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A. M. Mirochin*, N. F. Blagoveshchenskaya**, A. V. Shirochkov**, O. A. Troshichev**

* - Technical Center "Jupiter" ( 9 Krestovsky Av., St-Petersburg, 197042, Russia ).

**- Arctic and Antarctic Research Institute (38 Bering Str., St-Petersburg, 199397, Russia).

11.1. Introduction.

The catastrophic situation with the technological level of ground-based vertical ionospheric sounders in Russia became evident in the late 80's. The basic type of Russian vertical ionosonde with analogue recordings - the AIS (Automatic Ionospheric Station), which has been in operation since the International Geophysical Year (1957 - 59), needed to be replaced by a new type of ionosonde due to its having completely worn out. The necessity for a new modern type of ionosonde became urgent in this country, where the vertical ionosonde is the main tool for obtaining ionospheric data. Therefore many scientific institutes created their own ionosondes since they were unable to pay the big money required to order the complex commercial devices. Several types of such ionosondes ("Cyclon", "Parus" etc. ) have been described in different issues of the INAG Bulletins. Basically all these ionosondes were semi-professional devices built in the laboratories of scientific institutes. None of them was properly tested in the field. Unfortunately there is no coordinated program in Russia for establishing a national ionospheric network with proper financial sponsorship from the state. Therefore the search for an optimum type of ionosonde is continuing.

11.2. The BIZON ionosonde. General description.

Several years ago a technical center for research of scientific equipment, Jupiter, in Saint-Petersburg, in close collaboration with the scientists of the Arctic and Antarctic Research Institute produced a new type of advanced digital multi-functional ionosonde called BIZON with the primary intention of using it as a basic tool for ionospheric prediction purposes as well as for ionospheric research. The BIZON is a low cost, two-channel version of the modern digital ionosonde that can operate in three modes: vertical sounding, bistatic and monostatic oblique soundings. The BIZON includes the following separate industrially-made units :

(a) a two-channelled ionospheric receiver Liliya;

(b) a two-channelled digital signal processing system Minipreweck;

(c) a synchroniser;

(d) transmitter BIZON - R.

The ionosonde is controlled by a standard IBM PC AT-286 with a good software library designed for preliminary signal processing as well as for scaling ionograms, Ne-profile calculations and data storing. The ionosonde is made using standard transmitting and receiving antennas and for specific research projects it can operate with a complex antenna array. The existing software provides possibilities to communicate the ionospheric data by means of standard modem on dial-up or other communication lines. The BIZON is housed in the special functional table-like cabinet with the dimensions of height 0.85 m and width 1.35 m.

11.3. Possible outputs of the BIZON:

(a) The standard vertical ionograms (and the possibility of displaying any part of it with an enlarged scale).

(b) The amplitude and Doppler characteristics at any chosen frequency for a defined time interval.

(c) Doppler ionograms.

(d) Phase Soundings.

(e) Oblique monostatic Soundings (backscatter mode).

(f) Polarisation ionograms.

(g) Vertical absorption measurement at any chosen frequency (A1 mode of absorption measurements).

It is also possible to perform oblique, bistatic soundings between two Bizon's located at different geographical points. Two features of BIZON are worthy of special mentioning:

Technical details

Frequency range 0.5 - 30 MHz
Receiver bandwidths 1.2; 7.8; 15.0; 30.0 kHz
Receiver dynamic range 65 dB ( for each channel )
Gain control automatically selected fixed gain settings
Transmitting power 10 kW
Pulse widths 62.5 ; 125 ; 187.5 microseconds
Pulse repetition frequency 1 - 50 Hz
Number of range bins 500 ( selectable range start )
Range resolution 1 km
Amplitude resolution 1 %
Phase resolution 0.1
Doppler resolution Discrete Fourier transform has a resolution of 1/T, where T is selectable from 0.1 to 100 secs.
User Interface friendly software interface.
Power input 220 V, 50 - 60 Hz
Power consumption 3 kWA

(a) the two-channel receiver means precise phase measurements can be made;

(b) a wide dynamic range receiver, which could provide more reliable performance at high-latitudes where increased abnormal absorption in the lower ionosphere creates a "black - out" situation on many occasions.

11.4. BIZON field testing results.

One of the first BIZON units made underwent testing in different modes of sounding at the observatory of Arctic and Antarctic Research Institute located at 50 miles from Saint-Petersburg (latitude 59.95 N; longitude 30.70 E; invariant latitude 56.06 N). The tests are being made over several months in conditions of severe electromagnetic interference using a poor supply of power. The purpose of the testing was twofold: to check the technical and software parameters of ionosonde against their original design parameters as well as to be sure the BIZON can operate properly for a long time in a permanent sounding mode. The results of these tests were very successful and the BIZON proved a reliable performer. The next ionosonde units are under preparation for installation in observatories in the Arctic as well as in Antarctica. More detailed descriptions of the BIZON tests, in different modes of operation, are given below.

11.4.1. Vertical sounding.

A wide range of measurements can be made by the BIZON in the vertical sounding mode. First of all, a conventional ionogram with O/X separation is made. This mode of sounding is used for real-time operational information for different kinds of customers. Operator cannot alter the sounding program in this case. An output of each sounding is distributed as a message in the international URSI approved code. Besides that, it is possible to get an Amplitude Ionogram, a Doppler Ionogram as well as the angular and Direction of Arrival characteristics of the received signal (if the corresponding antennas are available). Ionospheric absorption using the A1 method is also possible. The ionograms are stored by using DBase code under the MS-DOS system. Data files are compressed (4:1) to save storage space. The ionogram can be processed immediately after recording and an operator can control this process. The software can filter the signal, remove certain frequencies, enlarge any part of the ionogram, present the ionogram in different coordinate systems etc. There is a special program for calculating Ne(h) profiles from the ionogram. Several periods of severe geomagnetic disturbances were recorded during the BIZON testing campaigns in January, February and March of 1994. Figure 1 shows the data from vertical sounding on February 16, 1994 for period 03.28 UT to 06.01 UT in a suburb of Saint-Petersburg. Noteworthy is the presence of the main ionospheric trough ( 03.28 UT ) at this comparatively low invariant latitude. It is an indication of significant equatorward displacement of the auroral oval during the geomagnetic storm.

11.4.2. Monostatic oblique sounding (backscatter mode).

This mode of sounding was made by scanning the frequency range of the BIZON and was performed from January 1994. The observations take place during the Regular World Days (RWD) of each month in the period from 15 UT till 03 UT. This mode of sounding from Saint-Petersburg allows monitoring of the position (in space and time) of the poleward wall of the main ionospheric trough as well as to explore the ionospheric features of magnetospheric substorms which usually take place far northward from Saint-Petersburg.

Two different kinds of sounding were used in these experiments:

(a) backscattering in the scanning frequency range with time interval from 3 to 30 minutes between each sounding;

(b) continuously backscattering at fixed frequencies during the period from 8 to 25 minutes when the amplitudes and Doppler frequency shifts were registered.

Some examples of these data are given. Figure 2 presents several backscatter ionograms taken in the frequency scan mode using signals from the F region. The simultaneous time variations of Doppler frequency shifts (in Hz) taken at the fixed frequencies 3.5 MHz and 5.5 MHz on February 16, 1994 are also shown. Figure 3 shows a sequence of backscatter ionograms, with reflections from auroral forms, taken during the storm on February 16, 1994. The frequency scan mode is used here. An interesting feature of these ionograms is the lowest trace which probably belongs to a slant F-layer. Figure 4 shows the three-dimensional impression of amplitudes and the time variations of Doppler frequency shifts taken at a fixed frequency of 4 MHz during a geomagnetic storm on January 12, 1994. The time interval is from 21.20 UT until 21.28 UT. The data in Fig.4 shows wave-like variations of both amplitudes and Doppler shifts with periods of 2-3 minutes. Most probably these wave-like variations of the ionospheric parameters are connected with the infrasonic waves produced by the movements of auroral arcs. The data in Fig. 4 clearly demonstrate equatorward shift of the region of wave-like variations of amplitude from a distance of 1800 km to a distance of 800 km in 8 minutes. The corresponding velocity of such movement is of the order of 2 km second-1 which is in reasonable agreement with other available estimations of velocity of the auroral forms.

The examples in Figures 1, 2, 3 and 4 show the capabilities of the BIZON to perform as a reliable ionosonde in an ionospheric network as well as a modern research ionosonde. Another conclusion which can be derived from the BIZON testing is that its technical reliability is rather high. This is a very important quality of an ionosonde proposed for performance in severe and uncomfortable conditions at polar observatories.

11.5. Availability

Everybody who is interested in obtaining this type of ionosonde is encouraged to contact the manufactures of the BIZON.

BIZON outputs

sample BIZON outputs

Mr. A. M. Mirochin Technical Center "Jupiter"
P. O. Box 93
Krestovsky avenue, 9
Saint-Petersburg, 197042, RUSSIA

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