Autonomous navigation for artificial satellites

An autonomous navigation system is considered that provides a satellite with sufficient numbers and types of sensors, as well as computational hardware and software, to enable it to track itself. Considered are attitude type sensors, meteorological cameras and scanners, one way Doppler, and image correlator

Uniaxial aerodynamic attitude control of artificial satellites

Within the context of a simple mechanical model the paper examines the movement of a satellite with respect to the center of masses under conditions of uniaxial aerodynamic attitude control. The equations of motion of the satellite take account of the gravitational and restorative aerodynamic moments. It is presumed that the aerodynamic moment is much larger than the gravitational, and the motion equations contain a large parameter. A two-parameter integrated surface of these equations is constructed in the form of formal series in terms of negative powers of the large parameter, describing the oscillations and rotations of the satellite about its lengthwise axis, approximately oriented along the orbital tangent. It is proposed to treat such movements as nominal undisturbed motions of the satellite under conditions of aerodynamic attitude control. A numerical investigation is made for the above integrated surface

On the Intermediate Orbits of the Earth's Artificial Satellites

Intermediate orbits of artificial earth satellit

Atmospheric drag on artificial satellites

By using observed values of dP/dt and a convenient model to represent the variable density (ρ) and the scale height (H) of the atmosphere, we calculate mean values for the effective cross-section (S) of a non-spherical satellite at every day during a period of about two and half months. For that calculation we assume in advance that the satellite tumbles around an axis perpendicular to thè longest axis of symmetry. For Satellite 1958 Epsilon (Explorer IV) the orientation of the axis of rotation has been determinated by an analysis of the variation in intensity of the measured radio-transmission from the satellite (Nau- mann,196l). A similar analysis has been carried out for the rocket of Sputnik III (Satellite 1958 δ1) based on its variations of visual brightness (Notni and 01eak,1959). Our results on the effective drag area show a good agreement with those obtained from both analysis. (Párrafo extraído a modo de resumen)Asociación Argentina de Astronomí

Atmospheric drag on artificial satellites

By using observed values of dP/dt and a convenient model to represent the variable density (ρ) and the scale height (H) of the atmosphere, we calculate mean values for the effective cross-section (S) of a non-spherical satellite at every day during a period of about two and half months. For that calculation we assume in advance that the satellite tumbles around an axis perpendicular to thè longest axis of symmetry. For Satellite 1958 Epsilon (Explorer IV) the orientation of the axis of rotation has been determinated by an analysis of the variation in intensity of the measured radio-transmission from the satellite (Nau- mann,196l). A similar analysis has been carried out for the rocket of Sputnik III (Satellite 1958 δ1) based on its variations of visual brightness (Notni and 01eak,1959). Our results on the effective drag area show a good agreement with those obtained from both analysis. (Párrafo extraído a modo de resumen)Asociación Argentina de Astronomí

Modern methods for the determination of polar motion and UT1

The applications and Doppler satellite observations, laser ranging to artificial satellites and the Moon, and astronomic radio interferometry to monitoring polar motion and Universal Time System 1 (UT1) are discussed. How and what each method is capable of measuring, fundamental limitations, and the present status of the developments of each method were reviewed. Evaluations of the various methods as candidates for the next generation international polar motion and UT1 monitoring service are summarized

Time and frequency stability for the Crustal Dynamics Project

Very long base interferometry (VLBI) and laser ranging to artificial satellites and the Moon were used to determined vector baselines between stations with precisions of about one part in 10 to the 8th power. Deformations and strain accumulations in active earthquake regions were determined by making frequent measurements of baselines between many stations in active areas near plate boundaries