RAPID – The Imaging Energetic Particle Spectrometer on Cluster

The RAPID spectrometer (Research with Adaptive Particle Imaging Detectors) for the Cluster mission is an advanced particle detector for the analysis of suprathermal plasma distributions in the energy range from 20–400 keV for electrons, 40 keV–1500 keV (4000 keV) for hydrogen, and 10 keV nucl^-1–1500 keV (4000 keV) for heavier ions. Novel detector concepts in combination with pin-hole acceptance allow the measurement of angular distributions over a range of 180° in polar angle for either species. Identification of the ionic component (particle mass A) is based on a two-dimensional analysis of the particle's velocity and energy. Electrons are identified by the well-known energy-range relationship. Details of the detection techniques and in-orbit operations are described. Scientific objectives of this investigation are highlighted by the discussion of selected critical issues in geospace.     

The Voyager Interstellar Mission

The Voyager Interstellar Mission began on January 1, 1990, with the primary objective being to characterize the interplanetary medium beyond Neptune and to search for the transition region between the interplanetary medium and the interstellar medium. At the start of this mission, the two Voyager spacecraft had already been in flight for over twelve years, having successfully returned a wealth of scientific information about the planetary systems of Jupiter, Saturn, Uranus, and Neptune, and the interplanetary medium between Earth and Neptune. The two spacecraft have the potential to continue returning science data until around the year 2020. With this extended operating lifetime, there is a high likelihood of one of the two spacecraft penetrating the termination shock and possibly the heliopause boundary, and entering interstellar space before that time. This paper describes the Voyager Interstellar Mission--the mission objectives, the spacecraft and science payload, the mission operations system used to support operations, and the mission operations strategy being used to maximize science data return even in the event of certain potential spacecraft subsystem failures. The implementation of automated analysis tools to offset and enable reduced flight team staffing levels is also discussed.     

FlexRay in aerospace and safety-sensitive systems

The FlexRay field bus has potential for integrating existing networks and as a shared local sub-system network in the next generation of airplanes - leveraging a low-cost, dependable bus designed for the automotive domain. Herein, we present an overview of FlexRay and investigate FlexRay's dependability for use as a field bus in the aerospace domain. FlexRay supports all major requirements for integrating systems on a single network, if controllers are deployed with a guardian to achieve good hardware fault coverage. Despite including a guardian, some vulnerability may remain, such as software-induced failures and physical layer properties.     

Observation of an outburst from the X-ray pulsator 0115+63

The Ariel 6 X-ray instruments observed 0115+63 during 1980 December 16–30, when the mean flux was 150 millicrab. Analysis of the 3.6s pulsations given a refined orbital period of 24.3155 ± 0.0002 days and a periastron angle of 47°. 15 ± 0°.13, setting a limit on the rate of advance of periastron since 1978 of 0.11 yr^–1. During the observation the pulse period was decreasing faster than during the 1978 outburst, but in the 3 year interval there had been a spin down.     

International space station: : Ready to fly

The International Space Station (ISS) is no longer a paper program, focused on design, development and planning. It is an operational program, with hardware soon to be launched and ground systems in place. Additional modules, components and elements are now under construction in almost all of the 16 ISS International Partner and Participant countries, with metal being bent, software being written, and testing ongoing. Crew members for the first four crews are in training in the U.S. and Russia, with the first crew launching in mid 1999. Mission control centers are fully functioning in Houston and Moscow, with operations centers in St. Hubert, Darmstadt, Tsukuba, Turino, and Huntsville going on line as they are required.

The International Space Station, as the largest international civil program in history, features unprecedented technical, managerial, and international complexity. Seven international partners and participants encompassing 15 countries are involved in the ISS. Each partner is contributing and will be operating separate pieces of hardware, to be integrated on-orbit into a single orbital station. Mission control centers, launch vehicles, astronauts/cosmonauts, and support services will be provided by partners across the globe, but must function in a coordinated, integrated fashion. This paper will review the accomplishments of the ISS Program and each of the Partners and Participants over the past year, focusing on completed milestones and hardware. It will also give a status report on the development of the remainder of the ISS modules and components by each Partner and Participant, and discuss upcoming challenges.     

A review of global satellite-derived snow products

Snow cover over the Northern Hemisphere plays a crucial role in the Earth’s hydrology and surface energy balance, and modulates feedbacks that control variations of global climate. While many of these variations are associated with exchanges of energy and mass between the land surface and the atmosphere, other expected changes are likely to propagate downstream and affect oceanic processes in coastal zones. For example, a large component of the freshwater flux into the Arctic Ocean comes from snow melt. The timing and magnitude of this flux affects biological and thermodynamic processes in the Arctic Ocean, and potentially across the globe through their impact on North Atlantic Deep Water formation.     

Second generation prototype design and testing for a high altitude Venus balloon

This paper describes the development of a second generation prototype balloon intended for flight in the upper atmosphere of Venus. The design of this new prototype incorporates lessons learned from the construction and testing of the first generation prototype, including finite element analyses of the balloon stresses and deformations, measured leak performance after handling and packaging, permeability and optical property measurements on material samples, and sulfuric acid testing. An improved design for the second generation prototype was formulated based on these results, although the spherical shape and 5.5 m diameter size were retained. The resulting balloon has a volume of 87 m³ and is capable of carrying a 45 kg payload at a 55 km altitude at Venus. The design and fabrication of the new prototype is described, along with test data for inflation and leakage performance.     

Ariel-6 medium energy spectral observations of active galaxies

X-ray spectra of the BL Lac type object Mkn 421 and several Seyfert type 1 galaxies; IIIZw2, MCG8-11-11 and NGC 4151, have been obtained using the Leicester University instrument on board the Ariel-6 satellite. The Mkn 421 spectrum is best represented by two powerlaw components, the soft component having 3.4 whilst the hard flux has 1.0. In MCG8-11-11 there is clear evidence for spectral variability between our observation in late 1979 and that of HEAO-1/A2 in 1977. The Ariel-6 spectrum of MCG8-11-11 can be fitted by a powerlaw of index 2.1 together with an iron line at 6.2 keV with an equivalent width of 1.6 keV. The first X-ray spectrum of IIIZw2 is also presented, fitting with a powerlaw we find an index of 1.7. With the exception of NGC 4151 there is no evidence for a significant column of cool material along the line of sight.     

A gas management system for an ultra long duration Titan blimp

This paper presents analyses, designs and experimental results for the gas management system of a hydrogen-filled blimp capable of flying in the lower atmosphere of Titan for a period of 1 year or more. The engineering strategy has two basic elements: first, to minimize leakage rates from the blimp envelope and ballonets; and second, to provide auxiliary subsystems to mitigate the life-limiting effects resulting from those leaks. Leak minimization is achieved through use of cryogenically compatible balloon materials and adhesives, and selection of ballonet geometries that minimize pinhole generation via folding and material fatigue. Hydrogen loss to the environment through leaks in the blimp envelope is compensated by producing new hydrogen through chemical processing of atmospheric methane. Nitrogen leaked into the blimp from the ballonets is removed by a carbon absorption system and periodically vented to the atmosphere. Data is presented on the measured leak rate from a full scale (13 m long) prototype blimp envelope and on the performance of a low mass, low power prototype device that generates hydrogen from methane. These results are factored in to an overall system design that quantifies the mass and power requirements for a minimum 1 year operational lifetime.