Peculiarities of Estimating the Aircraft Performance Characteristics of the Rocket-and-Space Facilities under Conditions of Fuzzy Data

One possible method is considered of deriving the well-posed (in the sense of A.N. Tikhonov) solutions to the problems of estimating the aircraft performance characteristics. The method is based on the results of measurements of the state parameters and geophysical conditions of the employment of the rocket-and-space facilities under conditions of uncertainty of the a priori data on measurement errors.     

SIGMA observations of hard X-ray and soft gamma-ray emission from X-ray binaries

After more than two years of operation, the imaging γ-ray SIGMA telescope has accumulated several days of observation toward well known X-ray binaries. Four bright sources falling in this category have been detected so far: The pulsar GX 1+4 near the center of our galaxy, the stellar wind accreting system 4U 1700-377, and the black hole candidates Cygnus X-1 and GX 339-4. Moreover, SIGMA have observed three transients sources, which turned out to be also hard X-ray sources : The burster KS 1731-260, Tra X-1, and the Musca Nova. The properties of these systems in the SIGMA domain will be reviewed and a spectral distinction between black holes and neutron stars will be sketched.     

Laboratory experiments of magnetospheric interest

Space-related laboratory experiments can play an important role as a complement to observations and active experiments in the magnetosphere. Excluding laboratory experiments for mere developing or testing of techniques for space experiments, we may distinguish between two major types: (1) partial scale model experiments and (2) experiments for clarifying basic plasma physical processes known or expected to be important in the magnetosphere (but without the ambition to simulate actual space configurations). The limitations and potentialities of both types are discussed and examples of experiments are given. It is concluded that there should be an increasing need for the experiments of the second type. In particular, they are needed for the clarification of the response of a thin plasma to electric fields and its ability to carry electric currents. This encompasses such key questions as the nature and role of anomalous resistivity (and electron runaway in its presence), the possible formation of double layers (and the acceleration processes associated with them) and rapid dissipation of magnetic-field energy.     

Modified Generalized Sign Test Processor for 2-D Radar

The modified generalized sign test processor is a nonparametric, adaptive detector for 2-D search radars. The detector ranks a sample under test with its neighboring samples and integrates (on a pulse-to-pulse basis) the ranks with a two-pole filter. A target is declared when the integrated output exceeds two thresholds. The first threshold is fixed and yields a 10-6 probability of false alarm when the neighboring samples are independent and identically distributed. The second threshold is adaptive and maintains a low false-alarm rate when the integrated neighboring samples are correlated and when there are nonhomogeneities, such as extraneous targets, in the neighboring cells. Using Monte Carlo techniques, probability of false-alarm results, probability of detection curves, and angular accuracy curves have been generated for this detector. The detector was built and PPI photographs are used to indicate the detector's performance when the radar is operated over land clutter.     

Transient Modeling of Synchronous Machine-Transformer-SCR Bridge

A rigorous mathematical model of a synchronouschine-machine-transformer-thyristor bridge unit is presented in state-space form with coefficients that are explicit functions of standard parameters. The developed model has a minimum order for each of the various operation modes of the bridge, and its form is such that it can be readily interfaced with any type of dc network connected to the bridge. In addition, the model has the capability to consider different types of transformer winding connections. In a digital simulation, the explicit form of the state model eliminates the need of matrix inversions at each integration step. This and the use of the ?, ? reference frame result in a high computing efficiency and accuracy. As an illustration, simulation results are shown of a case study where the unit is part of a high-power pulse generating system.     

OSIRIS-REx: Sample Return from Asteroid (101955) Bennu

In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions are New Horizons, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on January 1, 2019, and Juno, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in November 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennu’s resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.

     

EXOSAT observations of the BL Lac object Mkn 421

The BL Lac object Mkn 421 was observed by EXOSAT four times over a period of six days in February 1984. Significant X-ray variability was apparent on a timescale of less than a day, but with no accompanying spectral change. The source exhibited a very soft power law X-ray spectrum with an extremely low intrinsic column density (N_H10²⁰ cm^–2). There was no evidence for an additional hard component attributable to synchrotron self-Compton emission. The observations when combined with other published data imply that significant changes occur in the form of the broad-band UV/X-ray continuum of this source.     

Strategies for telecommunications and navigation in support of Mars exploration

The planned exploration of Mars will pose new and unique telecommunications and navigation challenges. The full range of orbital, atmospheric, and surface exploration will drive requirements on data return, energy-efficient communications, connectivity, and positioning. In this paper we will summarize the needs of the currently planned Mars exploration mission set, outline design trades and options for meeting these needs, and quantify the specific telecommunications and navigation capabilities of an evolving infrastructure.     

Main medical results of extended flights on space station Mir in 1986-1990

During 1986-1990 seven prime spacecrews (16 cosmonauts) have flown on-board the Mir orbital complex. The longest space mission duration was 366 days The principal objectives of the medical tasks were the maintenance of good health and performance of the spacecrews and conducting medical research programs which included study of the cardiovascular, motor, endocrine, blood, immune, and metabolic systems. Results obtained point to the ability of humans to readily adapt to a year-long stay in space and maintain good health and performance. Readaptation had a similar course as after other previous long-term space flights of up to 8 months in duration. Primary body system changes were not qualitatively different from findings after flights aboard the Salyut 6 and 7 space stations. In this case, during and after an 11-12 month flight, body system alterations were even less severe which was a result of adequate countermeasure use, their systematic and creative employment and maintenance of required environments to support life and work in space.