Papers by Patrícia Serrano Gonçalves
A scenario for an initial manned mission to Mars involves transits through the Van Allen Radiatio... more A scenario for an initial manned mission to Mars involves transits through the Van Allen Radiation Belts, a 30 day 'short surface stay' and a 400 day Cruise Phase (to/from the planet). The contribution to the total dose incurred through transiting the belts is relatively small and manageable. Estimates of the particle radiation hazard incurred during a 30 day stay on the surface (using ESA's Mars Energetic Radiation Environment Models dMEREM and e MEREM) indicate that the dose is not expected to be particularly challenging health-wise due to the shielding effect provided by the Martian atmosphere and the body of the planet. This is in accord with estimations obtained using the Langley HZETRN code. Estimates of GCR exposure in free space during the minimum phase of Solar Cycle 23 determined using the CREME2009 model are in reasonable agreement with published results obtained using HZETRN (which they exceed by about 10%). The Cruise Phase poses a significant radiation problem due to the cumulative effects of isotropic Galactic Cosmic Radiation over 400 days. The occurrence during this period of a large Solar Energetic Particle (SEP) event, especially if it has a hard energy spectrum, could be catastrophic health wise to the crew. Such particle events are rare but they are not currently predictable. An overview of mitigating strategies currently under development to meet the radiation challenge is provided and it is shown that the health problem posed by energetic particle radiation is presently unresolved.
The 'Mars Energetic Radiation Environment Models' (dMEREM and eMEREM) recently developed for the ... more The 'Mars Energetic Radiation Environment Models' (dMEREM and eMEREM) recently developed for the European Space Agency are herein used to estimate, for the first time, background Galactic Cosmic Ray (GCR) radiation and flare related solar energetic particle (SEP) events at three candidate martian landing sites under conditions where particle arrival occurred at solar minimum (December, 2006) and solar maximum (April, 2002) during Solar Cycle 23. The three landing sites were selected on the basis that they are characterized by significantly different hydrological conditions and soil compositions. Energetic particle data sets recorded on orbit at Mars at the relevant times were incomplete because of gaps in the measurements due to operational constraints. Thus, in the present study, comprehensive near-Earth particle measurements made aboard the GOES spacecraft were used as proxies to estimate the overall particle doses at each perspective landing site, assuming in each case that the fluxes fell off as 1/r 2 (where r is the helio-radial distance) and that good magnetic connectivity always prevailed. The results indicate that the particle radiation environment on Mars can vary according to the epoch concerned and the landing site selected. Particle estimations obtained using MEREM are in reasonable agreement, given the inherent differences between the models, with the related NASA Heavy Ion–Nucleon Transport Code for Space Radiation/HZETRN. Both sets of results indicated that, for short (30 days) stays, the atmosphere of Mars, in the cases of the SEPs studied and the then prevailing background galactic cosmic radiation, provided sufficient shielding at the planetary surface to maintain annual skin and blood forming organ/BFO dose levels below currently accepted ionizing radiation exposure limits. The threat of occurrence of a hard spectrum SEP during Cruise-Phase transfers to/from Mars over 400 days, combined with the associated cumulative effect of prolonged GCR exposure, poses an as yet unsolved hazard to prospective onboard personnel.
A test of the benchmark QED process e + e − → γγ(γ) is reported, using the data collected with th... more A test of the benchmark QED process e + e − → γγ(γ) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb −1 . The Born cross-section for the process e + e − → γγ(γ) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived.
The transverse profiles of Extensive Air Showers in the region of Xmax and its dependence with th... more The transverse profiles of Extensive Air Showers in the region of Xmax and its dependence with the composition of the primary particle is studied in this work. Simulations using Corsika shows, for energies in the range 10 14 −10 17 eV, a sizeable difference in the shape of the transverse profile for EAS initiated by Proton or by Iron. However this differences smooths out with increasing energies.
The high energy ionizing radiation environment in the solar system consists of three main sources... more The high energy ionizing radiation environment in the solar system consists of three main sources: the radiation belts, galactic cosmic rays and solar energetic particles. Geant4 is a Monte Carlo radiation transport simulation toolkit, with applications in areas as high energy physics, nuclear physics, astrophysics or medical physics research. In this poster, Geant4 applications to model and study the effects of the heliospheric radiation environment are presented. Specific applications are being developed to study the effect of the radiation environment on detector components, to describe the response and to optimise the design of radiation monitors for future space missions and to predict the radiation environment in Mars surface, orbits and moons.
The actual Martian radiation field is known to be higher than levels compatible with habitability... more The actual Martian radiation field is known to be higher than levels compatible with habitability conditions. This work defines critical geophysical parameters associated with geologic evolution and assesses their impact in terms of radiation environment and time evolution of habitability on Mars.
A multi-temporal extension of Linear Mixture Models (LMM) is investigated. Applied to a full ye... more A multi-temporal extension of Linear Mixture Models (LMM) is investigated. Applied to a full year sequence of MODIS 500 meters resolution images, timevarying Linear Mixture Models provide us with the interannual evolution of "vegetation", "soil" and "shadow" subpixel components. Reported work is a descriptive analysis of the results and stands as a preliminary study towards automatic multi-temporal LMM based characterization and classification of land cover.
New Worlds in Astroparticle Physics, 2006
The system architecture of a GEANT4 based simulation framework and its application to EUSO/ULTRA ... more The system architecture of a GEANT4 based simulation framework and its application to EUSO/ULTRA and AMS/RICH performance studies are presented. ULTRA (Ultraviolet Light Transmission and Reflection in the Atmosphere) is an experimental support activity of EUSO (Extreme Universe Space Observatory), an experiment devoted to the study of extreme energy cosmic rays and neutrinos. Relevant aspects of the ULTRA simulation, namely the description of optical processes and the simulation of Fresnel lenses using parameterisation/replication techniques are described. The RICH (Ring Imaging CHerenkov detector) of the AMS (Alpha Magnetic Spectrometer) experiment, will incorporate a dual radiator, made of a low refractive index material, aerogel, and of sodium fluoride (NaF). A more realistic description of Cherenkov photon transmission through the aerogel surface, based on Atomic Force Microscopy images, was implemented in GEANT4.
1IST, Instituto Superior Técnico, placeCityLisboa, country-regionPortugal 2LIP, Laboratório de In... more 1IST, Instituto Superior Técnico, placeCityLisboa, country-regionPortugal 2LIP, Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, placecountry-regionPortugal 3ESA-ESTEC, European Space Reasearch and Technology Centre, Noordwijk, The placecountry-regionNetherlands Abstract: In this work, a novel particle spectrometer is proposed to fulfil the need to map the space radiation environment for future space missions and to provide more accurate scientific data. The concept of the instrument brings together new radiation-hard technologies, for the photo-sensors and scintillating materials that will improve the quality of the data, while taking into account the limited resources such as mass, power and accommodation, allocated for space radiation monitors.
In this work, a novel particle spectrometer is proposed to fulfil the need to map the space radia... more In this work, a novel particle spectrometer is proposed to fulfil the need to map the space radiation environment for future space missions and to provide more accurate scientific data. The concept of the instrument brings together new radiation-hard technologies, for the photo-sensors and scintillating materials that will improve the quality of the data, while taking into account the limited resources such as mass, power and accommodation, allocated for space radiation monitors. The Multi-channel Array Particle Spectrometer (MAPS), can measure fluxes and energy dis-tributions of protons, ions, electrons and gammas in a wide energy range based on the D reconstruction of the particle track through the detector and its deposited energy in the active volume. It consists on a 8 x 8 segmented scintillator block built from 3.2 x 3.2 x 20 mm3 indi-vidual LYSO:Ce rods that are readout at both ends by two 64 pixel Silicon Photo-Multipliers (SiPMs) matrices, a new generation of high gain (105...
The high energy ionising radiation envi-ronment in the solar system consists of three main source... more The high energy ionising radiation envi-ronment in the solar system consists of three main sources: the radiation belts, galactic cosmic rays and solar energetic particles. Future Mars missions potentially carry significant risk from long-term exposure to ionising radiation. The Martian Ener-getic Radiation Environment Models, MEREM, were developed in order to simulate the Martian radiation environment. The models, eMEREM and dMEREM, respectively engineering and detailed Martian En-ergetic Radiation Environment Models, are based on the Geant4 and FLUKA radiation transport programs, combined with Mars Climate Database model for the atmosphere. MOLA (Mars Orbiter Laser Altimeter) data and gamma-ray spectrometer data have been used to define surface topology and surface composition (including presence of water), respectively.
When planning spacecraft and manned missions to Mars, detailed information about environmental co... more When planning spacecraft and manned missions to Mars, detailed information about environmental conditions and radiation on the planet is vital to reduce the chances of mission failure and to aid in the optimisation of the design process. MarsREC [1] tool showed that Radiation Environment is dependent on the soil composition and density, on atmosphere variations along the Martian year and on landing location. A GEANT4 detailed model is being designed, based on the Geant4 MarsREC[1] and PLANETOCOSMICS [2] codes, to permit the prediction of the Martian radiation environment for Mars planetary and moon landers or habitats. The tool will be available online and will be easy-to-use by mission designers and planners. Dependence on Atmospheric variations: Previous simulations based on the MarsREC [1] tool have shown that radiation environment at the surface of Mars depends on atmosphere variations along the Martian year and on landing location. This result is illustrated in Figure 1 [3], wh...
Due to fundamental limitations of accelerators, only cosmic rays can give access to centre-of- ma... more Due to fundamental limitations of accelerators, only cosmic rays can give access to centre-of- mass energies more than one order of magnitude above those reached at the LHC. In fact, extreme energy cosmic rays (1018 eV - 1020 eV) are the only possibility to explore the 100 TeV energy scale in the years to come. This leap by one order of magnitude gives a unique way to open new horizons: new families of particles, new physics scales, in-depth investigations of the Lorentz symmetries. However, the flux of cosmic rays decreases rapidly, being less than one particle per square kilometer per year above 1019 eV: one needs to sample large surfaces. A way to develop large-effective area, low cost, detectors, is to build a solar panel-based device which can be used in parallel for power generation and Cherenkov light detection. Using solar panels for Cherenkov light detection would combine power generation and a non-standard detection device.
Astronomy & Astrophysics, 2015
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Papers by Patrícia Serrano Gonçalves