Optical Ranging System Employing a High Power Injection Laser Diode

For many military applications small, lightweight range finders are required that operate at a high pulse repetition rate. It will be shown that a ranging system with an injection laser in the transmitter can fulfill these requirements. The performance of an optical ranging system employing a pulsed gallium arsenide laser diode transmitter, with peak powers up to 100 watts at room temperature is described. After a brief review of fundamental system parameters, calculations of the range capability of the system are given, based upon the Poisson distribution of photoelectron statistics. A discussion is presented on the experimental support of theoretical analysis.     

Short-Lived Radioactivities and the Birth of the sun

Now extinct short-lived radioactive isotopes were apparently extant in the early solar system. Their abundances can be inferred from isotopic effects in their daughter nuclei in primitive meteorites, and the deviation of these abundances from expectations from continuous galactic nucleosynthesis yields important information on the last nucleosynthetic events that contributed new nuclei to the solar system and on the general circumstances of the Sun's birth. In this paper we present a rudimentary model that attempts to reconcile the abundances of ten short-lived radioactivities in the early solar system. In broad outlines, the picture requires 1) that Type Ia supernovae maintained a steady ISM supply of ⁵³Mn and ¹⁴⁶Sm, 2) that the r-process events that slowly admixed new ¹⁰⁷Pd, ¹²⁹I, ¹⁸²Hf, and ²⁴⁴Pu nuclei to the solar system occurred over an interval of several hundred million years prior to solar system formation, and 3) that a massive star, by injecting only material outside its helium-exhausted core into the proto-solar nebula, contributed ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁶⁰Fe, and ¹⁸²Hf no more than one million years prior to the Sun's birth. In this picture, the live ¹⁸²Hf present in the early solar system was not due to r-process production but rather to a fast s-process in helium or carbon burning shell in the massive star. We conclude with a possible chemical-memory explanation for the putative ⁵³Cr/⁵²Cr gradient in the solar system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Interplanetary Origin of Intense,Superintense and Extreme Geomagnetic Storms

We present a review on the interplanetary causes of intense geomagnetic storms (Dst≤−100 nT), that occurred during solar cycle 23 (1997–2005). It was reported that the most common interplanetary structures leading to the development of intense storms were: magnetic clouds, sheath fields, sheath fields followed by a magnetic cloud and corotating interaction regions at the leading fronts of high speed streams. However, the relative importance of each of those driving structures has been shown to vary with the solar cycle phase. Superintense storms (Dst≤−250 nT) have been also studied in more detail for solar cycle 23, confirming initial studies done about their main interplanetary causes. The storms are associated with magnetic clouds and sheath fields following interplanetary shocks, although they frequently involve consecutive and complex ICME structures. Concerning extreme storms (Dst≤−400 nT), due to the poor statistics of their occurrence during the space era, only some indications about their main interplanetary causes are known. For the most extreme events, we review the Carrington event and also discuss the distribution of historical and space era extreme events in the context of the sunspot and Gleissberg solar activity cycles, highlighting a discussion about the eventual occurrence of more Carrington-type storms.     

Global behavior of the equatorial anomaly since 1999 and effects on GPS signals

Tools to generate VTEC maps were developed. These maps have been used to study the global behavior of the equatorial anomaly since 1999 up to now, and its effects on GPS signal. The VTEC data for any place around the world is based on IONEX data. In this way, a quick annual behavior of the VTEC may be analyzed, and also compared to the VTEC behavior for different places and different years. Based on these data an electron density model taking into account radial as well latitudinal and longitudinal gradients were developed. This model was incorporated in a 3D ray-tracing program. Using this program it was possible to compare the STEC conversion to the VTEC. As expected the results show that the lower the elevation angles of the Satellite Vehicle, the greater the error in the VTEC estimation.     

Enhancing Europe's capabilities in space research and technology: Towards a European Space Board

With the proposed implementation of a European space policy and the prospect of several major undertakings in the space domain the European Union should decide to set up a high-level independent body and confer on it the authority and means to provide expert advice on space-related subjects to its institutions, policy makers and agencies, as well as to the space research community. Although the political and legislative situation in the USA is different from that in Europe, such a body has existed there since 1959 and has proven most useful. The current situation in Europe is analysed and the arguments for setting up such a structure are presented. It is suggested that the foundations for this new advisory structure can be found in the existing European Space Science Committee, the European Science Foundation's expert committee on space research. A structure and remit is proposed for such a body and elements of its mode and means of operations are discussed.     

The IBEX Flight Segment

IBEX provides the observations needed for detailed modeling and in-depth understanding of the interstellar interaction (McComas et al. in Physics of the Outer Heliosphere, Third Annual IGPP Conference, pp. 162–181, 2004; Space Sci. Rev., 2009a, this issue). From mission design to launch and acquisition, this goal drove all flight system development. This paper describes the management, design, testing and integration of IBEX’s flight system, which successfully launched from Kwajalein Atoll on October 19, 2008. The payload is supported by a simple, Sun-pointing, spin-stabilized spacecraft with no deployables. The spacecraft bus consists of the following subsystems: attitude control, command and data handling, electrical power, hydrazine propulsion, RF, thermal, and structures. A novel 3-step orbit approach was employed to put IBEX in its highly elliptical, 8-day final orbit using a Solid Rocket Motor, which provided large delta-V after IBEX separated from the Pegasus launch vehicle; an adapter cone, which interfaced between the SRM and Pegasus; Motorized Lightbands, which performed separation from the Pegasus, ejection of the adapter cone, and separation of the spent SRM from the spacecraft; a ShockRing isolation system to lower expected launch loads; and the onboard Hydrazine Propulsion System. After orbit raising, IBEX transitioned from commissioning to nominal operations and science acquisition. At every phase of development, the Systems Engineering and Mission Assurance teams supervised the design, testing and integration of all IBEX flight elements.     

A liquid propulsion panorama

Liquid-propellant rocket engines are widely used all over the world, thanks to their high performances, in particular high thrust-to-weight ratio. The present paper presents a general panorama of liquid propulsion as a contribution of the IAF Advanced Propulsion Prospective Group.After a brief history of its past development in the different parts of the world, the current status of liquid propulsion, the currently observed trends, the possible areas of future improvement and a summarized road map of future developments are presented. The road map includes a summary of the liquid propulsion status presented in the “Year in review 2007” of Aerospace America.Although liquid propulsion is often seen as a mature technology with few areas of potential improvement, the requirements of an active commercial market and a renewed interest for space exploration has led to the development of a family of new engines, with more design margins, simpler to use and to produce associated with a wide variety of thrust and life requirements.