Influence of solar-geomagnetic disturbances on SABER measurements of 4.3 μm emission and the retrieval of kinetic temperature and carbon dioxide

Thermospheric infrared radiance at 4.3 μm is susceptible to the influence of solar-geomagnetic disturbances. Ionization processes followed by ion-neutral chemical reactions lead to vibrationally excited NO⁺ (i.e., NO⁺(v)) and subsequent 4.3 μm emission in the ionospheric E-region. Large enhancements of nighttime 4.3 μm emission were observed by the TIMED/SABER instrument during the April 2002 and October–November 2003 solar storms. Global measurements of infrared 4.3 μm emission provide an excellent proxy to observe the nighttime E-region response to auroral dosing and to conduct a detailed study of E-region ion-neutral chemistry and energy transfer mechanisms. Furthermore, we find that photoionization processes followed by ion-neutral reactions during quiescent, daytime conditions increase the NO⁺ concentration enough to introduce biases in the TIMED/SABER operational processing of kinetic temperature and CO₂ data, with the largest effect at summer solstice. In this paper, we discuss solar storm enhancements of 4.3 μm emission observed from SABER and assess the impact of NO⁺(v) 4.3 μm emission on quiescent, daytime retrievals of Tk/CO₂ from the SABER instrument.     

Pseudo-tomographic X-ray imaging for use in aviation security

This paper presents recent results obtained from a 3-D image modelling technique utilising line-scan X-ray equipment. The resultant images have properties similar to those obtained from a volume rendered X-ray computed tomography (CT) system     

Radioisotope detection and identification at high speeds using passive sensors

A network of radiation sensors for the protection of a military base against radiological/nuclear threats has been integrated in a testbed. Two key subsystems of this network are the array of sensitive radiation detectors and the subsystem for notifying the operators of radiation events. The alarm/alert notification subsystem automatically issues notifications to the command post in real-time. The resulting reporting to the command post appears to be adequate for non-technical operational personnel. The CONOPS for the protection system relies on the sensitive detection and identification of all radioactive sources well before the transporting vehicles reach the base gates. This is a unique feature of this protection system. Discriminating sodium-iodide detectors, in conjunction with plastic scintillators and neutron detectors comprise a high-performance detection subsystem. The use of various correlation techniques has permitted the demonstration of the detection of source strengths of tens of /spl mu/Ci moving at highway speeds and at several meters separation. A companion algorithm identifies the detected radioisotope when sufficient counts are available.     

Can a double component outflow explain the X-ray and optical lightcurves of Swift Gamma-Ray Bursts?

An increasing sample of Gamma-Ray Bursts (GRBs) observed by Swift show evidence of ‘chromatic breaks’, i.e. breaks that are present in the X-ray but not in the optical. We find that in a significant fraction of these GRB afterglows the X-ray and the optical emission cannot be produced by the same component. We propose that these afterglow lightcurves are the result of a two-component jet, in which both components undergo energy injection for the whole observation and the X-ray break is due to a jet break in the narrow outflow. Bursts with chromatic breaks also explain another surprising finding, the paucity of late achromatic breaks. We propose a model that may explain the behaviour of GRB emission in both X-ray and optical bands. This model can be a radical and noteworthy alternative to the current interpretation for the ‘canonical’ XRT and UVOT lightcurves, and it bears fundamental implications for GRB physics.     

Rosetta: The ESA comet rendezvous mission

Rosetta was selected in November 1993 for the ESA Cornerstone 3 mission, to be launched in 2003, dedicated to the exploration of the small bodies of the solar system (asteroids and comets). Following this selection, the Rosetta mission and its spacecraft have been completely reviewed: this paper presents the studies performed the proposed mission and the resulting spacecraft design.

Three mission opportunities have been identified in 2003–2004, allowing rendezvous with a comet. From a single Ariane 5 launch, the transfer to the comet orbit will be supported by planetary gravity assists (two from Earth, one from Venus or Mars); during the transfer sequence, two asteroid fly-bys will occur, allowing first mission science phases. The comet rendezvous will occur 8–9 years after launch; Rosetta will orbit around the comet and the main science mission phase will take place up to the comet perihelion (1–2 years duration).

The spacecraft design is driven (i) by the communication scenario with the Earth and its equipment, (ii) by the autonomy requirements for the long cruise phases which are not supported by the ground stations, (iii) by the solar cells solar array for the electrical power supply and (iv) by the navigation scenario and sensors for cruise, target approach and rendezvous phases. These requirements will be developed and the satellite design will be presented.     

Effect of Multi-wall System Composition on Survivability for Spacecraft Impacted by Orbital Debris

Long-duration spacecraft in low earth orbit such as the International Space Station (ISS) are highly susceptible to high-speed impacts by pieces of debris from past earth-orbiting missions. Among the hazards that accompany the penetration of a pressurized manned spacecraft are critical crack propagation in the module wall, crew hypoxia, and uncontrolled thrust due to air rushing out of the module wall hole. A Monte Carlo simulation tool was used to determine the effect of spacecraft wall construction on the survivability of ISS modules and crew following an orbital debris penetration. The simulation results indicate that enhanced shield wall designs (i.e., multi-wall systems with heavier inner bumpers) always lead to higher overall survivability of the station and crew due to an overwhelming decrease in likelihood of module penetration. The results of the simulations also indicate that changes in crew operations, equipment locations, and operation procedures can significantly reduce the likelihood of crew or station loss following an orbital debris penetration.     

Reliability Technology to Achieve Insertion of Advanced Packaging(RELTECH) program

A joint military-commercial effort to evaluate multichip module (MCM) structures is discussed. The program, Reliability Technology to Achieve Insertion of Advanced Packaging (RELTECH), has been designed to identify the failure mechanisms that are possible in MCM structures. The RELTECH test vehicles, technical assessment task, product evaluation plan, reliability modeling task, accelerated and environmental testing, and post-test physical analysis and failure analysis are described. The information obtained through RELTECH can be used to address standardization issues, through development of cost effective qualification and appropriate screen criteria, for inclusion into a commercial specification and the MIL-H-38534 general specification for hybrid microcircuits     

Study of the radiation fields in LEO with the Space Application of Timepix Radiation Monitor (SATRAM)

We present the analysis of data taken by the Space Application of Timepix Radiation Monitor (SATRAM). It is centred on a Timepix detector (300?$\mathrm{\mu }$m thick silicon sensor, pixel pitch 55?$\mathrm{\mu }$m, 256?×?256 pixels). It was flown on Proba-V, an Earth observing satellite of the European Space Agency (ESA) from an altitude of 820?km on a sun-synchronous orbit, launched on May 7, 2013. A Monte Carlo simulation was conducted to determine the detector response to electrons (0.5–7?MeV) and protons (10–400?MeV) in an omnidirectional field taking into account the shielding of the detector housing and the satellite. With the help of the simulation, a strategy was developed to separate electrons, protons and ions in the data. The measured dose rate and stopping power distribution are presented as well as SATRAM’s capability to measure some of the stronger events in Earth’s magnetosphere. The stopping power, the cluster height and the shape of the particle tracks in the sensor were used to separate electrons, protons and ions. The results are presented as well. Finally, the pitch angles for a short period of time were extracted from the data and corrected with the angular response determined by the simulation.     

Radar System Design for Track-While-Scan

The problem of selecting search radar system parameters to achieve desired track-while-scan performance is investigated at a fundamental theoretical level. The vehicle being tracked is modeled as an object traveling at a random velocity along a random highway. The radar is modeled as a noisy sampler which occassionally drops samples. The best achievable tracking performance in a least-squares error sense of this vehicle/sampler combination is analyzed in general and for a variety of specific situations.