Infrared radiation from compact X-ray sources

Observations of the X-ray binaries 4U 0115+634 and A 0535+262 performed in 1981 – 1982 revealed significant IR variabilities of these sources. 4U 0115+634 was observed twice, in the state close to X-ray activity, and in the state of low activity, thus changing from K = 7^m.75 to K > 9^m. A 0535+262 shows the temporal variations ranged from tens minutes to some days. The regular variations of IR brightness are suspected with teh period close to 104 s that corresponds to the period of axial rotation of neutron star in A 0535+262. The results obtained present arguments in favour of hypothesis that IR radiation is generated near the accreting neutron star and is possibly of maser nature.     

A simple model to predict solar radiation under clear sky conditions

Solar radiation is one of the major factors that dominate the thermal behaviors of aerostats in the daytime and the primary energy source of high altitude long endurance aerostats. Therefore, it is necessary to propose an accurate model to predict the solar irradiances. A comprehensive review of the well-known solar radiation models is conducted to help develop the new model. Based on the analysis of the existing models and the available radiation data, the extensive computer tests of the regression and optimization are conducted, from which the new solar radiation model for direct and diffuse irradiances under clear sky conditions is proposed. The new model has excellent prediction accuracy. The coefficient of determination for direct radiation is 0.992, with the root mean square error (RMSE) of 16.9 W/m² and the mean absolute error (MAE) of 2.2%. The coefficient of determination for diffuse radiation is 0.86, with RMSE = 8.7 W/m² and MAE = 9.9%. Comparisons with the well-known existing models show that the new model is much more accurate than the best existing ones.     

Evaluation of the contribution of different types of galaxies to the cosmic diffuse background based on γ-ray observations

The relative contribution to the γ-ray background of different types of sources, namely Seyfert Galaxies, Quasars, BL Lac objects, radio galaxies and field galaxies is estimated under the hypothesis that the cosmic diffuse flux is the result of a superposition of many unresolved galaxies. The γ-ray data indicate that the Seyfert volume emissivity matches that of the diffuse background at few hundred keV and exceeds it at higher energies by as much as a factor of about 4. Whilst normal galaxies contribute less than 0.1%, BL Lac objects, Quasars and Radio Galaxies may contribute as much as 5–10% each, even without significant evolution. In this paper we explore different ways of reconciling the observational data on active galaxies with the measured diffuse background level.     

Numerical modelling of radiance of the presumed dust torus around Mars in the 0.350-1 μm spectral range

Currently conducted studies on modelling of scattered solar radiation in the 0.350-1.00 μm range along the Phobos orbit around Mars are presented. Our calculations include various types of grains, various densities and scattering angles. The calculations are performed with the aid of LOWTRAN7 program. These studies are directly related to the photometer coupled to PFS (Planetary Fourier Spectrometer) planned for the Mars-96 mission.     

“Microquasars” and the X-ray background

The results of 1–20 μm infrared photometry of seven 3CR radio galaxies are discussed. The broad line galaxies all show steep infrared spectra with a power law index α −2.4 (F ∝ ν^+α) in direct continuation of the optical spectra. These spectra are far steeper than those observed in Seyfert 1 galaxies, the radio quiet counterparts of broad line radio galaxies. No infrared excesses were observed in narrow line radio galaxies. However, more sensitive observations are needed before any resemblance in the infrared between narrow line radio galaxies and Seyfert 2 galaxies can be excluded.     

The gamma-ray observatory mission objectives and its significance for gamma-ray astronomy

The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: 1) to study the nature of compact γ-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; 2) to search for evidence of nucleosynthesis especially in the regions of supernovae; 3) to study structural features and dynamical properties of our galaxy; 4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and 5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.     

Analysis of the space radiation doses obtained simultaneously at two different locations outside the ISS

Space weather and related ionizing radiation has been recognized as one of the main health concerns for the International Space Station (ISS) crew. The estimation of the radiation effect on humans outside the ISS requires at first order accurate knowledge of their accumulated absorbed dose rates, which depend on the global space radiation distribution, solar cycle and local variations generated by the 3D mass distribution surrounding the ISS. The R3DE (Radiation Risks Radiometer-Dosimeter for the EXPOSE-E platform) on the European Technological Exposure Facility (EuTEF) worked successfully outside of the European Columbus module between February 2008 and September 2009. A very similar instrument named R3DR for the EXPOSE-R platform worked outside the Russian Zvezda module of the ISS between March 2009 and August 2010. Both are Liulin-type detectors, Bulgarian-built miniature spectrometer-dosimeters. The acquired approximately 5 million deposited energy spectra from which the flux and absorbed dose rate were calculated with 10 s resolution behind less than 0.41 g cm⁻² shielding. This paper analyses the spectra collected in 2009 by the R3DE/R instruments and the long-term variations in the different radiation environments of Galactic Cosmic Rays (GCR), inner radiation belt trapped protons in the region of the South Atlantic Anomaly (SAA) and relativistic electrons from the Outer Radiation Belt (ORB). The R3DE instrument, heavily shielded by the surrounding structures, measured smaller primary fluxes and dose rates from energetic protons from the SAA and relativistic electrons from the ORB but higher values from GCRs because of the contribution from secondary particles. The main conclusion from this investigation is that the dose rates from different radiation sources around the International Space Station (ISS) have a large special and temporal dynamic range. The collected data can be interpreted as possible doses obtained by the cosmonauts and astronauts during Extra Vehicular Activities (EVA) because the R3DE/R instruments shielding is very similar to the Russian and American space suits average shielding (,  and ). Fast, active measurements are required to assess accurately the dose accumulated by astronauts during EVA.     

R3D-B2 – Measurement of ionizing and solar radiation in open space in the BIOPAN 5 facility outside the FOTON M2 satellite

Solar and space radiation have been monitored using the R3D-B2 radiation risks radiometer-dosimeter on board a recent space flight on the Russian satellite Foton M2 within the ESA Biopan 5 facility mounted on the outside of the satellite exposed to space conditions. The solar radiation has been assayed in four wavelength bands (UV-C, 170–280 nm, UV-B, 280–315 nm), UV-A (315–400 nm) and PAR (photosynthetic active radiation, 400–700 nm). The data show an increasing tumbling rotation of the satellite during the mission. The photodiodes do not show a cosine response to the incident light which has been corrected. After calibration of the signals using the extraterrestrial spectrum, doses have been calculated for each orbit, for each day and for the total mission as basic data for the biological material which has been exposed in parallel in the Biopan facility. Cosmic ionizing radiation has been monitored and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. Basic data tables were prepared to be used by other Biopan 5 experiments. The paper summarizes the results for the Earth radiation environment at the altitude (262–304 km) of the Foton M2 spacecraft. Comparisons with the predictions of NASA Earth radiation environment experimental models AE-8 and AP-8, and the PSB97 model are also presented, which calculate the fluxes of ionizing radiation from a simulation. AP-8 is a model for trapped radiation.     

Near infrared observations of comet Halley from Vega 2

Spatial distribution of the continuum radiation in the range of 0.95–1.9 μm presumes total dust production rate of the comet of 10ρ tonne s⁻¹ (ρ is the dust material density) and its angular distribution proportional cos . Observations of the water vapor band at 1.38 μ m reveal strong jets, their time shift from the dust jet measured in situ is consistent with gas velocity of 0.82±0.1 km s⁻¹ and dust velocity of 0.55±0.08 km s⁻¹. The OH vibrational-rotational bands observed are excided directly via photolysis of water vapor. Water vapor production rate deduced from the H₂O band and OH band intensities is 8×10²⁹ s⁻¹. Intensity of the CN(0,0) band result in the CN column density of 9×10¹² cm⁻², i.e. larger by a factor of 3 than given by the violet band.     

Human response to high-background radiation environments on Earth and in space

The main long-term objective of the space exploration program is the colonization of the planets of the Solar System. The high cosmic radiation equivalent dose rate represents an inescapable problem for the safe establishment of permanent human settlements on these planets. The unshielded equivalent dose rate on Mars ranges between 100 and 200 mSv/year, depending on the Solar cycle and altitude, and can reach values as high as 360 mSv/year on the Moon. The average annual effective dose on Earth is about 3 mSv, nearly 85% of which comes from natural background radiation, reduced to less than 1 mSv if man-made sources and the internal exposure to Rn daughters are excluded. However, some areas on Earth display anomalously high levels of background radiation, as is the case with thorium-rich monazite bearing sand deposits where values 200–400 times higher than the world average can be found. About 2% of the world’s population live above 3 km and receive a disproportionate 10% of the annual effective collective dose due to cosmic radiation, with a net contribution to effective dose by the neutron component which is 3–4 fold that at sea level. Thus far, epidemiological studies have failed to show any adverse health effects in the populations living in these terrestrial high-background radiation areas (HBRA), which provide an unique opportunity to study the health implications of an environment that, as closely as possibly achievable on Earth, resembles the chronic exposure of future space colonists to higher-than-normal levels of ionizing radiation. Chromosomal aberrations in the peripheral blood lymphocytes from the HBRA residents have been measured in several studies because chromosomal damage represents an early biomarker of cancer risk. Similar cytogenetic studies have been recently performed in a cohort of astronauts involved in single or repeated space flights over many years. The cytogenetic findings in populations exposed to high dose-rate background radiation on Earth or in space will be discussed.     

Relation between galactic and solar cosmic radiation at aviation altitude

Cosmic radiation bombards us at high altitude with ionizing particles; the radiation has a galactic component, which is normally dominant, and a component of solar origin. Cosmic ray particles are the primary source of ionization in the atmosphere above 1 km; below 1 km radon is a dominant source of ionization in many areas.     

A model for predicting the radiation exposure for mission planning aboard the international space station

The International Space Station Cosmic Radiation Exposure Model (ISSCREM) has been developed as a possible tool for use in radiation mission planning as based on operational data collected with a tissue equivalent proportional counter (TEPC) aboard the ISS since 2000. It is able to reproduce the observed trapped radiation and galactic cosmic radiation (GCR) contributions to the total dose equivalent to within ±20% and ±10%, respectively, as would be measured by the onboard TEPC at the Zvezda Service Module panel 327 (SM-327). Furthermore, when these contributions are combined, the total dose equivalent that would be measured at this location is estimated to within ±10%. The models incorporated into ISSCREM correlate the GCR dose equivalent rate to the cutoff rigidity magnetic shielding parameter and the trapped radiation dose equivalent rate to atmospheric density inside the South Atlantic Anomaly. The GCR dose equivalent rate is found to vary minimally with altitude and TEPC module location however, due to the statistics and data available, the trapped radiation model could only be developed for the TEPC located at SM-327. Evidence of the variation in trapped radiation dose with detector orientation and the East–West asymmetry were observed at this location.     

Experimental investigation of transient thermal behavior of an airship under different solar radiation and airflow conditions

Knowledge of the thermal behavior of airships is crucial to the development of airship technology. An experiment apparatus is constructed to investigate the thermal response characteristics of airships, and the transient temperature distributions of both hull and inner gas are obtained under the irradiation of a solar simulator and various airflow conditions. In the course of the research, the transient temperature change of the experimental airship is measured for four airflow speeds of 0 m/s (natural convection), 3.26 m/s, 5.5 m/s and 7.0 m/s, and two incident solar radiation values of 842.4 W/m² and 972.0 W/m². The results show that solar irradiation has significant influence on the airship hull and inner gas temperatures even if the airship stays in a ground airflow environment where the heat transfer is dominated by radiation and convection. The airflow around the airship is conducive to reduce the hull temperature and temperature nonuniformity. Transient thermal response of airships rapidly varies with time under solar radiation conditions and the hull temperature remains approximately constant in ∼5–10 min. Finally, a transient thermal model of airship is developed and the model is validated through comparison with the experimental data.     

COMPTEL results on the 1.809 MeV gamma-ray line from the Galactic-center region

The COMPTEL experiment on the Compton Gamma-Ray Observatory is designed to image celestial gamma radiation in the energy range from 0.75–30 MeV within a field of view of 1 steradian. It can locate stronger point sources with an accuracy better than 0.5° and is capable of mapping diffuse emission as well. The Galactic-center region was observed by COMPTEL for several 2-week periods in 1991/1992. These observations show evidence for 1.8 MeV line emission along the Galactic disk (attributed to radioactive ²⁶Al), extending over at least 40 degrees in longitude.     

A new model for atmospheric radiation under clear sky condition at various altitudes

Atmospheric radiation is one of the major factors that dominate the thermal behaviors of aerostats. A high-performance model is needed to evaluate the atmospheric radiation. Based on the atmospheric radiation database containing 24,862 data points compiled from 7 stations with the elevation from sea level to 2373 m and the reference code MODTRAN, a new atmospheric radiation model is proposed using regression and optimization software. It has excellent prediction accuracy with the coefficient of determination of 0.94, the root mean square error of 15.1 W/m², and the mean absolute percentage error of 4.13% for the database. Comparison with the well-known existing model shows that the new model has the highest prediction accuracy. The new model predictions agree with the MODTRAN calculations at various altitudes very well, and thus it can be used for estimating the thermal performances of a high altitude aerostat.     

Asymmetric precipitation in a coronal loop as explanation of a singular observed spectrum

Almost 10 years of solar submillimeter observations have shown new aspects of solar activity, such as the presence of rapid solar spikes associated with the launch of coronal mass ejections and an increasing submillimeter spectral component in flares. We analyse the singular microwave–submillimeter spectrum of an M class solar flare on 20 December, 2002. Flux density observations measured by Sun patrol telescopes and the Solar Submillimeter Telescope are used to build the radio spectrum, which is fitted using Ramaty’s code. At submillimeter frequencies the spectrum shows a component different from the microwave classical burst. The fitting is achieved proposing two homogeneous sources of emission. This theoretical fitting is in agreement with differential precipitation through a magnetically asymmetric loop or set of loops. From a coronal magnetic field model we infer an asymmetric magnetic structure at the flare location. The model proposed to quantify the differential precipitation rates due to the asymmetry results in a total precipitation ratio Q₂/Q₁≈10⁴–10⁵, where Q₁(Q₂) represents the total precipitation in the loop foot with the high (low) magnetic field intensity. This ratio agrees with the electron total number ratio of the two sources proposed to fit the radio spectrum.     

A preliminary look at the dust in comet Halley

Highlights of infrared observations of the dust are discussed and compared with first results from the space probes. An emission feature was detected at 3.4 μm; the 10 and 20 μm silicate features were well-observed; and far-infrared data out to 160 μm were obtained. Organic material seems to be abundant in grains and may explain the 3.4 μm emission. Calculations are presented for one example of organic material. A component of the grains may volatize at temperatures around 300 K.     

Observation bio-effect of SW-global solar radiation in Ilorin in the tropics

The annual variation of global (total) solar radiation measured over four (4) years (1995–1998) at Ilorin (8°32′N, 4°34′E) was studied and the bio-effects of the variation is herein reported. The weekly averages of the solar radiation flux were obtained and plotted. The profile of the weekly averages of the insolation shows two notable “wells” corresponding to the harmattan dry season and the rainy season. It was deduced that the duration of the seasons was directly proportional to the sizes of the “wells”, while the depths of the “wells” correspond to the severity of the causes of the “wells”. The fall and rise rates of the depth of the edges of the wells are inversely proportional to the ecological effects of the variation of the radiation. The rates of decrease and increase of the radiation flux affect the depths of the “wells” and were found to be rapid and shallow for the “Harmattan Well”, and gentle and deep for the “Rain Well”. The width (duration), rate of change and depth of the “Harmattan Well” bring about stress for both animals and plants.     

Microscopic approach to analyze solar-sail space-environment effects

Near-sun space-environment effects on metallic thin films solar sails as well as hollow-body sails with inflation fill gas are considered. Analysis of the interaction of the solar radiation with the solar-sail materials is presented. This analysis evaluates worst-case solar radiation effects during solar-radiation-pressure acceleration. The dependence of the thickness of solar sail on temperature and on wavelength of the electromagnetic spectrum of solar radiation is investigated. Physical processes of the interactions of photons, electrons, protons and α-particles with sail material atoms and nuclei, and inflation fill gas molecules are analyzed. Calculations utilized conservative assumptions with the highest values for the available cross sections for interactions of solar photons, electrons and protons with atoms, nuclei and hydrogen molecules. It is shown that for high-energy photons, electrons and protons the beryllium sail is mostly transparent. Sail material will be partially ionized by solar UV and low-energy solar electrons. For a hollow-body photon sail effects including hydrogen diffusion through the solar-sail walls, and electrostatic pressure is considered. Electrostatic pressure caused by the electrically charged sail’s electric field may require mitigation since sail material tensile strength decreases with elevated temperature. It also can substitute inflation-gas pressure loss due to gas diffusion and perforation by micrometeoroids impact to keep the sail inflated.     

Solar system planets observed with Suzaku

Recent results of solar system planets observed with the Japanese X-ray astronomy satellite Suzaku are reviewed. Thanks to the low instrumental background and good energy resolution, X-ray CCDs onboard Suzaku are one of the best probes to study diffuse X-ray emission. An overview of the Suzaku data of Jupiter and Earth is presented, along with preliminary results of Mars. Firstly, diffuse hard X-ray emission is discovered in 1–5 keV at Jovian radiation belts. Its spectrum is represented by a power-law continuum with a photon index of ∼1.4. This emission could originate from inverse-Compton scattering of solar photons by tens MeV electrons. Secondly, variable diffuse soft X-rays are serendipitously found during observations in the directions of the north ecliptic pole and galactic ridge. Good time correlations with the solar wind and emission lines found in the X-ray spectra are firm evidences of a solar wind charge exchange emission with Earth’s exosphere. Thirdly, diffuse X-ray emission from Martian exosphere via the solar wind charge exchange is investigated for the first time at solar minimum. A stringent upper limit on the density of the Martian exosphere is placed from the Suzaku data.