RadioAstron switches to interferometer mode

The search for petals has begun

On November 15 and 23, RadioAstron tests began in the mode of a ground-space interferometer - searching for petals, i.e. obtaining the first correlation between signals from space and ground-based radio telescopes. Both sessions at a wavelength of 18 cm were successful. Scientific data from the space radio telescope were recorded at a tracking and information collection station in the city of Pushchino, Moscow region. Three 32-meter antennas of the Russian Quasar system in Svetly, Zelenchukskoy, Badary, a 70-meter radio telescope near Evpatoria (Ukraine), a 64-meter antenna in Usu-da (Japan), and a 100-meter Effelsberg radio telescope took part in the observations as a ground arm. » (Germany), GBT (USA). A quick analysis of the data confirmed their suitability for processing in interferometer mode. The scientific data processing center of the AKC FIAN has begun a search for interference lobes. The November 15 observations were also supported by two telescopes on the European VLBI network, Metsahovi (Finland, 14 meters) and Onsala (Sweden, 20 meters), which detected the carrier frequency from the space radio telescope at 8.4 GHz. These Doppler measurements, as part of the European PRIDE program, will provide additional information about the satellite's orbital parameters. The first Space-Earth interferometric tests at a wavelength of 6 cm are planned for December 2011.

The first successful measurements of the distance to the Spectrum-R satellite using a laser rangefinder

Laser ranging is part of the Spektr-R complex of planned precision orbital measurements. Such measurements are used for high-precision reconstruction of the spacecraft orbit, necessary for correct processing of data from the operation of the ground-space interferometer. Early in the morning of November 15, the first laser ranging of the Spektr-R spacecraft was successfully carried out. From 5:30 to 6:30 Moscow time, the device was oriented with corner reflectors towards the Earth. The location was carried out by the French Côte d'Azur Observatory near the city of Grasse as part of the International Laser Ranging Service (ILRS). During 35 minutes of continuous operation of the station, 875 measurements were obtained, while the distance to the device during this time changed from 65 to 70 thousand km. The reflected signal contained virtually no noise. The error of the obtained measurements does not exceed 10 cm. The measurements are available at: ftp://cddis.gsfc.nasa.gov/sLr/data/npt_crd/radioastro/2011/

Pulsar PSR0329+54 and water maser in Orion KL

As part of the flight test program, successful observations of the pulsar PSR0329+54 were carried out on November 7 at 0.3 GHz, and on November 8 - the spectra of the water maser in the Orion KL object at a frequency of 22 GHz. The release of scientific and service information from the board to Earth during these observations was carried out through a high-speed satellite data transmission channel - a tracking and information collection station in the city of Pushchino (PRAO AKTs FIAN).

Bulletin of the Astrospace Center

FIAN

24.11.2011

www.asc.rssi.ru/radioastron/rus/

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Commentary TrV-Science

What are interferometric "lobes"?

The term "lobes" originally referred to the radiation pattern of conventional antennas, a function that describes in polar coordinates the magnitude of the antenna's response to radiation coming from different directions. It really looks like petals: the main one and the side ones, which for parabolic antennas are many times smaller than the main one. In radio interferometry with an ultra-long baseline, i.e. with independent recording of a broadband signal on radio telescopes, there are no physical lobes, and there is no physical interference. The recorded signals are provided with time stamps from atomic clocks, which provide synchronization during the initial data processing at the correlation center. Let's say there is a bright point source in the field of view of the interferometer antennas. The correlation of the signals measured at the two antennas is then calculated as a function of the relative time shift At (or signal phase delay) and its first derivative. If At and At' exactly correspond to the time of passage of the front of the radio wave from the source between the two antennas and the rate of its change, then a correlation peak arises, which can be called the lobe of an elementary interferometer. The difficulty is that the delay At, and especially its first derivative, is known in advance only approximately and also depends on time due to the movement of both antennas. That is why you have to look for the petals.

Next, the stage of reconstructing the radio image of the object begins, which is a formally incorrect inverse problem.