scholarly journals Airborne radar sounder for temperate ice: initial results from Patagonia

2009 ◽  
Vol 55 (191) ◽  
pp. 507-512 ◽  
Author(s):  
Rodrigo Zamora ◽  
David Ulloa ◽  
Gonzalo Garcia ◽  
Ronald Mella ◽  
José Uribe ◽  
...  
Keyword(s):  
Low Frequency ◽  
Digital Camera ◽  
Airborne Radar ◽  
Digital Receiver ◽  
Gps Receiver ◽  
Laser Altimeter ◽  
System A ◽  
Southern Patagonia ◽  
Radar Sounder ◽  
Initial Results

AbstractWe describe the development of a low-frequency airborne radar specifically designed for the sounding of temperate ice. The system operates at a central frequency of 1 MHz and consists of an impulse transmitter with an output voltage up to 5000 V and a digital receiver with a maximum gain of 80 dB. The radar was deployed on board a CASA 212 aircraft, which also carries a laser altimeter, an inertial navigation system, a digital camera and a GPS receiver. A description of the radar system is provided, as well as preliminary results obtained at Glaciar Tyndall, Campo de Hielo Sur (Southern Patagonia Icefield), where an ice depth of 670 m was reached.

scholarly journals Low-frequency radar sounding of ice in East Antarctica and southern Greenland

2014 ◽  
Vol 55 (67) ◽  
pp. 138-146 ◽  
Author(s):  
J. Mouginot ◽  
E. Rignot ◽  
Y. Gim ◽  
D. Kirchner ◽  
E. Le Meur
Keyword(s):  
Low Frequency ◽  
Radar Data ◽  
East Antarctica ◽  
Radar Signal ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Decameter Wavelength ◽  
Radar Sounder ◽  
Thickness Measurements ◽  
Southwest Greenland

AbstractWe discuss a decameter-wavelength airborne radar sounder, the Warm Ice Sounding Explorer (WISE), that provides ice thickness in areas where radar signal penetration at higher frequencies is expected to be limited. Here we report results for three campaigns conducted in Greenland (2008, 2009, 2010) and two in Antarctica (2009, 2010). Comparisons with higher-frequency radar data indicate an accuracy of ±55 m for ice-thickness measurements in Greenland and ±25 m in Antarctica. We also estimate ice thickness of the Qassimiut lobe in southwest Greenland, where few ice-thickness measurements have been made, demonstrating that WISE penetrates in strongly scattering environments.

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.

scholarly journals Helicopter-borne radio-echo sounding of Svartisen, Norway

1993 ◽  
Vol 17 ◽  
pp. 23-26 ◽  
Author(s):  
Michael Kennett ◽  
Tron Laumann ◽  
Cecilie Lund
Keyword(s):  
Low Frequency ◽  
Ice Thickness ◽  
Digital Receiver ◽  
Outlet Glacier ◽  
Northern Norway ◽  
Bed Topography ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Depth Sounding ◽  
Ice Radar

A helicopter-mounted low frequency ice-radar has been developed for the depth sounding of temperate glaciers. The radar consists of standard transmitter and digital receiver equipment. The long antennae are supported on a special aluminium and fibreglass construction which hangs 20 m below the helicopter. The radar has been used on Engabreen, an outlet glacier of the Svartisen Ice Cap in northern Norway, where ice thicknesses of up to 350 m were obtained. The results have been used to construct a map of bed topography of the lower part of Engabreen. This map is largely consistent with ice thickness data obtained by drilling.

scholarly journals Surface and subsurface radar equations for radar sounders

2020 ◽  
Vol 61 (81) ◽  
pp. 135-142 ◽  
Author(s):  
Mark S. Haynes
Keyword(s):  
Low Frequency ◽  
Lookup Tables ◽  
Scientists And Engineers ◽  
Radar Sounder ◽  
Radar Equation

AbstractThis work is a collection of radar equations for low-frequency radar sounding and radar in general that emphasize the form of the radar equation for different target and source geometries. This is meant as a handbook for scientists and engineers that work with or analyze radar sounder systems and interpret radar sounding echoes. Lookup tables summarize the results and derivations are provided for each equation.

Dynamic Modeling and Output Characteristic Analysis of a Micro Bistable Piezoelectric Generator

2015 ◽  
Vol 645-646 ◽  
pp. 995-1003
Author(s):  
Xin Hua Mao ◽  
Qing He ◽  
Ting Ting Huang
Keyword(s):  
Electromechanical Coupling ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Output Characteristic ◽  
Electromechanical Coupling Coefficient ◽  
Transfer Model ◽  
Characteristic Analysis ◽  
System A ◽  
Low Frequency Vibration ◽  
Piezoelectric Generator

For effectively harvesting the broadband and low-frequency vibration energies in real environment, a micro bistable piezoelectric generator, without containing magnet, is designed. On the basis of analysis the nonlinear behavior of the stiffness, damping and the electromechanical coupling coefficient about the bistable vibration system, a precise mechanical-electric transfer model is built. The output characteristic of the piezoelectric generator is simulated and tested. The results showed that the piezoelectric generator can effectively harvest the broadband and low frequency vibration energies. And the output voltage can meet the electricity demand of a wireless sensor network node. The structure of the piezoelectric generator does not contain magnets, and it is easy to realize miniaturization and integration.

SYSIPHE system: a state of the art airborne hyperspectral imaging system: initial results from the first airborne campaign

2014 ◽  
Author(s):  
Laurent Rousset-Rouviere ◽  
Christophe Coudrain ◽  
Sophie Fabre ◽  
Laurent Poutier ◽  
Trond Løke ◽  
...  
Keyword(s):  
Hyperspectral Imaging ◽  
Imaging System ◽  
State Of The Art ◽  
System A ◽  
Initial Results

A New Design of Signal Source for Crosstalk Test of Multi-Channel Data Acquisition System

2012 ◽  
Vol 246-247 ◽  
pp. 1012-1016 ◽  
Author(s):  
Yan Hu Shan ◽  
Yong Feng Ren ◽  
Guo Yong Zhen ◽  
Xin Quan Jiao
Keyword(s):  
Phase Shift ◽  
Data Acquisition ◽  
Low Frequency ◽  
Data Acquisition System ◽  
Acquisition System ◽  
Signal Source ◽  
Testing Method ◽  
System A ◽  
Rectangular Waveform ◽  
Effective Channel

For the multi-channel data acquisition system, crosstalk significantly affects the sample accuracy. Through analyzing the mode of multiplexer and the sampling timing sequence, we demonstrated that crosstalk effect mainly results from the switch of multiplexer for the low- frequency multi-channel data acquisition system. A new crosstalk testing method based on phase-shift rectangular waveform for the multi-channel data acquisition system was proposed. The phase-shift rectangular waveform was designed. Experiments were conducted to test crosstalk effect of the multi-channel data acquisition system. The experimental results were demonstrated that the proposed approach based on the phase-shift rectangular waveform exhibits a distinct feature in effective channel crosstalk testing, compared with waveforms of other types. Thus, the proposed method is effective to detect crosstalk of the multi-channel data acquisition system.

Reduction Methods of Structure Models for Control System Purposes

2016 ◽  
Vol 248 ◽  
pp. 119-126 ◽  
Author(s):  
Andrzej Koszewnik ◽  
Zdzisław Gosiewski
Keyword(s):  
Control System ◽  
High Frequency ◽  
Closed Loop ◽  
Flexible Structures ◽  
Low Frequency ◽  
Point Of View ◽  
Closed Loop Systems ◽  
System A ◽  
Reduction Methods ◽  
The Stability

To design vibration control system for flexible structures their mathematical model should be reduced. In the paper we consider the influence of the model reduction on the dynamics of the real closed-loop system. A simply cantilever beam is an object of consideration since we are able to formulate the exact analytical model of such structure. As a result of reduction the model with low frequency resonances is usually separated from the high frequency dynamics because high frequency part of the model is naturally strong damped. In order to estimate dynamical system for control purposes in the paper we applied a few orthogonal methods such as: modal, Rayleigh-Ritz and Schur decompositions. As it is shown all methods well calculate resonances frequencies but generate different anti-resonances frequencies. From control strategy in point of view of the flexible structures these anti-resonances have significantly influence on the stability and dynamics of the closed-loop systems.

The Use of Injection Locked Magnetrons as a Source Microwave Processing Applications

1994 ◽  
Vol 347 ◽  
Author(s):  
Chris M. Walker
Keyword(s):  
Low Cost ◽  
Cooling Water ◽  
Low Frequency ◽  
Cost Driver ◽  
System A ◽  
Order Of Magnitude ◽  
Radar Applications ◽  
L Band ◽  
Tube Life ◽  
Ku Band

ABSTRACTThe Injection Locked Magnetron (ILM) has been used as a source of coherent power in a number of radar systems. It has a number of characteristics that make it particularly suitable to heating applications, above competing tube types used in radar applications.Power available is dependent upon the frequency of operation, ranging from several hundred watts at Ku-band to tens of kilowatts at L-band. Operation could be either cw or pulsed, but at higher power levels pulsed operation would be required. Designs for tubes at 1 GHz and 15 GHz will be presented.ILMs could be made at any frequency from 800 MHz to 20 GHz, beyond which the magnetron becomes either too large to be practical or too small to fabricate. Locking bandwidths are typically 0.5%, sufficient to be able to guarantee the tube remains locked at the required operating frequency. A tuner would increase the tube life and compensate for frequency drift effects.The tube life is dependent on the desired frequency of operation, ranging from several hundred hours at high frequency to an order of magnitude higher at low frequency. Adding a tuner will increase this several fold. ILMs are inherently rugged and may be run in any orientation, having been developed for airborne radar applications. Tubes are operated directly into a circulator and consequently can operate into high VSWR.The magnetron is a low cost tube, hence its use in domestic microwave ovens. ELMs have a similar part count and complexity. Efficiency varies from approximately 45% in Ku-band to 80% at L-band. Operating voltages are lower for ILMs than other vacuum tubes, at 1 GHz a 100 kW system would require 20 kV and for a 15 GHz 200 watt system, a 2 kV power supply would be required. These would run in the region of 10% duty cycle, 1 kHz PRF. Tubes would have integral rare earth magnets and require cooling water. The required quantity of tubes would be the most significant cost driver.

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