Astronomy and astrophysics with the advanced X-ray astrophysics facility

The Advanced X-ray Astrophysics Facility (AXAF) planned for launch in the middle of the next decade will be a powerful new tool to enhance our understanding of the Universe. In this paper we describe the principal elements: the optics and the instruments. We review the instrument capabilities in order that potential users of AXAF may plan supporting research in the years prior to launch. We also review several of the scientific questions which AXAF is well suited to address.     

Some contributions of the ISIS program towards advances in knowledge of low latitude ionospheric phenomena

The ISIS (International Satellites for Ionospheric Studies) program yielded four scientific satellites, Alouette 1 and 2, and ISIS 1 and 2. This review is limited to the scientific contribution of the program to advances in knowledge relating to the portion of our atmosphere and ionosphere that lie within the plasmasphere. Topside ionograms form the principal data base from which global distributions of electron density and other geophysical parameters can be obtained. Ionospheric ducts and bubbles have also been studied with the aid of ionograms. The utilization of other instruments has facilitated investigations of ion composition, electron temperature and airglow variations.     

Scientific Planning and Commanding of the Rosetta Payload

ESA’s Rosetta mission was launched in March 2004 and is on its way to comet 67P/Churyumov-Gerasimenko, where it is scheduled to arrive in summer 2014. It comprises a payload of 12 scientific instruments and a Lander. All instruments are provided by Principal Investigators, which are responsible for their operations. As for most ESA science missions, the ground segment of the mission consists of a Mission Operations Centre (MOC) and a Science Operations Centre (SOC). While the MOC is responsible for all spacecraft-related aspects and the final uplink of all command timelines to the spacecraft, the scientific operations of the instruments and the collection of the data and ingestion into the Planetary Science Archive are coordinated by the SOC. This paper focuses on the tasks of the SOC and in particular on the methodology and constraints to convert the scientific goals of the Rosetta mission to operational timelines.     

Early Data from Aura and Continuity from Uars and Toms

Aura, the last of the large EOS observatories, was launched on July~15, 2004. Aura is designed to make comprehensive stratospheric and tropospheric composition measurements from its four instruments, HIRDLS, MLS, OMI and TES. These four instruments work in synergy to provide data on ozone trends, air quality and climate change. The instruments observe in the nadir and limb and provide the best horizontal and vertical resolution ever achieved from space. After over one year in orbit the instruments are nearly operational and providing data to the scientific community. We summarize the mission, instruments, and initial results and give examples of how Aura will provide continuity to earlier chemistry missions.     

An Overview of the Fast Auroral SnapshoT (FAST) Satellite

The FAST satellite is a highly sophisticated scientific satellite designed to carry out in situ measurements of acceleration physics and related plasma processes associated with the Earth's aurora. Initiated and conceptualized by scientists at the University of California at Berkeley, this satellite is the second of NASA's Small Explorer Satellite program designed to carry out small, highly focused, scientific investigations. FAST was launched on August 21, 1996 into a high inclination (83°) elliptical orbit with apogee and perigee altitudes of 4175 km and 350 km, respectively. The spacecraft design was tailored to take high-resolution data samples (or `snapshots') only while it crosses the auroral zones, which are latitudinally narrow sectors that encircle the polar regions of the Earth. The scientific instruments include energetic electron and ion electrostatic analyzers, an energetic ion instrument that distinguishes ion mass, and vector DC and wave electric and magnetic field instruments. A state-of-the-art flight computer (or instrument data processing unit) includes programmable processors that trigger the burst data collection when interesting physical phenomena are encountered and stores these data in a 1 Gbit solid-state memory for telemetry to the Earth at later times. The spacecraft incorporates a light, efficient, and highly innovative design, which blends proven sub-system concepts with the overall scientific instrument and mission requirements. The result is a new breed of space physics mission that gathers unprecedented fields and particles observations that are continuous and uninterrupted by spin effects. In this and other ways, the FAST mission represents a dramatic advance over previous auroral satellites. This paper describes the overall FAST mission, including a discussion of the spacecraft design parameters and philosophy, the FAST orbit, instrument and data acquisition systems, and mission operations.     

虚拟仪器在高校实验室建设中的应用探讨

虚拟仪器技术是当今测试技术发展的一个重要方向,其在大学科研和教学中有极其广阔应用空间。通过一个虚拟仪器的应用示例,讨论其在实验教学中应用前景。     

The Mars Odyssey Gamma-Ray Spectrometer Instrument Suite

The Mars Odyssey Gamma-Ray Spectrometer is a suite of three different instruments, a gamma subsystem (GS), a neutron spectrometer, and a high-energy neutron detector, working together to collect data that will permit the mapping of elemental concentrations on the surface of Mars. The instruments are complimentary in that the neutron instruments have greater sensitivity to low amounts of hydrogen, but their signals saturate as the hydrogen content gets high. The hydrogen signal in the GS, on the other hand, does not saturate at high hydrogen contents and is sensitive to small differences in hydrogen content even when hydrogen is very abundant. The hydrogen signal in the neutron instruments and the GS have a different dependence on depth, and thus by combining both data sets we can infer not only the amount of hydrogen, but constrain its distribution with depth. In addition to hydrogen, the GS determines the abundances of several other elements. The instruments, the basis of the technique, and the data processing requirements are described as are some expected applications of the data to scientific problems.     

Collecting Samples in Gale Crater, Mars; an Overview of the Mars Science Laboratory Sample Acquisition, Sample Processing and Handling System

The Mars Science Laboratory Mission (MSL), scheduled to land on Mars in the summer of 2012, consists of a rover and a scientific payload designed to identify and assess the habitability, geological, and environmental histories of Gale crater. Unraveling the geologic history of the region and providing an assessment of present and past habitability requires an evaluation of the physical and chemical characteristics of the landing site; this includes providing an in-depth examination of the chemical and physical properties of Martian regolith and rocks. The MSL Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem will be the first in-situ system designed to acquire interior rock and soil samples from Martian surface materials. These samples are processed and separated into fine particles and distributed to two onboard analytical science instruments SAM (Sample Analysis at Mars Instrument Suite) and CheMin (Chemistry and Mineralogy) or to a sample analysis tray for visual inspection. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments, Alpha Particle X-Ray Spectrometer (APXS), and the Mars Hand Lens Imager (MAHLI), on rock and soil targets. Finally, there is a Dust Removal Tool (DRT) to remove dust particles from rock surfaces for subsequent analysis by the contact and or mast mounted instruments (e.g. Mast Cameras (MastCam) and the Chemistry and Micro-Imaging instruments (ChemCam)).     

The Rosetta Lander (“Philae”) Investigations

The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations. Philae team members are listed in the acknowledgements     

Quantitative Assessments of the Martian Hydrosphere

In this paper, we review current estimates of the global water inventory of Mars, potential loss mechanisms, the thermophysical characteristics of the different reservoirs that water may be currently stored in, and assess how the planet’s hydrosphere and cryosphere evolved with time. First, we summarize the water inventory quantified from geological analyses of surface features related to both liquid water erosion, and ice-related landscapes. They indicate that, throughout most of Martian geologic history (and possibly continuing through to the present day), water was present to substantial depths, with a total inventory ranging from several 100 to as much as 1000 m Global Equivalent Layer (GEL). We then review the most recent estimates of water content based on subsurface detection by orbital and landed instruments, including deep penetrating radars such as SHARAD and MARSIS. We show that the total amount of water measured so far is about 30 m GEL, although a far larger amount of water may be stored below the sounding depths of currently operational instruments. Finally, a global picture of the current state of the subsurface water reservoirs and their evolution is discussed.     

Satellite Experiments Simultaneous with Antarctic Measurements (SESAME)

Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) is one of the four ground-based programmes within the NASA/ISAS Global Geospace Science (GGS) mission, itself part of the International Solar-Terrestrial Physics (ISTP) programme. The scientific objectives of SESAME are carefully selected to make an invaluable contribution to the GGS mission by capitalising on the unique geophysical advantages of Antarctica for geospace research. These arise mainly from the large displacement of the geographic and geomagnetic poles. Specifically, SESAME is designed to study the ionospheric effects of merging at the magnetopause, reconnection in the geomagnetic tail and its relationship to substorms, mapping of significant geospace boundaries to ionospheric altitudes, plasma wave generation and propagation at high latitudes, and ionosphere-thermosphere interactions. The experimental programme is centred at Halley (76° S, 27° W) but also utilises automatic geophysical observatories located poleward of Halley. The suite of instruments provides an excellent image of the inner boundary of geospace and thus is complementary to the GGS spacecraft measurements. The data products that will be supplied askey parameters to the GGS experimenters on a routine basis are described. A brief review of previous results is presented, and some of the significant scientific questions to be addressed using the combination of ground-based and space-based observations are discussed.     

Validation of techniques for space based remote sensing of auroral precipitation and its ionospheric effects

Knowledge of the spatial distribution of auroral precipitation and its associated ionospheric effects is important both to scientific studies of the Earth's environment and successful operation of defense and communication systems. Observations with the best spatial and temporal coverage are obtained through remote sensing from space-based platforms. Various techniques have been used, including the detection of visible, ultraviolet and X-ray emissions produced by the precipitating particles. Interpretation of the measurements is enabled through theoretical modeling of the interaction of precipitating particles with atmospheric constituents. A great variety of auroral precipitation exists, with each kind differing in the type and energy distribution of the particles, as well as in its spatial and temporal behavior. Viable remote sensing techniques must be able to distinguish at least the species of particle, the total energy flux, and the average energy. Methods based on visible, ultraviolet and X-ray emissions meet these requirements to varying degrees. These techniques and the associated space instrumentation have evolved in parallel over the last two decades. Each of the methods has been tested using simultaneous measurements made by space-based imaging systems and ground-based measurements made by radars and optical instruments. These experiments have been extremely helpful in evaluating the performance and practicality of the instruments and the results have been crucial in improving instrument design for future remote sensing platforms. The next decade will see continued development and test of remote sensing instruments and the measurements, in addition to providing important operational data, will be increasingly more critical in addressing a number of scientific problems in auroral and atmospheric physics.     

Studies of Comets in the Ultraviolet: The Past and the Future

The remote sensing of comets in the ultraviolet bandpass has been a valuable tool for studying the structure, composition, variability, and physical processes at work in cometary comae. By extension, these studies of comae have revealed key insights into the composition of cometary nuclei. Here we briefly review the ultraviolet studies of comets, and then take a look toward the future of such work as anticipated by the advent of several key new instruments. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Magnetostatic Cleanliness Program for the Cassini Spacecraft

The Cassini spacecraft, launched in October 1997 and expected to reach Saturn in 2004, carries two magnetometer experiments on a 10-m boom, one at the mid-section of the boom and the other situated at the end of the boom. In order to gather valid scientific magnetic field data and avoid electromagnetic interference, the spacecraft had to comply with stringent magnetostatic cleanliness requirements. This paper describes the results of the Cassini magnetics cleanliness program that achieved the goal of minimizing the magnetic field interference with Cassini’s DC magnetic field science instruments.     

The Magnetostatic Cleanliness Program for the Cassini Spacecraft

The Cassini spacecraft, launched in October 1997 and expected to reach Saturn in 2004, carries two magnetometer experiments on a 10-m boom, one at the mid-section of the boom and the other situated at the end of the boom. In order to gather valid scientific magnetic field data and avoid electromagnetic interference, the spacecraft had to comply with stringent magnetostatic cleanliness requirements. This paper describes the results of the Cassini magnetics cleanliness program that achieved the goal of minimizing the magnetic field interference with Cassini’s DC magnetic field science instruments.This revised version was published online in July 2005 with a corrected cover date.     

The Orbiting Astronomical Observatories

A review is presented of the Orbiting Astronomical Observatories Program together with a detailed of the OAO spacecraft and the four astronomical instruments currently being developed for the first three observations.     

The Rosetta Mission: Flying Towards the Origin of the Solar System

The ROSETTA Mission, the Planetary Cornerstone Mission in the European Space Agency’s long-term programme Horizon 2000, will rendezvous in 2014 with comet 67P/Churyumov-Gerasimenko close to its aphelion and will study the physical and chemical properties of the nucleus, the evolution of the coma during the comet’s approach to the Sun, and the development of the interaction region of the solar wind and the comet, for more than one year until it reaches perihelion. In addition to the investigations performed by the scientific instruments on board the orbiter, the ROSETTA lander PHILAE will be deployed onto the surface of the nucleus. On its way to comet 67P/Churyumov-Gerasimenko, ROSETTA will fly by and study the two asteroids 2867 Steins and 21 Lutetia.