Continuum radiometric complex

RATAN-600 continuum radiometers are placed in two HF feed cabins: N1 and N2. The complex consists of 12 radiometers in the wavelength range from 1 to 49 cm. Radiometers are used for convenience observations of radio sources. Complexes of continuum radiometers in recent years undergone considerable renovation. Due to the repetitive use of the resource of the cryogenic systems and the impossibility of mass purchasing a new cryogenic equipment, RATAN-600 cooled low noise amplifiers (LNA) in radiometers are replaced by "warm", that is operating without cooling.
The most suitable for use in radiometers on main characteristics the LNA of Scientific and Production Company (SPC) "Micran" (Tomsk, Russia) are recognized. In 2014 the reconstruction of cryogenic radiometers RATAN-600 to "warm" front-end LNAs is completed.
Their difference of the noise temperatures in contrast to cryogenic amplifiers is from 7 to 16 K in wavelength ranges of 6 cm, 3.5 cm and 2.6 cm, in view of losses of sealed waveguide input and thermal isolation in cryostat- halved. In the wavelength range of 1.4 cm the small loss of sensitivity be compensated by applying total power operating mode and double-channel design at all radiometers.
The second, very important part of efforts is the creation of new modern radio astronomy data acquisition systems. They allow to apply the new scheme for constructing the receiving equipment for the implementation of the higher sensitivity. The basic set of continuum radiometers is in the feed cabin N1 installed. The technical specifications of the radiometers are shown in Table 1.


Table 1 (state on 1.06.2016)

(cm)		 f0
(GHz)		 f
(GHz)		 T
(mK/s)		 TnLNA
(K)		Ta
(K)		 Tsys
(K)		 Design mode Comment
Feed cabin N1
1.0
30.0
4.0
6.0
180
35
240
MOD
"MARS-2", 3 Channels
1.4
21.7
2.5
6.0
92
30
190
TP
Micran LNA
2.7
11.2
0.8
5.0
28
25
100
BS
2 beams
3.6
8.3
0.8
4.5
21
23
90
TP
6.5
4.6
0.6
3.5
17
22
70
TP
2 channels
13.0
2.3
0.08
12*
35
25
95
TP
RFI
test observations
23.3
1.29
0.05
15*
21
50
105
TP
GSM RFI
test observations
49.0
0.6
0.12
25*
25
70
125
NAR
TV RFI
under construction

The second set of continuum radiometers is mounted in the feed cabin N2, the parameters shown in Table 2.

Table 2

(cm)		 f0
(GHz)		 f
(GHz)		 T
(mK/s)		 TnLNA
(K)		Ta
(K)		 Tsys
(K)		 Design mode Comment
Feed cabin N2
1.0
30.0
5.0
5.0
180
35
240
MOD
"MARS-3", 16 Channels
1.4
21.7
2.5
6.0
92
30
185
MOD
Eridan-2 with Micran LNA
2.7
11.2
0.8
5.0
28
25
100
TP
6.5
4.6
0.6
3.5
17
22
60
TP

Where:
  • - wavelength range,
  • f0 - central frequency,
  • f - bandwidth,
  • T - sensitivity by 1 s of integration time,
  • TnLNA - LNA noise temperature,
  • Ta - antenna noise temperature at medium elevations,
  • Tsys - system noise temperature,
  • BS - beam switching mode,
  • TP - total power mode,
  • NAR - noise added radiometer.

Figure 1. The line of uncooled LNA NPF "Micran" (Tomsk), introduced the RATAN-600.

Specifications of used SPC "Micran" amplifiers

Table 3
Bandwidth,
GHz		Product Noise Temperature,
dB(K)		Gain,
dB(K)		 Input-output
4.4-5.0
MALN4450-11
0.25 (17)
35
WG-WG
7.9-8.7
MALN7987-12
0.3 (21)
30
WG-Coax 7/3
10.9-11.7
MALN109117-12
0.4 (28)
36-38
WG-Coax 3.5/1.52
21.0-23.5
MALN210235-11
1.2 (92)
28-30
WG-Coax 3.5/1.52