Department of Solar system research
Нead of Department
Full Dr., Shematovich Valeriy I.
STRUCTURE OF THE DEPARTMENT
- The group of studying the dynamics of small bodies of the Solar system (chief Full Dr. of Sci. Rykhlova L.V. )
- The group of spacegeodynamics (chief Dr. Kuzin S.I.)
- The group of studying of planetary atmospheres (chief Full Dr. of Sci. Shematovich V.I.)
- Photometric, astrometric and spectral observations of small bodies of the Solar system
- Hazards due to comets and asteroids
- Study of small bodies of artificial and natural origin in near-Earth space and their connection with processes in the Solar system.
- Meteor investigations
- Photometric and astrometric observations of satellites and space debris
- Space geodynamics (scientific analysis of observational data of satellites for the purposes of astronomy and geophysics)
- Model of Solar flare
- Astrometric studies using optical space interferometry
- Dynamics of Earth’s rotation
- The study of the evolution of planetary atmospheres
Photometric, astrometric and spectral observations of small bodies of the Solar system
According to the classification of the International Astronomiical Union (IAU) accepted at the General Assembly that was held in 2006 in Prague (B5 resolution), minor bodies of the Solar Systems include all bodies rotating around the Sun that are neither planets or dwarf planets nor their sattelites. So almost all asteroids (excluding those ones that are classified as dwarf planets), meteoroids (of 0.1 to 50-100 m diameter), most part of transneptunian objects, all comets etc. are the minor bodies.
At present efforts of international tracking systems for small bodies of the Solar System are are concentrated at detection and monitoring of the objects approaching the Earth and characterizing by a notable risk of collision with our planet. The number of newly discovered objects (especially asteroids) grows exponentially. But it is equally important to investigate already discovered asteroids and comets.
Modern methods of multicolor photometry, spectroscopy and polarimetry using terrestrial sensors provide us with rather detailed information about an asteroid – its size, shape, speed and inclination of the rotation axis, the presence of his satellites, mineral composition, the density, the average size of the irregularities and even porosity of the surface. Of course, space missions can provide more detailed data and information on the internal structure of a celestial body, but they are very expensive and do not apply in mass investigations.
In the INASAN, an extensive research topic of small bodies is developed. On the basis of astrometric observations dynamic characteristics of asteroids are specified. Photometric observations using filters provide information on the color index and allow to determine the taxonomic class, i.e. the chemical composition of asteroids. Such information, on the one hand, is essential to understand the nature of these objects, the evolution of their orbits and their origin in the Solar System. On the other hand, the information is necessary for understanding of the level of danger in the event of a possible collision with the Earth of these bodies. It should be also noted that in recent years the interest in the problem of mining on asteroids is growing.
For nearly 60 years of the space exploration path humanity contaminated the near-Earth space with so-called space debris. The Scientific and Technical Subcommittee of the United Nations on the Peaceful Uses of Outer Space (COPUOS) is approved the definition of “space debris” term – a non-functional man-made objects and their fragments at Earth orbit or re-entering the atmosphere. The problem of space debris, the quantity and composition of the new population has long received the status of an international scientific problem and also studied at INASAN.
All works performed can be divided into three parts:
- The development and research of hardware systems for observations of small bodies of the Solar System and space debris objects. Software improving;
- Photometric, position and spectral observations of selected NEA (near-Earth asteroids), optical monitoring of space debris objects in selected areas of the near-Earth space and basis meteor observations;
- Theoretical modeling of physical and chemical characteristics of the small bodies of the Solar System, dynamics and origins of near-Earth objects, theoretical study of meteoroids streams, as well as numerical simulation of a solar flash.
To determine kinematic and physical characteristics of selected comets and asteroids at the Terskol observatory regular astronomical instruments (photometer, spectrometer and Stokes polarimeter) for the Zeiss-2000 and Zeiss-600 telescopes were established. Photometric observations are performed in standard photometric bands in narrowband “comet” filters and NEA spectra are recorded using Multi Mode Spectrometer of Cassegrain focus (MMCS) of Zeiss-2000 telescope and a Zeiss-600 telescope complex of dynamic spectroscopy. Software packages for the digital spectrum analysis have been developed, which are regularly updated and improved.
Regular observations and research of objects in geostationary and high-elliptical orbits carried out in the Zvenigorod observatory using a wide-angle Santel-500 telescope (optical power in the geostationary orbit area – 17th magnitude). A new radiation detector – CCDcamera FLI PL 4301 was collimated and installed on the Zeiss-2000 telescope complex on the Terskol peak. In the figures at the next page there are an example of a CCD-image produced on the FLI PL 4301 receiver of the Terskol observatory and senior researcher of the INASAN Bakhtigaraev N.S. near Zeiss-2000 telescope.
During 2011-2015, observations and identified characteristics of tens of selected asteroids, including potentially dangerous were made (coordinates, kinematic parameters, photometric values of magnitude and taxonomical class are defined).
The use of different methods of the light curves analysis for the first time allowed to estimate rotation parameters of some near-Earth asteroids (NEA). NEA-research are carried out in coordination with other observatories, represented in the list of Minor Planet Center (MPC), where the peak Terskol observatory assigned B18 international code, and the Zvenigorod observatory – code 102. Along the way, observations of objects from the list of MPC are conducted to confirm newly discovered objects to obtain astrometric data. Results sent to the MPC promptly. The methods of simultaneous or quasi-simultaneous joint measurements of physical parameters of asteroids using two or three observatories with special equipment with different accuracy and other characteristics were designed. Figures at the next page show an example of asteroid 348400 spectrum obtained in June 2015 at the peak Terskol observatory Zeiss-2000 telescope and the photometric curve constructed based on results of simultaneous photometric studies on the 0.5-m telescope in Krasnodar (international code C40 in the MPC list) with a CCD-photometer and on the Zeiss-1000 telescope in Simeiz (observatory code – 094) also with a CCD-photometer.
Criteria for the selection of most interesting asteroids have been developed in 2015 for a detailed study of their physical properties. On the basis of these criteria catalogue has been created for objects considered as possible targets for spaceflights to small celestial bodies of the Solar System, to carry out studies of their physical and chemical properties. The same catalogue used for photometric and spectroscopic measurements at observatories within the cooperation of Russia and CIS, formed by INASAN.
Research on the origin and dynamical evolution of comets is carried out. The fundamental role of the Oort cloud has been shown; the explanation has been given for the origin of Centaurs in orbits with large inclinations and semimajor axes a > 60 au, whose number of detections increases in recent years; dynamical mechanisms of the Centaur transition to the Jupiter family have been investigated; the end-states of the comet evolution have been studied.
The investigation of near-Earth object dynamics has shown that the majority of these objects reach orbits with small perihelion distances during their lifetime. We have found observed asteroids that evolve to orbits with perihelia near the Sun on short timescales in the past. It has been shown that the Chelyabinsk object was also near the Sun about one million years ago. Non-gravitational effects in the motion of near-Sun comets observed in a few apparitions have been determined.
Photometric and astrometric observations of satellites and space debris
Optical monitoring of space debris in the geostationary region and on high-elliptical orbits has been carried out using telescopes in Zvenigorod and Terskol observatories of the INASAN for seven years. 55 thousand measurements of space debris objects coordinates and magnitude estimates were obtained via Zvenigorod Santel-500 telescope only in 2014. At the Terskol observatory also a great amount of physical and orbital characteristics of smallsized space debris objects of complex shape on high orbits was obtained. Translational-rotational movement of space debris with a high of the mid-section area to mass ratio (area-to-mass ratio) was investigated, with results in the observational fact increase of such objects orbit eccentricity caused by the light pressure. It was found a large number of not previously observed debris objects.
Hazards due to comets and asteroids
Chelyabinsk body falling in 2013, of course, was not included in INASAN research plans. But INASAN immediately organized an expedition to the crash place and started to study a great number of (mostly video) material produced of witnesses, pre-atmospheric movement of the body, study of a possible link the Chelyabinsk meteorite with parent body of an asteroid, participated in numerous conferences, discussions and presentations in the press and on TV. Only in 2013 49 papers were published.
Currently INASAN is the head scientific organization in Russia on the asteroid-comet hazard problem. The Institute, in collaboration with colleagues from other RAS institutes, universities, high schools, industry enterprises, ministries and departments is working out the program of creation of the National system for space threats counteraction.
A network of wide-angle telescopes for the near-Earth space monitoring is being created in the INASAN as a part of the work on this subject. For today, an experimental model of a robotic observatory with a 20-cm wide-angle telescope Оfficina Stellare RH-200 with the field of view 3.5 degrees was created in the Zvenigorod observatory. It is planned to set robotic wideangle telescopes with diameter more than 30 cm on other observatories of the INASAN.
Meteor studies allow answering questions about the origin and evolution of small bodies in near-Earth space and are the only possibility of studying small bodies of the Solar system in the particle sizes range from microns to a few meters.
The meteor observation network was organized by INASAN. The observations are carried out at Zvenigorod observatory (INASAN), “Istra” and “Kaluga” stations together with Geophysical observatory “Mikhnevo” (IDG RAS), Observatory of Ryazan State University and “Sazhnevo” station. The few thousand meteor registrations were collected by five year of observations. Using observational data the characteristics (radiant, beginning heights, ending height, velocity, trajectory, orbit and etc.) of meteor showers and sporadic are analyzed. The influx of meteor particles to the Earth is estimating. For the first time at Russia and Europe the multi technique (optical and acoustical) meteor observations are carried out by INASAN and IDG RAS.
Model of solar flare
Historically, the Institute is supported Sun study subjects. Results obtained over the past 5 years, allowed to build a solar flash electrodynamic model explaining the origin of main manifestations of the flash. It is shown that solar cosmic rays with an energy of 20 GeV have been generated in the flash current sheet by proton acceleration. Flash model is consistent with observations via space vehicles. The current layer calculated position coincides with the observed position of the heat source of X-rays.
Space geodynamics (scientific analysis of observational data of satellites for the purposes of astronomy and geophysics)
We live on a dynamic planet in constant motion that requires long-term continuous quantification of its changes in a truly stable frame of reference. To study and understanding the Earth’s shape, the Earth’s gravity field and the Earth’s rotational motion the Global Geodetic Observing System (GGOS) was established. GGOS is the Observing System of the International Association of Geodesy (IAG).
GGOS integrates different geodetic techniques, different models and approaches in order to ensure a long-term, precise monitoring of the geodetic observables. Gravimetrical observatories are the GGOS’ part also.
GGOS integrates the geometric and gravimetric aspects of geodesy – driving continuous improvement in the quality of geodetic products through increased investment in different geodetic techniques.
To study our planet by astrometric and geodetic methods it needs to solve next three major tasks (see the figure above):
• high accuracy Earth’s point position determinations, change point’s position in time and geocenter movement monitoring;
• to study Earth’s polar motion, polar motion rate and its time evolution;
• Earth’s gravity field improvement and it time variations.
GGOS provides the observational basis to maintain a stable, accurate and global reference frame and in this function is crucial for all Earth observation and many practical applications.
DORIS measurements INASAN started DORIS data processing in 1997. The time series of weekly station positions and daily Earth Orientation Parameters (EOPs) on the regular basis submitted to the International DORIS Service (IDS).
As was mentioned above the geocenter movements monitoring is one of the important tasks of the space geodesy. The term “geocenter motion” is defined as the motion the center-of-mass (CM) of the total Earth system (including solid Earth and its fluid envelope) with respect to the center-of figure (CF) of the solid Earth surface.
Since satellites orbit CM and because geodetic stations are located on the surface of the solid Earth, the feasibility of determining geocenter motion using satellite tracking has long been recognized. Figure above shows the weekly DORIS geocenter time series determined at INASAN using the network shift approach for 1993-2015.0 time period. From the above figure one can see that X and Y components of the geocenter motion have apparent annual periods, while Z has broader amplitude variations compared to X and Y constituents. Estimated amplitudes of the INASAN annual geocenter variations at the epoch of 2010.0 are 3.4±0.5 mm, 4.4±0.5
Satellite laser range measurements (SLR)
The software package “GeoIN” (GEOdynamics INvestigations) was developed at INASAN in 2015. This package uses the latest modern precise algorithms and models for laser data processing and permits satellite’s orbit determinations both high and low satellite altitudes. It also provides ground station coordinates and Earth’s gravity field coefficients determination, polar motion coordinates estimation and geocenter motion monitoring. GeoIN takes into account different external forces acting for the satellite as gravitational and non-gravitational origin. Figure gives the first results obtained with the use of software package GeoIN: the Earth’s gravity field coefficient estimations (upper) and ΔUT1 corrections compared to IERS C04 (down) on the 2010.0 – 2014.0 time span.
In general the obtained values for the various geodynamics parameters (time series of the Earth’s gravity field coefficients, time series of polar motion) demonstrate comparable results
with those derived by different foreign laser analysis centers. The formal plane and height errors are in the range of 7-10 mm.
Data processing of the Global Navigation Systems (GNSS)
At the INASAN processing of the GPS (USA) and GLONASS (Russia) measurement data is performed. The results of the processing 15 continuously operating sites of the Russian
Fundamental Astronomic-Geodetic network (FAGS) on the 1-year interval (2013.5 – 2014.5) give the differences of the station coordinate estimations within the range 1-10 mm
obtained separately for GPS and GLONASS measurements. The formal errors are within the limits of 1-10 mm also. These results confirm the identical accuracy of the named GNSS systems.
Earth’s gravity field investigation and satellite gradientometry
INASAN began investigations in the sphere of the Earth’s gravity field determination using gradientometry measurements. Earth’s gravity field is one of the key physical fields of the Earth’s system. Different directions of the world geosciences community require information about Earth’s gravity field parameters (geodesy, geophysics, geodynamics, celestial mechanics and so on).
Further mathematical data processing from the different gradientometry projects permit us more precisely to study interior Earth’s processes and its interaction with the near Earth space.
Study changes in the dynamic Earth system, interaction it components and connection with the environment offer a huge theoretical and practical interest as it aids to predict global risk phenomena to society.
THE HEATING EFFICIENCY OF PLANETARY ATMOSPHERES WITH A PREDOMINANCE OF HYDROGEN
One of the major factors defining the state of a planetary atmosphere in the Solar or an extrasolar planetary system is the heating by the star’s radiation. This issue is of special importance for hot jupiters (giant planets at close to the host star orbits). After discovery of such planets it was found out that atmospheres of ssome of them overfill their Roche lobes that results in strong matter outflow from the planetary atmosphere.
The heating of the upper hydrogen atmosphere is caused by the absorption of XUV radiation of the parent star in the range og 1-100 nm. This range covers the extreme ultraviolet range (10-100nm, EUV) and soft X-ray radiation (1-10 nm). XUV radiation is absorbed mostly in the process of ionization of atomic hydrogen and helium as well as ionization, dissociation and dissociative ionization oh molecular hydrogen. The heating efficiency is defined as the relation of total rate of the local heating if the atmospheric gas to the rate of absorption of the stellar radiation. This parameter plays an important role in the processes of thermal dissipation of upper planetary atmospheres.
For example in calculations of the efficiency of the heating by the XUV radiation of a giant HD209458b that has the upper atmosphere consistingmainly from atomic and molecular hydrogen, the rates for absorption of the energy of XUV radiation of the parent star were estimated and, for the first time, for the accompanying flux of primary photoelectrons caused by collisions in transition H2 H area in the upper planetary atmosphere (see the figure).
It has been shown for the first time that the efficiency of heating by XUV radiation and radiation of the upper atmosphere where hydrogen dominates does not exceed 0.2 at main atmospheric heights if the influence of photoelectrons is taken into account. It is obtained that the profiles of heating efficiency obtained for the solar wind with 10 and 100 times increase of flux intensity in sof X-ray range 1-10 nm have no significant difference from the case with the standard solar spectrum. Therefore the calculated heeating efficiencies can
be also used for stars younger than the Sun after the scaling of the flux of photons in soft X-rau and EUV ranges in accordance with observational data. These results will make it possible to estimate the atmosphere’s outflow rate for planets in young systems wis stellar spectra are different from the solar one.
- Bagrov Alexander V. – Full Dr. of Sci., leading researcher
- Bakanas Elena S. – Dr., researcher
- Bolgova Galina T. -Dr., researcher
- Valyaev I.N. – researcher
- Emelyanenko Vyacheslav V. – Full Dr. of Sci., leading researcher
- Ibrahimov Mansur A. – Dr. of Sci., senior researcher
- Klyuikov А. А. – Dr. , senior researcher
- Kuzin Sergei P. – Dr., senior researcher
- Levkina Polina A. – Dr., researcher
- Leonov Vladislav A. – Dr., researcher
- Naroenkov Sergei A. – Dr., researcher
- Rykhlova Lidiya V. – Full Dr. of Sci., leading researcher, head of the Group
- Shematovich V.I. – Full Dr. of Sci., head of the Department
- Terentjeva Alexandra K. (researcher)
- Ebauer K. V. – researcher
- Milyaeva Lyubov V. – engineer