The INTEGRAL International Space Lab has been launched into a high-ellipse orbit for studies of gamma and hard X-ray emissions from space sources. The launch was carried out by the Russian PROTON carrier rocket equipped with the DM booster (produced by the Khrunichev Center and the ENERGIYA Corporation).
By Yuri MARKOV, test engineer, S. Lavochkin R&D Center (Khimki, Moscow Region)
The scene of action was the Baikonur Cosmodrome and the date was October 17, 2002. The clock was ticking away in the Mission Control at an alarming rate. The Director General of the Russian Aerospace Agency, Yu. Koptev was nervously smoking his cigarette. The air was filled with smoke and tension, and the reason was obvious. It was only a day before that the Soyuz-U carrier rocket, one of the most reliable of its kind, blew up during a launch at Plisetsk with the Photon European satellite designed for technological experiments in orbit. And although this time the rocket is different, the scientists and engineers at Baikonur are pursued by nagging worries about the outcome of the project which costs 600 mln dollars. But money is not the main thing. The project cost them years of hard work, hopes and ideas translated into instruments and equipment.
At 8:30 Moscow time (10:30 local time) the tense silence of the countdown was finally broken by the "Launch!" command. And the probe took off exactly on schedule.
Few hours later men at the Mission Control breathed a sigh of relief: the probe went into its calculated orbit, its solar panels opened up and everything else went exactly on schedule.
After this piece of launchpad drama, let us take a closer look at some of the technical details of the Integral. Its immediate predecessor was the Russian Granat probe equipped with gamma-X-ray astrophysical telescopes*. The same basic concept was behind the international Integral project-an international gamma-ray astrophysical lab. And I, for one, would use a more precise definition an international gamma-X-ray astrophysical lab. This is because the probe studies not only gamma, but also X-ray emissions**.
And what we are dealing with here are some real, recorded by instruments, rays coming from space which cannot penetrate the Earth atmosphere. This saves all life on our planet from these hard and lethal rays. And these rays have to be studied not only outside our atmosphere, but also outside the zone of action of radiation belts which distort measurements data. It is only a carrier rocket like our Proton, which is unparalleled in any other country, which can help solve a task of such complexity. The French Ariane, for example, can be launched into orbits mainly within the radiation belts of the Earth. And Proton can place your instruments into a unique 3-day synchronous (72 h) orbit. Its apogee of 153 thous. km and perigee of 9 thous. km make it possible to conduct observations for 85 percent of time outside of these belts and periodic passages over a certain point of the earth surface make it possible to obtain data literally in real time. What is more, Proton can place into a desired orbit a heavy probe like the Integral with a payload (research gear) of over 2 tons.
The range of interests of Integral belongs to a most promising areas of modern science-high-energy physics and plasma-in which scientists expect a real breakthrough in our knowledge of the micro- and macroworld.
There is an expression which literally means "the opposites meet". Indeed, by studying the microworld and its particles, we get a better understanding of the processes taking place within it and in the Universe. And the other way round. As the youngest Member of the Russian Academy V. Rubakov points out (was elected when he was only 42), "one is struck by the diversity of particles which tell us what is going on in remote space". And it was not accidental that Nobel Prize winners in physics last year were R. Daywill, M. Koshiba and R. Giocconi who are working at the "border" of "terrestrial" and "stellar" physics-astrophysics. As was stressed in the Nobel Committee citation the first two of these scientists provided a pioneering contribution to astrophysics, especially to the discovery of space neutrinos. And the third of them has practically founded what we call X-ray astronomy.
So, what will there be within "the range of vision" of Integra?! First and foremost-four black holes, neutron stars and supernovas, formation of some hitherto unknown chemical elements, active galactic nuclei, giant outbursts of energy, plasma heated up to billions of degreed and many other phenomena linked with high-energy processes.
As for the main scientific tasks on the list of Integral, they include: spectroscopy of sources of X-ray and gamma radiation in the center of the Galaxy and measuring their exact position; physical diagnostics of compact objects (white dwarfs, neutron stars, black holes) are studies of explosive nucleosyntheses (birth of chemical elements) in supernovas and analysis of the broad-band spectra of active nuclear quasars***; drawing a map of distribution of brightness of gamma-emission in the 1.8 MeV band and drawing a map of diffused galactic emissions in the annihila-
* See: Yu. Markov, "Space Telescopes", Science in Russia, No. 1, 2000.- Ed.
** See: A. Galperin, Yu. Ozerov, "Solar Gamma Rares", Science in Russia, No. 4, 1997.-Ed.
*** See: A. Finkelstein, "Quasar Radiointerfero-meter Network", Science in Russia, No. 5, 2001. -Ed.
tion* line of 511 keV which is of the greatest interest; scanning of galactic plane for detecting transient (short-life) X-ray and gamma sources; studies of gamma flashes in the broadest band of energies (optical light, X-rays and gamma rays), exact location of their sources.
For dealing with this range tasks Integral is equipped with four main instruments, including the most important SPT spectrometer developed by French and German scientists, and having a set of 19 Germanium detectors. In order to achieve high spectral resolution they are cooled down to 85 К by special cryogenic units. The image is produced by what is known as the coded mask method** because at high energies the method using reflection optics fails to produce the required results.
An important role is assigned to the IBIS gamma-telescope which is the responsibility of Italian scientists. It produces images with high angular resolution.
Danish scientists have put on board the Integral their X-ray telescope JEM-X which makes it possible to broaden the range of observations down to low energy levels.
Finally, the last of these instruments-the OMC optical monitor designed and built by Spanish experts. It helps with the optical identification of the sources of gamma flashes.
In the words of the project director on the Russian side, Academician R. Syunyaev, the instruments on board the new probe are two orders of magnitude more sensitive than their predecessors on the Granat and embody some of the most progressive ideas and technologies of the turn of the century.
The program as a whole is the responsibHity of the European Space Agency-the owner of the space probe, and the Integral Mission Control Center is located in Darmstadt, Germany. One should add to that the on-board and ground equipment was designed and built by the International Consortium of Scientific Organizations. Now it is responsible for the scientific support of the mission, although it should also be pointed out that actively involved in the project are both Russian and American experts.
This country today boasts excellent school of research in cosmology and astrophysics which are headed by internationally recognized authorities in the respective fields- academicians Ya. Zeldovich, M. Markov and B. Pontekorvo. Their followers, headed by Academician R. Syunyaev, and backed by the experience of development and nearly a decade of operation of the Granat probe, have worked out a set of scenarios for challenging experiments planned for Integral.
As for the total costs of the project which is estimated at 600 mln dollars, they were fairly shared among its participants. The contribution of the European Space Agency is 350 mln dollars while Russia on its part provided the carrier rocket, booster and the nose cone as well as the launch facili-
* Annihilation-transformation of particles and antiparticles into different particles upon collision. - Ed.
** Coded mask method concerns the projection by gamma rays of mask pattern, consisting of transparent and matt elements located in a certain sequence, upon detector matrixes. - Ed.
ties. In exchange this country has been "awarded" with all the collected data and a quarter of the observations time. Time sharing is the responsibility of the Scientific Council of the Russian Academy whose members include academicians V. Ginsburg, V. Zheleznyakov, G. Zatsepin, G. Krymsky, G. Christiansen and A. Chudakov as well as other leading experts.
The Russian Academy of Sciences has allocated 4 mm rubles for the establishment of the Scientific Data Center which can be received on a competitive basis. The main "users" of the "stellar data" include educational, academic and specialized institutes and universities of Moscow, St. Petersburg, Nizhni Novgorod, Kazan, Dubna and specialists of the RF Minatom. The torrent of data to be thus consumed amounts to 4 gigabytes per day on a round-the-clock basis for the whole duration of the mission- from two (guaranteed) to five years.
Finally, a few words on yet another related subject. In the opinion of some high- ranking officials, the successful launch of the Integral marks the end of the Russian space observatory Spektr-Roentgen-Gamma. This is also an international project and is included into Russia's Federal Program of Space Research. Our specialists, working in conjunction with their foreign counterparts, have designed up-to-date research instruments to the total tune of 200 mln dollars. But it will take another 56 mln dollars for the completion of tests and the launch itself. The Russian share is estimated at 35 mln dollars with the rest to be provided by the European Space Agency. Unfortunately, our Western partners have failed to honor their share of the deal and work of the Spektr is proceeding at a slow pace.
Having said that, let me try and demonstrate the importance of bringing the half- abandoned project to a fruitful compilation. The Integral energy range is 3 - 8,000 keV, and that of the Spektr 0,2 - 10,000; the energy resolutions are respectively 500 and 1,000 dE/E; angular resolution 8 and 10 ang. sec respectively; sky monitoring in the X-ray band is 50 and 100 percent.
That means that many sources of radiation are accessible to Spektr and inaccessible to Integral. Which means that studies with their help could conveniently supplement each other. What is more, a range of parameters of these space probes match and the two could be used to investigate one and same radiation sources. This would help increase the accuracy and authenticity of measurements. And the collected data could be compared which is another very important asset for science.
All of these things help explain the interest towards the Spektr project on the part of researchers of the Russian Academy, the Moscow and St. Petersburg universities, other educational centers as well as of the Minatom and other federal agencies. And we do hope that these hopes and expectations will finally materialize.
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