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Lowell Digisonde International, LLC

Lowell, MA, United States
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Agency: European Commission | Branch: FP7 | Program: CPCSA | Phase: INFRA-2011-1.2.2. | Award Amount: 5.89M | Year: 2011

The ESPAS project will provide the e-Infrastructure necessary to support the access to observations, the modeling and prediction of the Near-Earth Space environment. This includes the plasma and energetic particle environments that surround our planet as well as the neutral atmosphere at altitudes above 60 km. These environments are an important target for future research in areas such as space weather and Sun-climate studies. The ESPAS interface will provide access to a diverse set of databases that have been developed for the needs of different users. Thus a primary goal is to facilitate user access to heterogeneous data from multiple providers, ranging from ground-based observations acquired with multiple instruments and techniques, to data from satellite experiments, using a mixture of in-situ and remotely sensed techniques. The results of searches will be delivered in a scientist-friendly manner based on existing standards and protocols. The infrastructure will also be used as a test-bed for development of methodologies and standards for validation of models of the near-Earth environment. This will lead to validated predictions of conditions in that environment, and thus promote the transfer of space environment science products into commercial and operational applications.

Reinisch B.W.,University of Massachusetts Lowell | Reinisch B.W.,Lowell Digisonde International, LLC | Galkin I.A.,Lowell Digisonde International, LLC
Earth, Planets and Space | Year: 2011

Digisonde ionospheric sounders installed at 80+ locations in the world have gradually evolved their generally independent existence into a Global Ionospheric Radio Observatory (GIRO) portal. Today GIRO provides public access to 30+ million records of ionospheric measurements collected at 64 locations, of which 42 provide realtime feeds, publishing their measurement data within several minutes from their completion. GIRO databases holding ionogram and Doppler skymap records of high-frequency ionospheric soundings have registered connections from 123 organizations in 33 countries. Easy access to the global state of the ionospheric plasma distribution given in accurate and fine detail by the ionosonde measurements has inspired a number of studies of the ionospheric response to space weather events. Availability of GIRO data with minimal latency allows for the assimilation of the ionogram-derived data in real-time models such as the real-time extension planned for the International Reference Ionosphere. Copyright © The Society of Geomagnetism and Earth.

Ozhogin P.,University of Massachusetts Lowell | Tu J.,University of Massachusetts Lowell | Song P.,University of Massachusetts Lowell | Reinisch B.W.,University of Massachusetts Lowell | Reinisch B.W.,Lowell Digisonde International, LLC
Journal of Geophysical Research: Space Physics | Year: 2012

We present a newly developed empirical model of the plasma density in the plasmasphere. It is based on more than 700 density profiles along field lines derived from active sounding measurements made by the radio plasma imager on IMAGE between June 2000 and July 2005. The measurements cover all magnetic local times and vary from L = 1.6 to L = 4 spatially, with every case manually confirmed to be within the plasmasphere by studying the corresponding dynamic spectrogram. The resulting model depends not only on L-shell but also on magnetic latitude and can be applied to specify the electron densities in the plasmasphere between 2000 km altitude and the plasmapause (the plasmapause location itself is not included in this model). It consists of two parts: the equatorial density, which falls off exponentially as a function of L-shell; and the field-aligned dependence on magnetic latitude and L-shell (in the form of invariant magnetic latitude). The fluctuations of density appear to be greater than what could be explained by a possible dependence on magnetic local time or season, and the dependence on geomagnetic activity is weak and cannot be discerned. The solar cycle effect is not included because the database covers only a fraction of a solar cycle. The performance of the model is evaluated by comparison to four previously developed plasmaspheric models and is further tested against the in situ passive IMAGE RPI measurements of the upper hybrid resonance frequency. While the equatorial densities of different models are mostly within the statistical uncertainties (especially at distances greater than L = 3), the clear latitudinal dependence of the RPI model presents an improvement over previous models. The model shows that the field-aligned density distribution can be treated neither as constant nor as a simple diffusive equilibrium distribution profile. This electron density model combined with an assumed model of the ion composition can be used to estimate the time for an Alfven wave to propagate from one hemisphere to the other, to determine the plasma frequencies along a field line, and to calculate the raypaths for high frequency waves propagating in the plasmasphere. © 2012. American Geophysical Union. All Rights Reserved.

Adebesin B.O.,Landmark University | Adeniyi J.O.,University Of Ilorin | Adimula I.A.,University Of Ilorin | Reinisch B.W.,Lowell Digisonde International, LLC
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

Average values of ionosonde hmF2 data acquired from an African equatorial station have been used to determine vertical plasma drift (Vz) measurements during period of low solar activity. Pre-noon peak was around 1000. h LT for all seasons. The peak daytime F2 drift is higher during the equinoctial months with an average of 18.1 m/s than the solsticial months (14.7 m/s). At nighttime, Vz is characterized first by upward enhancement around 1900. h LT with a range of 0.3-8.0. m/s, then by a downward reversal. The highest enhancement was recorded in December solstice and start earliest during the March equinox. The peak reversal values are 13.3, 10.7, 9.0 and 4.2 m/s for December Solstice, September Equinox, March Equinox and June Solstice respectively. The observed simultaneous post-sunset rise in hmF2 and in vertical E× B drift together with a sharp drop in NmF2 at all season infer that electrons moving away from the equator are at a region of low recombination loss rate. The abrupt faster drift of the plasma away from the equator as indicated by the pre-reversal enhancement (PRE) in upward plasma drift is responsible for the sharp drop in NmF2 immediately after sunset. Some past results were also confirmed in this work. © 2013 Elsevier Ltd.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.39K | Year: 2013

ABSTRACT: Over the horizon radar (OTHR) systems survey large areas searching for targets several thousand kilometers away by using ionospherically reflected high frequency (HF) radio waves. Accurate coordinate-registration (CR) of the targets requires detailed knowledge of the electron density profile (EDP) of the ionosphere between the radar and the targets. Our proposal outlines a realistic path toward providing in near real-time the specification of the ionospheric electron density distribution including wave modulations caused by traveling ionospheric disturbances (TIDs). The International Reference Ionosphere (IRI) model is used as a background model. Digisondes are proposed for the measurement of the ionospheric characteristics for real-time assimilation into the IRI model: foF2, foF1, foE, hmF2, hmF1, hmE, B0, B1, and D1. This real-time procedure will create the IRI Real-Time Assimilative Model (IRTAM). The Digisondes also measure the Doppler frequencies and arrival angles of ionospherically reflected HF signals from which the TID wave parameters are derived in real-time. The detected TID electron density waves can then be superimposed on the IRTAM electron distribution. The Huang-Reinisch2006 raytracing algorithm will be used to calculate the ray path through IRTAM. A computer simulation of this process will be conducted under Phase-I. BENEFIT: The rapid EDP and TID specifications technique proposed can be directly integrated into the existing Digisonde GIRO network in support of OTHR operations. The GIRO network can also easily be expanded by deploying additional commercially available Digisondes.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 823.73K | Year: 2013

ABSTRACT: It is proposed to build the breadboard functional proof unit of a new space borne instrument DPTIS (Double-Probe & Topside Ionosphere Sounder) that simultaneously measures in situ electric fields and the vertical electron density profiles from the spacecraft altitude to the F2 layer peak. The instrument is designed for a small satellite and integrates an RF Topside-Ionosphere-Sounder (TIS) with Double-Probe (DP) electric field sensors. Availability of six booms, configured into three orthogonal dipoles and 3 isolated double probes, is assumed. The TIS scans from 0.1 - 30MHz and specifies the wave polarization (O/X) and the echo angles-of-arrival for ionospheric skymap construction. Heritage from IMAGER/RPI and Digisondes is used, providing high programming flexibility that can adapt to diverse spacecraft orbits. Ionogram cadences of 10s provide high spatial resolution. Heritage autoscaling software derives real-time electron density profiles from the spacecraft altitude to the F2 peak. For the double-probe measurements, isolated spheres are mounted at the end of six antenna booms. The DPs will measure the 3 electric field components from DC to 1 KHz. DP voltages are continuously sampled at 2.5kS/s. DP design and processing is based on heritage instrumentation that UNH developed and delivered for the MMS and other missions. BENEFIT: Unambiguous measurement of the topside electron density profiles will provide unique data for the specification of the topside electron density distribution, which is otherwise only provided by incoherent scatter radars at a few points and at limited times. Assimilation of these data into an ionospheric model like IRI RTAM or GAIM will for the first time provide an accurate real-time assimilative model for the ionospheric electron density specification up to the spacecraft altitude (~1000 km). A fleet of topside satellites with DPTIS can provide near real-time high resolution maps of foF2 and hmF2 over the oceans and land, complementing the ground-based ionosonde measurements, as well as global near real time specifications of the topside electron density profiles which are affecting all transionospheric radio signals, including GPS. Ionospheric research missions in the F layer, both above or below the F2 peak, for detailed studies of equatorial spread F and scintillations, or auroral and polar cap irregularity structures can easily be carried out with DPITS because of its flexible programmability.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.97K | Year: 2015

ABSTRACT:Oblique-Ionogram (OI) measurements contain valuable information for operational high-frequency radio services that rely on ionospherically reflected signals. The proposed Lowell Oblique-Ionogram Autoscaler, LOIA will automatically extract and identify the echo traces of ionospherically reflected radio signals in digital OI data records. LOIA will be designed to process a variety of both polarization-tagged and -untagged oblique ionograms. It will operate an intelligent system for trace extraction from OI images based on a bio-plausible model of pre-attentive vision. The intelligent vision model will use a signal detector and a long-range analyzer of potential trace elements to determine if they belong to the same trace. Thus extracted traces will be cross-matched with predicted trace shapes for identification. The predicted shapes will be computed using real-time ionospheric specifications available from the Global Ionospheric Radio Observatory (GIRO) and the IRI Real-Time Assimilative Model IRTAM available from the Lowell GIRO Data Center. Once the extracted traces are identified, LOIA will run an iterative model fit for accurate evaluation of the F layer maximum usable frequencies, MUFo and MUFx.BENEFIT:The Lowell Oblique-Ionogram Autoscaler LOIA can become a powerful tool for companies that provide diagnostics and operational support for the optimization of the operation of HF direction finding and Over-the-Horizon Radar services. LOIA will extract and identify in realtime the echo traces contained in digital ionogram images, and provide the midpoint electron density profiles.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 747.76K | Year: 2014

ABSTRACT: Over-The-Horizon-Radar (OTHR) systems survey large areas searching for targets hundreds to thousands kilometers away. Accurate coordinate-registration (CR) of detected targets requires raytracing and accurate specification of the bottomside ionosphere. The proposed Real-Time EDP & TID (RETID) Specification System is based on the proven IRI electron density model and measurements by DPS4D ionosondes that provide the electron density profiles (EDPs) and the characteristic layer specifications. The DPS4Ds also collect the Doppler Frequency & Angles-of-arrival (AoA) Sounding (FAS) data associated with Traveling Ionospheric Disturbance (TID) wave structures. FAS measurements are also made on CW signals from transmitters of opportunity. The FAS measurements are analyzed in terms of the TID wave vector and amplitude. EDP and FAS data are ingested in real time in databases at the Lowell GIRO Data Center (LGDC). The layer characteristics foF2, hmF2, foF1, ... are assimilated in real-time in the IRI model to generate the IRI Real-time Assimilative Model IRTAM which is updated every 15 min. The TID density modulation is superimposed on IRTAM forming the TID-IRTAM. Using measured AoAs, the target location is specified by raytracing through the TID-IRTAM. Comparison of measured oblique ionograms between DPS4Ds with simulated oblique ionograms validates the RETID system performance. BENEFIT: The proposed RETID system takes advantage of existing ionospheric sensors, the DPS4Ds in the Digisonde Global Ionosphere Radio Observatory (GIRO) [Reinisch and Galkin, 2011], and the associated data infrastructure at LGDC. The existing instruments, the DPS4Ds, measure both the ionospheric profile specifications and the TID parameters. The RETID approach is cost effective and can be applied at any region in the world that has at least a few operating DPS4Ds. The RETID system supports operations like OTHR and HF Geolocation that measure the arrival angles of HF skywaves by providing accurate coordinate registration.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.19K | Year: 2012

ABSTRACT: The design of a new instrument for a small satellite is described that incorporates the specifications for an RF Topside Ionospheric Sounder (TIS) with Double Probe (DP) electric field sensors. Six 7.5-m booms, configured into three orthogonal 15-m tip-to-tip dipoles and 3 orthogonal double probes (DP), are assumed. The proposed"DPTIS"instrument can be flown within or above the ionosphere. The TIS design scans frequencies from 0.1 - 30 MHz and specifies the wave polarization (O/X) in the ionograms and the echo angle-of-arrival for ionospheric skymaps. The TIS design uses LDI/UML heritage from the IMAGER/RPI instrument and ground-based Digisondes and provides high programming flexibility to accommodate diverse S/C orbits. Ionogram/radio-skymap cadences of 10 s will provide high spatial resolution. Heritage autoscaling software can derive real-time electron density profiles from the S/C altitude to the F2-layer peak. The double probe measurements use isolated spheres mounted at the end of the 6 antenna booms. The DP will measure the field components from ~DC to 1 KHz. Outside the ionogram/skymap time windows the DP voltages are continuously sampled at nominally 4 kS/s. The DP design and processing is based on heritage instrumentation that UNH developed and delivered for the MMS and other missions. BENEFIT: The DPTIS design is sufficiently flexible to fly on research missions in the F layer, both above or below the F2 peak for detailed studies of equatorial spread F and scintillations, or on a fleet of topside surveying missions for the mapping of the global ionosphere. Accurate near real-time topside electron density profiles can be ingested into the GAIM model and will constrain the model in terms of foF2, hmF2, and accurate topside profiles to ~1,000 km altitude in all regions including those currently inaccessible with ground-based observations.

Lowell Digisonde International, LLC | Date: 2012-10-02

portable analysis instruments for ionospheric measurements and research; radio echo sounders; portable sounders for making measurements of the ionosphere; analysis instruments to determine radio signal propagation in support of radio communications or radio surveillance operations; and instruments for automatically collecting and analyzing ionospheric measurements for the purpose of selecting optimum operating frequencies for obliquely propagated communication or radar propagation paths.

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