Pravidelné semináře pořádáme jednou měsíčně (říjen–červen, zpravidla první pondělí v měsíci) od 13 hod v seminární místnosti pracoviště Ondřejov.
04. 03. 2013
From Kepler to fine orbit tuning of GOCE
Abstract: Johanes Kepler, living in Prague, utilized observations carried out by Tycho Brahe also on the Czech territory to formulate the law known today as the “3rd Kepler law”. We recall it in its classical form and will derive it for relationship between the mean motion and selected mean semi-major axis of orbit of an artificial Earth satellite (AES) accounting for the polar flattening of the Earth. This simple tool has amazing applications in selection of orbits of AES to fulfill given tasks “at the best”. There is a close relation between density of ground tracks by satellite data, on which in turn precision and resolution of products derived from such measurements are dependent, and semi-major axis (or height of flight) of the satellite used. We tell the story of the GRACE satellites, which during their free decay in the atmosphere encountered important orbit resonances during those the density of ground tracks significantly (but temporarily) decreased. Consequently, also the quality of the monthly solutions for the variations of the gravity field has decreased. What we learned from GRACE, we applied for orbit choice of GOCE, the first satellite equipped by a gravity gradiometer. In this matter, we joined the manager of the GOCE project Dr. Rune Flobergahen, ESA. GOCE is also equipped by ultraprecise ion motor for orbit corrections so that the height of flight can be kept within unbelievably small range ±5 m. It is feasible to choose and keep the orbit at selected higher order resonance and by this way to reach the maximum quality of products derived from gradiometric measurements. This process is called „fine orbit tuning“. Orbit choice for remote sensing AES affects significantly the accuracy of the results derived from their measurements, thus our approach captured interest of ESA in the project of bistatic altimetric satellite GNSS-R. We also investigated the orbit choice for planetary orbiters of Mars, Venus and the Moon from viewpoint of possible most accurate determination of gravity field parameters of these bodies.
Dále pořádáme menší semináře jednotlivých oddělení:
Semináře slunečního oddělení
Každé úterý v 13:00 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
23/04/2013, 13:00Non-linear force-free magnetic dip models of quiescent prominence fine structuresAbstract: We use 3D non-linear force-free magnetic field modelling of prominence/filament magnetic fields to develop the first 2D models of individual prominence fine structures based on the 3D configuration of the magnetic field of the whole prominence. We then use an iterative technique to fill the magnetic dips produced by the 3D modelling with realistic prominence plasma in hydrostatic equilibrium and with a temperature structure that contains the prominence-corona transition region. With this well-defined plasma structure the radiative transfer can be treated in detail in 2D and the resulting synthetic emission can be compared with prominence/filament observations. Such non-linear force-free magnetic dip models are able to produce synthetic hydrogen Lyman spectra in a qualitative agreement with a range of quiescent prominence observations. Moreover, the plasma structure of these models agrees with the gravity induced prominence fine structure models which have already been shown to produce synthetic spectra in good qualitative agreement with several observed prominences.
Zářivě-(magneto)hydrodynamické semináře
Zpravidla 1x za 14 dní ve čtvrtek od 11 hod (říjen–červen) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
(informace nejsou k dispozici)
Semináře oddělení GPS
Zpravidla v knihovně pracoviště Praha–Spořilov v různé dny.
V nejbližší době nejsou plánovány žádné semináře.