Development of thermal sensors and drilling systems for lunar and planetary regoliths

We consider some novel concepts for thermal properties experiments aboard lunar landers or rovers, that may lead to an improved understanding of both the structure of the lunar near surface layers and the lunar thermal history. The new instruments could be developed using the experience and heritage from recently developed systems, like the Rosetta Lander thermal conductivity experiment MUPUS and existing designs used for terrestrial measurements of thermal conductivity. We describe shortly the working principle of such sensors and the main challenges faced when using them in the airless regolith layers of the Moon or other airless bodies. In addition new concepts to create appropriate drill holes for thermal and other measurements in the lunar regolith are discussed.     

Lower-mesospheric inversion layers over brazilian equatorial region using TIMED/SABER temperature profiles

Lower-mesospheric inversion layers (MILs) were studied using the temperature profiles observed by TIMED/SABER over Cariri (7.5°S, 36.5°W), Brazil, in 2005. A total 175 MILs were identified with the maximum occurrence in April and October and the minimum in January and July. The lower MIL is located in a height region from 70 to 90 km, with the peak at around 83 ± 4 km with the temperature of 205 ± 5 K, and the thickness of 4–10 km. The results show large amplitudes of MILs during equinoxes and minimum in solstices, with a clear semiannual variation. A general feature of lower MIL in monthly mean profile was observed twice a year, one from February to May, and the other from August to October with a downward shift of the top level. These results suggest that formation and long persistence of MIL is an important factor to investigate propagation of atmospheric gravity waves in the mesosphere-lower thermosphere (MLT) region.     

Remote upgrading of a space-borne instrument

The main purposes of experiment “Obstanovka” (“Environment” in Russian) consisting of several instruments are to measure a set of electromagnetic and plasma phenomena characterizing the space weather conditions, and to evaluate how such a big and highly energy consuming body as the International Space Station disturbs the surrounding plasma, and how the station itself is charged due to the operation of so many instruments, solar batteries, life supporting devices, etc. Two identical Langmuir electrostatic probes are included in the experiment “Obstanovka”. In this paper the Langmuir probes for “Obstanovka” experiment are described, including the choice of geometry (spherical or cylindrical), a more reliable method for the sweep voltage generation, an adaptive algorithm for the probe’s operation. Special attention is paid to the possibility for remote upgrading of the instrument from the ground using the standard communication channels.     

Properties of Staggered PRF Radar Spectral Components

Expressions for moving target indicator (MTI) improvement factor limitation due to pulse repetition frequency (PRF) staggering and loss of target detectability for various values of Doppler frequency in the passband are presented. It is also shown that the product of variance of stagger periods and clutter variance is an important parameter determining the performance of a staggered PRF MTI radar.     

Dynamics of Momentum Biased Spacecraft in a Near-Polar Orbit

The equations of motion of a momentum biased spacecraft are derived in a general form. The spacecraft is assumed to be orbiting in a near-elliptical orbit. An aerodynamic torque model which accounts for the atmospheric superrotation is assumed. The equilibrium attitude angles are obtained in terms of modified Bessel functions. Analytic expressions for the long-term motion of the momentum biased axis are derived for special cases. The analysis is applicable to the Magsat mission.     

Design of the HEAO Main Bus Shunt Regulator

The High Energy Astronomy Observatory (HEAO) main bus regulator contains a redundant error amplifier (REA) and a 12-section sequenced shunt transconductance amplifier (STA) in which not more than three and not less than one shunt section are in an active control mode regardless of a failure in any one of the twelve sections. The part of the work concerned with the shaping of the frequency response of the REA and STA minor feedback loops and of the teolator major feedback loop is described. Emphasis is on the application of a general design technique embodying a "design-analyze-measure iteration loop," in which a first-cut design and analysis is corrected ard improved after experimental observation of discrepancies and deficiencies. In particular, an incipient high-frequency oscillation was thereby reliably eliminated. It is demonstrated that analysis techniques involving a minimum of algebra can provide full quantitative information on an efficient and reliable system design.