Multi-Frequency Synthesis in K-band

The Multi-Frequency Synthesis (MFS) permits to realize a good quality imaging of the continuum radio sources in short time. Switching between N values of frequency is equivalent at some assumptions to the switching between spatial frequencies and therefore equivalent to the operating simultaneously of N space radio telescopes distributed along the line Earth - RadioAstron. If two-element interferometer operate simultaneously at two frequencies, it is possible to measure the amplitudes and difference phases of two spatial frequencies.

The RadioAstron mission will operate one K-band circular polarized channel at fixed frequency 22,232 GHz. The second simultaneously operating channel with opposite circular polarization can switched in the band from 18,392 GHz to 25,112 GHz with f_max / f_min = 1,37. It permits to construct one-dimensional image in time determined the integration time for each channel multiplied on the number switching frequencies. Two-dimensional imaging is possible to make twice per orbit with maximum angular resolution and 1 - (f_min / f_max)² = 46% of elliptic area on the UV plane. It is significant that this values are independent from the size and others parameters of the orbit. In general one K-band RadioAstron channel with fixed frequency will be unchanging and compatible with all the ground radio telescopes. The tunable K-band RadioAstron channel will be compatible with the EVLA K-band.

Some advantages of the MFS-method.

• The one-dimensional imaging of the sources in time shorter than one hour with extremely high angular resolution and at any part of the orbit.
• The two-dimensional imaging in time 3-5 days along all orbit and in time of 0.5-1 day near perigee.
• The obtaining of the spectrum of different elements of the image.
• A determination of the angular size - frequency dependence connected with scattering, or absorption, or other physical processes.
• A construction of the map of linear polarization and map of the rotation measure or map of the circular polarization, and also determination a degree of polarization changing with the frequency.
• A determination of the differential coordinates and the proper motions with extremely high accuracy.
• An investigations of the own variability structure of the sources and/or their scintillation variability in interstellar or own envelope plasma as function of the frequency.

The observation modes can be selected for realization the mentioned above targets. The frequencies of tunable channel for MFS are 18.392, 19.352, 20.312, 21.272, 22.232, 23.192, 24.152, and 25.112 GHz. The band width of each frequency position is 32 MHz

Technical specification and more details about MFS-method may be see in Memo 3, ASC, 1999.

• Basic Information
• Spacecraft Design
• Orbit
• Space Radio Telescope
• Multi-Frequency Synthesis in K-band
• Data and Phase Links
• Ground Support of the RadioAstron
• Observations
• Data Processing
• Status of the Mission
• Progress of the RadioAstron Project in Pictures