33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013THE ASTROPARTICLE PHYSICS CONFERENCE

Space Mission Lomonosov on Study Gamma-Ray Bursts and UHECRA.M. AMELUSHKIN1 , V.V. BENGHIN1 , V.V. BOGOMOLOV1, G.K. GARIPOV1 , E.S. GORBOVSKOY2, B. GROSSAN3,A.F. IYUDIN1 , B.A. KHRENOV1 , P.A. KLIMOV1 , J. LEE4 , V.M. LIPUNOV2 , G. NA4 , V.I. OSEDLO1 , M.I. PANASYUK1 ,I.H. PARK4 , V.L. PETROV1, S.A. SHARAKIN1, YU. SHPRITS5 , G.F. SMOOT3, S.I. SVERTILOV1 , N.N. VEDENKIN1 ,I.V. YASHIN1

1 Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow, Russia2 Lomonosov Moscow State University, Shternberg Astronomical Institute, Moscow, Russia3 Berkeley Center for Cosmological Physics, Berkeley, California, USA4 Department of Physics, Sungkyunkwan University, Seobu-ro, Jangangu, Suwonsi, Gyeongido, 440-746, Korea5Institute of Geophysics and Planetary Physics, UCLA, 405 Hilgard Ave / 7127, Los Angeles, CA, USA.

panasyuk@sinp.msu.ru

Abstract: The main idea of Lomonosov space mission is to study extreme astrophysical phenomena in theUniverse, such as cosmic gamma-ray bursts (GRB) and ultra-high energy cosmic rays (UHECR). GRB beingone of the most powerful events in the Universe occur not only in gamma-range, but also in optics and UV.Due to unusually powerful brightness of GRBs, studying of their properties allows the researchers to look inthe epoch of early Universe, i.e. to study evolution of stars and stellar populations with red shift starting fromz ∼ 0.1. Other extreme phenomenon in the Universe is a flux of UHECR, which is most likely produced in ActiveGalactic Nuclei (AGN). The fundamental problem is to estimate maximal particle energy, to which they could beaccelerated in such sources. AGN are very distant objects, UHECR go a long way before coming to the Earth.During their propagation UHECR lose energy due to photo-production of secondary particles (mostly pions) onthe microwave background photons. It leads to a natural limit of observable cosmic ray particle energy, Greisen-Zatsepin-Kuzmin limit,and to UHECR energy spectrum cut-off at energy of about 5 ·1019 eV. Studies of mentionedabove problems of extreme phenomena dictate scientific objectives of large scale space experiment Lomonosovwith a specific set of instruments: detectors of GRB in wide range of wavelengths (in optics, ultra-violet, X-raysand gamma-rays) and large aperture telescope for recording fluorescence light from the atmosphere generatedby UHECR. Main parameters and brief description of these instruments are presented.

Keywords: Lomonosov, UHECR, GRB.

1 IntroductionStudies of extremely high energy and power processes suchas GRB and UHECR are of great importance not only forunderstanding these phenomena, but also for developingtheory of the early Universe.

GRBs are observed as short (from dozens of millisecondsup to dozens of seconds) increases of gamma-quanta fluxwith quanta energies from 105 eV up to at least 109 eV.Discovered in 60s years of 20th century they are still at thecutting edge of astrophysics. These phenomena being themost powerful in the Universe occur not only in gamma-range, but also in optics and UV. The power of the explosionof these most bright astrophysical objects achieves 1051–1053 erg/s. GRB optical emission lasts up to several hours oreven days, it can be an evidence of afterglow which appearsafter a giant explosion in the external shock wave expandingin the interstellar space and stellar wind of the exploded star.Probably, it is a process of collapse of a fast-rotating verymassive star to a black hole in the case of so-called long-duration (more than a few seconds) bursts or merging of aneutron stars in tight binary system in the case of so-calledshort-duration (less than a second) bursts. However, thosemodels are under discussion and nature of this extraordinaryphenomenon is still unknown. Due unusually powerfulbrightness of GRBs, studying of their properties allowsresearchers to look in epoch of the early Universe, i.e. tostudy evolution of stars and stellar populations within the

wide range of red shift from z ∼ 0.1 up to z ∼ 15–20, whichis more than 98% of age of the Universe.

The other extreme phenomena in the Universe are ultra-high energy cosmic rays, which are most likely produced bythe Active Galactic Nuclei (AGN). The fundamental prob-lem is to estimate maximal particle energy, to which theycould be accelerated in such sources, and whether there isa maximum energy to which particles can be acceleratedanywhere in the Universe. Because AGN are very distantobjects, UHECR go a long way before coming to the Earth.During their propagation UHECR lose energy due to photo-production of secondary particles (mostly pions) on the mi-crowave background photons. It leads to a natural limit ofobservable cosmic ray particle energy and to UHECR en-ergy spectrum cut-off at the photo-production energy thresh-old, i.e. about 5 ·1019 eV (Greisen-Zatsepin-Kuzmin cut-off). However, at present we have only limited and contra-dictory information from ground-based experimental arraysabout the energy spectrum and composition of cosmic parti-cles at extremely high energies. UHECR detectors on boardof satellites promise to get new and rich information in thisinteresting field of science [1, 2, 3, 4].

Space Mission Lomonosov33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013

2 Scientific objectivesMentioned above problems of extreme phenomena studiesdictate the scientific objectives of Lomonosov space mis-sion:

• detection of GRBs within optical and gamma rangesin order to study optical prompt emission and precur-sors;

• studies of UHECR at energies ∼ 1020 eV, nearGZK energy spectrum cut-off;

• studies of transient phenomena in the upper at-mosphere, started during the previous MSU spaceprojects Universitetsky–Tatiana and Universitetsky–Tatiana-2 [5, 6];

• detection of the magnetosphere particles, which arepossible sources of transient and quasi-stationaryphenomena in the upper atmosphere.

The objective of GRB studies during the Lomonosov mis-sion is to accomplish simultaneous burst detection withinthe gamma-rays and optics ranges along with possibleprompt emission in observation of precursor light curves.This possibility provides unique information about GRBcentral engine functioning. On this way we plan to use suc-cessive experience of ground-based system of wide fieldcameras and robotic telescopes MASTER, which had de-tected the prompt emission of several GRBs in September,2010 [7]. The point is to use the co-aligned GRB gamma-ray monitor detectors and wide field optical cameras, whichshould be operated continuously and store the data on trig-ger from GRB gamma-ray monitor. In this case the field ofview (FOV) of the optical camera will be inside the FOV ofgamma-ray detector and there will not be needed to redi-rect the optical system. Thus, the time delay between opticand gamma-ray signals will be zero, and even the event pre-history including the possible precursors could be recorded.Another approach is based on fast re-orientation techniqueusing MEMS technology or very fast (during less than 1 s)rotating mirror. In this case source indication for opticalsystem is given by trigger from X-ray imager.

Another goal of the Lomonosov mission is UHECR stud-ies. The Earth’s atmosphere will be used as a “target” forUHECR particle interaction and for development of cas-cades of secondary particles, called extensive air show-ers (EAS). EAS characteristics can provide us informationabout the primary particle parameters. The bulk of EASsecondary particles ionize molecules of atmospheric nitro-gen and lead to fluorescence glow, which looks like a pointsource moving with light velocity during very short time(tens of microseconds). There is also Cherenkov light gen-erated by EAS particles (mainly electrons and positrons)moving with velocity higher than velocity of light in the at-mosphere. Fluorescence and Cherenkov light intensity pro-vides information on EAS track in the atmosphere. Charac-teristics of the track will give information on energy of pri-mary particle and its arrival direction. Thus the instrumentcapable to measure EAS track is needed - in Lomonosovmission it is TUS telescope.

TUS instrument will be also able to detect so-called tran-sient luminous events (TLEs) in the upper atmosphere. Thenature of TLEs is associated with atmospheric electricityphenomena. During the high-altitude electric discharges be-tween the clouds and ionosphere (at altitudes of 10–100 km)

short-time (with duration 1–100 milliseconds) bursts ofelectromagnetic radiation within wide spectral range (fromvisual light up to UV and even X-rays and gamma-rays)are observed. Current experimental data about dischargesin the upper atmosphere have shown that these phenomenaare global, number of discharges and the energy released inthese discharges are so high that we can expect certain rela-tions between discharge phenomena and other geophysicalphenomena.

Studies of charge particle fluxes in the near-Earth spaceand especially the high energy magnetospheric electronscould be considered as an associated goal of the mission.Radiation environment at low satellite orbits (altitudesless than ∼ 500–600 km) is basically determined by thefluxes of quasi-trapped and precipitated particles of theEarth’s radiation belts and the solar particles penetratingmainly into the polar caps regions. Scientific payload of theLomonosov satellite will include a complex of instrumentsfor studies of processes of charged particles penetrationinto the upper atmosphere of the Earth and for analysis ofradiation conditions at low altitudes.

3 InstrumentationScientific equipment installed on-board Lomonosov satelliteincludes a number of instruments intended for solvingscientific problems mentioned above:

• set of instruments for GRB study including gamma-ray monitor BDRG, optical wide-field camerasSHOK, UFFO instrument consisting of UV and X-ray telescopes;

• UHECR detector TUS for imaging of EAS tracks inthe atmosphere;

• set of instruments for studies of energetic particlefluxes in the near-Earth space including magnetome-ter, high energy electron detector ELFIN and chargeand neutral particle monitor DEPRON.

3.1 Space telescope TUSOrbital telescope TUS (Tracking Ultraviolet Set up) isintended for observations of UV (240–400 nm wavelength)radiation from EAS particles in the night atmosphere ofthe Earth.

Detector consists of two main parts: mirror-concentratorwith area of ∼ 2 m2 and photo detector composed of256 pixels, located at the mirror focus. TUS technologicalparameters are: mass ∼ 60 kg, power consumption ∼65 W, data rate 250 Mbytes/day. Details of TUS telescopeconstruction and operation are presented in [8]. In figure 1TUS telescope is shown on-board of Lomonosov satellite.

3.2 Gamma-ray burst monitor BDRG andwide-field optical cameras SHOKs

The BDRG instrument is intended for monitoring andlocating of gamma-ray sources at the celestial vault withinthe gamma-range and for the production of the trigger signalfor the SHOK wide-field optic cameras.

BDRG provides:

• monitoring of the transient astrophysical phenomena(GRBs, “X-ray novas”, “Soft gamma-ray repeaters”,etc.);

Space Mission Lomonosov33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013

Figure 1: Detector TUS.

Figure 2: Detector BDRG (one unit).

• timing of soft gamma-radiation of the X-ray doublestars and pulsars;

• patrol of solar radiation within the gamma-range.

BDRG instrument consists of three identical gamma-raydetector units (BDRG-1, BDRG-2, BDRG-3) with axes nor-mally directed to each other. In Fig. 2 one of BDRG unitsis shown. The system as a whole allows to observe halfof celestial sphere and to produce rectangular coordinatesystem with the axes coinciding with the axes of the detec-tors. Each gamma-ray burst is detected by one of detectorsor by a combination of two or three detectors. In the lastcase directing cosines which set the location of the sourceagainst the detecting system can be determined by the ratioof the counting rate amplitude increases in each detector tothe total amplitude (the counting rate) which characterisesthe total flux falling on the detecting system. This methodprovides accuracy of the localisation of gamma-ray burstsource on the sky for the most powerful events 1◦–4◦ [9].

SHOK instrument (Russian abbreviation for “Opticalcamera of super-wide field of view”) consists of two sta-tionary wide-angle fast cameras, Fig. 3. Their field of viewis situated within the area of gamma-bursts’ detection ofother instruments onboard Lomonosov satellite.

Figure 3: Detector SHOK (one camera).

Figure 4: Mutual position of fields of view of gammadetectors and optical cameras.

Each SHOK unit is an optical camera with a widefield of view, which must be within the field of view ofthe corresponding detector of the gamma-bursts monitor,figure 4. Due to this feature it is possible to detect the burstwithin the optical and gamma-ray ranges simultaneously,and in the case of continuous observations a significantopportunity for measuring of optical curves of the gamma-ray burst prompt emission and their precursors’ detectingare provided.

Field of view of each camera is about 1000 squaredegrees, and maximum framing rate is about 5–7 frames/sec.In fact, cameras record “a movie” continuously, and in caseof gamma-ray burst detection part of this movie can betransmitted to the Earth.

Among the bursts it is possible to process the images inorder to find optical transients: supernova, novae, “orphan”bursts, asteroids and near-space objects and space debris.

It must be emphasized that SHOK device will be thefirst orbital experiment with cameras of super-wide field.Development of detection methods of dangerous asteroidsand space debris from space are of particular interest.

3.3 UFFO instrumentUFFO instrument consists of 20-cm UV-optic telescopeSMT with fast rotating mirror and wide-field X-ray imagerUBAT.

Space Mission Lomonosov33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013

Figure 5: Detector UFFO.

The main goal of the observations by means of the UV-telescope SMT is the recording of the intrinsic radiationof gamma-ray burst due to opportunity of very fast (∼ 1 s)rotation of the mirror focusing in the region of the burstlocalisation at the moment of the trigger of gamma-monitoror UBAT instrument which allows to obtain images withinX-range [10]. The UBAT instrument is based on combina-tion of a coding mask and position-sensitive detector withpixels produced of LYSO scintillator. In figure 5 UFFO in-strument is presented.

3.4 Instruments for magnetosphere study:DEPRON and ELFIN-L

DEPRON instrument (Dosimeter of Electrons, PROtons andNeutrons) is intended for the measurements of the absorbeddoses and linear energy transfer spectra from high-energyelectrons, protons and nuclei of space radiation, and fordetecting of thermal and slow neutrons flux.

The instrument includes:

• charged particles dosimeter based on semiconductordetector;

• thermal neutrons detector based on gas-dischargecounter SI13N;

• circuits for analogous and digital processing of detec-tors’ signals, for information storage and analysis;

• power supply units for the detectors and electronics.

The ranges of the neutron flux density measured bymeans of SI13N counters for the neutrons within the energyrange of 10−3–102 eV is 0.1–102 neutrons/cm2s.

The ELFIN-L (Electron Loss and Fields Investigator forthe Lomonosov mission) instrument is a joint project of theInstitute of Geophysics and Planetary Physics at the Uni-versity of California, Los-Angeles (IGPP/UCLA) and Sko-beltsyn Institute of Nuclear Physics of M.V. LomonosovMoscow State University. It consists of a Flux Gate Magne-tometer (FGM), an Energetic Particle Detector for Electrons(EPDE), and an Energetic Proton Detector for Ions (EPDI).

The main scientific objective of the MSU-UCLA col-laboration is to understand the dominant mechanisms ofthe loss of energetic electrons and ions. Energetic particlescreate hazardous environment for satellites and humans inspace and cause a number of satellite failures.

3.5 The information unitLomonosov on-board equipment also includes informationunit, which is needed in to provide control of the scientific

equipment complex on-board the satellite. It is collecting,storing and transmitting of the telemetric information to theEarth.

The service systems of the basic satellite platform can’tfit the requirements of the unique scientific experiments,high-operative control of the equipment and huge volume ofscientific information, therefore it was necessary to developa special information unit.

4 ConclusionsSet of instruments installed on-board Lomonosov satelliteprovides studies of wide range of problems of modernastrophysics and space physics. The main of them (UHECRand GRB) are for studies of extreme events at cosmologicaldistances.

Acknowledgment:This work was partially supported by fundsfrom Megagrant 11.634.31.0076.

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