Investigation of the role of aziridine bonding agents on the aging of the composite solid rocket propellant(CSRP)

The role of bonding agents on the aging characteristics is one of the important research topics.Aging program of the prepared propellant samples was conducting as follows:Five samples,two free of bonding agents,and three containing an aziridine based bonding agents(MAPO,HX-752,MAT4),four samples based on different bonding and curing agents all were aged at 70 ℃.The prepared bonding agent "MAT4" gave remarkable improvements and resulted in highly stable mechanical properties comparing with HX-752 or MAPO.The selected bonding agents family inhibited the rate of decomposition of the propellants during the aging periods and supported the propellant matrix against decomposition at the elevated temperatures.      

The Plasma and Suprathermal Ion Composition (PLASTIC) Investigation on the STEREO Observatories

The Plasma and Suprathermal Ion Composition (PLASTIC) investigation provides the in situ solar wind and low energy heliospheric ion measurements for the NASA Solar Terrestrial Relations Observatory Mission, which consists of two spacecraft (STEREO-A, STEREO-B). PLASTIC-A and PLASTIC-B are identical. Each PLASTIC is a time-of-flight/energy mass spectrometer designed to determine the elemental composition, ionic charge states, and bulk flow parameters of major solar wind ions in the mass range from hydrogen to iron. PLASTIC has nearly complete angular coverage in the ecliptic plane and an energy range from ～0.3 to 80 keV/e, from which the distribution functions of suprathermal ions, including those ions created in pick-up and local shock acceleration processes, are also provided.     

The THEMIS Array of Ground-based Observatories for the Study of Auroral Substorms

The NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) project is intended to investigate magnetospheric substorm phenomena, which are the manifestations of a basic instability of the magnetosphere and a dominant mechanism of plasma transport and explosive energy release. The major controversy in substorm science is the uncertainty as to whether the instability is initiated near the Earth, or in the more distant >20 Re magnetic tail. THEMIS will discriminate between the two possibilities by using five in-situ satellites and ground-based all-sky imagers and magnetometers, and inferring the propagation direction by timing the observation of the substorm initiation at multiple locations in the magnetosphere. An array of stations, consisting of 20 all-sky imagers (ASIs) and 30-plus magnetometers, has been developed and deployed in the North American continent, from Alaska to Labrador, for the broad coverage of the nightside magnetosphere. Each ground-based observatory (GBO) contains a white light imager that takes auroral images at a 3-second repetition rate (“cadence”) and a magnetometer that records the 3 axis variation of the magnetic field at 2 Hz frequency. The stations return compressed images, “thumbnails,” to two central databases: one located at UC Berkeley and the other at the University of Calgary, Canada. The full images are recorded at each station on hard drives, and these devices are physically returned to the two data centers for data copying. All data are made available for public use by scientists in “browse products,” accessible by using internet browsers or in the form of downloadable CDF data files (the “browse products” are described in detail in a later section). Twenty all-sky imager stations are installed and running at the time of this publication. An example of a substorm was observed on the 23rd of December 2006, and from the THEMIS GBO data, we found that the substorm onset brightening of the equatorward arc was a gradual process (>27 seconds), with minimal morphology changes until the arc breaks up. The breakup was timed to the nearest frame (<3 s) and located to the nearest latitude degree at about ±3^oE in longitude. The data also showed that a similar breakup occurred in Alaska ～10 minutes later, highlighting the need for an array to distinguish prime onset.     

New Horizons: Anticipated Scientific Investigations at the Pluto System

The New Horizons spacecraft will achieve a wide range of measurement objectives at the Pluto system, including color and panchromatic maps, 1.25–2.50 micron spectral images for studying surface compositions, and measurements of Pluto’s atmosphere (temperatures, composition, hazes, and the escape rate). Additional measurement objectives include topography, surface temperatures, and the solar wind interaction. The fulfillment of these measurement objectives will broaden our understanding of the Pluto system, such as the origin of the Pluto system, the processes operating on the surface, the volatile transport cycle, and the energetics and chemistry of the atmosphere. The mission, payload, and strawman observing sequences have been designed to achieve the NASA-specified measurement objectives and maximize the science return. The planned observations at the Pluto system will extend our knowledge of other objects formed by giant impact (such as the Earth–moon), other objects formed in the outer solar system (such as comets and other icy dwarf planets), other bodies with surfaces in vapor-pressure equilibrium (such as Triton and Mars), and other bodies with N₂:CH₄ atmospheres (such as Titan, Triton, and the early Earth).     

Ionospheric response of equatorial and low latitude F-region during the intense geomagnetic storm on 24–25 August 2005

In this investigation, we present and discuss the response of the ionospheric F-region in the South American and East Asian sectors during an intense geomagnetic storm in August 2005. The geomagnetic storm studied reached a minimum Dst of −216 nT at 12:00 UT on 24 August. In this work ionospheric sounding data obtained of 24, 25, and 26 August 2005 at Palmas (PAL; 10.2° S, 48.2° W; dip latitude 6.6° S), São José dos Campos (SJC, 23.2° S, 45.9° W; dip latitude 17.6° S), Brazil, Ho Chi Minh City, (HCM; 10.5° N, 106.3° E; dip latitude 2.9° N), Vietnam, Okinawa (OKI; 26.3° N, 127.8° E; dip latitude 21.2° N), Japan, are presented. Also, the GPS observations obtained at different stations in the equatorial and low-latitude regions in the Brazilian sector are presented. On the night of 24–25 August 2005, the h′F variations show traveling ionospheric disturbances associated with Joule heating in the auroral zone from SJC to PAL. The foF2 variations show a positive storm phase on the night of 24–25 August at PAL and SJC during the recovery phase. Also, the GPS-VTEC observations at several stations in the Brazilian sector show a fairly similar positive storm phase on 24 August. During the fast decrease of Dst (between 10:00 and 11:00 UT) on 24 August, there is a prompt penetration of electric field of magnetospheric origin that result in abrupt increase (∼12:00 UT) in foF2 at PAL, SJC (Brazil) and OKI (Japan) and in VTEC at IMPZ, BOMJ, PARA and SMAR (Brazil). OKI showed strong oscillations of the F-region on the night 24 August resulted to the propagation of traveling atmospheric disturbances (TADs) by Joule heating in the auroral region. These effects result a strong positive observed at OKI station. During the daytime on 25 August, in the recovery phase, the foF2 observations showed positive ionospheric storm at HCM station. Some differences in the latitudinal response of the F-region is also observed in the South American and East Asian sectors.     

GNSS single frequency ionospheric range delay corrections: NeQuick data ingestion technique

A study of the performance of the NeQuick model and the Klobuchar model for GNSS single frequency range delay correction on a global scale was done using data for moderate solar activity. In this study NeQuick was used in the way intended for Galileo. This study is to assess the performance of the two models at each ionospheric geographic region during moderate solar activity as previously published studies were concentrated only on high solar activity. The results obtained showed that NeQuick outperformed Klobuchar for the whole year at the three geographical regions of the ionosphere. In terms of monthly root mean square of mismodeling, NeQuick outperformed Klobuchar by 15 TECU or more at low-latitudes, 5 TEC or more at mid-latitudes, and 1 TECU or more at high-latitudes.     

Digital signal processing and numerical analysis for radar in geophysical applications

Numerical solutions for signal processing are described in this work as a contribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar’s range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated.     

Testing the three-dimensional IRI-SIRMUP-P mapping of the ionosphere for disturbed periods

This paper describes the three-dimensional (3-D) electron density mapping of the ionosphere given as output by the assimilative IRI-SIRMUP-P (ISP) model for three different geomagnetic storms. Results of the 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at two testing ionospheric stations: Roquetes (40.8°N, 0.5°E), Spain, and San Vito (40.6°N, 17.8°E), Italy. The reference ionospheric stations from which the autoscaled foF2 and M(3000)F2 data as well as the real-time vertical electron density profiles are assimilated by the ISP model are those of El Arenosillo (37.1°N, 353.3°E), Spain, Rome (41.8°N, 12.5°E), and Gibilmanna (37.9°N, 14.0°E), Italy. Overall, the representation of the ionosphere made by the ISP model is better than the climatological representation made by only the IRI-URSI and the IRI-CCIR models. However, there are few cases for which the assimilation of the autoscaled data from the reference stations causes either a strong underestimation or a strong overestimation of the real conditions of the ionosphere, which is in these cases better represented by only the IRI-URSI model. This ISP misrepresentation is mainly due to the fact that the reference ionospheric stations covering the region mapped by the model turn out to be few, especially for disturbed periods when the ionosphere is very variable both in time and in space and hence a larger number of stations would be required. The inclusion of new additional reference ionospheric stations could surely smooth out this concern.     

Design and performance of a vacuum-UV simulator for material testing under space conditions

This paper describes the construction and performance of a VUV-simulator that has been designed to study degradation of materials under space conditions. It is part of the Complex Irradiation Facility at DLR in Bremen, Germany, that has been built for testing of material under irradiation in the complete UV-range as well as under proton and electron irradiation. Presently available UV-sources used for material tests do not allow the irradiation with wavelengths smaller than about 115 nm where common Deuterium lamps show an intensity cut-off. The VUV-simulator generates radiation by excitation of a gas-flow with an electron beam. The intensity of the radiation can be varied by manipulating the gas-flow and/or the electron beam.