Operating Network of Phase-Based Ionosondes (Dynasondes)
M. Rietveld 1, N. Zabotin 2, T. Bullett 2,3, R. Livingston 4, S. Kolesnik 5
1 EISCAT Scientific Association , 2 University of Colorado at Boulder, 3 NOAA/NGDC, 4 Scion Associates Inc., 5 Tomsk State University
Abstract
Dynasonde is an ideology of precision ionospheric radio sounding based on
rigorously taking into account phase characteristics of a radio echo. Unique
products of phase ionosondes intended for various Space Weather-related
applications include: echo recognition and noise discrimination, echo
classification into traces, scaling of standard ionospheric parameters, 3-D
plasma density inversion (NeXtYZ) including true vertical profile with error
bars, small-scale irregularity diagnostics, and vector velocities, all obtained
directly and autonomously from ionogram data. At present there are three
systems in the world which operate continuously and are fully based on the
precision phase principles. These reside at EISCAT Tromsø observatory, at
EISCAT Svalbard observatory, and at Tomsk State University (Russia). The
latter system uses the newest HF Radar ("VIPIR") built by Scion Associates.
Data and analysis results from all three stations are stored in a distributed
relational SQL database network. These are accessible to a broad research
community either directly or, in abridged version, through the NOAA/NGDCbased SPIDR system. We report details of the network operation and describe
its web portal Dynasonde Navigator (http://dynserv.eiscat.uit.no) hosted by
EISCAT.
To understand why Dynasonde analysis software provides more quality and
more diverse results than any other existing method, it is necessary to look at
fundamentals: at how it treats the raw I and Q data (quadrature components of
the received signal) provided by the sounding system.
The old tradition, originating in the
years of analog sounding systems,
is to treat the ionogram as an
image. Usually this image is plotted
using signal amplitude expressed
in dB: A = 10·log(I2+Q2). Very limited
phase-based information (e.g, a polarization tag to distinguish between
O and X reflections) may be used.
But all essential first steps of data
processing (echo detection, echo
classification into traces, trace
selection, and determination of
important physical parameters)
were done as image processing
procedures.
Dynasonde
data
processing
primarily uses phase-based information, complementing it with the amplitude
information only where it is especially relevant. The phase is defined as P =
atan2(Q,I).
3-Dimensional Plasma Density Inversion (NeXtYZ)
NeXtYZ is the first ionogram inversion scheme created in the era of PCs. It
provides the following advantages:
• NeXtYZ yields the actual vertical fp(h) profile, plus the vertical profile of
horizontal gradients;
• treatment of magnetic field effects is free of the biases caused by
assumption of vertical propagation;
• ordinary and extraordinary echoes are used equally in NeXtYZ allowing
better characterization of under-represented (valley, night E) ionospheric
regions;
• NeXtYZ uses state-of-the-art models for underlying ionization and the E-F
valley;
• NeXtYZ provides extensive statistical information for estimation of fp(h)
profile uncertainties.
Vector velocity calculations are provided for all significant ionospheric
structures individually:
The algorithm of velocity calculations is based on the large statistics of
ionogram echoes, without requiring a dedicated mode of operation.
Diversity of Analysis Results Makes Relational SQL Database a Natural
Solution for Their Local Storage
The figure on the right shows results of the
phase-based echo recognition procedure
performed by dynasonde analysis software
in the “time of arrival” domain. This is the
same recording from which the raw
amplitude image was used above. A total of
six independent physical parameters,
together with their uncertainties, are
determined for each echo.
In this process, ionospheric roughness is the main factor influencing actual
uncertainties. Average practical values of the uncertainties for high-latitude
EISCAT Tromsø location are:
Group Range
± 100 m
Horizontal echolocations ± 1 km
Doppler Velocity
± 3 m/s
Polarization
± 1 deg
This accuracy is unmatched by other processing methods.
The next analysis steps (echo classification into traces and trace selection),
are done using the list of echoes supplied with accurate physical parameters.
This is also an innovative approach in the field of ionospheric radio sounding.
These steps are critical for dependable autonomous data processing. Accurate
parameters allow application of an extended set of physical criteria to avoid
blunders. This is how Dynasonde ideology resolves the problem of
dependability of autonomous data processing at the level not achievable for
preceding techniques.
In addition to the standard ionospheric parameters, unique Dynasonde
products include: dependable autonomous scaling of standard ionospheric
parameters, 3-D plasma density inversion (NeXtYZ), small-scale irregularity
diagnostics, and vector velocities, all obtained autonomously and directly from
ionogram data.
SQL databases have a lot of
standard software solutions for
data access and retrieval. One of
them, MySQL Query Browser, is
shown on the left. Many research
tasks are accomplished through a
common API and a direct access
to a database using a secure
connection.
Three continuously operating ionosondes based on precision phase principles
form an initial segment of future network
Dynasonde Navigator: web portal for the network of phase ionosondes
The three stations are at highlatitude (EISCAT Tromsø), at
extremely high-latitude (EISCAT
Svalbard) and at mid-latitude
(Tomsk, Russia) locations. All
three are now continuously
providing results of their
measurements through their
own web sites on the Internet
and through the NOAA/NGDC’s
SPIDR system.
EISCAT Tromsø is the oldest existing Dynasonde
location. A very successful partially digital NOAA HF
Radar developed in the early 1980’s is being used
there (see photo on the right). This is a 6-antenna 2receiver system supplied with an advanced logperiodic vertex-down zigzag transmit antenna. This
system has been extensively used in development of
modern versions of all Dynasonde methods.
EISCAT Svalbard is an ionosonde location which is the
closest to the Earth’s North Pole. Basically this is the
NOAA HF Radar of the same design that in Tromsø (see
photos on the left), but in a mobile implementation.
This is a 4-antenna 2-receiver system supplied with an
inverse delta transmit antenna. This system had served
previously at the British Antarctic Survey’s Halley Bay
observatory in Antarctica, and it was recently (in 2008)
relocated to EISCAT Svalbard observatory.
Ionospheric observatory of Tomsk State University is
the 5th in the world and the oldest continuously
operating ionospheric facility in Russia (since 1936). In
2009 it was equipped with the newest fully digital Scion
HF Radar ("VIPIR"). This is an 8-antenna 8-receiver
system supplied with a rhombic transmit antenna. The
radar’s photo is on the right, images of the antenna
system are below.
Home page of the web portal (http://dynserv.eiscat.uit.no).
The EISCAT’s Dynasonde Database contains
results of data analysis for EISCAT Tromsø
station since June 2009, for EISCAT Svalbard
station since September 2009, and also
contains results of earlier data processing for
three stations (Bear Lake Obs., Utah from
February 2003 to June 2006, EISCAT Tromsø
from June 2003 to December 2006, and
Lycksele, Sweden from March 2004 to August
2005).
Dynamically updated “Latest Ionogram” and “Last 48 Hours” pages of the web portal are
shown above. Other graphical tools, including the database interface, are represented below.
Home page of a modern Dynasonde system is itself an instrument of
ionospheric monitoring and research
In addition, for those who
are not familiar with SQL,
a web-based interface is
provided for each station
connected to the Internet
that allows
a) retrieval of several
kinds
of
ionogramrelated information, in
both
textual
and
graphical formats;
b) execution of complex
queries intended for
selection of the analysis
results subject to several
conditions.
An example data query: A 7month-long series of eastward
drift velocity values when zenith
angle of the Sun was between 45
and 50 degrees and foE was less
than 2 MHz.
Other modern ionosondes with capability to perform precision phase-based measurements
Four other Scion HF Radar ("VIPIR") installations are fully capable to perform precision
phase-based measurements, but do not yet operate continuously:
(1) NOAA/NGDC, Boulder, Colorado,
(2) NASA’s Wallops Flight Facility, Wallops Island, Virginia,
(3) Jicamarca Radio Observatory, Peru,
(4) National Central University, Taiwan.
To get full access to the present analysis results and to the local database one
needs to have a User Name and a Password that are obtained from the system
administrator. A limited access is attainable with User Name "Guest" and
Password "Guest". However, even without logging in one can obtain a few key
pieces of information. There is a reduced-size automatically renewed image of the
latest ionogram. One needs only to keep the Internet browser open to stay
current. The scripts on this page are browser- and system-independent.
Acknowledgements
The authors appreciate contributions to important specific areas of the effort which are
described here from the following collaborators: G. Zhbankov – development of NeXtYZ
inversion routines in 2002-2009; L. Zabotina – software development and support in 20032010; A. Senior – fixing of BPG mode on legacy dynasonde systems in 2009; J.W. Wright
and M.L.V. Pitteway – analysis software development before 2006.