Spectrometric complex of RATAN-600.
The contemporary state and the observant possibilities.

The spectrometric complex of the RATAN-600 radio telescope is intended for investigation of centimeter radio lines and allocated in the secondary mirror cabin N 2. It consists of microwave receivers and spectrum analyzers which parameters are tabulated below. There is a system of stable computer driven local oscillators that have accuracy about 10 to degree -8.

Table 1
Range Type T_n, K T_n, K T_( physic. )
( cm ) LNA LNA System K

Table 2
Spectrum analyzers Wide Band Number of channels Resolution
Filter bank 1.24230
Acousto optical 501000110
Digital autocorrelation 2.512819

User has an opportunity to arrange the necessary spectrometer structure. Spectrometer driving system is accomplished with two DVK-4 computers and one IBM PC and make possible to develop radio line observations on the frequency band pass of the input low noise amplifiers ( LNA ):

  • 1.3 - 1.8 GHz ( radio lines of HI at wavelength 21 cm, all four lines of OH at wavelength 18 cm ),
  • 4.5 - 5.5 GHz ( H_2CO line at 6.2 cm ),
  • 21.5 - 22.5 GHz ( H_2O line at 1.35 cm ).

The performance of spectrometric complex is controlled by program driving system ( PDS ) and the data gathering and recording system ( DGS ).
DGS realizes :

  • attaching cycles of gathering of the spectral channels to the real sidereal time scale,
  • converts analogues signals to digital codes,
  • synchronizes PDS operating with digital recording system.
    The digital recording system is fulfilled in CAMAC standard on the base of IBM PC.

For adjustment of the spectral reseivers to changing observational conditions the next preparatory operations are automatically fulfilled before each observation:

  • arrangement of necessary spectrometer gain in dependance of the level of system noise signal on the wide band channel detector,
  • compensation of noise signals difference in the semiperiods of antenna and its equivalent.

Special software batch was created for carrying out of spectrometric observation in the various modes:

  • long time observations with drift of sky through fixed beam of radio telescope;
  • tracking of the sources with moving primary horn in the region where aberrations are unessential;
  • reference sources observations with reduction them and output of the results immediately after finishing of observations.

PDS supplies modulation and compensation modes of spectrometer operations. The last one is implemented with acoustic optical analyzer in the range of integration time up to 20--30 min. and gives advantage in sensitivity by two times. The data obtained are recorded to the computer hard disk and immediately displayed on the monitor. Then these data may be reduced to antenna temperature scale, cleaned from interferences and arranged to necessary format. Further they may be transmitted through the local network of the RATAN-600 to the central server or to any computer in the network. They may be accumulated on the Zip-diskettes too. An example of HI drift curves is shown on the Figure.

The special soft ware was created for consequent reduction. It makes possible, in the first place, to see obtained data on the screen and to take any hard copy of drift curves, profiles or contours in any region of coordinates. Secondly, data may be reduced for

  • finding and eliminating interferences,
  • selecting and excluding extensive background with the help of spline interpolation,
  • Gauss analysis along with R.A. axis for selecting of the local components and measuring of their parameters.
  • Also spectral analysis is available with the help of fast Fourier transform and computation of structural functions.

All these function work with displaying results on the screen and store them on the files. For three dimensional data ( alpha , delta , V ) there is an opportunity to obtain a cross-section with any pairs of coordinates. The equipment and soft wear are in operation during many years and have displayed their high operational quality. The losses of observational time due to equipment failure are no more then 3%, that is much less than due to weather conditions, power supply or operator mistakes.