Measuring Vacuum Ultraviolet Radiation from High-Temperature Nitrogen

In this technique, small blunt models are launched into a mixture of nitrogen and neon in a ballistic range, and the radiation from the shock layer on the forward face of the model is measured during the last few microseconds of flight by a radiometer directly in the flight path of the model. The ultraviolet radiation is sensed with the phosphor sodium salicylate. Comparison with other techniques and a brief summary of results are given.     

Temperature and moisture conditions for life in the extreme arid region of the Atacama desert: four years of observations including the El Niño of 1997-1998

The Atacama along the Pacific Coast of Chile and Peru is one of the driest and possibly oldest deserts in the world. It represents an extreme habitat for life on Earth and is an analog for life in dry conditions on Mars. We report on four years (September 1994-October 1998) of climate and moisture data from the extreme arid region of the Atacama. Our data are focused on understanding moisture sources and their role in creating suitable environments for photosynthetic microorganisms in the desert surface. The average air temperature was 16.5 degrees C and 16.6 degrees C in 1995 and 1996, respectively. The maximum air temperature recorded was 37.9 degrees C, and the minimum was -5.7 degrees C. Annual average sunlight was 336 and 335 W m(-2) in 1995 and 1996, respectively. Winds averaged a few meters per second, with strong f?hn winds coming from the west exceeding 12 m s(-1). During our 4 years of observation there was only one significant rain event of 2.3 mm, which occurred near midnight local time. We suggest that this event was a rainout of a heavy fog. It is of interest that the strong El Ni?o of 1997-1998 brought heavy rainfall to the deserts of Peru, but did not bring significant rain to the central Atacama in Chile. Dew occurred at our station frequently following high nighttime relative humidity, but is not a significant source of moisture in the soil or under stones. Groundwater also does not contribute to surface moisture. Only the one rain event of 2.3 mm resulted in liquid water in the soil and beneath stones for a total of only 65-85 h over 4 years. The paucity of liquid water under stones is consistent with the apparent absence of hypolithic (under-stone) cyanobacteria, the only known primary producers in such extreme deserts.     

Physical properties of the natural satellites

This paper reviews the physical nature of the satellites of the planets, excluding the Moon but including the rings of Saturn. Emphasis is placed on the best studied objects: Titan, Phobos and Deimos, the four Galilean satellites (Io, Europa, Ganymede, and Callisto), and the rings of Saturn.The authors dedicate this paper to the memory of Gerard P. Kuiper, who died on 24 December 1973. It was his pioneering research begun in the early 1940's that opened the era of physical studies of the satellites. That work, together with his lifelong study of the origin of the system of planets and satellites, provided the foundation upon which much of the work reviewed in this paper is based.     

Space as a frontier – the role of human motivation

Despite several false-starts, commercial space is showing signs of activity similar to those in historic frontiers. A comparative study shows a variety of aspects in common; specific environmental enablers that can be labeled technology, legislation and charisma. Charisma can be defined as the human motivation behind frontier activities. Technology and the social systems defined as legislation tend to dominate plans of those engineering frontier activity. However, national, economic and personal ideologies are what drive the frontier. Technology and legislation are the tools by which these ideologies achieve their goals.     

A space exploration strategy that promotes international and commercial participation

NASA has created a plan to implement the Flexible Path strategy, which utilizes a heavy lift launch vehicle to deliver crew and cargo to orbit. In this plan, NASA would develop much of the transportation architecture (launch vehicle, crew capsule, and in-space propulsion), leaving the other in-space elements open to commercial and international partnerships. This paper presents a space exploration strategy that reverses that philosophy, where commercial and international launch vehicles provide launch services. Utilizing a propellant depot to aggregate propellant on orbit, smaller launch vehicles are capable of delivering all of the mass necessary for space exploration. This strategy has benefits to the architecture in terms of cost, schedule, and reliability.     

Position-fixing using the USSR's GLONASS C/A code

The possibility of the USSR's global satellite navigation system GLONASS and the NAVSTAR Global Positioning System using a common navigation system can only be determined following exhaustive testing of two systems in a variety of satellite and receiver modes and configurations. The authors describe their first attempts to carry out basic position-fixing and timing measurements with a single-channel, sequencing digital receiver in a C/A code phase-measurement mode using the GLONASS satellites. The receiver used to produce the fixes was a digital sequencing unit with a single stage of downconversion and followed by 1-bit quantization. Code acquisition was accomplished using 1-Q channels measuring code phase. The number of satellites available in the present preoperational phase heavily restricts the time and satellite configurations which can be tested. However, the results have encouraged the authors to propose a range of experiments aimed at evaluating the two systems and eventual integration     

Contributions of the French Institut Géographique National (IGN) to the International DORIS Service

DORIS is one of the four geodetic space techniques participating to the Global Geodetic Observing System (GGOS). Since the early development of this system, the Institut Géographique National played a specific and active role. Within, the International DORIS Service (IDS), IGN is in a particular position. While it is responsible for the installation and the maintenance of the DORIS ground tracking stations, it also handles one of the two IDS data center delivering DORIS data and products and has been an IDS Analysis Center for years, providing all possible IDS products, in particular the latest ignwd08 time series in preparation of ITRF2008. This paper explains the different aspects of the IGN contribution to IDS from an historical point of view, presents current activities and scientific results and provides a perspective for future activities. Recent DORIS results show a 10 mm precision or better when more than four DORIS satellites are available. Comparisons between recent DORIS solutions (ign07d02 and ign09d02) and past ITRF realizations show that errors are shared between the DORIS and the ITRF realizations. Some problems related to DORIS data processing are also discussed and possible ways to solve them in the future are discussed. In particular, we can now reject the tropospheric origin of the problem detected in the Envisat data after the software upload of October 12, 2004. A few applications in geodesy (terrestrial reference frame, Earth’s polar motion) and geophysics are also discussed as a natural extension of these service-type activities.