An ionosonde, or chirpsounder, is a special

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

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 an ...

. The basic ionosonde technology was invented in 1925 by Gregory Breit and

Merle A. Tuve Merle Anthony Tuve (June 27, 1901 – May 20, 1982) was an American geophysicist who was the Chairman of the Office of Scientific Research and Development's Section T, which was created in August 1940. He was founding director of the Johns Hopkins ...

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 Sir Robert Alexander Watson Watt (13 April 1892 – 5 December 1973) was a Scottish pioneer of radio direction finding and radar technology. Watt began his career in radio physics with a job at the Met Office, where he began looking for accura ...

Components

An ionosonde consists of: * A

high frequency High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) 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 ...

(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 100–400 km (60 to 250 miles), 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 waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has a m ...

. 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 time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ma ...

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 charasteristic 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 image that we call ionogram.

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 system ...

transmitter is a

shortwave radio Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...

transmitter that sweeps the HF

radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 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 a ...

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 Over-the-horizon radar (OTH), sometimes called beyond the horizon radar (BTH), is a type of radar system with the ability to detect targets at very long ranges, typically hundreds to thousands of kilometres, beyond the radar horizon, which is ...

systems. An analysis of current 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

*http://www.ngdc.noaa.gov/stp/iono/ionogram.html : NOAA Ionosonde portal to information and data services *http://www.ngdc.noaa.gov/stp/IONO/Dynasonde/ : 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 Observatoy 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