An ionosonde, or chirpsounder, is a special

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

for the examination of the

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

. The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve and further developed in the late 1920s by a number of prominent physicists, including Edward Victor Appleton. The term ''

'' and hence, the etymology of its derivatives, was proposed by Robert Watson-Watt.

Components

An ionosonde consists of: * A

high frequency High frequency (HF) is the ITU designation for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one ...

(HF) radio transmitter, automatically tunable over a wide range. Typically the frequency coverage is 0.5–23 MHz or 1–40 MHz, though normally sweeps are confined to approximately 1.6–12 MHz. * A tracking HF receiver which can automatically track the frequency of the transmitter. * An antenna with a suitable radiation pattern, which transmits well vertically upwards and is efficient over the whole frequency range used. * Digital control and data analysis circuits. The transmitter sweeps all or part of the HF frequency range, transmitting short pulses. These pulses are reflected at various layers of the ionosphere, at heights of , and their echos are received by the receiver and analyzed by the control system. The result is displayed in the form of an

ionogram An ionosonde, or chirpsounder, is a special radar for the examination of the ionosphere. The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve and further developed in the late 1920s by a number of prominent phys ...

, a graph of reflection height (actually time between transmission and reception of pulse) versus

carrier frequency In telecommunications, a carrier wave, carrier signal, or just carrier, is a periodic waveform (usually sinusoidal) that conveys information through a process called ''modulation''. One or more of the wave's properties, such as amplitude or fre ...

. An ionosonde is used for finding the optimum operation frequencies for broadcasts or two-way communications in the high frequency range.

Ionogram

An ionogram is a display of the data produced by an ionosonde; technically speaking one may call the data used to make the display as the ionogram but often this is simply implied. It is a graph of the virtual height of the ionosphere plotted against frequency. Ionograms are often converted into electron density profiles. Data from ionograms may be used to measure changes in the Earth's

due to

space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ion ...

events. Note that in the ionogram above the legend can be more clearly understood as having "Vx-" and "Vx+" to replace respectively "X-" and "X+". These refer to the vertical reflection of the eXtraordinary kind. "Vo-" and "Vo+" refer to the Ordinary reflection. An Ordinarily reflected wave is the one that behaves as though there were no geomagnetic field. ARTIST is the software program used to "scale" (deduce or calculate) the characteristic parameter values shown in the table on the left. The version shown here is "5", which is the latest as of March 2022. Ion2Png is the software program used to create the ionogram image.

Chirp transmitter

chirp A chirp is a signal in which the frequency increases (''up-chirp'') or decreases (''down-chirp'') with time. In some sources, the term ''chirp'' is used interchangeably with sweep signal. It is commonly applied to sonar, radar, and laser syste ...

transmitter is a

shortwave radio Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the High frequency, high frequency band (HF), which extends from 3 to 30& ...

transmitter that sweeps the HF

radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...

on a regular schedule. If one is monitoring a specific frequency, then a ''chirp'' is heard (in CW or SSB mode) when the signal passes through. In addition to their use in probing

ionospheric The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

properties,Peter Martinez, G3PLX: Chirps and HF Propagation http://jcoppens.com/radio/prop/g3plx/index.en.php these transmitters are also used for over-the-horizon radar systems. An analysis of existing transmitters has been done using SDR technology.Pieter-Tjerk de Boer, PA3FWM: Chirp Signals analyzed using SDR http://websdr.ewi.utwente.nl:8901/chirps/ For better identification of chirp transmitters the following notation is used: :, where the repetition rate is the time between two sweeps in seconds and the chirp offset is the time of the first sweep from 0 MHz after a full hour in seconds. If the initial frequency is greater than 0 MHz, the offset time can be linearly extrapolated to 0 MHz.

References

External links

: NOAA Ionosonde portal to information and data services
ngdc.noaa.gov
: NOAA Dynasonde: Real-time Ionospheric Explorer by advanced and prototype analysis methods. *http://aintel.bi.ehu.es/chirps-data/chirps.html *http://ulcar.uml.edu/digisonde.html : Lowell Center for Atmospheric Research, MA, USA *http://ulcar.uml.edu/stationlist.html : Ionosonde (partial) station list by location * http://car.uml.edu/common/DIDBFastStationList : DIDBase Fast Station list *http://www.iono.noa.gr : National Observatory of Athens, Greece *http://www.sil.sk.ca/content/cadi : Canadian Advanced Digital Ionosonde (CADI) {{refend Ionosphere Radar Infographics Radar meteorology

Components

Ionogram

Chirp transmitter

See also

References

Further reading

External links