Orbital position as a function of time

2021 ◽  
pp. 141-180
Author(s):  
Howard D. Curtis
Keyword(s):  
Orbital Position

Monitoring of the Orbital Position of a Geostationary Satellite by the Spatially Separated Reception of Signals of Digital Satellite Television

2017 ◽  
Vol 13 (1) ◽  
pp. 41-45
Author(s):  
M.P. Kaliuzhniy ◽  
◽  
F.I. Bushuev ◽  
Ye.S. Sibiriakova ◽  
O.V. Shulga ◽  
...  
Keyword(s):  
Geostationary Satellite ◽  
Satellite Television ◽  
Orbital Position

scholarly journals Comparison of Two Methods of Producing Adaptation of Saccade Size and Implications for the Site of Plasticity

1998 ◽  
Vol 79 (2) ◽  
pp. 704-715 ◽  
Author(s):  
Charles A. Scudder ◽  
Ekatherina Y. Batourina ◽  
George S. Tunder
Keyword(s):  
Relative Size ◽  
Neural Mechanisms ◽  
The Other ◽  
Rapid Adaptation ◽  
Adaptive Mechanisms ◽  
Saccade Size ◽  
Orbital Position ◽  
One Step ◽  
Induced Changes ◽  
Visual Error

Scudder, Charles A., Ekatherina Y. Batourina, and George S. Tunder. Comparison of two methods of producing adaptation of saccade size and implications for the site of plasticity. J. Neurophysiol. 79: 704–715, 1998. Saccade accuracy is known to be maintained by adaptive mechanisms that progressively reduce any visual error that consistently exists at the end of saccades. Experimentally, the visual error is induced using one of two paradigms. In the first, the horizontal and medial recti of trained monkeys are tenectomized and allowed to reattach so that both muscles are paretic. After patching the unoperated eye and forcing the monkey to use the “paretic eye,” saccades initially undershoot the intended target, but gradually increase in size until they almost acquire the target in one step. In the second, the target of a saccade is displaced in midsaccade so that the saccade cannot land on target. Again saccade size adapts until the target can be acquired in one step. Because adaptation with the latter paradigm is very rapid but adaptation using the former is slow, it has frequently been questioned whether or not the two forms of adaptation depend on the same neural mechanisms. We show that the rate of adaptation in both paradigms depends on the number of possible visual targets, so that when this variable is equated, adaptation occurs at similar rates in both paradigms. To demonstrate further similarities between the result of the two paradigms, an experiment using intrasaccadic displacements was conducted to show that rapid adaptation possesses the capacity to produce gain changes that vary with orbital position. The relative size of intrasaccadic displacements were graded with orbital position so as to mimic the position-dependent dysmetria initially produced by a single paretic extraocular muscle. Induced changes in saccade size paralleled the size of the displacements, being largest for saccades into one hemifield and being negligible for saccades into the other hemifield or in the opposite direction. Collectively, the data remove the rational for asserting that adaptation produced by the two paradigms depends on separate neural mechanisms. We argue that adaptation produced by both paradigms depends on the cerebellum.

A new metoposaurid amphibian from the upper Triassic Maleri formation of Central India

1965 ◽  
Vol 250 (761) ◽  
pp. 1-52 ◽  
Keyword(s):  
Close Association ◽  
Relative Rate ◽  
Nasal Bone ◽  
Central India ◽  
Morphological Characters ◽  
Upper Triassic ◽  
Godavari Valley ◽  
Orbital Position ◽  
Lacrimal Bone ◽  
Improved Methods

Improved methods of collection have led to the discovery of much better amphibian fossils from localities in the Upper Triassic Maleri formation of the Pranhita Godavari Valley. Some preliminary observations regarding the Maleri sediments and their relationship with the overlying and underlying rocks are noted. A composite restoration of the skull is given. The pattern of the dermal roofing bones, the shape of the skull and the position of the orbits clearly indicate that the material belongs to a metoposaurid amphibian. A new metoposaur species, Metoposaurus maleriensis is proposed and a description is given of its skull, braincase and palate. The presence of a prominent additional nasal bone on each side, exposed on the skull roof in one of the skulls of M. maleriensis and its absence in other skulls of this metoposaur is noted and the possible explanation for this condition is put forward. The position of the orbits varies according to the size of the skull; a comparison is made between the two more complete specimens to show that the orbits are more posteriorly placed in larger skulls. It is suggested that this difference in orbital position is probably due to the relative rate of activity of two zones of intensive growth in the skull, anterior and posterior to the orbits. Postcranial material includes three clavicles, interclavicle, humerus, ischium and eight intercentra including that of an atlas. These have also been assigned to M. maleriensis on the basis of close association and osteological characters. Study of the Maleri metoposaur and its comparison with the other adequately known genera, Metoposaurus from the Keuper of Europe and ‘Eupelor' from the Upper Triassic of North America, has demonstrated the weak foundation on which metoposaur genera are based. The position of the lacrimal bone has been used as one of the main morphological characters distinguishing between the previously recognized metoposaur genera. However, this character is variable within a subspecies recognized by Colbert & Imbrie, which suggests caution in its use in distinguishing between genera. The recognition of this feature further emphasizes the extremely close similarity between the metoposaur genera, already commented on by previous authors. The suggestion is made that these genera are morphologically indistinguishable and a revised taxonomy of the metoposaurs is put forward. The upper and lower stratigraphic limits of the metoposaurs are examined, and it is found that the metoposaurs are restricted to horizons equivalent to Carnian and Norian. The fauna associated with the metoposaurs in different parts of the world is discussed, and it is concluded that the age of the Maleri fauna is not younger than Middle Norian and probably not older than Carnian

scholarly journals SPATIAL CHARACTERIZATION OF TELECOMMUNICATION SATELLITES VISIBLE ABOVE THE REPUBLIC OF SERBIA

2020 ◽  
Vol 10 (2) ◽  
Author(s):  
Slaviša Đukanović ◽  
Vladimir Mladenović ◽  
Milan Gligorijević ◽  
Danijela Milošević ◽  
Ivona Radojević Aleksić
Keyword(s):  
Satellite Communication ◽  
Base Station ◽  
Satellite Telecommunication ◽  
High Speeds ◽  
Satellite Télécommunication ◽  
Telecommunication Infrastructure ◽  
Orbital Position ◽  
The Republic ◽  
The City

This paper deals with the general technical, spatial, and temporal characteristics of satellite telecommunications systems. Particular attention was paid to the peculiarities of the territory of the Republic of Serbia in terms of implementation and use of modern satellite telecommunication infrastructure. The overview shows how and on which way to use various satellite telecommunication systems to configure and exploit next-generation networks, especially modern communications such as 5G technology and IoT. Their work cannot be imagined without the high speeds and high frequencies that allow us to transmit a wealth of information - from short messages/news to HD video on a mobile phone. We need either a base station network or in the case of the high seas or areas where the base station system is difficult to imagine, we need satellite communication. The paper presents data that give a numerical and graphical overview of geostationary satellites visible from the territory of the city of Belgrade, depending on the orbital position and the associated angle of azimuth and elevation, which would also be valid for the leading territory of Serbia.

Eye movements induced by pontine stimulation: interaction with visually triggered saccades

1987 ◽  
Vol 58 (2) ◽  
pp. 300-318 ◽  
Author(s):  
D. L. Sparks ◽  
L. E. Mays ◽  
J. D. Porter
Keyword(s):  
Visual Target ◽  
Motor Command ◽  
Feedback Signal ◽  
Eye Position ◽  
Saccadic System ◽  
Position Signal ◽  
Orbital Position ◽  
A Site ◽  
Induced Changes ◽  
Pontine Stimulation

1. Rhesus monkeys were trained to look to brief visual targets presented in an otherwise darkened room. On some trials, after the visual target was extinguished but before a saccade to it could be initiated, the eyes were driven to another orbital position by microstimulation of the paramedian pontine reticular formation. If, as current models of the saccadic system suggest, a copy of the motor command is used as a feedback signal of eye position, failure to compensate for stimulation-induced movements would indicate that stimulation occurred at a site beyond the point from which the eye position signal was derived. 2. Animals compensated for perturbations of eye position induced by stimulation of most pontine sites by making saccades that directed gaze to the position of the visual target. With stimulation at other pontine sites, compensatory saccades did not occur. 3. Pontine stimulation sometimes triggered, prematurely, impending visually directed saccades. The direction and amplitude of the premature movement depended upon the location of the briefly presented visual target. The amplitude of the premature movement was also a function of the interval between the stimulation train and the impending saccade. These data suggest that input signals for the horizontal and vertical pulse/step generators develop gradually during the presaccadic interval. Saccade trigger signals need to be delayed until the formation of these signals is completed. 4. The implications of these findings for models of the saccadic system are discussed. Robinson's local feedback model of the saccadic system can explain compensation for pontine stimulation-induced changes in eye position but cannot easily account for the failure to compensate for perturbations in eye position produced by stimulation at other sites. Modified versions of Robinson's model, which assume that the input signal to the pulse/step generator is the desired displacement of the eye, can account for both compensation and the failure to compensate since two separate neural integrators are employed. However, these models ignore kinematic arguments that commands to the extraocular muscles must specify the absolute position of the eye in the orbit rather than a relative movement from a previous position.

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