New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope
At present time the modernization of the giant decametric radio telescope UTR-2 is under way. New back-end facilities and methods which open up new possibilities for radio astronomical observations are developed. Some equipment was made in cooperation with Austrian and French radio astronomers. Curr...
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| Published in: | Кинематика и физика небесных тел |
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| Date: | 2005 |
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Головна астрономічна обсерваторія НАН України
2005
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| Cite this: | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope / K.M. Sidorchuk, A.A. Konovalenko, H.O. Rucker, A. Lecacheux, L. Denis, M.A. Sidorchuk, S.L. Rashkovsky, V.V. Dorovsky, V.V. Zakharenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 57-60. — Бібліогр.: 4 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860078669789134848 |
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| author | Sidorchuk, K.M. Konovalenko, A.A. Rucker, H.O. Lecacheux, A. Denis, L. Sidorchuk, M.A. Rashkovsky, S.L. Dorovsky, V.V. Zakharenko, V.V. |
| author_facet | Sidorchuk, K.M. Konovalenko, A.A. Rucker, H.O. Lecacheux, A. Denis, L. Sidorchuk, M.A. Rashkovsky, S.L. Dorovsky, V.V. Zakharenko, V.V. |
| citation_txt | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope / K.M. Sidorchuk, A.A. Konovalenko, H.O. Rucker, A. Lecacheux, L. Denis, M.A. Sidorchuk, S.L. Rashkovsky, V.V. Dorovsky, V.V. Zakharenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 57-60. — Бібліогр.: 4 назв. — англ. |
| collection | DSpace DC |
| container_title | Кинематика и физика небесных тел |
| description | At present time the modernization of the giant decametric radio telescope UTR-2 is under way. New back-end facilities and methods which open up new possibilities for radio astronomical observations are developed. Some equipment was made in cooperation with Austrian and French radio astronomers. Current back-end facilities and methods used at the UTR-2 radio telescope are described and compared with former traditional methods, equipment and their characteristics. Some prospects regarding current progress in developing new generation of back-end facilities are also discussed. The main focus of the presentation is the observation methods and equipment applied at the UTR-2 radio telescope for the investigation of continuum radio sources: Galactic background, discrete sources (preparation for the catalogue of sources in the whole Northern Sky), SNR, HII regions. Some results of using the new back-end facilities (such as Digital Spectral Polarimeter) and processing methods are presented.
|
| first_indexed | 2025-12-07T17:15:29Z |
| format | Article |
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NEW METHODS AND EQUIPMENT OF DECAMETRIC
RADIO ASTRONOMY FOR CONTINUUM OBSERVATION
AT THE UTR-2 RADIO TELESCOPE
K. M. Sidorchuk1, A. A. Konovalenko1, H. O. Rucker2, A. Lecacheux3, L. Denis3,
M. A. Sidorchuk1, S. L. Rashkovsky1, V. V. Dorovsky1, V. V. Zakharenko1
1Institute of Radio Astronomy, NAS of Ukraine
4 Chervonopraporna Str., Kharkiv, Ukraine
e-mail: rai@ira.kharkov.ua
2Space Research Institute
6 Schmiedlstrasse, Graz, Austria
3Observatoire de Paris – CNRS URA 1757
F-92195 Meudon Cedex, France
At present time the modernization of the giant decametric radio telescope UTR-2 is under way.
New back-end facilities and methods which open up new possibilities for radio astronomical obser-
vations are developed. Some equipment was made in cooperation with Austrian and French radio
astronomers. Current back-end facilities and methods used at the UTR-2 radio telescope are de-
scribed and compared with former traditional methods, equipment and their characteristics. Some
prospects regarding current progress in developing new generation of back-end facilities are also
discussed. The main focus of the presentation is the observation methods and equipment applied at
the UTR-2 radio telescope for the investigation of continuum radio sources: Galactic background,
discrete sources (preparation for the catalogue of sources in the whole Northern Sky), SNR, H II
regions. Some results of using the new back-end facilities (such as Digital Spectral Polarimeter)
and processing methods are presented.
INTRODUCTION
At present time the modernization of giant decameter UTR-2 radio telescope, located near Kharkiv is under
way. A lot of work has been done by us and also together with French colleagues (Paris–Meudon Observatory)
and Austrian colleagues (Space Research Institute, Graz). The main subject of our joint efforts is the develop-
ment and implementation of modern back-end facilities and data processing methods for the UTR-2 radio
telescope. In the frame of INTAS joint projects during last five years of cooperation we had conducted four
joint observational campaigns [4] with use of new Digital Spectral Polarimeter [3], which allowed us to greatly
improve sensitivity, time and frequency resolution of the radio telescope. Specially designed data processing
methods and observational algorithms allowed us to decrease duration of observations in several times. The main
focus of the presentation is the observational methods and equipment applied at the UTR-2 radio telescope for
the investigation of continuum radio sources: Galactic background, discrete sources (preparation for the discrete
sources catalogue in the whole Northern Sky), supernova remnants, H II regions.
MODERNIZATION OF THE UTR-2 RADIO TELESCOPE
T-shaped UTR-2 radio telescope [1] can be represented as shown in Fig. 1a: North–South antenna and East–
West antenna are phased with electrical phase system based on switched delay lines. Phase system produces
knife-like antenna patterns for both antennas. The phase system has six outputs: first is the output from East–
West antenna, i.e., knife-like beam, which is 0.5◦ wide in East–West direction and 15◦ wide in North–South
direction. Outputs from second to sixth are five knife-like beams formed from North–South antenna. These
beams are 15◦ wide in East–West direction and 0.5◦ wide in North–South direction and are separated by 0.5◦
in each declination. All these outputs are then put to back-end facilities. Before modernization of back-end
facilities the receivers were set, i.e., a filter bank with six frequency channels and five independent beams, thus
forming 30-channel receiver. On output from the receiver we obtained five pencil-like beams, which were formed
in a process of multiplication of North–South and East–West antenna signals. Later on thirty channels these
signals were digitized and stored with eight-bit A/D converter.
c© K. M. Sidorchuk, A. A. Konovalenko, H. O. Rucker, A. Lecacheux, L. Denis, M. A. Sidorchuk, S. L. Rashkovsky,
V. V. Dorovsky, V. V. Zakharenko, 2004
57
Figure 1. Scheme of UTR-2 radio telescope with classic and new back-end facilities
A new scheme was developed in the process of modernization. As can be seen in Fig. 1b, antenna and phase
system remained the same, and we only changed the old 30-channel filter bank with a new digital receiver.
This receiver (Digital Spectral Polarimeter) had been created in France, at the Paris–Meudon Observatory in
cooperation with the Space Research Institute in Graz. The block diagram of the DSP is as follows: radio
frequency block for two independent inputs, which were fed with North–South antenna central beam and East–
West antenna beam. The radio frequency block performs filtration and frequency transformation to base band.
The block is controlled through a serial communication port allowing to choose central frequency. The base
band signal is then digitized and passed to real-time by Fast Fourier Transform module which produces power
spectra of input channels and calculates cross spectrum –multiplication of both channels spectrum, thus creating
pencil-like beam.
Each of 30 receivers used in the filter bank have their own tunable frequency and fixed bandwidth of 40 kHz.
Receivers are grouped in sets of six units per one antenna beam. In total, there are five such groups. Typically,
we use following frequencies for these sets of receivers: 10, 12.6, 14.7, 16.7, 20, and 25 MHz. Dynamic range
of this system is determined by A/D converter module used, and is 48 dB. During the observation we must
manually slightly tune the frequencies of filter bank receivers in order to choose frequency bands free from
interferences.
The filter bank covered frequency range from 10 to 25 MHz, but we could only use six different frequencies
with 40 kHz bandwidth. In such conditions we could not avoid interferences, which are very common and strong
at decameter wavelength band. We had implemented several methods of detecting interferences, but they were
not always successful. Still, a lot of data were damaged and could not be processed.
Main characteristics of the old and new systems are listed in Table 1. The modernization lifted us to a new
Table 1. Characteristics of old and new back-end facilities
Frequency resolution, kHz Number of channels Dynamic range, dB
Filter bank 40 5×6 48
DSP 12 2×1024 70
58
level. With the DSP we cover 12 MHz continuous frequency band, divided into 1024 channels. Each channel is
12 kHz wide, so typical interference signal fits completely in one or two channels. We developed and implemented
a method, which allowed us to automatically clean spectrum from interferences.
Now we can perform radio astronomical observations in very difficult interference conditions. For 80% of
observational time on average 15% of spectrum is affected by interferences. With the cleaning algorithm we
can use 85% of frequency band. Thus, frequency coverage of the full DSP band is 12×0.85 MHz, instead of
40×6 kHz maximum for the filter bank. The spectrum of observed objects is a power-law, i.e., it does not
contain any fine structures, thus allows us to increase sensitivity by 42 times in comparison with old back-end
system.
DISCRETE SOURCES SURVEY
Owing to the modernization and the progress of computers and numerical techniques the data processing
methods for various radio astronomical tasks have been considerably improved. We had developed a new
automatic algorithm of discrete sources detection [2]. It has allowed us to make the data processing procedure
nearly completely automatic and increase reliability of the whole process. Nowadays, we had observed and
processed seventy percents of the Northern Sky. The latest part of the discrete sources survey was processed
using improved methods. In the latest observational campaign we covered approximately one steradian of
the sky. As a result, 483 sources were detected. The coverage map is shown in Fig. 2.
Figure 2. Coverage of the celestial sphere by the present part of the survey
GALACTIC BACKGROUND RADIATION OBSERVATIONS
Using the new back-end facilities we had developed improved algorithm for Galactic background radiation
observations. To speed up the process of observation we implemented fast scanning technique. Each 10 seconds
the diagram pattern of the radio telescope switches to target slightly different sky region. We change the beam
position in declination. Right ascension scanning is performed due to rotation of the Earth. During ten-day
experiment we covered thirty percents of the Northern Sky. In Fig. 3 you can see contour brightness map of
sky region, namely from 12 to 60 degrees in declination. Frequency range for the map is 17–25 MHz. To obtain
a map we used our interference-cleaning algorithm. Some areas still contain interference. The map is only
obtained from North–South antenna. Its beam has knife-like form. You can see traces from Cassiopeia A,
Cygnus A, and Crab Nebula. In former conditions and with old equipment and methods it would have taken
us several years to build such a big map.
Using new equipment and methods of map building and interference cleaning we observed a lot of other
continuum sources: supernova remnants, H II regions, and Galactic clusters.
Figure 3. Experimental Galactic background map
59
PROSPECTS
The modernization of UTR-2 radio telescope is continuing now. We are developing new digital receiver together
with French and Austrian colleagues. It will have the possibilities similar to the Digital Spectral Polarimeter
with some new features.
Figure 4. Diagram of perspective digital receiver for UTR-2
Radio frequency block, as the DSP, has tunable central frequency. But it does not perform frequency
conversion to base band. The signal on output from the block is placed at 70 MHz starting frequency with
14 MHz bandwidth. The next block is an A/D converter, which operates at 56 MHz sampling frequency,
performing undersampling frequency of input signals. Then undersampled data is processed in Digital Down
Conversion (DDC) block, which produces output base band signal. Due to flexibility of modern digital circuits
we can choose sub-bands of full bandwidth from 14 MHz down to 800 kHz. The next block is a programmable
digital processing unit. Typical task for it is FFT transformation. But it is also possible to get raw waveform
data or reprogram the block any time to perform some different tasks. The characteristics of this receiver are
listed in Table 2.
Table 2. Characteristics of perspective back-end facility for UTR-2
Frequency range Frequency resolution Time resolution Continuous frequency band
10–70 MHz 400 Hz – 14 kHz 1 ms /waveform 14 MHz– 800 kHz
CONCLUSION
We had significantly improved performance of the world’s largest decameter UTR-2 radio telescope and deve-
loped new methods and equipment, which allowed us to obtain new astrophysical results. Also, we got a lot
of experience with operating giant decameter radio telescope and processing its data. In a scope of LOFAR
concept our experience can be very useful. The modernization of the UTR-2 is not stopped. We are continuing
to develop modern back-end facilities and data processing methods to use with UTR-2.
Acknowledgements. The work was partially supported by INTAS with the grants INTAS 97–1964 and INTAS
03–51–5727.
[1] Braude S. Ya., Megn A. V., Ryabov B. P., et al. // Astrophys. and Space Sci.–1978.–54, N 3.
[2] Braude S. Ya., Rashkovsky S. L., Sidorchuk K. M., et al. Decametric survey of discrete sources in the northern
sky // Astrophys. and Space Sci.–2002.–280, N 3.–P. 235–300.
[3] Lecacheux A., Rosolen C., Clerc V., et al. Digital techniques for ground based, low frequency radio astronomy //
Proc. SPIE.–1998.–3357.–P. 533–542.
[4] Rucker H. O., Lecacheux A., Konovalenko A. A., et al. New frontiers in decameter radio astronomy // Planetary
radio emissions: Proc. of the 5th Intern. Workshop, Graz, Austria, April 2–4, 2001 / Eds H. O. Rucker, M. L. Kaiser,
Y. Lelanc.–P. 51–61.
60
|
| id | nasplib_isofts_kiev_ua-123456789-79603 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0233-7665 |
| language | English |
| last_indexed | 2025-12-07T17:15:29Z |
| publishDate | 2005 |
| publisher | Головна астрономічна обсерваторія НАН України |
| record_format | dspace |
| spelling | Sidorchuk, K.M. Konovalenko, A.A. Rucker, H.O. Lecacheux, A. Denis, L. Sidorchuk, M.A. Rashkovsky, S.L. Dorovsky, V.V. Zakharenko, V.V. 2015-04-03T15:06:20Z 2015-04-03T15:06:20Z 2005 New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope / K.M. Sidorchuk, A.A. Konovalenko, H.O. Rucker, A. Lecacheux, L. Denis, M.A. Sidorchuk, S.L. Rashkovsky, V.V. Dorovsky, V.V. Zakharenko // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 57-60. — Бібліогр.: 4 назв. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79603 At present time the modernization of the giant decametric radio telescope UTR-2 is under way. New back-end facilities and methods which open up new possibilities for radio astronomical observations are developed. Some equipment was made in cooperation with Austrian and French radio astronomers. Current back-end facilities and methods used at the UTR-2 radio telescope are described and compared with former traditional methods, equipment and their characteristics. Some prospects regarding current progress in developing new generation of back-end facilities are also discussed. The main focus of the presentation is the observation methods and equipment applied at the UTR-2 radio telescope for the investigation of continuum radio sources: Galactic background, discrete sources (preparation for the catalogue of sources in the whole Northern Sky), SNR, HII regions. Some results of using the new back-end facilities (such as Digital Spectral Polarimeter) and processing methods are presented. The work was partially supported by INTAS with the grants INTAS 97–1964 and INTAS 03–51–5727. en Головна астрономічна обсерваторія НАН України Кинематика и физика небесных тел MS1: Decameter Radioastronomy New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope Article published earlier |
| spellingShingle | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope Sidorchuk, K.M. Konovalenko, A.A. Rucker, H.O. Lecacheux, A. Denis, L. Sidorchuk, M.A. Rashkovsky, S.L. Dorovsky, V.V. Zakharenko, V.V. MS1: Decameter Radioastronomy |
| title | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope |
| title_full | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope |
| title_fullStr | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope |
| title_full_unstemmed | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope |
| title_short | New methods and equipment of decametric radio astronomy for continuum observation at the UTR-2 radio telescope |
| title_sort | new methods and equipment of decametric radio astronomy for continuum observation at the utr-2 radio telescope |
| topic | MS1: Decameter Radioastronomy |
| topic_facet | MS1: Decameter Radioastronomy |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79603 |
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