Abstract We measured inflammatory and neural markers of disease from 7 days to one year after induction of experimental autoimmune encephalomyelitis (EAE) by immunization with myelin oligodendrocyte ...glycoprotein (MOG) peptide. Axon loss began before behavioral signs when T cell infiltration and microglial activation were very subtle. Remyelination was only detectable ultrastructurally. Axon numbers in the dorsal column plateau around day 30 p.i. while behavioral measures (EAE scores, rotarod, grip strength) partially recover. These results provide a starting point for testing potential neuroprotective treatments for multiple sclerosis (MS).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Inflammation, demyelination, gliosis and axonal degeneration are pathological hallmarks of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis. Axonal damage is thought to ...contribute to irreversible damage and functional impairment, but is difficult to quantify. Conventional MRI has been used to assess the inflammatory and demyelinating aspects of MS lesions, but more sensitive and specific methods are needed to identify axonal damage to monitor disease progression and to determine efficacy of putative neuroprotective agents. We used high resolution diffusion tensor imaging (DTI) and fibre tracking to examine the spinal cord in rats with focal dorsal column inflammatory or demyelinating lesions to determine whether DTI measures can be used to detect pathology at the site of the focal lesion and to measure axonal damage in tracts distal to the focal lesion. Distant from the focal lesion, total axon counts, degenerating axon counts and SMI-31 staining, but not Luxol fast blue staining, were significantly correlated with fractional anisotropy, axial diffusivity and radial diffusivity, all of which are derived from the DTI data. These data suggest that high resolution DTI may be a more sensitive method than conventional imaging for detecting axonal damage at sites distant from inflammation.
Spacecraft for deep space come in a variety of sizes as befits their missions, from the large, flagship-class spacecraft such as Cassini or Galileo to smaller craft such as New Horizons (Pluto) or ...Lunar and Martian landers classified by NASA as Discovery or New Frontiers missions. All missions are constrained in mass, power, or cost, or frequently all three. A communications system that reduces demands on these resources enables, for example, either increased science return (by devoting more resources to the payload) or more such missions to be flown (by helping to meet critical mass or power margins). In this paper, we review the evolution and current capabilities of deep-space transponders and transceivers, noting the differences that lend themselves to particular classes of missions. We report on the development of a flexible, low-power, low-cost, deep-space transceiver architecture for competed mission sets such as Discovery, Mars Scout, and New Frontiers, one that possesses unique communications and radio science capabilities. This state-of-the-art transceiver architecture leverages from high-performance commercial integrated circuit technology and frequency synthesis and digital signal-processing techniques, lending itself to integration, miniaturization, and further power reduction. A transceiver based on this architecture, developed for the space-borne New Horizons spacecraft's primary communications link and uplink radio science experiment, is reviewed in this paper. We conclude discussion of the modern deep-space transceiver architecture with a description of near-term and long-term future functional and performance communications and radio science enhancements to the transceiver.
The Kuiper Belt is a broad, torus-shaped region in the outer Solar System beyond Neptune’s orbit. It contains primordial planetary building blocks and dwarf planets. NASA’s New Horizons spacecraft ...conducted a flyby of Pluto and its system of moons on 14 July 2015. New Horizons then continued farther into the Kuiper Belt, adjusting its trajectory to fly close to the small Kuiper Belt object (486958) 2014 MU69 (henceforth MU69; also informally known as Ultima Thule). Stellar occultation observations in 2017 showed that MU69 was ~25 to 35 km in diameter, and therefore smaller than the diameter of Pluto (2375 km) by a factor of ~100 and less massive than Pluto by a factor of ~106. MU69 is located about 1.6 billion kilometers farther from the Sun than Pluto was at the time of the New Horizons flyby. MU69’s orbit indicates that it is a “cold classical” Kuiper Belt object, thought to be the least dynamically evolved population in the Solar System. A major goal of flying past this target is to investigate accretion processes in the outer Solar System and how those processes led to the formation of the planets. Because no small Kuiper Belt object had previously been explored by spacecraft, we also sought to provide a close-up look at such a body’s geology and composition, and to search for satellites, rings, and evidence of present or past atmosphere. We report initial scientific results and interpretations from that flyby.
On July 14, 2015, the New Horizons mission accomplished the first flyby of Pluto–Charon, achieving full mission success during its primary mission. Less than 4 years later, during its first extended ...mission, New Horizons flew by Arrokoth, a 36-km contact binary trans-Neptunian object in the Kuiper Belt, on January 1, 2019. Along the way, New Horizons imaged numerous distant Kuiper Belt objects, performed important heliophysics science including complex Lyman-α radiation scans, and measured the dust and zodiacal light from regions never before explored. This article provides an overview of the New Horizons spacecraft and its engineering performance, as well as potential strategies for extending the mission far beyond its original design lifetime. Details on the mass and power budgets, as well as descriptions of key innovations to meet the challenges posed by the mission, offer insight into the engineering accomplishments that led to mission success. Trended data on the power, thermal, and propulsion systems substantiate projections of the mission's potential to continue its exploration beyond the heliopause until ~2050.
One component of the REX instrument on NASA's New Horizons spacecraft was an investigation of the radio continuum radiation from Pluto and Charon during the flyby on 14 July 2015. The planetary ...thermal emission was recorded at a wavelength of 4.17 cm (7.18 GHz) during approach, departure, and specifically on the non-illuminated hemispheres of Pluto and Charon during the respective intervals between occultation ingress and egress. We derive the brightness temperatures for these disk-resolved and unresolved observations. The mean values and 1σ deviations of brightness temperature for the unresolved sunlit disk are 33.2 ± 1.4 K and 47.2 ± 5.3 K for Pluto and Charon, respectively, consistent with the global albedos of the two bodies as well as with previous ground-based estimates at smaller wavelengths. A slightly colder temperature of 29.0 ± 2.5 K was determined for the disk-integrated nightside of Pluto and a larger drop in temperature was observed for Charon (40.9 ± 0.9 K), implying a smaller thermal inertia for Charon than Pluto. The measured brightness temperature of Pluto across the nightside diametric scan reached a maximum of 29.0 ± 1.5 K in the center of the disk. The profile shape is attributed to an emissivity effect, which favors thermal emission toward higher elevation angles. As a first approximation, the effective emissivity for thermal emission is calculated for the case when Pluto and Charon are uniformly smooth homogenous spheres. Under this assumption, the effective emissivity for these observations is close to unity for all probable surface constituents, implying that the effective temperature of the Pluto subsurface is only a few percent higher than the observed brightness temperature. A considerably lower subsurface emissivity is implied, however, if the higher atmospheric temperatures near the surface determined from the REX occultation measurements are also valid for the subsurface.
•Radio thermal emission of Pluto and Charon was measured at the wavelength λ = 4.17 cm during the New Horizons flyby in 2015.•Both dayside and nightside observations were recorded.•The brightness temperatures on the dayside are consistent with ground-based observations.•The nightside brightness temperatures of both Pluto and Charon are colder than on the dayside.•The brightness temperature of Pluto is higher than that of Charon, in agreement with their measured optical albedos.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
7.
The New Horizons Spacecraft Fountain, Glen H.; Kusnierkiewicz, David Y.; Hersman, Christopher B. ...
Space science reviews,
10/2008, Volume:
140, Issue:
1-4
Journal Article
Peer reviewed
Open access
The New Horizons spacecraft was launched on 19 January 2006. The spacecraft was designed to provide a platform for seven instruments designated by the science team to collect and return data from ...Pluto in 2015. The design meets the requirements established by the National Aeronautics and Space Administration (NASA) Announcement of Opportunity AO-OSS-01. The design drew on heritage from previous missions developed at The Johns Hopkins University Applied Physics Laboratory (APL) and other missions such as Ulysses. The trajectory design imposed constraints on mass and structural strength to meet the high launch acceleration consistent with meeting the AO requirement of returning data prior to the year 2020. The spacecraft subsystems were designed to meet tight resource allocations (mass and power) yet provide the necessary control and data handling finesse to support data collection and return when the one-way light time during the Pluto fly-by is 4.5 hours. Missions to the outer regions of the solar system (where the solar irradiance is 1/1000 of the level near the Earth) require a radioisotope thermoelectric generator (RTG) to supply electrical power. One RTG was available for use by New Horizons. To accommodate this constraint, the spacecraft electronics were designed to operate on approximately 200 W. The travel time to Pluto put additional demands on system reliability. Only after a flight time of approximately 10 years would the desired data be collected and returned to Earth. This represents the longest flight duration prior to the return of primary science data for any mission by NASA. The spacecraft system architecture provides sufficient redundancy to meet this requirement with a probability of mission success of greater than 0.85. The spacecraft is now on its way to Pluto, with an arrival date of 14 July 2015. Initial in-flight tests have verified that the spacecraft will meet the design requirements.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper presents the RF telecommunications system designed for the New Horizons mission, NASA's planned mission to Pluto, with focus on new technologies developed to meet mission requirements. ...These technologies include an advanced digital receiver—a mission-enabler for its low DC power consumption at 2.6
W secondary power. The receiver is one-half of a card-based transceiver that is incorporated with other spacecraft functions into an integrated electronics module, providing further reductions in mass and power. Other developments include extending APL's long and successful flight history in ultrastable oscillators (USOs) with an updated design for lower DC power. These USOs offer frequency stabilities to 1 part in 10
13, stabilities necessary to support New Horizons’ uplink radio science experiment. In antennas, the 2.1
m high-gain antenna makes use of shaped sub- and main reflectors to improve system performance and achieve a gain approaching 44
dBic. New Horizons would also be the first deep-space mission to fly a regenerative ranging system, offering up to a 30
dB performance improvement over sequential ranging, especially at long ranges.
The paper will provide an overview of the current system design and development and performance details on the new technologies mentioned above. Other elements of the telecommunications system will also be discussed.
Note: New Horizons is NASA's planned mission to Pluto, and has not been approved for launch. All representations made in this paper are contingent on a decision by NASA to go forward with the preparation for and launch of the mission.
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The radio thermal emission from Pluto was observed from the New Horizons spacecraft at a wavelength of 4.2 cm along two scans across the planetary disk shortly after closest approach to Pluto on 14 ...July 2015. The measurements were performed as part of the New Horizons Radio Science Experiment (REX) using the 2.1 m High Gain Antenna (HGA) and the spacecraft's X-Band receiver. The HGA boresight first scanned along a diametric chord across the Pluto disk and then reversed direction to traverse a chord that crossed close to Pluto's winter pole. The diametric scan reveals a “hot spot” on the Pluto nightside associated with an optically bright region centered roughly at the planetocentric coordinates 280° E, 55° S, imaged in 2002–03 with the Hubble Space Telescope. The nightside was also found to be warmer than the dayside during the polar scan. The highest emission was not observed at the maximum southern latitude, however, but rather near the outbound Pluto limb at lower latitude. The REX emission profile from the polar scan is qualitatively consistent with a bright U-shaped polar cap observed on Pluto's Charon-facing hemisphere during the recurring Pluto/Charon mutual events in the late 1980's. The REX radiometer measurements show distinct variations in microwave brightness that constrain volatile transport models and provide unique information on the thermal structure and composition on the regions in winter night during the New Horizons encounter at Pluto.
•Thermal emission of Pluto was measured at λ = 4.2 cm as part of the New Horizons Radio Science Experiment REX on 14 July 2015.•Two high-resolution scans were recorded: one diametrically through the center of Pluto and a second one passing near the winter pole.•The ground track of the diametric scan was nearly identical to that of the lower resolution nightside scan performed between Pluto occultation ingress and egress.•A maximum in the nightside thermal emission was associated with an optically bright spot in the Southern Hemisphere observed from Earth in 2002-2003.•The brightness temperature increased monotonically from 20 K to 37 K during the winter pole scan.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The New Horizons mission to Pluto is the first deep space mission to include the capability of supporting regenerative PN ranging. During the current phase of the mission, sequential tone ranging ...supports the mission navigation requirements but regenerative ranging will expand the conditions (antenna selection, integration time, etc.) over which ranging will be successful during any extended mission following the Pluto fly-by, to objects in the Kuiper belt. Experience with regenerative ranging is being obtained now in preparation for its use in an extended mission. During most of 2012, New Horizons was in a hibernation state. Tracking was conducted between late April and early July. Six regenerative ranging passes were performed to bookend this interval; 2 at the beginning and 4 at the end. During that time, the distance between the spacecraft and Earth was in excess of 22 Astronautical Units (AU) and the Pr/No levels were below 15 dB-Hz. A seventh regenerative ranging pass was performed in May at a higher signal level in order to test the acquisition of the ranging code by the spacecraft during a variety of conditions. The consistency of the regenerative range measurements with the adjacent sequential tone ranging measurements has been demonstrated and serves as a check on the calibration of the regenerative ranging system conditions. The range measurement precision has been shown to follow the predictions that are based on the uplink and downlink signal power. The regenerative ranging system has been shown to acquire the uplink ranging code with and without a commanded reset and regardless of the noise bandwidth setting of the system. This paper will present the data that was obtained during 2012 and will describe the analysis results for the regenerative ranging experience during 2012.
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