features of RATAN-600
1. Very effective "near field zone" atmospheric noise filtration =>...
2.Low "confusion" limitdue
to resolution much greater than that of the simple dish with the same
3.The world largest reflector type and the only "total power aperture synthesis" system gives the brightness temperature sensitivity equal to the antenna temperature sensitivity,
as for all interferometric arrays. It is possible
to reach the same brightness temperature resolution with
aperture synthesis but using much longer integration time, again by factor about square of the ratio of
physical to synthesized apertures.
4.Practically no aberrationsat high elevation angles and multi-frequencies and matrix receiver modes of operation can be done easily (Fig 3) .
Fig.4. The focal plane of RATAN-600 Secondary mirror #1 with a horn feedRATAN-600 has the collecting surface by factor 1000 greater, then any other space and balloon radio telescopes dedicated for the CMBA measurements. It means, that all kind of the discrete objects may be observed very efficiently.
Fig. 5 RATAN-600 Secondary mirror #5 is under preparation now for "CG"
Fig.6 Topography of 8 element MMIC feed SUBARRAY at 26-30 GHz which is being tested now
Fig. 8 Multi-beam feed array with 10 000 receiver elements may be installed in the focal plane of the RATAN-600 Secondary mirror #6 ()
Fig.7. 4 element MMIC sub-array prototype at 26-30 GHz.
a. “Black Clouds” , that is Sunyaev- Zeldovich
effect at z>>1 may be discovered in many directions. This effect
was originally observed in Sankt-Petersburg in 1970 and now it is clear,
that the density of such objects in the Early Universe may
be very high, up to 100 000/str, (new Cambridge- NRAO estimation). Amplitude
of this effect does not depend on the redshift in radio domain
and may be the only indication of the cluster hot gas at z>>1
(see 6 <Z<1000 Objects).
b. LBO, Lyman Break Objects with z>>1 with no emission in optics, as well as dusty primeval galaxies (PG) due to positive K- correction may be observed with RATAN-600 at 1 cm better, then at sub mm waves with 1m Space dish.
Structure of the Universe at 2 < z < 5 may be traced using HZ USSRG approach, because mean red shift of the few mJy population of FRII USSRG should be close to 3 and even radio photometric red shifts will be accurate enough to check the observable LSS with numerous predictions. (see "Z =3Universe")
Using high sensitive RATAN-600 COLD strip survey at 7 frequencies with high resolution we improved limit on the Galactic synchrotron and free-free emission just at the scales of the Sakharov Oscillations, 1-0.1 degrees. Much smaller effect from free- free components then expected earlier was found (by factor 10). It moves the optimal frequency from 100GHz to 30GHz. We select this frequency as the central one in our project. Frequency domain of new generation RATAN-600 experiments is shown on the Fig.9 (from Max Tegmark's CMB data analysis center) .
Three variant of the receiving 30GHz system was discussed : 1-2 world best deeply cooled InPHEMT receivers, small array (8-16) of the best receivers of the type we are using at RATAN-600, and the very dense array of the MMIC broad band room temperature InPHEMT receivers with about 300K system temperature. At present, we are close to the last variant. Up to 300 receivers of this type can be installed along the 3,88 m focal line of the secondary mirror (parabolic cylinder) without any aberration in the 1 steradian field at at high elevation angle. Even at much lower elevation angle all aberrations will be inside the scales under investigation. 2-3 lines of one- dimensional matrix receivers are also under consideration, they can help to reach sensitivity level above the expected one in all the next generation projects of this type .
Antenna configuration and Sky coverage
RATAN-600 is a multi- mode instrument and can use 1 quarter of the whole ring absolutely independently. In ZENITH mode only we use all the ring in the single mode. Great importance of the problems to be solved by CMBA experiments has brought us to the following solution: one quarter of the ring will be used with absolute priority of the CMBA program as long as we need to get the desirable level of sensitivity. Five year (COBE-type) program does not seem to be too much.
83% of the whole sphere are visible from RATAN-600 site. Cosmic variance
noise may be suppressed by a number of independent pixels only, but forgiven
total time of experiment and for a given receiver noise there is an optimum
sky coverage, which we have calculated for all the 5 first peaks, l=200,
500, 800, 1100, 1400. It occurred, that only for l=200 receiver noise permits
us to observe almost whole sky, but
for the higher l we need the receivers much better then PLANCK SURVEYOR
one to be close to the Cosmic variance limit. At the same time, the Cosmic
variance is not of the very great importance for l >1000 and we can have
1% accuracy with small sky coverage. At present, we have
made full computer model of the experiment and limit our self by 1 steradian.
RATAN-600 panel surface was being improvedduring last three years and it significantly reduced antenna scattering background at 1 cm and shorter wavelengths . The surface maps of RATAN-600 North and South sectors before and after correction are shown in Fig. 10 a,b.
It is not easy to make very accurate estimates due to quick changes at the market. As far as most of the experiment components are available except the new receiver system, we hope, that 1.2 mln USD can solve the financial problem. It is a small fraction of the cost of the Space based missions.
RATAN-600 can (and should) be used for CMBA experiments, which are one of the key experiments in the present day Science, connected with the understanding of the Nature, formation of the Universe, light, matter, structure and with formation of the Physical Lows
Russian “Sakharov Oscillation” PROJECT may be started immediately, it
is a complimentary one to the next generation mm and submm experiments
of the next century and can help in the refining of the scientific goals
of these future and costly projects.