86 research outputs found
A Radiation Hardened by Design CMOS ASIC for Thermopile Readouts
A radiation hardened by design (RHBD) mixed-signal application specific integrated circuit (ASIC) has been designed for a thermopile readout for operation in the harsh Jovian orbital environment. The multi-channel digitizer (MCD) ASIC includes 18 low noise amplifier channels which have tunable gain/filtering coefficients, a 16-bit sigma-delta analog-digital converter (SDADC) and an on-chip controller. The 18 channels, SDADC and controller were designed to operate with immunity to single event latchup (SEL) and to at least 10 Mrad total ionizing dose (TID). The ASIC also contains a radiation tolerant 16-bit 20 MHz Nyquist ADC for general purpose instrumentation digitizer needs. The ASIC is currently undergoing fabrication in a commercial 180 nm CMOS process. Although this ASIC was designed specifically for the harsh radiation environment of the NASA led JEO mission it is suitable for integration into instrumentation payloads 011 the ESA JUICE mission where the radiation hardness requirements are slightly less stringent
Thermal Radiometer Signal Processing Using Radiation Hard CMOS Application Specific Integrated Circuits for Use in Harsh Planetary Environments
Thermal radiometers such as proposed for the Europa Clipper flyby mission require low noise signal processing for thermal imaging with immunity to Total Ionizing Dose (TID) and Single Event Latchup (SEL). Described is a second generation Multi- Channel Digitizer (MCD2G) Application Specific Integrated Circuit (ASIC) that accurately digitizes up to 40 thermopile pixels with greater than 50 Mrad (Si) immunity TID and 174 MeV-sq cm/mg SEL. The MCD2G ASIC uses Radiation Hardened By Design (RHBD) techniques with a 180 nm CMOS process node
THE ACTION OF TERRAMYCIN ON THE GROWTH OF STRAINS OF INFLUENZA, HERPES SIMPLEX, AND RABIES VIRUSES IN CHICK EMBRYOS AND MICE
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72961/1/j.1749-6632.1950.tb42175.x.pd
A Radiation Hard Multi-Channel Digitizer ASIC for Operation in the Harsh Jovian Environment
In 1995, the Galileo spacecraft arrived at Jupiter to conduct follow-up experiments on pathfinder Pioneer and key Voyager discoveries especially at Io, Europa, Ganymede and Callisto. These new observations helped expand our scientific knowledge of the prominent Galilean satellites; studies revealed diversity with respect to their geology, internal structure, evolution and degree of past and present activity. Jupiter's diverse Galilean satellites, of which three are believed to harbor internal oceans, are central to understanding the habitability of icy worlds. Galileo provided for the first time compelling evidence of a near-surface global ocean on Europa. Furthermore, by understanding the Jupiter system and unraveling the history of its evolution from initial formation to the emergence of possible habitats and life, gives insight into how giant planets and their satellite systems form and evolve. Most important, new light is shed on the potential for the emergence and existence of life in icy satellite oceans. In 2009, NASA released a detailed Jupiter Europa Mission Study (EJSM) that proposed an ambitious Flagship Mission to understand more fully the satellites Europa and Ganymede within the context of the Jovian system. Key to EJSM is the NASA led Jupiter Europa Orbiter (JEO) and the ESA led Jupiter Ganymede Orbiter (JGO). JEO and JGO would execute a choreographed exploration of the Jovian system before settling into orbit around Europa and Ganymede, respectively. The National Academies Planetary Decadal Survey, 2011 has listed the NASA-led JEO as the second highest priority mission for the decade 2013-2022, and if chosen it would be launched in 2020 with arrival at Jupiter in 2025. If the JEO mission is not chosen it is anticipated that there will be opportunities in future decadal cycles. Jupiter Orbit Insertion (JOI) begins a 30-month Jovian system tour followed by nine months of science mapping after Europa Orbit Insertion (EOI) in July 2028. The orbiter will ultimately impact the surface of Europa after the mission is completed. The current JEO mission concept includes a range of instruments on the payload, to monitor dynamic phenomena (such as Io's volcanoes and Jupiters atmosphere), map the Jovian magnetosphere and its interactions with the Galilean satellites, and characterize water oceans beneath the ice shells of Europa and Ganymede. The payload includes a low mass (3.7 Kg) and low power (< 5 W) Thermal Instrument (TI) concept for measuring possible warm thermal anomalies on Europa s cold surface caused by recent (< 10,000 years) eruptive activity. Regions of anomalously high heat flow will be identified by thermal mapping using a nadir pointing, push-broom filter radiometer that provides far-IR imagery in two broad band spectral wavelength regions, 8-20 m and 20-100 m, for surface temperature measurements with better than a 2 K accuracy and a spatial resolution of 250 m/pixel obtained from a 100 Km orbit. The temperature accuracy permits a search for elevated temperatures when combined with albedo information. The spatial resolution is sufficient to resolve Europa's larger cracks and ridge axial valleys. In order to accomplish the thermal mapping, the TI uses sensitive thermopile arrays that are readout by a custom designed low-noise Multi-Channel Digitizer (MCD) ASIC that resides very close to the thermopile linear array outputs. Both the thermopile array and the MCD ASIC will need to show full functionality within the harsh Jovian radiation environment, operating at cryogenic temperatures, typically 150 K to 170 K. In the following, a radiation mitigation strategy together with a low risk Radiation-Hardened-By-Design (RHBD) methodology using commercial foundry processes is given for the design and manufacture of a MCD ASIC that will meet this challenge
'On the difference between the short and long gamma-ray bursts'
We argue that the distributions of both the intrinsic fluence and the
intrinsic duration of the gamma-ray emission in gamma-ray bursts from the BATSE
sample are well represented by log-normal distributions, in which the intrinsic
dispersion is much larger than the cosmological time dilatation and redshift
effects. We perform separate bivariate log-normal distribution fits to the
BATSE short and long burst samples. The bivariate log-normal behaviour results
in an ellipsoidal distribution, whose major axis determines an overall
statistical relation between the fluence and the duration. We show that this
fit provides evidence for a power-law dependence between the fluence and the
duration, with a statistically significant different index for the long and
short groups. We discuss possible biases, which might affect this result, and
argue that the effect is probably real. This may provide a potentially useful
constraint for models of long and short bursts.Comment: A.A. in press ; significantly revised version of astro-ph/0007438; 16
pages 5 PS figure
The Minimum Variability Time Scale and its Relation to Pulse Profiles of Fermi GRBs
We present a direct link between the minimum variability time scales
extracted through a wavelet decomposition and the rise times of the shortest
pulses extracted via fits of 34 Fermi GBM GRB light curves comprised of 379
pulses. Pulses used in this study were fitted with log-normal functions whereas
the wavelet technique used employs a multiresolution analysis that does not
rely on identifying distinct pulses. By applying a corrective filter to
published data fitted with pulses we demonstrate agreement between these two
independent techniques and offer a method for distinguishing signal from noise.Comment: Accepted for publication in MNRAS Letters. 4 pages, 4 figure
Unveiling the origin of X-ray flares in Gamma-Ray Bursts
We present an updated catalog of 113 X-ray flares detected by Swift in the
~33% of the X-ray afterglows of Gamma-Ray Bursts (GRB). 43 flares have a
measured redshift. For the first time the analysis is performed in 4 different
X-ray energy bands, allowing us to constrain the evolution of the flare
temporal properties with energy. We find that flares are narrower at higher
energies: their width follows a power-law relation w~E^{-0.5} reminiscent of
the prompt emission. Flares are asymmetric structures, with a decay time which
is twice the rise time on average. Both time scales linearly evolve with time,
giving rise to a constant rise-to-decay ratio: this implies that both time
scales are stretched by the same factor. As a consequence, the flare width
linearly evolves with time to larger values: this is a key point that clearly
distinguishes the flare from the GRB prompt emission. The flare 0.3-10 keV peak
luminosity decreases with time, following a power-law behaviour with large
scatter: L_{pk}~ t_{pk}^{-2.7}. When multiple flares are present, a global
softening trend is established: each flare is on average softer than the
previous one. The 0.3-10 keV isotropic energy distribution is a log-normal
peaked at 10^{51} erg, with a possible excess at low energies. The flare
average spectral energy distribution (SED) is found to be a power-law with
spectral energy index beta~1.1. These results confirmed that the flares are
tightly linked to the prompt emission. However, after considering various
models we conclude that no model is currently able to account for the entire
set of observations.Comment: MNRAS submitte
Gamma-ray bursts and X-ray melting of material to form chondrules and planets
Chondrules are millimeter sized objects of spherical to irregular shape that
constitute the major component of chondritic meteorites that originate in the
region between Mars and Jupiter and which fall to Earth. They appear to have
solidified rapidly from molten or partially molten drops. The heat source that
melted the chondrules remains uncertain. The intense radiation from a gamma-ray
burst (GRB) is capable of melting material at distances up to 300 light years.
These conditions were created in the laboratory for the first time when
millimeter sized pellets were placed in a vacuum chamber in the white
synchrotron beam at the European Synchrotron Radiation Facility. The pellets
were rapidly heated in the X-ray and gamma-ray furnace to above 1400C melted
and cooled. This process heats from the inside unlike normal furnaces. The
melted spherical samples were examined with a range of techniques and found to
have microstructural properties similar to the chondrules that come from
meteorites. This experiment demonstrates that GRBs can melt precursor material
to form chondrules that may subsequently influence the formation of planets.
This work extends the field of laboratory astrophysics to include high power
synchrotron sources.Comment: 4 pages, 4 figures. Full resolution figures available from A&
The CAESAR New Frontiers Mission: Comet Surface Sample Acquisition and Preservation
NASA recently selected the Comet Astrobiology Exploration Sample Return (CAESAR) mission for Phase A study in the New Frontiers Program. This mission will acquire and return to Earth for laboratory analysis at least 80 g of surface material from the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter 67P). CAESAR will characterize the surface region sampled, preserve the sample in a pristine state, and return evolved volatiles by capturing them in a separate gas reservoir. The system protects both volatile and non-volatile components from contamination or alteration thatwould hamper their scientific analysis. Laboratory analyses of comet samples provide unparalleled knowledge about the presolar history through the initial stages of planet formation to the origin of life
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