First Order Sea Clutter Cross Section for HF Hybrid Sky-Surface Wave Radar

This paper presents a modified method to simulate the first order sea clutter cross section for high frequency (HF) hybrid sky-surface wave radar, based on the existent model applied in the bistatic HF surface wave radar. The modification focuses on the derivation of Bragg scattering frequency and the ionosphere dispersive impact on the clutter resolution cell. Meanwhile, an analytic expression to calculate the dispersive transfer function is derived on condition that the ionosphere is spherical stratified. Simulation results explicate the variance of the cross section after taking account of the influence triggered by the actual clutter resolution cell, and the spectral width of the first order sea clutter is defined so as to compare the difference. Eventually, experiment results are present to verify the rationality and validity of the proposed method

Relativistic Particle Beams as a Resource to Solve Outstanding Problems in Space Physics

The Sun\u27s connection with the Earth\u27s magnetic field and atmosphere is carried out through the exchange of electromagnetic and mass flux and is regulated by a complex interconnection of processes. During space weather events, solar flares, or fast streams of solar atmosphere strongly disturb the Earth\u27s environment. Often the electric currents that connect the different parts of the Sun-Earth system become unstable and explosively release the stored electromagnetic energy in one of the more dramatic expressions of space weather—the geomagnetic storm and substorm. Some aspects of the magnetosphere-ionosphere connection that generates auroral arcs during space weather events are well-known. However, several fundamental problems remain unsolved because of the lack of unambiguous identification of the magnetic field connection between the magnetosphere and the ionosphere. The correct mapping between different regions of the magnetosphere and their foot-points in the ionosphere, coupled with appropriate distributed measurements of plasma and fields in focused regions of the magnetosphere, is necessary to establish unambiguously that a given magnetospheric process is the generator of an observed arc. We present a new paradigm that should enable the resolution of the mapping ambiguities. The paradigm calls for the application of energetic electron beams as magnetic field tracers. The three most important problems for which the correct magnetic field mapping would provide closure to are the substorm growth phase arcs, the expansion phase onset arcs and the system of arcs that emerge from the magnetosphere-ionosphere connection during the development of the early substorm expansion phase phenomenon known as substorm current wedge (SCW). In this communication we describe how beam tracers, in combination with distributed measurements in the magnetosphere, can be used to disentangle the mechanisms that generate these critical substorm phenomena. Since the application of beams as tracers require demonstration that the beams can be injected into the loss cone, that the spacecraft potentials induced by the beam emission are manageable, and that sufficient electron flux reaches the atmosphere to be detectable by optical or radio means after the beam has propagated thousands of kilometers under competing effects of beam spread and constriction as well as effects of beam-induced instabilities, in this communication we review how these challenges are currently being addressed and discuss the next steps toward the realization of active experiments in space using relativistic electron beams

Orbital debris research at NASA Johnson Space Center, 1986-1988

Research on orbital debris has intensified in recent years as the number of debris objects in orbit has grown. The population of small debris has now reached the level that orbital debris has become an important design factor for the Space Station. The most active center of research in this field has been the NASA Lyndon B. Johnson Space Center. Work is being done on the measurement of orbital debris, development of models of the debris population, and development of improved shielding against hypervelocity impacts. Significant advances have been made in these areas. The purpose of this document is to summarize these results and provide references for further study

Comets: Gases, ices, grains and plasma

The program and abstracts of the 97 papers delivered at the colloquium are presented. Cometary nuclei, comet dust, the coma, ion tails, several comet missions, and cometary origin and evolution were discussed

Primjene planetarnog radio interferometrijskog i Dopplerovog eksperimenta (PRIDE) na orbitere i sletače

PRIDE: the Planetary Radio Interferometry and Doppler Experiment (Duev et al. 2012) is an initiative by the Joint Institute for VLBI ERIC (JIVE) providing ultraprecise estimates of spacecraft state vectors (spatial coordinates and velocities) as a function of time, utilizing phase-referenced Very Long Baseline Interferometry (VLBI) tracking and radial Doppler measurements. This method is applicable to any radioemitting spacecraft, and the results can be used in a plethora of disciplines from planetary science to high-precision celestial mechanics, gravimetry and fundamental physics. This Thesis includes an overview of the scheduling procedure for a future PRIDE observation of two active spacecraft in Mars’ orbit, involving the European VLBI Network (EVN) and Very Long Baseline Array (VLBA) telescopes, as well as a demonstration of the data processing pipeline for a PRIDE experiment performed with the Mars Express orbiter in 2013. The resulting observables are applied to a radio occultation study of the Martian atmosphere, yielding vertical refractivity, density, pressure and temperature parameters. Furthermore, future opportunities for PRIDE are investigated in terms of a potential bistatic radar experiment with ESA’s JUpiter Icy moons Explorer (JUICE) mission, enabling a study of the surface of the Jovian moon Europa, as well as applications to the Lander Radioscience (LaRa) experiment which is designed to study the geological composition of Mars’ interior. The quality of the Doppler data from the single European VLBI Network (EVN) antennas is comparable to closed-loop Doppler data obtained by dedicated deep space tracking systems like NASA’s Deep Space Network and ESA’s Estrack (Bocanegra-Bahamón et al. 2018), proving that PRIDE data could enhance the science return of missions not initially designed for radio science experiments.PRIDE: Planetary Radio Interferometry and Doppler Experiment (Duev et al. 2012) inicijativu pokrenuo je Joint Institute for VLBI ERIC (JIVE) s ciljem ultra-preciznog mjerenja vektora stanja svemirskih letjelica (njihovih prostornih koordinata i brzina) kao funkcije vremena, koristeći fazno referenciranu dugobazičnu interferometriju (VLBI) i radijalna Doppler mjerenja. Ova je metoda primjenjiva na bilo koju letjelicu s radioemiterom, a rezultati imaju bogatstvo primjena u disciplinama od planetarne znanosti do visokoprecizne nebeske mehanike, gravimetrije i fundamentalne fizike. Ovaj Rad uključuje pregled postupka planiranja buduće PRIDE opservacije za dvije trenutno aktivne letjelice u Marsovoj orbiti koristeći European VLBI Network (EVN) i Very Long Baseline Array (VLBA) mreže teleskopa, a ujedno i primjer obrade podataka za prethodno izvršen PRIDE eksperiment s Mars Express orbiterom u 2013. godini. Izračunate opservable primijenjene su na radiookultacijsko proučavanje Marsove atmosfere, dajući vertikalne profile refraktivnosti, gustoće, tlaka i temperature. Nadalje, istražene su buduće prilike za primjenu PRIDE-a u okviru potencijalnog eksperimenta s bistatičkim radarom za ESA-inu misiju JUpiter Icy moons Explorer (JUICE), omogućavajući proučavanje površine Jupiterovog mjeseca Europe, kao i primjena na Lander Radioscience (LaRa) eksperiment koji je dizajniran za proučavanje geološke kompozicije Marsove unutrašnjosti. Kvaliteta Doppler podataka s European VLBI Network (EVN) antena usporediva je s Doppler podacima iz zatvorene petlje dobivenim na namjenskim sistemima za praćenje u dubokom svemiru, npr. NASA-in Deep Space Network i ESA-in Estrack (Bocanegra-Bahamón et al. 2018), što ukazuje da PRIDE podaci mogu obogatiti znanstvene rezultate misija koje nisu inicijalno dizajnirane za radioeksperimente

Development of Radio Frequency Interference Detection Algorithm for Passive Microwave Remote Sensing

Radio Frequency Interference (RFI) signals are man-made sources that are increasingly plaguing passive microwave remote sensing measurements. RFI is of insidious nature, with some signals low power enough to go undetected but large enough to impact science measurements and their results. With the launch of the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite in November 2009 and the upcoming launches of the new NASA sea-surface salinity measuring Aquarius mission in June 2011 and soil-moisture measuring Soil Moisture Active Passive (SMAP) mission around 2015, active steps are being taken to detect and mitigate RFI at L-band. An RFI detection algorithm was designed for the Aquarius mission. The algorithm performance was analyzed using kurtosis based RFI ground-truth. The algorithm has been developed with several adjustable location dependant parameters to control the detection statistics (false-alarm rate and probability of detection). The kurtosis statistical detection algorithm has been compared with the Aquarius pulse detection method. The comparative study determines the feasibility of the kurtosis detector for the SMAP radiometer, as a primary RFI detection algorithm in terms of detectability and data bandwidth. The kurtosis algorithm has superior detection capabilities for low duty-cycle radar like pulses, which are more prevalent according to analysis of field campaign data. Most RFI algorithms developed have generally been optimized for performance with individual pulsed-sinusoidal RFI sources. A new RFI detection model is developed that takes into account multiple RFI sources within an antenna footprint. The performance of the kurtosis detection algorithm under such central-limit conditions is evaluated. The SMOS mission has a unique hardware system, and conventional RFI detection techniques cannot be applied. Instead, an RFI detection algorithm for SMOS is developed and applied in the angular domain. This algorithm compares brightness temperature values at various incidence angles for a particular grid location. This algorithm is compared and contrasted with other algorithms present in the visibility domain of SMOS, as well as the spatial domain. Initial results indicate that the SMOS RFI detection algorithm in the angular domain has a higher sensitivity and lower false-alarm rate than algorithms developed in the other two domains.Ph.D.Atmospheric and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86308/1/samisra_1.pd

Middle Atmosphere Program. Handbook for MAP. Volume 30: International School on Atmospheric Radar

Broad, tutorial coverage is given to the technical and scientific aspects of mesosphere stratosphere troposphere (MST) meteorological radar systems. Control issues, signal processing, atmospheric waves, the historical aspects of radar atmospheric dynamics, incoherent scatter radars, radar echoes, radar targets, and gravity waves are among the topics covered

Evaluation of the Maser-equipped Radar Set AN/MPS-34 and Area Precipitation Measurement Indicator: Final Report

published or submitted for publicationis peer reviewedOpe