Ionosphere monitoring and inter-frequency bias determination using Galileo: First results and future prospects

We present first results of using the European Global Navigation Satellite System (GNSS) Galileo for determining the Total Electron Content (TEC). Furthermore, we describe a calibration technique which can be used to determine GNSS inter-frequency and inter-system biases along with calibrated TEC.     

Satellite orbits in Levi-Civita space

In this paper we consider satellite orbits in central force field with quadratic drag using two formalisms. The first using polar coordinates in which the satellite angular momentum plays a dominant role. The second is in Levi-Civita coordinates in which the energy plays a central role. We then merge these two formalisms by introducing polar coordinates in Levi-Civita space and derive a new equation for satellite orbits which unifies these two paradigms. In this equation energy and angular momentum appear on equal footing and thus characterize the orbit by its two invariants. Using this formalism we show that equatorial orbits around oblate spheroids can be expressed analytically in terms of Elliptic functions. In the second part of the paper we derive in Levi-Civita coordinates a linearized equation for the relative motion of two spacecrafts whose trajectories are in the same plane. We carry out also a numerical verification of these equations.     

Standard data procedures for future space projects

After a general definition of data- and instrument autonomy and an introduction to the End-to-End Data System concept the future guidelines for “Packet Telemetry and -Telecommand” are overviewed. These and other guidelines have been initiated by a NASA/ESA working group and further developed by an international “$\text{C}$onsultative $\text{C}$ommittee for $\text{S}$pace $\text{D}$ata $\text{S}$ystems” (CCSDS), coordinated with 6 space agencies. The status of these documents is reviewed, especially the document on Packet Telemetry, which has reached a mature stage. A pilot project, $\text{A}$utonomous $\text{P}$ayload $\text{C}$ontrol (APC), for the study and the demonstration of these new procedures is introduced shortly.     

Optical focussing with soft X-rays and in the extreme ultraviolet

Space Science Reviews -     

A review of lighter-than-air progress in the United States and its technological significance

Lighter-than-air vehicles are being studied and developed as solutions to problems in transportation and in communications and service. These vehicles include balloons, balloon-airship systems and airships. Tethered balloons of streamline form have been developed for both military (surveillance) and civil (telecommunications) applications. These are capable of flying at 4600 m altitude in 100 km/hr winds and supporting payloads up to 1678 kg. Other applications include use of natural shaped balloons for logging in forested areas and for transport of cargo from ship-to-shore. Free balloons have been flown up to 51, 812 m and 7624 kg have been carried to 34,440 m. Balloon-like remotely piloted airships are being studied and developed as high altitude geo-stationary platforms for telecommunication and surveillance. Many new and lower cost benefits would result from the successful development of this type. The carrying of heavy large-volume cargoes promises to be an important and unique application for airships which are designed to achieve precise hovering while being loaded or unloaded. Several types are being studied for this purpose. Other new applications include use of airships for airport feeder passenger transport, and as large long endurance naval patrol vehicles. Technology programs must be developed which will enable new airships to be designed and built. These would include studies in aerodynamics, materials, structures, propulsion, and operational techniques. The advancement of these new concepts is handicapped by the lack of an established industry, confidence, and the complexity and cost of development. Yet where success has been achieved, it has been worth the risk. Government support is required to achieve these goals.     

A Survey of Electronic Attitude Measurement Systems

Introducing rectangular coordinates for the reference coordinate system and the space-vehicle fixed-coordinate system, it will be shown that the transformation matrixes between both coordinate systems which describe the attitude of the space vehicle can be easily computed as functions of the rectangular coordinates of two precise directions known in both coordinate systems. In detail, an electronic attitude measurement will be described based on two precise propagation directions of RF waves. In order to measure the propagation direction in the space-vehicle fixed-coordinate system, a very general interferometer is described. This interferometer is characterized by the fact that the antennas of the interferometer are arbitrarily distributed on the surface of the space vehicle and that the electronic computation of the coordinates of the propagation direction of an RF wave is extremely simple. The design and some modifications of this system are discussed