Trapped particle energy spectrum in shuttle middeck

We describe the differential energy spectrum of trapped particles measured by a solid-state charged particle telescope in the mid-deck of the Space Shuttle during the period of solar maximum. The telescope was flown in two high altitude flights at 28.5° and 57° inclination. Assuming, as is normally done, that the variations of Shuttle orientation during the missions lead to average isotropic incident spectra, the observed spectrum disagrees significantly from AP8 model calculations. This indicates the need to take into consideration the variations of solid-angle direction relative to the magnetic field. The measurements show that there is a very significant flux of secondary light ions. The energy spectra of these ions does not agree with the production spectrum from radiation transport calculations based on omni-directional AP8 Max model as an input energy spectrum.

We also describe measurements of linear energy transfer spectra using a tissue equivalent proportional counter (TEPC) flown both in the mid-deck and the payload bay of the Space Shuttle. Comparisons are made between linear energy transfer spectral measurements AP8 model-based radiation transport predictions, and thermoluminescent dosimeter (TLD) measurements. The absorbed dose-rate measurements using TLD's are roughly 25% lower than the TEPC-measured dose rate measurements.     

Search for ultraviolet shuttle glow

The Space Shuttle Columbia flown in January 1986 carried two ultraviolet experiments (UVX) designed to observe very weak diffuse emission from various astronomical sources at wavelengths below 3200 Å with moderate spectral resolution. Such observations are extremely sensitive to the presence of any shuttle induced ultraviolet glow, since the wavelength range, 1200–3200 Å, includes strong emission lines or bands of species such as O, NO, and OH which are predicted to radiate strongly by models of the shuttle glow. The UVX spectrometers are sensitive to emission features as faint as 0.1 Rayleighs. Emissions from O₂, O and NO are detected and shown to be consistent with an atmospheric origin.     

Contribution of secondaries to the radiation environment on space missions.

Calculations to predict the radiation environment for spacecraft in low earth orbit sometimes ignore the contribution from secondary radiation products. However, the contribution of secondaries, particularly neutrons, on heavy spacecraft or in planetary bodies can be of concern for biological systems. The Shuttle Activation Monitor (SAM) and Cosmic Radiation Effects and Activation Monitor (CREAM) experiments provide valuable data on secondary (as well as primary) radiation effects. Comparisons have been made between induced activity from flight-exposed samples, induced activity in a ground-irradiated sample, and Monte Carlo-derived predictions with and without secondaries. These comparisons show that for a flight-exposed sample, predictions which omit the secondary contribution result in a spectrum that is too low by a factor of 2. The addition of the secondaries results in a predicted spectrum that closely matches the measured data.     

Centaurus A: Multiwavelength observations of the nearest active galaxy from radio to gamma-rays

Centaurus A (Cen A, NGC 5128) is the nearest active galaxy and, notably, the viewing angle with respect to the jet axis is very large (> 70°). A first contemporaneous OSSE, COMPTEL, and EGRET spectrum obtained in October 1991 covers an energy range from 50 keV up to 1 GeV. This γ-ray broad-band spectrum was taken when Cen A was in an intermediate emission state as defined by the BATSE X-ray light-curve. The first simultaneous multiwavelength spectrum from radio to γ-rays was measured in July 1995 when Cen A was in a low emission state (the prevailing state for the last 7 years). The different spatial and temporal resolution in the different frequency regimes produces problems in the construction and interpretation of the multiwavelength spectra. These are addressed in this paper. The detection of emission > 1 MeV makes the inclusion of such high-energy emission into models for the spectral energy distribution mandatory.     

Optical observations from the space shuttle

A brief survey is given of UV and visual observations made from the Space Shuttle. These include five astronomy experiments, four UV and one visual, some of which were affected by contamination originating with the Shuttle and its environment.     

Hard X-ray and metric/decimetric spatially resolvedobservations of the 10 April 2002 solar flare

The GOES M8.2 flare on 10 April 2002 at 1230 UT was observed at X-ray wavelengths by RHESSI and atmetric/decimetric wavelengths by the Nançay Radioheliograph (NRH). We discuss the temporal evolution of X-ray sources together with the evolution of the radio emission sites observed at different coronal heights by the NRH. While the first strong HXR peak at energies above 50 keV arises from energy release in compact magnetic structures (with spatial scales of a few 10⁴ km) and is not associated with strong radio emission, the second one leads to energy release in magnetic structures with scales larger than 10⁵ km and is associated with intense decimetric/metric and dekametric emissions. We discuss these observations in the context of the acceleration sites of energetic electrons interacting at the Sun and of escaping ones.     

Effects of increased shielding on gamma-radiation levels within spacecraft.

The Shuttle Activation Monitor (SAM) experiment was flown on the Space Shuttle Columbia (STS-28) from 8-13 August, 1989 in a 57 degrees, 300 km orbit. One objective of the SAM experiment was to determine the relative effect of different amounts of shielding on the gamma-ray backgrounds measured with similarly configured sodium iodide (NaI) and bismuth germante (BGO) detectors. To achieve this objective twenty-four hours of data were taken with each detector in the middeck of the Shuttle on the ceiling of the airlock (a high-shielding location) as well as on the sleep station wall (a low-shielding location). For the cosmic-ray induced background the results indicate an increased overall count rate in the 0.2 to 10 MeV energy range at the more highly shielded location, while in regions of trapped radiation the low shielding configuration gives higher rates at the low energy end of the spectrum.     

Morphology of OI 8446 Å dayglow emission

A comprehensive model is developed to study the atomic oxygen OI 8446 Å dayglow emission. The emission rate profiles and intensities are obtained using the recently developed Solar2000 EUV (Extreme Ultra Violet) flux model. These emission profiles are used to construct the morphology of the 8446 Å emission between equator and 45°N in the northern hemisphere. The longitudinal variation of 8446 Å dayglow emission is found about 5% and is not included in the presentation of morphology. A span of five years is chosen to study the effect of varying solar activity on the morphology of the OI 8446 Å dayglow emission. The morphology is studied on April 3 which lies under the equinox conditions. In year 2001 the solar F10.7 index on the chosen date was as high as 223.1 which is the case of solar maximum. From the present calculations it is found that the intensity does not vary linearly with the F10.7 solar index. The morphology shows that the region of maximum emission rate expands towards the higher latitudes as F10.7 solar index increases. The similar effects have also been found in the morphology of 7320 Å dayglow emission (Sunil Krishna and Singh, 2009). The similarities in the morphology of 7320 Å and 8446 Å dayglow emissions further suggest that the photoelectron flux has strong bearing on the production of these emissions.     

Solar radio emissions

In this paper, we present a tutorial review which was presented at the first Advanced School on Space Environment (ASSE 2004). We first describe the basics of radioastronomy definitions, and discuss radiation processes relevant to solar radio emissions like plasma emission, free–free bremsstrählung and gyromagnetic emissions. We illustrate these fundamentals by describing recent solar radio observations and the constraints they bring on different solar physical parameters. We focus on solar radio emissions from the quiet sun, active regions and during explosive events known as solar flares, and how the latter can bring quantitative informations on the particles responsible for the emission. Finally, particular attention is paid to new radio diagnostics obtained at very high frequencies in the millimeter/submillimeter range, as well as to radio emissions relevant to Space Weather studies.     

NASA' s life sciences and space radiation biology.

Plans for the various missions in which men and women are expected to participate during the next 10 years are outlined. Such missions include flights of up to three months duration in low earth orbit as well as possible short excursions to geosynchronous orbit. Research activities are described which cover the full spectrum of physiological and psychological responses to space flight. These activities are shown to contribute to the ongoing Shuttle program and the future Space Station. The paper includes a summary of the major technical thrusts needed to support extended habitation in space.     

Secondary radiation environments in heavy space vehicles and instruments.

Secondary radiations produced by the interactions of primary cosmic rays and trapped protons with spacecraft materials and detectors provides an important, and sometimes dominant, radiation environment for sensitive scientific instruments and biological systems. In this paper the success of a number of calculations in predicting a variety of effects will be examined. The calculation techniques include Monte Carlo transport codes and semi-empirical fragmentation calculations. Observations are based on flights of the Cosmic Radiation Environment and Activation Monitor at a number of inclinations and altitudes on Space Shuttle. The Shuttle experiments included an active cosmic-ray detector as well as metal activation foils and passive detector crystals of sodium iodide which were counted for induced radioactivity soon after return to earth. Results show that cosmic-ray secondaries increase the fluxes of particles of linear energy transfer less than 200 MeV/(gm cm-2), while the activation of the crystals is enhanced by about a factor of three due to secondary neutrons. Detailed spectra of induced radioactivity resulting from spallation products have been obtained. More than a hundred significant radioactive nuclides are included in the calculation and overall close agreement with the observations is obtained.     

Description, analysis and impact of major solar activity during recent U.S. Shuttle missions.

Since STS-26, three large solar events have occurred during Shuttle missions; a geomagnetic storm during STS-29 and solar particle events (SPEs) during STS-28 and -34. The maximum dose to a crew attributed to an SPE was estimated to be 30 microGy (70 microSv). Time-resolved dosimetry measurements of the SPE dose during STS-28 were made using the Air Force Radiation Monitoring Equipment (RME)-III. Comparison of calculated and measured dose demonstrated a discrepancy, possibly a result of deficiencies in the geomagnetic cutoff model used. This experience demonstrates that dose from an SPE is strongly dependent on numerous factors such as orbit inclination, SPE start time, spectral parameters and geomagnetic field conditions; the exact combination of these factors is fortuitous. New sources of data and procedures are being investigated, including real-time tracking of auroral oval positions or determination of particle cutoff latitudes, for incorporation into operational Shuttle radiation support practices.     

Infrared observations of contaminants from shuttle flight 51-F

A small helium cooled infrared telescope, IRT, was flown on the Shuttle in July/August 1985. The principle astrophysical objectives were to measure the large scale structure of sources and the background radiation. A cold shutter was incorporated to permit absolute flux measurements. Additionally, the engineering objectives included setting upper limits on the infrared radiation from the local environment. Even though the local background overwhelmed the astrophysical background, astronomical sources were still detectable superimposed on this background radiation. Data are presented covering the spectral range from 2μm to 120μm. The spatial, spectral and temporal variations are described. Based on the spectral character and variability in different wavelength bands, the background radiation does not appear to have a single origin. In this paper the results on the Shuttle environment will be presented. The astrophysical results will be presented elsewhere.     

Radiation measurements on the flight of IML-2.

The second flight of the International Microgravity Laboratory (IML-2) on Space Shuttle flight STS-65 provided a unique opportunity for the intercomparison of a wide variety of radiation measurement techniques. Although this was not a coordinated or planned campaign, by sheer chance, a number of space radiation experiments from several countries were flown on this mission. There were active radiation measuring instruments from Japan and US, and passive detectors from US, Russia, Japan, and Germany. These detectors were distributed throughout the Space Shuttle volume: payload bay, middeck, flight deck, and Spacelab. STS-65 was launched on July 8, 1994, in a 28.45 degrees x 306 km orbit for a duration of 14 d 17 hr and 55 min. The crew doses varied from 0.935 mGy to 1.235 mGy. A factor of two variation was observed between various passive detectors mounted inside the habitable Shuttle volume. There is reasonable agreement between the galactic cosmic ray dose, dose equivalent and LET spectra measured by the tissue equivalent proportional counter flown in the payload bay with model calculations. There are significant differences in the measurements of LET spectra measured by different groups. The neutron spectrum in the 1-20 MeV region was measured. Using fluence-dose conversion factors, the neutron dose and dose equivalent rates were 11 +/- 2.7 microGy/day and 95 +/- 23.5 microSv/day respectively. The average east-west asymmetry of trapped proton (>3OMeV) and (>60 MeV) dose rate was 3.3 and 1.9 respectively.     

Recent observations of the very low frequency interplanetary radio emission

Observations of radio emissions in the frequency range of 2 to 3 kHz have been made in the distant heliosphere by the Voyager 1 and 2 plasma wave instruments. Based primarily on wideband observations made periodically throughout the cruise phases of the missions the radio emission, first observed in 1982, appears to have been present almost continuously since 1983. The spectrum is complex, usually showing two peaks, one near 2 and another near 3 kHz. Occasionally, only one of the peaks is observed. A possible source for the radio emissions is the terminal shock in the outer heliosphere.     

BBXRT observations of supernova remnants

The Broad Band X-Ray Telescope (BBXRT) was designed to perform sensitive, moderate resolution spectroscopy of cosmic X-ray sources in the 0.3–10 keV band from the Space Shuttle. During its nine-day flight in December, 1990, the BBXRT observed a variety of supernova remnants and related objects. We present results from some of these observations, emphasizing the ability of the BBXRT to perform spatially-resolved spectroscopy. The improved spectral resolution and efficiency over previous instruments makes possible measurements of previously undetectable lines, and the broad bandpass allows simultaneous measurements of lines from oxygen through iron.     

The nature of nonthermal X-ray filaments near the galactic center

Recent Chandra and XMM-Newton observations reported evidence of two X-ray filaments G359.88−0.08 (SgrA-E) and G359.54+0.18 (the ripple filament) near the Galactic center. The X-ray emission from these filaments has a nonthermal spectrum and coincides with synchrotron emitting radio sources. Here, we report the detection of a new X-ray feature coincident with a radio filament G359.90−0.06 (SgrA-F) and show more detailed VLA, Chandra and BIMA observations of the radio and X-ray filaments. In particular, we show that radio emission from the nonthermal filaments G359.90−0.06 (SgrA-F) and G359.54+0.18 (the ripple) has a steep spectrum whereas G359.88−0.08 (SgrA-E) has a flat spectrum. The X-ray emission from both these sources could be due to synchrotron radiation. However, given that the 20 km s⁻¹ molecular cloud, with its intense 1.2 mm dust emission, lies in the vicinity of SgrA-F, it is possible that the X-rays could be produced by inverse Compton scattering of far-infrared photons from dust by the relativistic electrons responsible for the radio synchrotron emission. The production of X-ray emission from ICS allows an estimate of the magnetic field strength of 0.08 mG within the nonthermal filament. This should be an important parameter for any models of the Galactic center nonthermal filaments.     

Planned NASA space infrared astronomy experiments

A summary is presented of the present status of the NASA space infrared astronomy program. Projects described include the Infrared Astronomy Satellite (IRAS), Small Infrared Telescope on Spacelab 2 (IRT), Cosmic Background Explorer (COBE), Shuttle Infrared Telescope Facility (SIRTF), Space Telescope (ST), and the Large Deployable Reflector (LDR). The important technical developments achieved in these programs are also discussed, as well as critical needs for future missions.