Table mountain observatory support to other programs

The Table Mountain Observatory (TMO) facilities include well equipped 24 inch and 16 inch telescopes with a 40 inch telescope (owned by Pomona College) due for completion during FY 89. This proposal is to provide operational support (equipment maintenance, setup, and observing assistnce) at TMO to other programs. The program currently most heavily supported by this grant is the asteroid photometry program directed by A. W. Harris. During 1987, about 20 asteroids were observed, including a near-earth asteroid, 1951 Midas. The photometric observations are used to derive rotation periods, estimate shapes and pole orientations, and to define the phase relations of asteroids. The E class asteroid 64 Angelina was observed, and showed the same opposition spike observed of 44 Jysa, last year. Comet observations are made with the narrow band camera system of David Rees, University College London. Observational support and training was provided to students and faculty from Claremont Colleges for variable star observing programs. Researchers propose to continue the asteroid program, with emphasis on measuring phase relations of low and high albedo asteroids at very low phase angles, and supporting collaborative studies of asteroid shapes

The Roles of the Terms of Trade and Nontraded-Good-Prices in Exchange Rate Variations

This paper demonstrates that disturbances to supplies or demands for internationally traded goods affect exchange-rates differently than do disturbances in markets for nontraded goods. The paper develops a stochastic two-country equilibrium model of exchange rates, asset prices, and goods prices, with two internationally traded goods and a nontraded good in each country. Optimal portfolios differ across countries because of differences in consumption bundles. Changes in exchange-rates, asset prices, and goods prices occur in response to underlying disturbances to supplies and demands for goods. We examine the ways in which responses of the exchange-rate are related to parameters of tastes and production shares, and we discuss conditions under which these exchange-rate responses are "large" compared to the responses of ratios of nominal price indexes.

Self-fulfillment Expectations, Speculation Attacks, and Capitol Controls

This paper examines the endogenous implementation of capital controls in the context of a fixed exchange rate regime. It is shown that if there exists a non-zero probability that the policymaker's response to a speculative attack on official foreign reserves will be the introduction of controls, such an attack may occur even when current and expected monetary policy is consistent with a permanently viable, control-free fixed exchange rate regime. Consequently, capital controls may be the outcome of self- fulfilling expectations rather than the result of imprudent economic policies.

Asset Markets, Tariffs, and Political Risk

The paper examines a simple model in which exogenous political risk creates uncertainty about tariffs. The model predicts a relation between consumption and tariffs that differs radically from that implied by models without asset markets or political risk. Given the probability distribution of tariffs, domestic consumption and utility (ex post) are lower in states of the world with a domestic tariff and no foreign tariff than with a foreign tariff and no domestic tariff.This conclusion emerges despite the fact that the opposite would be obtained in the absence of asset markets. So economists should not be surprised if observed relations between consumption and tariffs differ from the predictions of static theory in either time-series or cross-sections.

Near Earth asteroid orbit perturbation and fragmentation

Collisions by near earth asteroids or the nuclei of comets pose varying levels of threat to man. A relatively small object, approximately 100 meter diameter, which might be found on an impact trajectory with a populated region of the Earth, could potentially be diverted from an Earth impacting trajectory by mass driver rocket systems. For larger bodies, such systems would appear to be beyond current technology. For any size object, nuclear explosions appear to be more efficient, using either the prompt blow-off from neutron radiation, the impulse from ejecta of near-surface explosion for deflection, or as a fragmenting charge. Practical deflections of bodies with diameters of 0.1, 1, and 10 km require interception, years to decades prior to earth encounter, with explosions a few kilotons, megatons, or gigatons, respectively, of equivalent TNT energy to achieve orbital velocity changes or destruction to a level where fragments are dispersed to harmless spatial densities

The Classification and Perfomance of Alternative Exchange-Rate Systems

Owing to dissatisfaction with the IMF’s de jure classification of exchange-rate regimes, a substantial literature has emerged presenting de facto classifications of exchange-rate systems and using the latter classifications to compare performances of alternative regimes in terms of key macroeconomic variables. This paper critically reviews the literature on de facto regimes. In particular the paper (1) describes the main methodologies that have been used to construct de facto codings, (2) surveys the empirical literature generated by de facto regime codings, and (3) lays-out the problems inherent in constructing de facto classifications. The empirical literature is found to yield few robust findings. We argue that the as-yet unfulfilled objective of this literature, and the major research agenda for the future in this area, lies in the need of a more thorough investigation of the degree of monetary-policy independence without relying exclusively on movements in exchange rates, an agenda the attainment of which is made especially challenging because of the lack of comprehensive and reliable data on reserves and interest rates.Exchange-rate regimes; Economic growth; Inflation; Bipolar hypothesis

A free-space optical communications link to an unmanned aerial vehicle.

Free-space optics (FSO) is an optical communications technology in which information is transmitted through the atmosphere on modulated optical beams. At the time of the development of FSO, it was envisioned to be a possible solution for provision of connectivity between customer premises and the optical backbone of today's telecommunications infrastructure. Due to limitations in the performance of FSO technology under adverse weather conditions, it is unable to provide sufficiently reliable connectivity for permanent telecommunications and networking applications. This dissertation investigates the deployment of FSO communications links to provide a temporary high-bandwidth communication line between a ground station and an unmanned aerial vehicle (UAV). The deployment of FSO links for ground-to-UAV communications is analyzed from the standpoint of feasibility based on beam steering tolerances and beam divergences, along with platform vibration analysis and active beam steering element comparisons. A mathematical model of a ground-to-UAV communication link is developed. Furthermore, an experimental analysis of a mechanical gimbal's accuracy and repeatability is performed. A wavelength diversity scheme in the presence of atmospheric turbulence is proposed to improve the alignment process. Finally, a wavelength diversity scheme is discussed which allows for transmission through radiation fog

Mapping Terrestrial Impact Craters with the TanDEM-X Digital Elevation Model

The TanDEM-X mission generates a global digital elevation model (DEM) with unprecedented properties. We use it for mapping confirmed terrestrial impact craters as listed in the Earth Impact Database. Both for simple and complex craters detailed investigations of the morphology of the particular structure and of the surrounding terrain can be performed