Open-loop tracking of rising and setting GNSS radio-occultation signals from an Airborne Platform: Signal model and statistical analysis

2013 ◽  
Author(s):  
K.-N. Wang ◽  
P. Muradyan ◽  
J. L. Garrison ◽  
J. S. Haase ◽  
B. Murphy ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Radio Occultation ◽  
Open Loop ◽  
Signal Model

scholarly journals Open-Loop Tracking of Rising and Setting GPS Radio-Occultation Signals From an Airborne Platform: Signal Model and Error Analysis

2016 ◽  
Vol 54 (7) ◽  
pp. 3967-3984 ◽  
Author(s):  
Kuo-Nung Wang ◽  
James L. Garrison ◽  
Ulvi Acikoz ◽  
Jennifer S. Haase ◽  
Brian J. Murphy ◽  
...  
Keyword(s):  
Error Analysis ◽  
Radio Occultation ◽  
Open Loop ◽  
Signal Model ◽  
Gps Radio Occultation

scholarly journals GPS radio occultation with TerraSAR-X and TanDEM-X: sensitivity of lower troposphere sounding to the Open-Loop Doppler model

2014 ◽  
Vol 7 (12) ◽  
pp. 12719-12733 ◽  
Author(s):  
F. Zus ◽  
G. Beyerle ◽  
S. Heise ◽  
T. Schmidt ◽  
J. Wickert
Keyword(s):  
Radio Occultation ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Systematic Difference ◽  
Open Loop ◽  
Negative Bias ◽  
Upper Troposphere ◽  
Gps Radio Occultation ◽  
Global Positioning ◽  
Data Source

Abstract. The Global Positioning System (GPS) radio occultation (RO) technique provides valuable input for numerical weather prediction and is considered as a data source for climate related research. Numerous studies outline the high precision and accuracy of RO atmospheric soundings in the upper troposphere and lower stratosphere. In this altitude region (8–25 km) RO atmospheric soundings are considered to be free of any systematic error. In the tropical (30° S–30° N) Lower (<8 km) Troposphere (LT), this is not the case; systematic differences with respect to independent data sources exist and are still not completely understood. To date only little attention has been paid to the Open Loop (OL) Doppler model. Here we report on a RO experiment carried out on-board of the twin satellite configuration TerraSAR-X and TanDEM-X which possibly explains to some extent biases in the tropical LT. In two sessions we altered the OL Doppler model aboard TanDEM-X by not more than ±5 Hz with respect to TerraSAR-X and compare collocated atmospheric refractivity profiles. We find a systematic difference in the retrieved refractivity. The bias mainly stems from the tropical LT; there the bias reaches up to ±1%. Hence, we conclude that the negative bias (several Hz) of the OL Doppler model aboard TerraSAR-X introduces a negative bias (in addition to the negative bias which is primarily caused by critical refraction) in our retrieved refractivity in the tropical LT.

scholarly journals Stability Analysis and Optimal Design for Virtual Impedance of 48 V Server Power System for Data Center Applications

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5253
Author(s):  
Chien-Chun Huang ◽  
Sheng-Li Yao ◽  
Huang-Jen Chiu
Keyword(s):  
Open Loop ◽  
Buck Converter ◽  
Output Impedance ◽  
Signal Model ◽  
Passive Components ◽  
The Past ◽  
Feedback Compensation ◽  
Series Systems ◽  
The Relationship ◽  
Virtual Impedance

In the past literature on virtual impedance to series systems, most of the discussion focused on stability without in-depth research on the system design of the series converter and the overall output impedance. Accordingly, this study takes an open-loop resonant LLC converter series-connected closed-loop Buck converter as an example. First, the conditions required for the direct connection of the small-signal model in the series, the effect of feedback compensation on the input impedance of the load stage, the operating frequency, and passive components of the two-stage converter are discussed in detail―the relationship between the matching and the output impedance. Afterwards, a mathematical model is used to discuss the effect of adding parallel virtual impedance on the output impedance of the overall series converter and then derive an optimized virtual impedance design. Finally, an experimental platform of 48 V to 12 V and maximum wattage of 96 W are implemented. The output impedance of the series converter is measured with an impedance analyzer to verify the theoretical analysis proposed in this paper.

GPS profiling of the lower troposphere from space: Inversion and demodulation of the open-loop radio occultation signals

2006 ◽  
Vol 33 (14) ◽  
Author(s):  
S. Sokolovskiy ◽  
C. Rocken ◽  
D. Hunt ◽  
W. Schreiner ◽  
J. Johnson ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Lower Troposphere ◽  
Open Loop ◽  
Space Inversion

Analysis of the Open-Loop Linear Range and Construction of the Small-Signal Model of DCCT Applied to the FTPMF System

2020 ◽  
Vol 30 (4) ◽  
pp. 1-5
Author(s):  
Shaozhe Zhang ◽  
Zhenglei Wang ◽  
Qinying Liu ◽  
Jianfeng Xie ◽  
Houxiu Xiao ◽  
...  
Keyword(s):  
Open Loop ◽  
Linear Range ◽  
Small Signal ◽  
Signal Model ◽  
Small Signal Model

Cryospheric Applications of Novel GNSS Grazing Angle Reflections Collected by Spire CubeSats

2020 ◽  
Author(s):  
Vu Nguyen ◽  
Takayuki Yuasa ◽  
Oleguer Nogués-Correig ◽  
Dallas Masters ◽  
Linus Tan ◽  
...  
Keyword(s):  
Sea Ice ◽  
Radio Occultation ◽  
Grazing Angle ◽  
Precise Orbit Determination ◽  
Atmospheric Temperature ◽  
Open Loop ◽  
Electron Content ◽  
Total Electron ◽  
Mean Sea Surface ◽  
Ice Surfaces

&lt;p&gt;Spire Global operates the world&amp;#8217;s largest and rapidly growing constellation of CubeSats performing GNSS based science and Earth observation. Currently, the Spire constellation, with many satellites in polar orbits, performs a variety of GNSS science, including radio occultation (GNSS-RO), ionosphere and space weather measurements, and precise orbit determination. These satellites have been primarily tasked to perform GNSS-RO to produce accurate profiles of atmospheric temperature, pressure, and water vapor and to collect millions of daily ionospheric total electron content measurements. Previous work showed that grazing angle reflections of GNSS signals off of ocean and sea ice surfaces serendipitously collected during radio occultation measurements had the potential to perform precision altimetry (&lt; 10 cm) over sea ice surfaces.&lt;/p&gt;&lt;p&gt;In 2019, Spire reprogrammed its STRATOS GNSS science receiver to collect grazing angle reflection observations on Spire's large constellation of orbiting GNSS-RO satellites. To accomplish this, the open-loop tracking used in GNSS-RO collection was modified to perform open-loop prediction and tracking of grazing angle reflections between 5-30 deg elevation. Initial results confirm coherency of reflections over most sea ice surfaces and some open ocean surfaces. Full altimetric processing has been performed and is being productionized, confirming&amp;#160; sub-10 cm precision over sea ice where reflections were coherent, with some initial measurements showing altimetric height precision less than 2 cm RMS relative a mean sea surface (e.g., DTU18). Due to the large number of current and planned GNSS-RO satellites as Spire's constellation scales to over 100 operating GNSS-RO satellites, this technique has excellent potential to complement other sensors such as ICESat-2 and Cryosat-2.&lt;/p&gt;&lt;p&gt;A larger production period has now begun on multiple Spire satellites that will result in much larger quantities of diverse cryospheric measurements (sea ice as well as ice sheets will be sampled). We will present further results of this new and potentially revolutionary technique to use existing orbiting GNSS-RO satellite constellations to perform precision sea ice altimetry.&lt;/p&gt;

scholarly journals Venus Express radio occultation observed by PRIDE

2019 ◽  
Vol 624 ◽  
pp. A59 ◽  
Author(s):  
T. M. Bocanegra-Bahamón ◽  
G. Molera Calvés ◽  
L. I. Gurvits ◽  
G. Cimò ◽  
D. Dirkx ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Open Loop ◽  
Test Case ◽  
Deep Space ◽  
Processing Pipeline ◽  
Ground Station ◽  
Long Baseline ◽  
Doppler Data ◽  
Error Propagation Analysis ◽  
Venus Express

Context. Radio occultation is a technique used to study planetary atmospheres by means of the refraction and absorption of a spacecraft carrier signal through the atmosphere of the celestial body of interest, as detected from a ground station on Earth. This technique is usually employed by the deep space tracking and communication facilities (e.g., NASA’s Deep Space Network (DSN), ESA’s Estrack). Aims. We want to characterize the capabilities of the Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique for radio occultation experiments, using radio telescopes equipped with Very Long Baseline Interferometry (VLBI) instrumentation. Methods. We conducted a test with ESA’s Venus Express (VEX), to evaluate the performance of the PRIDE technique for this particular application. We explain in detail the data processing pipeline of radio occultation experiments with PRIDE, based on the collection of so-called open-loop Doppler data with VLBI stations, and perform an error propagation analysis of the technique. Results. With the VEX test case and the corresponding error analysis, we have demonstrated that the PRIDE setup and processing pipeline is suited for radio occultation experiments of planetary bodies. The noise budget of the open-loop Doppler data collected with PRIDE indicated that the uncertainties in the derived density and temperature profiles remain within the range of uncertainties reported in previous Venus’ studies. Open-loop Doppler data can probe deeper layers of thick atmospheres, such as that of Venus, when compared to closed-loop Doppler data. Furthermore, PRIDE through the VLBI networks around the world, provides a wide coverage and range of large antenna dishes, that can be used for this type of experiments.

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