The Rosat mission

The primary scientific objective of the ROSAT mission is to perform the first all sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. Consequently a large number of new sources (> 10⁵) will be discovered and located with an accuracy of 1 arcmin. After completion of the survey which will take about half a year the instrument will be used for detailed observations of selected targets.The X-ray telescope consists of a fourfold nested Wolter type I mirror system with 80 cm aperture and 240 cm focal length, and three focal plane detectors. In the baseline version these will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 2⁰ × 2⁰.     

The Polar Ionospheric X-ray Imaging Experiment (PIXIE)

The Polar Ionospheric X-ray Imaging Experiment (PIXIE) is an X-ray multiple-pinhole camera designed to image simultaneously an entire auroral region from high altitudes. It will be mounted on the despun platform of the POLAR spacecraft and will measure the spatial distribution and temporal variation of auroral X-ray emissions in the 2 to 60 keV energy range on the day side of the Earth as well as the night. PIXIE consists of two pinhole cameras integrated into one assembly, each equipped with an adjustable aperture plate that allows an optimum number of nonoverlapping images to be formed in the detector plane at each phase of the satellite's eccentric orbit. The aperture plates also allow the pinhole size to be adjusted so that the experimenter can trade off spatial resolution against instrument sensitivity. In the principal mode of operation, one aperture plate will be positioned for high spatial resolution and the other for high sensitivity. The detectors consist of four stacked multiwire position-sensitive proportional counters, two in each of two separate gas chambers. The front chamber operates in the 2–12 keV energy range and the rear chamber in the 10–60 keV range. All of the energy and position information for each telemetered X-ray event is available on the ground. This enables the experimenter to adjust the exposure timepostfacto so that energy spectra of each X-ray emitting region can be independently accumulated. From these data PIXIE will provide, for the first time, global images of precipitated energetic electron spectra, energy inputs, ionospheric electron densities, and upper atmospheric conductivities.     

The comptel experiment on the NASA Gamma-Ray Observatory

The imaging Compton telescope COMPTEL will be flown on the NASA Gamma-Ray Observatory at the beginning of the next decade. The instrument with its wide field of view and improved angular resolution will provide the first sky survey at MeV energies, as well as deep studies of galactic and extragalactic gamma-ray point sources and diffuse emission. The hardware preparations are close to completion, with calibrations to be done in 1987 prior to integration of the instrument onto the observatory carrying 3 other gamma ray detectors.     

Instrumentation for X-ray astronomy

Less than five decades ago, the first X-ray observations of the sky were made using simple devices such as film and geiger counters with crude collimators. These instruments were carried aloft by sounding rockets and made observations lasting only a few minutes at most. Today, orbiting observatories, utilizing high-resolution CCDs at the focus of arc sec optics, have lifetimes measured in years. To maintain the pace of discovery in X-ray astronomy, detectors must continue to evolve into devices of ever increasing sensitivity and sophistication. Further progress depends upon a host of technologies: grazing incidence optics, proportional counters, semiconductors, calorimeters, etc. In this article we present a brief qualitative overview of these technologies and of the principles behind them, as well as some examples of how they are employed in scientific missions for X-ray observations at energies up to 100 keV.     

Water Cherenkov detectors:MILAGRO

This paper discusses the properties of using the water Cherenkov technique to detect air showers in the few hundred GeV to 100 TeV energy range. The responses of a 6 m² 2 m deep water Cherenkov counter and that of a 6 m² 10cm thick scintillator-lead sandwich counter to air shower electrons and photons is described. The advantages of water Cherenkov detector is outlined. Its application to do VHE gamma ray astronomy is discussed with particular reference to the MILAGRO telescope currently under construction. Milagro, a water-Cherenkov detector to do gamma ray astronomy above 100 Gev, uses an existing pool 60m × 80m by 8m, located in the Jemez mountains near Los Alamos, NM. The threshold of the MILAGRO detector is comparable to atmospheric Cherenkov detectors, however it has several advantages over these optical detectors. MILAGRO can operate 24 hours a day in all weather conditions and it has an open aperture which allows it to view the entire northern sky every day. These capabilities allow for a systematic all-sky survey to be done for the first time at these energies. MILAGRO will measure the Crab spectrum with high significance over a wide energy range, it will detect and measure the spectra from AGN's such as MRK 421 and it will search for short duration bursts from GRBs and possibly evaporating PBHs.     

The BOOMERANG experiment

The BOOMERANG (Balloon Observations Of Millimetric Extragalactic RAdiation aNd Geophysics) experiment is an international effort to measure the Cosmic Microwave Background (CMB) anisotropy on angular scales of 20 to 4°, with unprecedented sensitivity, sky and spectral coverage. The telescope will be flown from Antarctica by NASA-NSBF with a long duration stratospheric balloon (7–14 days), and is presently scheduled for flight in 1995–1996. The experiment is designed to produce an image of the Cosmic Microwave Background with high sensitivity and large sky coverage. These data will tightly constrain the baryon density, the reionization history, and the formation of large-scale structure in the universe. BOOMERANG will test technologies and return science data that are essential to the design of a future space-borne mission to map CMB anisotropy.     

ATM: general description of the processes and influencing factors

The purpose of this article is to provide the reader with a broad understanding of the Air Traffic Management system and of the various interconnecting issues involved. Such understanding of what is the ATM system, its purpose, processes and influencing factors is, indeed, essential if we want to analyse the problems of today and the type of solutions that will need to be developed and implemented today and in the future to meet the challenges of a safe and efficient handling of air traffic in the European sky.     

The X-ray/Gamma-ray Spectrometer on the Near Earth Asteroid Rendezvous Mission

An X-ray/gamma-ray spectrometer has been developed as part of a rendezvous mission with the near-Earth asteroid, 433 Eros, in an effort to answer fundamental questions about the nature and origin of asteroids and comets. During about 10 months of orbital operations commencing in early 1999, the X-ray/Gamma-ray Spectrometer will develop global maps of the elemental composition of the surface of Eros. The instrument remotely senses characteristic X-ray and gamma-ray emissions to determine composition. Solar excited X-ray fluorescence in the 1 to 10 keV range will be used to measure the surface abundances of Mg, Al, Si, Ca, Ti, and Fe with spatial resolutions down to 2 km. Gamma-ray emissions in the 0.1 to 10 MeV range will be used to measure cosmic-ray excited elements O, Si, Fe, H and naturally radioactive elements K, Th, U to surface depths on the order of 10 cm. The X-ray spectrometer consists of three gas-filled proportional counters with a collimated field of view of 5° and an energy resolution of 850 eV @ 5.9 keV. Two sunward looking X-ray detectors monitor the incident solar flux, one of which is the first flight of a new, miniature solid-state detector which achieves 600 eV resolution @ 5.9 keV. The gamma-ray spectrometer consists of a NaI(Tl) scintillator situated within a Bismuth Germanate (BGO) cup, which provides both active and passive shielding to confine the field of view and eliminate the need for a massive and costly boom. New coincidence techniques enable recovery of single and double escape events in the central detector. The NaI(Tl) and BGO detectors achieve energy resolutions of 8.7% and 14%, respectively @ 0.662 MeV. A data processing unit based on an RTX2010 microprocessor provides the spacecraft interface and produces 256-channel spectra for X-ray detectors and 1024-channel spectra for the raw, coincident, and anti-coincident gamma-ray modes. This paper presents a detailed overview of the X-ray/Gamma-ray Spectrometer and describes the science objectives, measurement objectives, instrument design, and shows some results from early in-flight data.     

The Interstellar Boundary Explorer High Energy (IBEX-Hi) Neutral Atom Imager

The IBEX-Hi Neutral Atom Imager of the Interstellar Boundary Explorer (IBEX) mission is designed to measure energetic neutral atoms (ENAs) originating from the interaction region between the heliosphere and the local interstellar medium (LISM). These ENAs are plasma ions that have been heated in the interaction region and neutralized by charge exchange with the cold neutral atoms of the LISM that freely flow through the interaction region. IBEX-Hi is a single pixel ENA imager that covers the ENA spectral range from 0.38 to 6 keV and shares significant energy overlap and overall design philosophy with the IBEX-Lo sensor. Because of the anticipated low flux of these ENAs at 1 AU, the sensor has a large geometric factor and incorporates numerous techniques to minimize noise and backgrounds. The IBEX-Hi sensor has a field-of-view (FOV) of 6.5°×6.5° FWHM, and a 6.5°×360° swath of the sky is imaged over each spacecraft spin. IBEX-Hi utilizes an ultrathin carbon foil to ionize ENAs in order to measure their energy by subsequent electrostatic analysis. A multiple coincidence detection scheme using channel electron multiplier (CEM) detectors enables reliable detection of ENAs in the presence of substantial noise. During normal operation, the sensor steps through six energy steps every 12 spacecraft spins. Over a single IBEX orbit of about 8 days, a single 6.5°×360° swath of the sky is viewed, and re-pointing of the spin axis toward the Sun near perigee of each IBEX orbit moves the ecliptic longitude by about 8° every orbit such that a full sky map is acquired every six months. These global maps, covering the spectral range of IBEX-Hi and coupled to the IBEX-Lo maps at lower and overlapping energies, will answer fundamental questions about the structure and dynamics of the interaction region between the heliosphere and the LISM.     

The Role of Magnetic Fields in the Interstellar Medium of the Milky Way

Synchrotron radiation is generated throughout the Milky Way. It fills the sky, and carries with it the imprint of the magnetic field at the point of origin and along the propagation path. Observations of the diffuse polarized radio emission should be able to provide information on Galactic magnetic fields with detail matching the angular resolution of the telescope. I review what has been learned from existing data, but the full potential cannot be realized from current observations because they do not adequately sample the frequency structure of the polarized emission, or they lack information on large-scale structure. I discuss three surveys, each overcoming one of these limitations, and show how use of complementary data on other ISM tracers can help elucidate the role of magnetic fields in interstellar processes. The focus of this review is on the small-scale field, on sizes comparable with the various forms of interaction of stars with their surroundings. The future is bright for this field of research as new telescopes are being built, designed for the survey mode of observation, equipped for wideband, multichannel polarization observations.     

合成视景系统的机遇与挑战

基于三维地形显示的合成视景系统结合空中隧道等新技术,为飞行员提高情形认知、降低工作量,同时也给传统驾驶舱显示、飞行安全、航线运营等带来不同程度的影响,特别是对驾驶舱显示将是划时代变革。综述机遇与挑战并结合航空发展,预测合成视景系统在10～15年内必将广泛应用。     

TeV radiation from galactic sources

The detection of the Crab Nebula as a steady source of TeV gamma rays puts the field of Very High Energy Gamma-Ray Astronomy on a firm observational basis and permits a critical re-assessment of the claims for the detection of a multitude of episodic binary sources. A new generation of detectors in the TeV and PeV energy regions is coming on-line; together with the telescopes of the Gamma-Ray Observatory these instruments will present a new perspective on one of the last frontiers of astronomy.     

Wide angle air Cerenkov detectors

For a number of important questions in VHE/UHE cosmic ray physics wide angle air Cerenkov detectors offer superior performance compared to scintillator arrays or air Cerenkov telescopes. On hand of the HEGRA air Cerenkov detector AIROBICC the general principle and performance will be discussed. Ideas and prospects for a detector with an energy threshold around 1 to 3 TeV will be presented.     

Infrared Imaging Surveyor: IRIS

Based on the experience of the IRTS, a new infrared satellite mission, Infrared Imaging Surveyor:IRIS is now being proposed to ISAS. The IRIS will be thrown into the sun synchronous orbit at 900km altitude by the MV rocket which is now under development in ISAS. With use of new cryogenic technologies, considerably light weight with large aperture telescope is designed. Owing to the large format states-of-art array detectors, the IRIS has an enormous capability for the survey observation, and will provide new discoveries on the formation and evolution of galaxies, brown dwarfs, protoplanetary disk, interstellar matter and so on.     

Ceramic photocell implants could restore sight

Researchers are perfecting the use of ceramic photocells for retinal implantation. The work is being done at the Space Vacuum Epitaxy Center in Houston, TX. The photocells are the results of experiments with oxide detectors conducted in space using the Wake Shield Facility. Artificial retinas are constructed of 100,000 microscopic ceramic detectors attached to a polymer film, which disintegrates after implantation. Initially, four arrays will be implanted, totalling 400,000 detectors per eye. If successful, two additional arrays would be implanted. Human trials are expected to begin in 2002.     

Aircraft design and development

The creative process of aircraft design is driven by the needs and opportunities of the future market. From these needs, covering the requirements from the entire air transport system, specific targets are to be derived. Referring to today's products new designs are subsequently generated, aiming to meet the targets anticipated. Experience has shown that a significant gap will probably appear between the status and the desired targets. Besides design aspects such as the a/c capacity and range, the development of new technologies is mandatory to minimize or even eliminate the width of the gap, thus ensuring the achievement of future market demands by new aircraft designs.     

GLRT Detectors for Aircraft Wake Vortices in Clear Air

 In this article, radar echoes of aircraft wake vortices are modeled as weighted sums of the frequency components of the echoes with a special covariance matrix for the weighted coefficients. With a proposed detection scheme, two generalized likelihood ratio test (GLRT) detectors are derived respectively for aircraft wake vortices with time-varying and time-invariant Doppler spectra. Then the analytical expressions for detection and false alarm probabilities of the detectors are derived and three factors are investigated which mainly influence the detection performance, i.e., the Doppler extension and uncertainty of the aircraft wake vortex, and the number of the detection cells. The results indicate that, the signal-to-noise ratio (SNR) loss induced by Doppler extension is generally several decibels. The SNR loss due to Doppler uncertainty is approximately proportional to the logarithm of the number of spectrum lines in the uncertain Doppler spectrum intervals. For a large number of detection cells, the SNR gain is approximately proportional to the square root of the number of the detection cells.     

Neutron Monitor Response Functions

The neutron monitor provides continuous ground-based recording of the hadronic component in atmospheric secondary radiation which is related to primary cosmic rays. Simpson (1948) discovered that the latitude variation of the secondary hadronic component was considerably larger than the muon component suggesting the response of a neutron monitor is more sensitive to lower energies in the primary spectrum. The different methods of determining the neutron monitor response function of primary cosmic rays are reviewed and discussed including early and recent results. The authors also provide results from a new calculation (Clem, 1999) including angle dependent yield functions for different neutron monitor types which are calculated using a simulation of cosmic ray air showers combined with a detection efficiency simulation for different secondary particle species. Results are shown for IGY and NM64 configurations using the standard ¹⁰BF₃ detectors and the new ³He detectors to be used in the Spaceship Earth Project (Bieber et al., 1995). The method of calculation is described in detail and the results are compared with measurements and previous calculations. A summary of future goals is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Far Infrared Explorer (FIRE)

We describe the Far IR Explorer, a MIDEX-class orbital mission designed to survey the entire sky at millimeter and sub-millimeter wavelengths. The primary science goal of FIRE is to map the Cosmic Microwave Background with 20 resolution and 1 ppm precision. In addition, FIRE will measure diffuse radio and infrared emission from the Galaxy with unprecedented sensitivity, and will uniformly survey the entire sky to a limiting flux density of <100 mJy (3 ).