Space Radio Telescope
The space radio telescope antenna consists of a deployable parabolic reflector (10-m diameter) which is made of 27 carbon fiber petals and central solid portion (3 m in diameter). The radio telescope has focus to diameter ratio F/D=0.43 and overall RMS surface accuracy 0.7 mm. Observing frequencies: 0.324, 1.66, 4.83 and 18.4-25.1 GHz.
A concentric feed arrangement at prime focus will provide the possibility of observing at two frequencies or two circular polarizations simultaneously. All LO frequencies on board will be derived from high stability reference signal transmitted from ground tracking stations which are equipped with the hydrogen maser oscillators. The satellite also carries a rubidium oscillator and hydrogen maser oscillator for independent synchronization mode. Guarantee operational lifetime for the bus and science payload is 5 years with possible prolongation up to 10 years.
The table 4 summarizes parameters of the RadioAstron receiver system:
|Observing frequency (MHz)||327||1665||4830||18392-25112|
|Bandwidth (MHz) for each polarization||4||32||32||32|
|System temperature (K)||70||50||50||60|
|SRT sensitivity (Jy)||8200||3500||3500||7000|
Low noise amplifiers at L, C and K are cooled to 100 K by on-board radiation cooling system. LNA for P band is at room temperature (about 300 K). At any frequency there are two receivers one for left and one for right circular polarizations.
In the spectral mode the central frequency of the K-band receiver can be tuned in two windows (21160-21288 and 22136-22232 MHz in both polarizations), in order to observe redshifted (from -300 to +1300 km/s and from +12700 to +14500 km/s) H20 masers.