scholarly journals Analysis of rain fade mitigation using site diversity technique in southern tropical region of India

2017 ◽  
Vol 7 (1.1) ◽  
pp. 622 ◽  
Author(s):  
S Harika ◽  
S Nagarjuna ◽  
T V. Naveen ◽  
G Sanjay Harshanth ◽  
K Ch. Sri Kavya ◽  
...  
Keyword(s):  
Signal Strength ◽  
Tropical Region ◽  
Radio Waves ◽  
The Earth ◽  
Rain Drops ◽  
Geographical Position ◽  
Satellite Microwave ◽  
Site Diversity ◽  
Microwave Link ◽  
Diversity Technique

In order to design a reliable earth to satellite microwave link at certain frequencies in tropical region due to multi propagation we come across fading which means variation of attenuation of a signal with time, geographical position and radio frequency. The radio waves propagating through the earth atmosphere is attenuated due to the presence of atmospheric particles such as water vapor, rain drops and the ice particles which absorb and scatter the radio waves and consequently degrade the performance of the microwave link and there is probability of loss of signal strength, to mitigate this problem Site Diversity Technique is used from the different Fade Mitigation Techniques. The analysis of Site Diversity Gain Model based on the measured rainfall data has been done.  

Ultra Short Baseline (USBL) Calibration for Positioning of Underwater Objects

2019 ◽  
Vol 2 (2) ◽  
pp. 73-85
Author(s):  
Bagus Septyanto ◽  
Dian Nurdiana ◽  
Sitti Ahmiatri Saptari
Keyword(s):  
Acoustic Wave ◽  
Scale Factor ◽  
Positioning System ◽  
Radio Waves ◽  
Short Baseline ◽  
Error Angle ◽  
Satellite Navigation System ◽  
The Earth ◽  
Underwater Positioning ◽  
Radio Signals

In general, surface positioning using a global satellite navigation system (GNSS). Many satellites transmit radio signals to the surface of the earth and it was detected by receiver sensors into a function of position and time. Radio waves really bad when spreading in water. So, the underwater positioning uses acoustic wave. One type of underwater positioning is USBL. USBL is a positioning system based on measuring the distance and angle. Based on distance and angle, the position of the target in cartesian coordinates can be calculated. In practice, the effect of ship movement is one of the factors that determine the accuracy of the USBL system. Ship movements like a pitch, roll, and orientation that are not defined by the receiver could changes the position of the target in X, Y and Z coordinates. USBL calibration is performed to detect an error angle. USBL calibration is done by two methods. In USBL calibration Single Position obtained orientation correction value is 1.13 ̊ and a scale factor is 0.99025. For USBL Quadrant calibration, pitch correction values is -1.05, Roll -0.02 ̊, Orientation 6.82 ̊ and scale factor 0.9934 are obtained. The quadrant calibration results deccrease the level of error position to 0.276 - 0.289m at a depth of 89m and 0.432m - 0.644m at a depth of 76m

Automated Determination of the Position of Ships by Satellites

1967 ◽  
Vol 20 (03) ◽  
pp. 281-285
Author(s):  
H. C. Freiesleben
Keyword(s):  
Celestial Body ◽  
World Wide ◽  
Artificial Satellites ◽  
Radio Waves ◽  
The Moon ◽  
Position Determination ◽  
The Earth ◽  
Navigational Aids ◽  
Automated Determination

It has recently been suggested that 24-hour satellites might be used as navigational aids. To what category of position determination aids should these be assigned ? Is a satellite of this kind as it were a landmark, because, at least in theory, it remains fixed over the same point on the Earth's surface, in which case it should be classified under land-based navigation aids ? Is it a celestial body, although only one tenth as far from the Earth as the Moon ? If so, it is an astronomical navigation aid. Or is it a radio aid ? After all, its use for position determination depends on radio waves. In this paper I shall favour this last view. For automation is most feasible when an object of observation can be manipulated. This is easiest with radio aids, but it is, of course, impossible with natural stars.At present artificial satellites have the advantage over all other radio aids of world-wide coverage.

scholarly journals Precision Pulsar Timing with NASA's Deep Space Network

2015 ◽  
Vol 11 (A29B) ◽  
pp. 367-369
Author(s):  
Lawrence Teitelbaum ◽  
Walid Majid ◽  
Manuel M. Franco ◽  
Daniel J. Hoppe ◽  
Shinji Horiuchi ◽  
...  
Keyword(s):  
Low Frequency ◽  
Radio Waves ◽  
Deep Space ◽  
Radio Pulsars ◽  
Deep Space Network ◽  
Space Network ◽  
The Earth ◽  
Pulsar Timing ◽  
Initial Results ◽  
Stable Rotation

AbstractMillisecond pulsars (MSPs) are a class of radio pulsars with extremely stable rotation. Their excellent timing stability can be used to study a wide variety of astrophysical phenomena. In particular, a large sample of these pulsars can be used to detect low-frequency gravitational waves. We have developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs. The DSN operates clusters of large dish antennas (up to 70-m in diameter), located roughly equidistant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations over the next few years.

The Innovative Entrepreneur

2019 ◽  
pp. 17-36
Author(s):  
Arthur M. Diamond
Keyword(s):  
Tacit Knowledge ◽  
Subject Matter ◽  
Cognitive Diversity ◽  
Trial And Error ◽  
Radio Waves ◽  
Walt Disney ◽  
The Earth ◽  
Steve Jobs ◽  
The Subject ◽  
The Universe

Cognitively diverse project entrepreneurs are the ones most likely to succeed at making a ding in the universe. Project entrepreneurs are more effective because they are more likely to persevere at achieving their project and at undertaking new breakthrough innovations. Cyrus Field, Marconi, Walt Disney, Sam Walton, and Steve Jobs were project entrepreneurs. Innovative entrepreneurs are likely to either know less theory, or to take theory less seriously, which allows them to try what theory says is impossible. For instance, the physics of Marconi’s day said that his radio waves should go straight into space rather than curve with the earth to cross the Atlantic. Conversely, innovative entrepreneurs often have more tacit knowledge. Innovative entrepreneurs pursue serendipitous observations or slow hunches, often through trial-and-error experiments, and may benefit from cognitive diversity, such as dyslexia and Asperger’s syndrome. What inventors and entrepreneurs know is the subject matter of the epistemology of innovation.

The investigation of the Universe by radio astronomy

1961 ◽  
Vol 16 (1) ◽  
pp. 65-68
Keyword(s):  
Wavelength Range ◽  
Radio Astronomy ◽  
Outer Space ◽  
Sunspot Cycle ◽  
Short Wave ◽  
Radio Waves ◽  
Residual Noise ◽  
The Earth ◽  
Long Wave ◽  
The Universe

Although nearly all the major advances in radio astronomy have taken place during the last fifteen years the basic discoveries were made 30 years ago. At that time Jansky realized that the residual noise in his receiving equipment had a daily sidereal variation and must be the result of radio waves reaching the earth from outer space, and Appleton in the U. K. with Breit and Tuve in America through their studies of the ionosphere laid the foundation of the radio echo techniques of radio astronomy. The radio emission from outer space can be received on earth in the wavelength range from a few millimetres to 10 or 20 metres. The short wave end is limited by absorption in the atmosphere and the long wave end by the ionosphere, and this upper limit tends to vary in sympathy with ionospheric conditions throughout the sunspot cycle. These hindrances will soon be overcome when suitable equipment can be carried in earth satellites; then it should be possible to determine the true wavelength range of these extraterrestrial emissions.

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