (IMS), a data processing unit, and an actuator that rotates CAPS in order to view a large fraction of the space environment. The IMS makes high sensitivity, mass resolved measurements of the various ion distribution functions. This sensor represents a significant step forward in ion mass spectrometry. The design employs a unique cylindrically symmetric linear electric field region in which some fraction of the initial ions reflect. Since the time-of-flight (TOF) is independent of these ions' energies, extremely high mass resolution measurements can be made while maintaining the very high sensitivity achievable with TOF plasma spectrometers. Ions and neutrals which do not reflect in this region are simultaneously analyzed in a straight-through TOF section. These two complementary techniques provide hot plasma composition measurement with mass resolutions (m/Δm) of >50 and ∼8 for geometric factors of ∼10 -3 and ∼10 -4 [cm 2 sr eV/eV] per 11° x 22.5° pixel, respectively.

This chapter contains sections titled: Introduction Kinetic Measurement Objectives Directional Analysis Energy Analysis Mass Analysis Spacecraft Charging Data Analysis Conclusions