The commercial development of space: is an international regulatory framework needed?

The commercial space sector to date has failed to develop comprehensive regulations--"rules of the road"--for its international activities. Within the next 5 years, conflicts with respect to international trade in satellite sales and launch services could emerge, highlighting the need for such a regulatory framework. If the commercial space sector is to continue to develop, it is important to begin discussions now, before these conflicts become significant, on the elements of an appropriate international regulatory framework. The existing framework for space activities was developed when government, not commercial, space activities were dominant, or was adapted from regulations in other sectors such as terrestrial telecommunications.     

Autonomous orbit maintenance system

Orbit maintenance is a major cost factor for Earth satellites in specialized orbits, such as a repeating ground track, or in formations. While autonomous attitude control is well established, the spacecraft's orbit is usually uncontrolled or maintained by ground station commands. For small, lower cost satellites, operations costs can be a dominant element of both cost and risk. This implies a need for low-cost autonomous orbit maintenance in order to allow such systems to be economically viable, particularly in today's constrained budget environment.

In addition, if the position of the spacecraft is controlled, it is therefore known in advance. Thus, mission planning can be done as far in advance as desired, without the need for replanning and frequent updating due to unpredictable orbit decay. An interesting characteristic of autonomous orbit maintenance is that it typically requires less software, and less complex software, than does orbit control from the ground. In many cases, an onboard orbit propagator is not needed.     

Space visions from a new generation

Through experiences at the International Space University's 1995 Summer Session, the authors became aware of generational differences of opinion with regard to visions for future space activities. The faculty members had expansionary visions of space exploration and colonization, while the students, having grown up in a very different environment, had concerns which centered around using space to improve life on Earth. This paper addresses possible explanations for these different perspectives. The visions of this younger generation are those which will shape the space policy of the future and are even beginning to shape it today.     

2010: The Symbionic Cockpit

The cockpit of the year 2010 is described in terms of both the capabilities and systems it contains and how the pilot interacts with it. A brief mission narrative is provided describing seveal hours in the life of the Manta air superiority fighter. This is followed by a discussion of the pilot interface components employed in the cockpit including hueristic voice, instrument panel display, canopy display, and holographic display systems. The concept of a ``symbionic' system is then introduced, describing in some detail the capabilities and features of a cockpit system that senses the physiological and mental state of the pilot and responds accrodingly. Finally, conclusions and predictions are made that summarize and emphasize the points made in the paper.     

Chemical evolution on the giant planets and Titan

We summarize the current status of atmospheric chemistry in the atmospheres of the outer solar system with special emphasis on the question of HCN formation on Jupiter, differences between polar and equatorial compositions on Jupiter, the coloration of the Great Red Spot, and the unique environment of Titan.     

New information on Saturn and its rings from multi-frequency VLA data

High resolution radio data of Saturn have been obtained at 1.3, 2, 6, and 21 cm, at different inclination angles of the ring plane. Preliminary results of limb darkening curves on the planet and optical depth measurements in the rings are described.     

The interpretations of ultraviolet observations of comets

Summary Ultraviolet observations of comets from above the Earth's atmosphere have provided excellent new results and improved older ground based observations (OH) by an order of magnitude. Satellites are especially suitable because long integration times and observations during extended time intervals are possible.The existing cometary L observations have confirmed the relatively high overall gas production rates on the order of 10³⁰ molecule s^–1. The results strongly support the concept of an icy conglomerate solid cometary nucleus. Additional observations of hydroxyl and oxygen favor water to be one of the most abundant molecules in comets. The observations are in agreement with the predominent role of water in the evaporation process of the nuclear ices but are not proof in themselves.Water did not outnumber other consitutents by orders of magnitude in comets Bennett and Kohoutek. At least in these comets, carbon-containing molecules were possibly as numerous as water. Determination of the carbon scale length is necessary for a more quantitative statement.A hydrogen velocity of 7–9 km s^–1 was observed in comet Bennett as well as in comet Kohoutek for a variety of heliocentric distances and varying production rates. Determinations of the outflow velocity from L isophotes agree with line profile observations of L and H. Hydroxyl may constitute the main source for the hydrogen atoms with v _H - 8 km s^–1. The decay process, however, leading to this particular velocity is not yet known. Possibly a large portion of the OH radicals do not decay into hydrogen atoms or at least not into slow ones. If the high velocity component of 20 km s^–1 or more comprises a larger amount (up to 50%), most of the quoted hydrogen production rates must be revised upward.The intrinsic cometary brightness is only a very crude indicator of a comet's actual gas production rate as shown by comparison of comets Bennett and TSK. Comets can be successfully used as (extra ecliptic) space probes to measure interplanetary quantities, e.g., the curvature of the extended hydrogen clouds can be used for the absolute determination of the solar emission independent of instrumental calibration. Generally time dependent hydrogen density models must be used for the interpretation. The strength of the ultraviolet L emission favors its measurement as a standard procedure for the observation of comets (possibly together with OH (3090 Å)). These observations provide the most accurate results on the total cometary gas production rate and its variation with heliocentric distance.Dedicated to Professor L. Biermann in recognition of his inspiring guidance.On leave of absence from Max-Planck-Institut für Physik und Astrophysik, Munich.