The ORGANIC experiment on EXPOSE-R on the ISS: Flight sample preparation and ground control spectroscopy

In March of 2009, the ORGANIC experiment integrated into the European multi-user facility EXPOSE-R, containing experiments dedicated to Astrobiology, was mounted through Extra Vehicular Activity (EVA) externally on the International Space Station (ISS). The experiment exposed organic samples of astronomical interest for a duration of 97 weeks (∼22 months) to the space environment. The samples that were returned to Earth in spring 2011, received a total UV radiation dose during their exposure including direct solar irradiation of >2500 h, exceeding the limits of laboratory simulations. We report flight sample preparation and pre-flight ultraviolet–visible (UV–Vis) characterization of the ORGANIC samples, which include 11 polycyclic aromatic hydrocarbons (PAHs) and three fullerenes. The corresponding time-dependent ground control monitoring experiments for ORGANIC measured over ∼19 months are presented and the results anticipated upon return of the samples are discussed. We present the first UV–Vis spectrum of solid circobiphenyl (C₃₈H₁₆). Further, we present the first published UV–Vis spectra of diphenanthro[9,10-b′,10′-d]thiophene (C₂₈H₁₆S), dinaphtho[8,1,2-abc,2′,1′,8′-klm]coronene (C₃₆H₁₆), tetrabenzo[de,no,st,c′d′]heptacene (C₄₂H₂₂), and dibenzo[jk,a′b′]octacene (C₄₀H₂₂) in solid phase and in solution. The results of the ORGANIC experiment are expected to enhance our knowledge of the evolution and degradation of large carbon-containing molecules in space environments.     

Comparison of the transport codes HZETRN,HETC and FLUKA for a solar particle event

The protection of astronauts and instrumentation from galactic cosmic rays and solar particle events is one of the primary constraints associated with mission planning in low earth orbit or deep space. To help satisfy this constraint, several computational tools have been developed to analyze the effectiveness of various shielding materials and structures exposed to space radiation. These tools are now being carefully scrutinized through a systematic effort of verification, validation, and uncertainty quantification. In this benchmark study, the deterministic transport code HZETRN is compared to the Monte Carlo transport codes HETC-HEDS and FLUKA for a 30 g/cm² water target protected by a 20 g/cm² aluminum shield exposed to a parameterization of the February 1956 solar particle event. Neutron and proton fluences as well as dose and dose equivalent are compared at various depths in the water target. The regions of agreement and disagreement between the three codes are quantified and discussed, and recommendations for future work are given.     

Error Probabilities in PCM/FM with Phase-Lock Loop Discriminators

Previous literature has analyzed PCM/FM telemetry systems using idealized FM demodulators at the receiver. However, in many systems operating today, phase-lock loop demodulators are employed which depart noticeably from ideal operation as the loop falls ?out of lock.? In this paper an approximate expression for error probability is derived, which clearly indicates the effect of the loop on the previously published data using ideal discriminators. It is shown that the presence of the loop becomes apparent at input signal-to-noise ratios below approximately 3.5 dB, while the amount of error increase over the ideal case depends, to a large extent, upon the shape of IF filtering being used.     

Future Commercial Directions in Environmental Remote Sensing from Space

Potential developments are considered for commercial applications of environmental remote sensing from space. The key areas affecting the possible growth of commercial markets that apply the sciences of meteorology, oceanography, and hydrology are discussed and projections made for 1985-2000. These areas include technology developments, markets, fiscal issues, political/legal/regulatory issues, and others. The growth will not be primarily limited by technology, but important uncertainties exist in the fiscal, political, and market development areas. With proper definition of government and commercial roles, both sectors can continue to maintain U. S. leadership in this area.     

Solar Ultraviolet Bursts

The term “ultraviolet (UV) burst” is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016–2017.     

The X-Ray Spectrometer on the MESSENGER Spacecraft

NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12° field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes XRS’s science objectives, technical design, calibration, and mission observation strategy.     

The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft

The Energetic Particle and Plasma Spectrometer (EPPS) package on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury is composed of two sensors, the Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma Spectrometer (FIPS). EPS measures the energy, angular, and compositional distributions of the high-energy components of the in situ electrons (>20 keV) and ions (>5 keV/nucleon), while FIPS measures the energy, angular, and compositional distributions of the low-energy components of the ion distributions (<50 eV/charge to 20 keV/charge). Both EPS and FIPS have very small footprints, and their combined mass (∼3 kg) is significantly lower than that of comparable instruments.     

Investigations of irregularities in remote plasma regions by radio sounding: applications of the radio plasma imager on image

The Radio Plasma Imager (RPI) on the IMAGE mission operates like a radar by transmitting and receiving coherent electromagnetic pulses. The RPI is designed to receive mirror-like (specular) reflections and coherent scatter returns. Long-range echoes of electromagnetic sounder waves are reflected at remote plasma cutoffs. Thus, analyses of RPI observations will yield the plasma parameters and distances to the remote reflection points. The RPI will employ pulse compression and spectral integration techniques, perfected in ground-based ionospheric digital sounders, in order to enhance the signal-to-noise ratio in long-range magnetospheric sounding. When plasma irregularities exist in the remote magnetospheric plasmas being probed by the sounder waves, echo signatures may become complicated. Experience in ionospheric sounding under such conditions indicates that sounding echo strengths can actually be enhanced by the presence of irregularities, and ground-based sounding indicates that coherent detection techniques can still be employed. In this paper we investigate the conditions that will allow coherent signals to be detected by the RPI and the signatures of scattering to be expected in the presence of multi-scale irregularities. Sounding of irregular plasma structures in the plasmasphere, plasmapause and magnetopause are also discussed.