ALBERT

Description: The Dawn spacecraft carries a visible and infrared mapping spectrometer (VIR) [1] that has acquired spectra for the wavelength range 0.25-5.0 m at various spatial resolutions covering much of the vestan surface [2]. Through comparison of VIR spectra with laboratory spectra of howardite, eucrite and diogenite meteorites, the distribution of more diogenite-rich and more eucrite-rich terranes on Vesta have been mapped [3], but these maps are qualitative in nature. The available laboratory spectra are not well-integrated with detailed sample petrology or composition limiting their utility for lithologic mapping. Importantly, howardites are now recognized to come in two subtypes, regolithic and fragmental [4]. The former are breccias assembled in part from true regolith, while the latter have had much less exposure to the space environment. We are attempting to develop a more quantitative basis for mapping the distribution of lithologic types on Vesta through acquiring laboratory spectra on splits of howardites that have been petrologically and chemically characterized [5]. Noble gas analyses have been done on some allowing identification of those howardites that have been exposed in the true regolith of Vesta [6].

Description: Distributions of absorbed dose and DNA clustered damage yields in various organs and tissues following the October 1989 solar particle event (SPE) were calculated by coupling the FLUKA Monte Carlo transport code with two anthropomorphic phantoms (a mathematical model and a voxel model), with the main aim of quantifying the role of the shielding features in modulating organ doses. The phantoms, which were assumed to be in deep space, were inserted into a shielding box of variable thickness and material and were irradiated with the proton spectra of the October 1989 event. Average numbers of DNA lesions per cell in different organs were calculated by adopting a technique already tested in previous works, consisting of integrating into "condensed-history" Monte Carlo transport codes--such as FLUKA--yields of radiobiological damage, either calculated with "event-by-event" track structure simulations, or taken from experimental works available in the literature. More specifically, the yields of "Complex Lesions" (or "CL", defined and calculated as a clustered DNA damage in a previous work) per unit dose and DNA mass (CL Gy-1 Da-1) due to the various beam components, including those derived from nuclear interactions with the shielding and the human body, were integrated in FLUKA. This provided spatial distributions of CL/cell yields in different organs, as well as distributions of absorbed doses. The contributions of primary protons and secondary hadrons were calculated separately, and the simulations were repeated for values of Al shielding thickness ranging between 1 and 20 g/cm2. Slight differences were found between the two phantom types. Skin and eye lenses were found to receive larger doses with respect to internal organs; however, shielding was more effective for skin and lenses. Secondary particles arising from nuclear interactions were found to have a minor role, although their relative contribution was found to be larger for the Complex Lesions than for the absorbed dose, due to their higher LET and thus higher biological effectiveness. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Description: The CCU and Incubator are habitats under development by SSBRP for gravitational biology research on ISS. They will accommodate multiple specimen types and reside in either Habitat Holding Racks, or the Centrifuge Rotor, which provides selectable gravity levels of up to 2 g. The CCU can support multiple Cell Specimen Chambers, CSCs (18, 9 or 6 CSCs; 3, 10 or 30 mL in volume, respectively). CSCs are temperature controlled from 4-39 degrees C, with heat shock to 45 degrees C. CCU provides automated nutrient supply, magnetic stirring, pH/O2 monitoring, gas supply, specimen lighting, and video microscopy. Sixty sample containers holding up to 2 mL each, stored at 4-39 degrees C, are available for automated cell sampling, subculture, and injection of additives and fixatives. CSCs, sample containers, and fresh/spent media bags are crew-replaceable for long-term experiments. The Incubator provides a 4-45 degrees C controlled environment for life science experiments or storage of experimental reagents. Specimen containers and experiment unique equipment are experimenter-provided. The Specimen Chamber exchanges air with ISS cabin and has 18.8 liters of usable volume that can accommodate six trays and the following instrumentation: five relocatable thermometers, two 60 W power outlets, four analog ports, and one each relative humidity sensor, video port, ethernet port and digital input/output port.

Description: PURPOSE: To investigate the long-term effects of total body irradiation (TBI) on the incidence and time course of ocular complications. MATERIALS AND METHODS: Rhesus monkeys treated with TBI photon doses up to 8.5 Gy and proton doses up to 7.5 Gy were studied at intervals up to 25 years post-irradiation. They were compared with control groups with a similar age distribution. Cataract formation and ocular fundus lesions were scored according to a standardized protocol. Fluorescein angiography and histopathology was performed in selected animals. RESULTS: Cataract formation occurred after a latent period of 3-5 years. Significant cataract induction was observed for photon-doses of 8 and 8.5 Gy and beyond 20 years after proton irradiation. The severity of the lesions represents significant impairment of vision and would require cataract surgery if similar results occurred in human bone marrow transplant patients. Fluorescein angiography demonstrated a normal pattern of retinal vessels in 13 out of 14 animals (93%) from the irradiated group and in eight out of nine animals (89%) from the control group. No additional lesions apart from age-related degenerative changes could be demonstrated. Histological evaluation revealed no radiation-associated vasculopathy. CONCLUSIONS: Radiation alone for doses up to 8.5 Gy of photons does not carry a potential risk for fundus pathology, whereas clinically important cataract induction should be anticipated within 5 years after photon doses of 8.0 and 8.5 Gy and proton doses in excess of 2.5 Gy.

Description: Cross-sections and appearance potentials for the production of various negative ion species by electron impact on SiH4 have been measured. They are compared with two previous measurements which widely differ with each other. Hess' law has been applied to predict the various possible channels of dissociation.

Description: Pressure-broadening parameters for 19 transitions of the millimeter and submillimeter wave spectrum of NO2 have been obtained experimentally. Results for broadening by N2, O2, and He are presented and compared with earlier theoretical calculations of the N2 and O2 parameters. A discussion of the relation between theoretical calculations and experimental measurements is presented.

Description: For many years it has been suggested that lava tubes on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava tubes has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith layer and rock. The chemical composition has been chosen as typical of the lunar regions where the largest number of lava tube candidates are found. Particles have been transported all through the regolith and the rock, and received particles flux and doses have been calculated. The radiation safety of lunar lava tubes environments has been demonstrated.

Description: The NCRP has recently defined RBE values and a new quantity (Gy-Eq) for use in estimation of deterministic effects in space shielding and operations. The NCRP's RBE for neutrons is left ambiguous and not fully defined. In the present report we will suggest a complete definition of neutron RBE consistent with the NCRP recommendations and evaluate attenuation properties of deterministic effects (Gy-Eq) in comparison with other dosimetric quantities.

Description: Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary concept to the final design. For the last few decades, we have pursued deterministic solutions of the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard Finite Element Method (FEM) geometry common to engineering design methods. A single ray trace in such geometry requires 14 milliseconds and limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given.

Description: The Supersonic Transport (SST) program, proposed in 1961, first raised concern for the exposure of pregnant occupants by solar energetic particles (SEP), and neutrons were suspected to have a main role in particle propagation deep into the atmosphere. An eight-year flight program confirmed the role of SEP as a significant hazard and of the neutrons as contributing over half of the galactic cosmic ray exposures, with the largest contribution from neutrons above 10 MeV. The FAA Advisory Committee on the Radiobiological Aspects of the SST provided operational requirements. The more recent lowering of ICRP-recommended exposure limits (1990) with the classification of aircrew as "radiation workers" renewed interest in GCR background exposures at commercial flight altitudes and stimulated epidemiological studies in Europe, Japan, Canada and the USA. The proposed development of a High Speed Civil Transport (HSCT) required validation of the role of high-energy neutrons, and this resulted in ER-2 flights at solar minimum (June 1997) and studies on effects of aircraft materials on interior exposures. Recent evaluation of health outcomes of DOE nuclear workers resulted in legislation for health compensation in year 2000 and recent European aircrew epidemiological studies of health outcomes bring renewed interest in aircraft radiation exposures. As improved radiation models become available, it is imperative that a corresponding epidemiological program of US aircrew be implemented. Published by Elsevier Ltd on behalf of COSPAR.