Etat de l'art sur la photogrammetrie et la teledetection

This State-of-the-Art is established from the main results of the Symposium of Commission VII of the International Society of Photogrammetry and Remote Sensing held in Toulouse (France) in 1982. It shows the important impact of Remote Sensing in all fields of application and the interest of meetings between specialists of Photogrammetry and of Remote Sensing.     

Sur des conditions d''amorçage par onde de choc de la détonation du nitrométhane

Results concerning the thermodynamic and mechanical properties of nitromethane (N.M.) at pressures up to 11 GPa are presented. The pressure is generated either by an incident shock wave or by a shock wave reflected within a medium prepressurized by a first shock wave. Calculation of the temperature behind these shock waves, based on the Walsh-Christian model, calls, in particular, upon the knowledge of the N.M. shock polar relative to normal temperature and pressure conditions, but also of those corresponding to prepressurized states.

Taking advantage of the phenomena of N.M. electric polarization under shock, we determine, on the one hand, the relation between pressure and particle velocity and, on the other hand, the influence of pressure conditions on induction delays of the explosive.

According to calculation, for a same pressure level the N.M. temperature behind a single shock is higher than that obtained by two successive compressions.

Experimentally, we observe that N.M. compressed at 11 GPa by means of two shock waves does not detonate (during the observation time of about 0,5 μs), while in the case of a single shock wave of the same amplitude the induction delay is lower than 0.1 μs. These results show the important role of temperature, as opposed to that of pressure.     

Resolution du probleme des instabilites sur le moteur Viking

(Resolution of the instability problem on Viking motor)—This paper gives the experimental and theorical work program which has permitted one to resolve the Viking motor instability problems and to ensure the L03 launching, one year after the L02 launching failure. After an exploration phase of search for working anomalies, instabilities have been characterized, acceptation procedure has been ratified, and different modifications have been tried.Theoretical work associated with the synthesis of experimental results have led to the finishing touch of operation and stability representative models. The pointing out of specific parameters has influenced the research of some solutions and the orientation of future works.     

La prévention des instabilités pogo sur ariane 1

This article presents the organization of POGO studies on the Ariane 1 launcher, the input data for the systems, the studies concerning the first stage L140, the second stage L33 and the constructive conclusions drawn from these studies.     

Single-impulse transfers from orbits of artificial satellites to orbits around <Emphasis Type="Italic">L</Emphasis><Subscript>1</Subscript> or <Emphasis Type="Italic">L</Emphasis><Subscript>2</Subscript> libration points

In the context of the restricted circular three-body problem a method for constructing families of periodic orbits is described. Each orbit contains a segment of transfer from artificial satellite orbit of a smaller body to an orbit around L ₁ or L ₂ points of the Sun-Earth and Earth-Moon systems, a segment of multiple flyby of this libration point, and a segment of return to the artificial satellite orbit. Dependences of velocities at the pericenter on the pericenter radius are given.     

Precipitation of subrelativistic-energy electrons near the polar boundary of the Earth radiation belt according to the data of measurements on the <Emphasis Type="Italic">Vernov</Emphasis> and <Emphasis Type="Italic">Lomonosov</Emphasis> satellites

The work is devoted to observations of sharp growths of magnetospheric electron fluxes in the vicinity of the polar boundary of the outer radiation belt of the Earth according to the data of measurements on the Vernov and Lomonosov satellites. This precipitation was observed at the high-latitude boundary of the outer radiation belt toward the equator from the isotropization boundary, and can be caused by scattering waves of various physical natures, including electromagnetic and electrostatic waves.     

Sunspot oscillations as derived from the <Emphasis Type="Italic">SOHO</Emphasis>/MDI magnetograms

As a result of processing long (up to 144 h) series of sunspot magnetograms obtained on the SOHO (Solar and Heliospheric Observatory) spacecraft with the MDI (Michelson Doppler Imager) instrument it is shown that the mode with a period of 800–1300 min is a limiting low-frequency oscillation mode of the magnetic field of a sunspot as a whole. Its period is essentially and nonlinearly depends on the sunspot magnetic field strength. In addition to this mode, higher harmonics are also revealed in the sunspot oscillation spectra in the bands 40–45, 60–80, 135–170, 220–250, and 480–520 min. The oscillation power in these bands monotonically and rapidly decreases with increasing frequency, which is characteristic for overtones arising due to the nonlinear nature of oscillations. The limiting oscillation mode stably exists in sunspots for 1.5–2 days, which coincides with the average lifetime of a supergranular cell. The mode with the period of 35–48 h observed in the power spectrum is not an eigen mode of sunspots, because its period is independent of its magnetic field strength. Probably, it occurs as a quasiperiod of an external exciting force caused by disturbances from supergranular cells surrounding the sunspot.