Spektr R (Radio-Astron)

Spektr R (Radio-Astron)

The Spektr-R (formerly RadioAstron) project is an international collaborative mission to launch a free flying satellite carrying a 10-meter radio telescope in high apogee orbit around the Earth. The aim of the mission is to use the space telescope to conduct interferometer observations in conjunction with the global ground radio telescope network in order to obtain images, coordinates, motions and evolution of angular structure of different radio emitting objects in the Universe with the extraordinary high angular resolution.

The orbit of RadioAstron satellite will have apogee radius in the range up to 350 000 km. The spacecraft's operational lifetime will be no less than five years. Space-ground Very Long Baseline Interferometer (VLBI) measurements with this orbit will provide morphological and coordinate information on galactic and extragalactic radio sources with fringe size up to 8 micro arc second at the shortest wavelength 1.35 cm.

The RadioAstron program, initiated by Astro Space Center (ASC) of Lebedev Physical Institute of Russian Academy of Sciences (RAS) in collaboration with other institutions of RAS and Federal Space Agency (FSA), has expanded into a broad international collaboration: scientists from over 20 countries are constructing the instruments, planning the mission profile, and assuring ground radio telescopes support for RadioAstron. Russia will provide the satellite, most of the on-board hardware, interferometer integration and all kinds of the tests. General designer of satellite and SRT construction is Lavochkin Association (LA) of the RosKosmos.

Several other countries contribute to the on-board scientific payload. The 92-cm receiver is being built in India (RAC - Radio Astronomy Center of TATA Institute of Fundamental Research) and Russia, the 18-cm receiver in Australia (CSIRO - Commonwealth Scientific and Industrial Research Organization), the 6-cm receiver by Russia, the 1.35-cm receiver by Finland (HUT - Helsinki University of Technology) and upgraded in USA (National Radio Astronomy Observatory- NRAO) and Russia (Moscow Institute of Radio-engineering and Electronics - IRE), rubidium on-board frequency standard was built by the European Space Agency (ESA) at Neuchatel observatory in Switzerland. H-maser on-board frequency standard is being developed in Russia (Nizhny Novgorod). Russian (ASC) recording system will be able to accept a digital data stream at a maximum data rate of 128 Mbit/s. The correlator will be able to process the data from up to 5 interferometer stations (including the space element) at a maximum data rate of 128 Mbit/s. NRAO will operate tracking station at Green Bank, and will allocate processing time on the VLBA correlator. NASA has constructed tracking station in Australia and electronic complex for tracking station in Russia. On board operating spacecraft system and command communication center near Evpatoria (Crymea) and Bear Lake (near Moscow) are under preparation by Ukraine and Russia.

Main scientific goal of the mission is the study of various astronomical objects with unprecedented angular resolution up to few millionth of an arcsecond. The resolution achieved with RadioAstron will allow us in principle to study the following phenomena and problems:

• central engine of AGN and physical processes near super massive black holes providing an acceleration of cosmic rays - size, velocity and shape of emitting region in the core, spectrum, polarization and variability of emitting components;
• cosmological models, dark matter and dark energy - by studying dependence of above mentioned AGN's parameters with redshift, and by observing gravitational lensing;
• structure and dynamics of star and planets forming regions in our Galaxy and in AGN - by studying maser and Mega maser radio emission;
• neutron (quark?) stars and black holes in our Galaxy, their structure and dynamics - by VLBI and measurements of visibility scintillations, proper motions and parallaxes;
• structure and distribution of interstellar and interplanetary plasma - by fringe visibility scintillations of pulsars;
• building of high accuracy astronomical reference system of coordinates;
• building of high accuracy model of the Earth gravity field.

Originally the satellite was to be built on the Spektr bus, a derivative of the Prognoz-EW-Bus and to be launched on a Proton-K Blok-DM-2 booster, but budget problems have forced a redesign. Now it was based on the smaller Navigator bus and was launched on a Zenit-3F combination.

In January 2019 Spektr-R malfunctioned and controllers were unable to reestablish contact. In April 2019, the mission was declared to be over.