The IMAGE mission will be the first of its kind, designed to comprehensively image a variety of emissions from the Earth's magnetosphere, with sufficient time resolution to follow the dynamics associated with the development of magnetospheric storms. Energetic neutral atoms (ENA) emitted from the ring current during storms are one of the key emissions that will be imaged. This paper describes the characteristics of the High Energy Neutral Atom imager, HENA. Using pixelated solid state detectors, imaging microchannel plates, electron optics, and time of flight electronics, HENA is designed to return images of the ENA emitting regions of the inner magnetosphere with 2 minute time resolution, at angular resolution of 8 degrees or better above the energy of 50 keV/nucleon. HENA will also image separately the emissions in hydrogen, helium, and oxygen above 30 keV/nucleon. HENA will reject energetic ions below 200 keV/charge, allowing ENA images to be returned in the presence of ambient energetic ions. HENA images will reveal the distribution and the evolution of energetic ion distributions as they are injected into the ring current during geomagnetic storms, as they drift about the Earth on both open and closed drift paths, and as they decay through charge exchange to pre-storm levels. Substorm ion injections will also be imaged, as will the regions of low altitude, high latitude ion precipitation into the upper atmosphere. 相似文献
The magnetic fields that dominate the structure of the Sun's atmosphere are controlled by processes in the solar interior, which cannot be directly observed. Magnetic activity is found in all stars with deep convective envelopes: young and rapidly rotating stars are very active but cyclic activity only appears in slow rotators. The Sun's 11-year activity cycle corresponds to a 22-year magnetic cycle, since the sunspot fields (which are antisymmetric about the equator) reverse at each minimum. The record of magnetic activity is aperiodic and is interrupted by episodes of reduced activity, such as the Maunder Minimum in the seventeenth century, when sunspots almost completely disappeared. The proxy record from cosmogenic isotopes shows that similar grand minima recur at intervals of around 200 yr. The Sun's large-scale field is generated by dynamo action rather than by an oscillator. Systematic magnetic cycles are apparently produced by a dynamo located in a region of weak convective overshoot at the base of the convection zone, where there are strong radial gradients in the angular velocity . The crucial parameter (the dynamo number) increases with increasing and kinematic (linear) theory shows that dynamo action can set in at an oscillatory (Hopf) bifurcation that is probably subcritical. Although it has been demonstrated that the whole process works in a self-consistent model, most calculations have relied on mean-field dynamo theory. This approach is physically plausible but can only be justified under conditions that do not apply in the Sun. Still, mean-field dynamos do reproduce the butterfly diagram and other key features of the solar cycle. An alternative approach is to study generic behaviour in low-order models, which exhibit two forms of modulation, associated with symmetry-breaking and with reduced activity. Comparison with observed behaviour suggests that modulation of the solar cycle is indeed chaotic, i.e. deterministically rather than stochastically driven. 相似文献
The Plasma Experiment for Planetary Exploration (PEPE) flown on Deep Space 1 combines an ion mass spectrometer and an electron
spectrometer in a single, low-resource instrument. Among its novel features PEPE incorporates an electrostatically swept field-of-view
and a linear electric field time-of-flight mass spectrometer. A significant amount of effort went into developing six novel
technologies that helped reduce instrument mass to 5.5 kg and average power to 9.6 W. PEPE’s performance was demonstrated
successfully by extensive measurements made in the solar wind and during the DS1 encounter with Comet 19P/Borrelly in September
2001.
P. Barker is deceased. 相似文献
A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery
Program mission to the planet Mercury. Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) launched
successfully in 2004 and will journey more than six years before entering Mercury orbit to begin a one-year investigation.
The GRNS instrument forms part of the geochemistry investigation and will yield maps of the elemental composition of the planet
surface. Major elements include H, O, Na, Mg, Si, Ca, Ti, Fe, K, and Th. The Gamma-Ray Spectrometer (GRS) portion detects
gamma-ray emissions in the 0.1- to 10-MeV energy range and achieves an energy resolution of 3.5 keV full-width at half-maximum
for 60Co (1332 keV). It is the first interplanetary use of a mechanically cooled Ge detector. Special construction techniques provide
the necessary thermal isolation to maintain the sensor’s encapsulated detector at cryogenic temperatures (90 K) despite the
intense thermal environment. Given the mission constraints, the GRS sensor is necessarily body-mounted to the spacecraft,
but the outer housing is equipped with an anticoincidence shield to reduce the background from charged particles. The Neutron
Spectrometer (NS) sensor consists of a sandwich of three scintillation detectors working in concert to measure the flux of
ejected neutrons in three energy ranges from thermal to ∼7 MeV. The NS is particularly sensitive to H content and will help
resolve the composition of Mercury’s polar deposits. This paper provides an overview of the Gamma-Ray and Neutron Spectrometer
and describes its science and measurement objectives, the design and operation of the instrument, the ground calibration effort,
and a look at some early in-flight data. 相似文献
On the basis of the experience gained during the previous french-russian missions on board MIR about the adaptation processes of the cardio-vascular system, a new laboratory has been designed. The objective of this “PHYSIOLAB” is to have a better understanding of the mechanisms underlying the changes in the cardio-vascular system, with a special emphasis on the phenomenon of cardio-vascular deconditioning after landing.
Beyond these scientific objectives, it is also intended to use PHYSIOLAB to help in the medical monitoring on-board MIR, during functional tests such as LBNP.
PHYSIOLAB will be set up in MIR by the French cosmonaut during the next french-russian CASSIOPEE mission in 1996. Its architecture is based on a central unit, which controls the experimental protocols, records the results and provides an interface for transmission to the ground via telemetry. Different specific modules are used for the acquisition of various physiological parameters.
This PHYSIOLAB under development for the CASSIOPEE mission should evolve towards a more ambitious laboratory, whose definition would take into account the results obtained with the first version of PHYSIOLAB. This “second generation” laboratory should be developed in the frame of wide international cooperation. 相似文献
The following substances were isolated under the influence of space-flight factors in cosmic experiments aboard the Mirorbital station: an MIB-90 monoisolant, which is distinguished by its morphological and biochemical properties and enhanced productivity, was isolated from the Bacillus thuringiensisssp. Kurstaki var. Z-52culture, which is a producer of the plant protection agent Lepidocide; and MIA-74 and MIP-89 monoisolants, which are highly active toward heavy petroleum fractions (C23–C33), were isolated from the Arthrobacter OC-1culture, which is a producer of biodegradants for petroleum. 相似文献
NASA is very interested in improving its ability to monitor and forecast the radiation levels that pose a health risk to space-walking astronauts as they construct the International Space Station and astronauts that will participate in long-term and deep-space missions. Human exploratory missions to the moon and Mars within the next quarter century, will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and solar activity is presently unpredictable, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. Today, numerous models have been developed and used to predict radiation exposure. Such a model is the Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronautics. SPENVIS, which has been assessed to be an excellent tool in characterizing the radiation environment for microelectronics and investigating orbital debris, is being evaluated for its usefulness with determining the dose and dose-equivalent for human exposure. Thus far. the calculations for dose-depth relations under varying shielding conditions have been in agreement with calculations done using HZETRN and PDOSE, which are well-known and widely used models for characterizing the environments for human exploratory missions. There is disagreement when assessing the impact of secondary radiation particles since SPENVIS does a crude estimation of the secondary radiation particles when calculating LET versus Flux. SPENVIS was used to model dose-depth relations for the blood-forming organs. Radiation sickness and cancer are life-threatening consequences resulting from radiation exposure. In space. exposure to radiation generally includes all of the critical organs. Biological and toxicological impacts have been included for discussion along with alternative risk mitigation methods--shielding and anti-carcinogens. 相似文献
To improve the interpersonal climate of crewmembers involved with long-duration space missions, it is important to understand the factors affecting their interactions with each other and with members of mission control. This paper will present findings from a recently completed NASA-funded study during the Shuttle/Mir program which evaluated in-group/out-group displacement of negative emotions; changes in tension, cohesion, and leader support over time; and cultural differences. In-flight data were collected from 5 astronauts, 8 cosmonauts, and 42 American and 16 Russian mission control personnel who signed informed consent. Subjects completed a weekly questionnaire that assessed their mood and perception of their work group's interpersonal climate using questions from well-known, standardized measures (Profile of Mood States, Group and Work Environment Scales) and a critical incident log. There was strong evidence for the displacement of tension and dysphoric emotions from crewmembers to mission control personnel and from mission control personnel to management. There was a perceived decrease in commander support during the 2nd half of the missions, and for American crewmembers a novelty effect was found on several subscales during the first few months on-orbit. There were a number of differences between American and Russian responses which suggested that the former were less happy with their interpersonal environment than the latter. Mission control personnel reported more tension and dysphoria than crewmembers, although both groups scored better than other work groups on Earth. Nearly all reported critical incidents came from ground subjects, with Americans and Russians showing important differences in response frequencies. 相似文献