NASA’s
Lucy
mission spacecraft was launched on 16 October 2021 and will perform the initial in situ investigation of the Jovian Trojan asteroids (Levison et al.
2021
,
2024
). The Lucy LOng Range ...Reconnaissance Imager (L’LORRI) is a panchromatic visible light (420–795 nm, 50% QE points), narrow-angle (field of view = 0.29°), high spatial resolution (1.0
′′
pixel
−1
) imager used on the
Lucy
mission for both science observations and optical navigation. L’LORRI is designed to provide maps of the sunlit portions of the Trojan surfaces to a resolution of ∼10 m (after deconvolution), which will enable crater counting to constrain the surface ages. L’LORRI’s high sensitivity and large dynamic range permits imaging of the low albedo Trojans at moderately large phase angles (down to I/F values of ∼0.0014 with SNR ≈ 30 using an exposure time of 100 ms), as well as providing early acquisitions of the Trojans during the approach phase, searches for Trojan activity that are ∼10× better than can be obtained from Earth, and deep searches for potential Trojan satellites down to
V
≈
20.4
at spatial resolutions far surpassing that available from Earth. This paper describes the L’LORRI instrument design and the requirements that drove the design. We present results from L’LORRI’s ground calibration campaign, summarize the L’LORRI in-flight calibration plan, and describe typical L’LORRI operations scenarios during the Trojan flybys. We also present an analysis of in-flight data taken during the first year of
Lucy
operations, which show that most aspects of L’LORRI’s performance are nominal (i.e., as predicted), but the telescope’s point spread function is slightly degraded relative to pre-flight predictions. Nevertheless, L’LORRI is still expected to fulfill all of its scientific objectives, which should revolutionize our view of the Jovian Trojans.
We present a time‐of‐flight mass spectrometer design for the measurement of ions in the ~30 keV to 10 MeV range for protons (up to ~40 MeV and ~150 MeV for He and heavy ions, respectively) and ~30 ...keV to 1 MeV range for electrons, covering half of the sky with 80 apertures. The instrument, known as the “Mushroom,” owing to its shape, solves the field of view problem for magnetospheric and heliospheric missions that employ three‐axis stabilized spacecraft, yet still require extended angular coverage; the Mushroom is also compatible with a spinning spacecraft. The most important new feature of the Mushroom is the method through which uncomplicated electrostatic optics and clean position sensing combine to permit many apertures to fit into a compact, low‐mass sensor head (or wedge), several of which (ideally eight) compose a full instrument. Most of the sensor head's volume is an empty, equipotential region, resulting in the modest 250 g mass of each 10‐aperture wedge. The Mushroom is capable of separating ion species across most of its energy range and angular field of view. For example, separation of the neighboring 3He and 4He isotopes is excellent; the full width at half maximum mass resolution has been measured to be 0.24 amu to 0.32 amu, respectively. Converting this to a Gaussian width σm in mass m, this represents a σm/m mass resolution better than 0.04. This separation is highly desirable for the flight program for which the first Mushroom was built, the Solar Probe Plus mission. More generally, we estimate the mass resolution to be σm/m ≈ 0.1, but this is energy, mass, and angularly dependent. We also discuss the solid‐state detector stack capability, which extends the energy range of protons and helium, with composition, to ~100 MeV.
Key Points
Anisotropy, pitch angle distributions, and large field of view are important for energetic ion and electron science
The “Mushroom” instrument has been developed by JHU/APL to provide needed large FOV and angular resolution
The first Mushroom, EPI‐Lo, part of the ISʘIS investigation on Solar Probe Plus, has achieved excellent composition and spatial separation
The Energetic Particle Detector Rodríguez-Pacheco, J; Wimmer-Schweingruber, R F; Mason, G M ...
Astronomy and astrophysics (Berlin),
10/2020, Letnik:
642
Journal Article
Recenzirano
Odprti dostop
After decades of observations of solar energetic particles from space-based observatories, relevant questions on particle injection, transport, and acceleration remain open. To address these ...scientific topics, accurate measurements of the particle properties in the inner heliosphere are needed. In this paper we describe the Energetic Particle Detector (EPD), an instrument suite that is part of the scientific payload aboard the Solar Orbiter mission. Solar Orbiter will approach the Sun as close as 0.28 au and will provide extra-ecliptic measurements beyond ∼30° heliographic latitude during the later stages of the mission. The EPD will measure electrons, protons, and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of megaelectronvolts/nucleons. For this purpose, EPD is composed of four units: the SupraThermal Electrons and Protons (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) plus the Instrument Control Unit that serves as power and data interface with the spacecraft. The low-energy population of electrons and ions will be covered by STEP and EPT, while the high-energy range will be measured by HET. Elemental and isotopic ion composition measurements will be performed by SIS and HET, allowing full particle identification from a few kiloelectronvolts up to several hundreds of megaelectronvolts/nucleons. Angular information will be provided by the separate look directions from different sensor heads, on the ecliptic plane along the Parker spiral magnetic field both forward and backwards, and out of the ecliptic plane observing both northern and southern hemispheres. The unparalleled observations of EPD will provide key insights into long-open and crucial questions about the processes that govern energetic particles in the inner heliosphere.
There is a pressing need for scientific methods that provide independent proof of the authenticity of animal produce for human consumption. Results of two feasibility studies suggest that the ...analysis of natural stable isotope compositions of carbon, nitrogen and sulphur is one potential tool for the verification of the geographical origin and feeding history of beef cattle. Beef reared in the USA (23 samples) and Brazil (10 samples) was isotopically different from northern European beef (35 samples), mainly because of contrasting proportion of plants with C
3 and C
4 photosynthetic pathways in the cattle diets. Combined C, N and S stable isotope ratio analysis also separated organically (15 samples) and conventionally (17 samples) produced Irish beef, even though underlying mechanisms are not yet fully understood.
We studied northern flying squirrel (Glaucomys sabrinus) demography in the eastern Washington Cascade Range to test hypotheses about regional and local abundance patterns and to inform managers of ...the possible effects of fire and fuels management on flying squirrels. We quantified habitat characteristics and squirrel density, population trends, and demography in three typical forest cover types over a four-year period. We had 2034 captures of flying squirrels over 41 000 trap nights from 1997 through 2000 and marked 879 squirrels for mark-recapture population analysis. Ponderosa pine (Pinus ponderosa) forest appeared to be poorer habitat for flying squirrels than young or mature mixed-conifer forest. About 35% fewer individuals were captured in open pine forest than in dry mixed-conifer Douglas-fir (Pseudotsuga menziesii) and grand fir {Abies grandis) forests. Home ranges were 85% larger in pine forest (4.6 ha) than in mixed- conifer forests (2.5 ha). Similarly, population density (Huggins estimator) in ponderosa pine forest was half (1.1 squirrels/ha) that of mixed-conifer forest (2.2 squirrels/ha). Tree canopy cover was the single best correlate of squirrel density (r = 0.77), with an apparent threshold of 55% canopy cover separating stands with low-from high-density populations. Pradel estimates of annual recruitment were lower in open pine (0.28) than in young (0.35) and mature (0.37) forest. High recruitment was most strongly associated with high understory plant species richness and truffle biomass. Annual survival rates ranged from 45% to 59% and did not vary among cover types. Survival was most strongly associated with understory species richness and forage lichen biomass. Maximum snow depth had a strong negative effect on survival. Rate of per capita increase showed a density-dependent response. Thinning and prescribed burning in ponderosa pine and dry mixed conifer forests to restore stable fire regimes and forest structure might reduce flying squirrel densities at stand levels by reducing forest canopy, woody debris, and the diversity or biomass of understory plants, truffles, and lichens. Those impacts might be ameliorated by patchy harvesting and the retention of large trees, woody debris, and mistletoe brooms. Negative stand-level impacts would be traded for increased resistance and resilience of dry-forest landscapes to now-common, large-scale stand replacement fires.
This report describes service-learning in a first-year majors biology course in which students serve throughout the semester with community partners for an average of 25 hours/student. All of the ...partnerships are based on providing engaging hands-on biology activities for youth in underserved urban areas surrounding the campus. Students in the course have designed new lessons and activities, supported biology labs, mentored younger students, and facilitated afterschool science clubs. Throughout the course, integration between the students' service experience in the community and their learning in the course is emphasized. This is accomplished in multiple ways including class discussion, group activities, feedback from the instructor and teaching assistant, and weekly blogs. A three-year average of anonymous university-wide course evaluations suggested that students in this service-learning course considered their biology course to be highly rigorous. In both blogs and anonymous surveys students reported that their service and its integration with the course not only advanced their professional skills and sense of community engagement, but also enhanced their learning in biology.
Stable isotope ratio analysis of light elements (including C, N, and S) is a powerful tool for inferring the production and geographic origins of animals. The objectives of this research were to ...quantify experimentally the isotopic turnover of C, N, and S in bovine skeletal muscle (LM and psoas major) and to assess the implications of the turnover for meat authentication. The diets of groups (n = 10 each) of beef cattle were switched from a control diet containing barley and unlabelled urea to an experimental diet containing maize, ¹⁵N-labeled urea, and seaweed for periods of up to 168 d preslaughter. The feeding of the experimental diet was clearly reflected by the δ¹³C, δ¹⁵N, and δ³⁴S values of the LM and psoas major muscles, but isotopic equilibrium was not reached in either muscle for C, N, or S after 168 d of feeding the experimental diet. The slow turnover in skeletal muscle was reflected by the C and N half-lives of 151 and 157 d for LM and 134 and 145 d for psoas major, respectively, and by an S half-life of 219 d in LM. It is concluded that the turnover of light elements (C, N, and S) in bovine skeletal muscles is a slow process; therefore, skeletal muscles contain isotopic information on dietary inputs integrated over a long period of time (months to years).
Vitamin K-dependent γ-glutamyl carboxylase catalyzes the conversion of glutamyl residues to γ-carboxyglutamate. Its substrates include vertebrate proteins involved in blood coagulation, bone ...mineralization, and signal transduction and invertebrate ion channel blockers known as conotoxins. Substrate recognition involves a recognition element, the γ-carboxylation recognition site, typically located within a cleavable propeptide preceding the targeted glutamyl residues. We have purified two novel γ-carboxyglutamate-containing conotoxins, Gla-TxX and Gla-TxXI, from the venom of Conus textile. Their cDNA-deduced precursors have a signal peptide but no apparent propeptide. Instead, they contain a C-terminal extension that directs γ-carboxylation but is not found on the mature conotoxin. A synthetic 13-residue “postpeptide” from the Gla-TxXI precursor reduced the K m for the reaction of the Conus γ-carboxylase with peptide substrates, including FLEEL and conantokin-G, by up to 440-fold, regardless of whether it was positioned at the N- or C-terminal end of the mature toxin. Comparison of the postpeptides to propeptides from other conotoxins suggested some common elements, and amino acid substitutions of these residues perturbed γ-carboxylation of the Gla-TxXI peptide. The demonstration of a functional and transferable C-terminal postpeptide in these conotoxins indicates the presence of the γ-carboxylation recognition site within the postpeptide and defines a novel precursor structure for vitamin K-dependent polypeptides. It also provides the first formal evidence to prove that γ-carboxylation occurs as a post-translational rather than a cotranslational process.
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