Results 1 - 10 of 9347
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[en] We present an improved method to compute the radiative momentum transfer in the Pioneer 10 and 11 spacecraft that takes into account both diffusive and specular reflection. The method allows for more reliable results regarding the thermal acceleration of the deep-space probes, confirming previous findings. A parametric analysis is performed in order to set upper and lower bounds for the thermal acceleration and its evolution with time.
[en] A theory where the gravitational field of a mass induces a gravitational field contribution from the cosmos is presented. In this theory, entities of both net positive and net negative energy come into existence throughout the cosmos with a maximum lifetime in accordance with Heisenberg's uncertainty principle. A model of the resulting contribution that these entities make to the gravitational field is provided and is shown to lead to both the baryonic Tully-Fisher relationship and the Pioneer anomaly. (author)
[en] The sounding rocket mission MAIUS-1 has the objective to create the first Bose–Einstein condensate in space; therefore, its scientific payload is a complete cold atom experiment built to be launched on a VSB-30 sounding rocket. An essential part of the setup is an ultrahigh vacuum system needed in order to sufficiently suppress interactions of the cooled atoms with the residual background gas. Contrary to vacuum systems on missions aboard satellites or the international space station, the required vacuum environment has to be reached within 47 s after motor burn-out. This paper contains a detailed description of the MAIUS-1 vacuum system, as well as a description of its qualification process for the operation under vibrational loads of up to 8.1 g_R_M_S (where RMS is root mean square). Even though a pressure rise dependent on the level of vibration was observed, the design presented herein is capable of regaining a pressure of below 5 × 10"−"1"0 mbar in less than 40 s when tested at 5.4 g_R_M_S. To the authors' best knowledge, it is the first UHV system qualified for operation on a sounding rocket.
[en] Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude ∼8.5x10-8 cm/s2 , directed towards the Sun. Two independent codes and physical strategies have been used to analyze the data. A number of potential causes have been ruled out. We discuss future kinematic tests and possible origins of the signal. copyright 1998 The American Physical Society
[en] This review is to remind scientists of the older generation of some memorable historical pages and of many famous researchers, teachers and colleagues. For the younger researchers and foreign colleagues it will be useful to get to know about pioneer advancements of the Soviet scientists in the field of information and mathematical supply for cosmonautic problems on the eve of the space era. Main attention is paid to the scientific experiments conducted on the piloted space vehicles and the research teams who created the information and mathematical tools for the first space projects. The role of Mstislav Vsevolodovich Keldysh, the Major Theoretician of cosmonautics, is particularly emphasized. He determined for the most part the basic directions of development of space research and remote sensing of the Earth and planets that are shortly called remote sensing
[en] We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission
[en] Voyager 2 (V2) crossed the heliopause at 119.0 au on 2018 day 309, after which it observed compressive (longitudinal) magnetic field fluctuations along the average magnetic field direction in the very local interstellar medium (VLISM) at distances from 119.00 to 121.48 au and latitudes 32.°2 to 32.°4 S in heliographic inertial coordinates from 2018 day 309 to 2019 day 230. This result confirms the observations of longitudinal magnetic field fluctuations by Voyager 1 (V1) between 124.14 and 128.71 au at 34.°6N (∼2–7 au upwind of the heliopause) from 2013 day 133 to 2014 day 235. V1 crossed the heliopause at 121.58 au and 34.°5N on 2012 day 238. It came as a surprise to find it seemed that V1 observed transverse (Alfvénic) fluctuations of B between 131.40 and 135.98 au at latitude 34.°6–34.°7N (∼10–14 au upwind of the heliopause) from 2015 day 145 to 2016 day 248. The most recent V1 observations show the possible presence of transverse fluctuations of B in the VLISM from 141.44 to 146.01 au at 34.°7–34.°8N (∼20–24 au from the heliopause) between 2018 day 75 and 2019 day 178. Together, these observations show that longitudinal (compressive) magnetic field fluctuations are transmitted through the heliopause from the heliosheath into the VLISM, and are then converted into transverse (Alfvénic) fluctuations at ∼130 au (∼8 au from the heliopause) that are observed out at 146 au (∼24 au from the heliopause).
[en] Modern data intensive science involves heterogeneous and structured data sets in sophisticated data formats. Scientists need access to distributed computing and data sources and support for remote access to expensive, multinational specialized instruments. Scientists need effective software for data analysis, querying, accessing and visualization. The interaction between computer science and science and engineering becomes essential for the automation of data manipulation. The key solution uses the Service-oriented Architecture (SOA) in the field of science and Grid computing. The goal of this paper is managing the scientific data received by the Lyulin-5 particle telescope used in MATROSHKA-R experiment performed at the International Space Station (ISS). The dynamics of radiation characteristics and their dependency on the time and the orbital parameters have been established. The experiment helps the accurate estimation of the impact of space radiation on human health in long-duration manned missions
[en] The outer edge of Saturn's B ring is strongly affected by the nearby 2:1 inner Lindblad resonance of Mimas and is distorted approximately into a centered elliptical shape, which at the time of the Voyager 1 and 2 encounters was oriented with its periapse toward Mimas. Subsequent observations have shown that the actual situation is considerably more complex. We present a complete set of historical occultation measurements of the B-ring edge, including the 1980 Voyager 1 and 1981 Voyager 2 radio and stellar occultations, the 1989 occultation of 28 Sgr, two independently analyzed occultations observed with the Hubble Space Telescope in 1991 and 1995, and a series of ring profiles from 12 diametric (ansa-to-ansa) occultations observed in 2005, using the Cassini Radio Science Subsystem (RSS). After making an approximate correction for systematic errors in the reconstructed spacecraft trajectories, we obtain orbit fits to features in the rings with rms residuals well under 1 km, in most cases. Fits to the B-ring edge in the RSS data reveal a systematic variation in the maximum optical depth at the very edge of the ring as a function of its orbital radius. We compare the B-ring measurements to an m = 2 distortion aligned with Mimas, and show that there have been substantial phase shifts over the past 25 years. Finally, we present freely precessing equatorial elliptical models for 16 features in the Cassini Division. The inner edges of the gaps are generally eccentric, whereas the outer edges are nearly circular, with ae < 0.5 km.
[en] Let me talk you today about the fourth-generation space station while providing some historical context. To date, mankind has created four space stations. The first generation space station, Salyut, was launched in 1971, the second-generation, Skylab, in 1973, and the third-generation, Mir, in 1986. The fourth-generation is the International Space Station (ISS) launched in 1998, with 16 participating countries, namely Brazil, Canada, Japan, Russia, United States, and 11 countries of the European Union. It contains far more modules than the third-generation, Mir. Its various modules include Canada's robotic arms, Japan's Kibo module, Russia's emergency escape system, the United States' Unity/Destiny module, and so on. Thirty years ago on this very day, April 11, the modern mariner Dodge Morgan received attention globally for his success in sailing solo non-stop around the world in just 150 days on the 18 meter boat, named American Promise. On April 12, 55 years ago, Soviet cosmonaut Yuri Gagarin became the first human in space on the Vostok 1 spacecraft. On April 12, 35 years ago, the first U.S. space shuttle Columbia was successfully launched and orbited the earth 36 times before returning safely. These milestones marked the beginning of the era of space shuttles for humanity. I believe that all of these historical days are a result of mankind's indomitable will and continuous challenge toward the advancement of scientific technology. Just as the world joined forces to build the International Space Station, I hope GIF member countries and the Agency will work closely together toward the early commercialization of the fourth generation nuclear system.