Aeronautical telemetry using multiple-antenna transmitters

The placement of multiple antennas on an air vehicle is one possible practice for overcoming signal obstruction created by vehicle maneuvering during air-to-ground transmission. Unfortunately, for vehicle attitudes where more than one of these antennas has a clear path to the receiving station, this practice also leads to self-interference nulls, resulting in dramatic degradation in the average signal integrity. This paper discusses application of unitary space-time codes such as the Alamouti transmit diversity scheme and unitary differential space-time codes to overcome the self-interference effect observed in such systems. The mathematical foundations of these techniques within the context of this application as well as computational performance gains associated with their implementation are provided. Issues such as the cost of channel estimation for trained techniques as well as the throughput performance of nondifferential and differential schemes for realistic air-vehicle motion are analyzed     

Some regularities in the relationship of limb coronal mass ejections with eruptive prominences and post-eruptive arcades

A positive correlation is shown to exist between the angular sizes (in the sky plane) of eruptive prominences and/or post-eruptive arcades and coronal mass ejections (CMEs) associated with them. New regularities are found that characterize the relationship between the latitude of eruptive prominences (post-eruptive arcades) and the latitude position of CMEs associated with them in the field of view of a coronagraph. An interpretation of these regularities is given.     

Fiber-optic gyros and quartz accelerometers for motion control

In article the opportunity of use strapdown inertial navigation system (SINS) on the base of fiber-optic gyroscopes and quartz accelerometers corrected from star sensors and satellite navigation equipment (SNE) for perspective interplanetary spacecrafts motion control on phases of interplanetary trajectory insertion, trajectory correction, and braking during transition to Mars orbit is investigated. Results of onboard control complex accuracy characteristics estimation are presented at the given dynamic spacecraft scheme which is taking into account the liquid oscillations in tanks and structure elements elasticity. At modelling the errors of measuring devices installation, errors of SINS initial alignment and instrumental errors of SINS sensitive elements, variation of control engines parameters were taken into account. The structure of the developed complex of imitation modelling of interplanetary spacecraft controlled motion is resulted. Estimations of active flight legs realization accuracy were received by a method of statistical modelling of spacecraft controlled motion     

Effects of Local Detachment of a Melt from Ampoule Walls,Crystal Vibration,and Magnetic Field at Crystal Growth under Zero Gravity

A numerical investigation of the melt flow and heat and mass transfer is carried out at the crystal growth under zero gravity, when the melt detachment from ampoule walls, crystal vibration, and various magnetic fields are active. Specific features of the melt flow are demonstrated depending on the size of a detachment zone adjacent to the crystallization boundary. The velocity of the averaged flow generated by crystal vibration is determined as a function of the vibration intensity. It is shown that the crystal vibration cannot compensate a thermal capillary flow (caused by detachment of the melt from the ampoule wall) and reduce the macrosegregation of impurities. It is shown that the application of steady and rotating magnetic fields are inefficient for all ampoule methods of crystal growth under microgravity conditions.     

On electromagnetic phenomena in Mercury’s magnetosphere

Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury’s and Earth’s magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury’s magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.     

Solar wind turbulence during the solar cycle deduced from Galileo coronal radio-sounding experiments

Seven coronal radio-sounding campaigns were carried out during the active lifetime of the Galileo spacecraft in the years 1994–2002. The observational data analyzed in the present work are S-band frequency fluctuation measurements recorded during the solar conjunctions at different phases of solar activity cycle #23, specifically: periods near solar maximum (three conjunctions), near solar minimum (three conjunctions) and during the ascending phase (one conjunction). These data are all applicable to low heliographic latitudes, i.e. to the slow solar wind. The rms frequency fluctuation and power-law index of the frequency fluctuation temporal spectra are determined as a function of heliocentric distance. The turbulence power spectrum tends to be flatter inside ca. 20 solar radii during all phases of the solar cycle. This coincides with a transition in the flow from the inner acceleration region to the outer region of constant velocity. The radial falloff rate and absolute level of the rms frequency fluctuation are essentially invariant over the solar cycle.     

Rosetta Asteroid Targets: 2867 Steins and 21 Lutetia

In preparation for the flyby of the Rosetta spacecraft, the state of the knowledge of 21 Lutetia and 2867 Steins obtained by ground based observations is reported. Preliminary determination of shape and/or size, rotational properties and taxonomic types are presented for both asteroids. The dusty environment of the targets has been studied in order to help in defining safe fly-by trajectories without the risk of damaging collisions. The expected science return from the asteroid fly-by is also discussed.     

Radiation measurements on the flight of IML-2.

The second flight of the International Microgravity Laboratory (IML-2) on Space Shuttle flight STS-65 provided a unique opportunity for the intercomparison of a wide variety of radiation measurement techniques. Although this was not a coordinated or planned campaign, by sheer chance, a number of space radiation experiments from several countries were flown on this mission. There were active radiation measuring instruments from Japan and US, and passive detectors from US, Russia, Japan, and Germany. These detectors were distributed throughout the Space Shuttle volume: payload bay, middeck, flight deck, and Spacelab. STS-65 was launched on July 8, 1994, in a 28.45 degrees x 306 km orbit for a duration of 14 d 17 hr and 55 min. The crew doses varied from 0.935 mGy to 1.235 mGy. A factor of two variation was observed between various passive detectors mounted inside the habitable Shuttle volume. There is reasonable agreement between the galactic cosmic ray dose, dose equivalent and LET spectra measured by the tissue equivalent proportional counter flown in the payload bay with model calculations. There are significant differences in the measurements of LET spectra measured by different groups. The neutron spectrum in the 1-20 MeV region was measured. Using fluence-dose conversion factors, the neutron dose and dose equivalent rates were 11 +/- 2.7 microGy/day and 95 +/- 23.5 microSv/day respectively. The average east-west asymmetry of trapped proton (>3OMeV) and (>60 MeV) dose rate was 3.3 and 1.9 respectively.     

Coordinated Continual Planning Methods for Cooperating Rovers

Eight evaluation metrics are used to compare and contrast three coordination schemes for a system that continuously plans to control collections of rovers (or spacecraft) using collective mission goals instead of goals or command sequences for each spacecraft. These schemes use a central coordinator to either: 1) micromanage rovers one activity at a time; 2) assign mission goals to rovers; or 3) arbitrate mission goal auctions among rovers. A self-commanding collection of rovers would autonomously coordinate itself to satisfy high-level science and engineering goals in a changing partially understood environment - making the operation of tens or even a hundred spacecraft feasible