On algebraic compilers and planetary fly-by orbits

This paper reports on two major technology events of great significance in the field of Astronautics which were conceived and developed at the MIT Instrumentation Laboratory during the decade of the fifties. It is a personal memoir by the author on two important topics which should be a part of the written history of our field.Part one details the conception and development by Dr J. Halcombe Laning, Jr of “George”, the world's first algebraic compiler for use on Project Whirlwind—MIT's first experimental all-digital computer. This was indeed challenging since Whirlwind at that time had but 1024 sixteen-bit words. Dr Laning began work in the summer of 1952 and the first version of the George compiler was finished in March of 1953.In the early fifties many people were debating the feasibility of a system for translating algebraic formulae into computer programs which would allow the engineer to avoid the all too painstaking and error-prone task of writing programs using basic computer code. But Hal Laning was the first to do it.In part two of this paper, the author explores the early concepts of energy exchange between a spacecraft and a planet during a close encounter of these two celestial objects. The fact that this energy transfer could be exploited for useful purposes in the development of interplanetary orbits was first documented in an MIT Instrumentation Laboratory report published in April of 1958. The topic has been the subject of recent papers at several IAF congresses, but they failed to recognize the early work at MIT. As a part of this important history, the author describes his own work to develop a round-trip orbit to Mars using the planet Venus for a gravity assist to shorten the flight time from three years to one and a quarter years. The first orbit of this type was obtained by the author on 26 January 1961. To the author's knowledge, no one has even suggested that practical three-dimensional multiple fly-by orbits had been constructed at an earlier date.     

Plant responses to reduced air pressure: advanced techniques and results.

Knowledge on air pressure impacts on plant processes and growth is essential for understanding responses to altitude and for comprehending the way of action of aerial gasses in general, and is of potential importance for life support systems in space. Our research on reduced air pressure was extended by help of a new set-up comprising two constantly ventilated chambers (283 L each), allowing pressure gradients of +/-100 kPa. They provide favourable general growth conditions while maintaining all those factors constant or at desired levels which modify the action of air pressure, e.g., water vapour pressure deficit and air mass flow over the plants. Besides plant growth parameters, transpiration and CO2 gas exchange are determined continuously. Results are presented on young tomato plants grown hydroponically, which had been treated with various combinations of air pressure (400-700-1000 hPa), CO2 concentration and wind intensity for seven days. At the lowest pressure transpiration was enhanced considerably, and the plants became sturdier. On the other hand growth was retarded to a certain extent, attributable to secondary air pressure effects. Therefore, even greater limitations of plant productivity are expected after more extended periods of low pressure treatment.     

Hemispheric differences in the earth radiation budget derived from Nimbus-7 related to climate studies

Earth Radiation Budget (ERB) data from Nimbus-7 over the period November 1978 – June 1980 has consistently shown strong hemispheric differences when analyzed over different temporal and spatial scales. Hemispheric variations in time latitude cross sections of net and emitted radiation were found to be caused by changes in the Earth-Sun distance and continental effects.Maps of annual range for the entire Earth calculated from monthly averages showed areas of high and low variability of the different ERB parameters. The ERB of these regional areas were examined and most of the variability was found to lay in the large amplitude of the annual solar cycle. Variations in the global annual cycle of albedo /1/ are studied with respect to differences in latitudinal averaged albedo. The anomaly in the annual cycle of global averaged albedo was found to be caused by tropical albedo changes.     

Increasing Frequency Spectrum Utilization in Mobile Systems

In mobile radio communication systems, one of the most significant problems is to use the radio frequency spectrum as efficiently as possible, because the radio frequency spectrum is finite. This paper classifies a variety of techniques for increasing frequency spectrum utilization. Next, it is clarified that our proposed ``new channel assignment algorithm' is more efficient than other algorithms through simulation analysis.     

Phase gradient autofocus-a robust tool for high resolution SARphase correction

The phase gradient autofocus (PGA) technique for phase error correction of spotlight mode synthetic aperture radar (SAR) imagery is examined carefully in the context of four fundamental signal processing steps that constitute the algorithm. We demonstrate that excellent results over a wide variety of scene content, and phase error function structure are obtained if and only if all of these steps are included in the processing. Finally, we show that the computational demands of the fun PGA algorithm do not represent a large fraction of the total image formation problem, when mid to large size images are involved     

应用微机校定三相变压器的联结组及标号

三相变压的联结组标号对其正常运行极为重要，必须校定，而目前变还缺少全面快捷的校定方法和设备。本文介绍采用微机系统来实现联结组桔的校定，首先把四类联结组差别区分开，然后分析指出同一类联结组中，除有六种正序标号外，存在六种逆序标号，提出用新的筛选法能简捷地判别校定同一类的十二种标号，当微机系统进行实际测试时，必须考虑电源电压三相不对称程序的影响，故经数学推导得出用实测计算值代替理想计算值作判别比较的基     

Concept of solenoidally stabilized reflector dishes in space

The idea of stabilizing the shape of a reflector dish for a space-based radiotelescope by an extensive magnetic field is considered. We outline a construction where the axes of rotational symmetry of the dish lie on the axes of rotational symmetry of a large circular solenoid. Its magnetic field produces a stabilizing pressure by acting on a distribution of dipole moment on the dish. In cosmic regions where the gravity gradient is smaller than the solar radiation pressure, large receiver apertures and large area-to-mass ratios of the dish are attainable. The latter might lead to a higher shape accuracy of the reflecting surface compared to the truss frame stabilization. We calculate the distribution of dipole moment that gives a parabolic surface in the approximation of no dish elasticity and no magnetic dish-dish interaction. A disadvantage is the relative large mass of the solenoid. However, we find that it can be about three times smaller in diameter than the dish.     

Assessment of Space Station design and operation through Bioastronautics.

The paper reviews the main elements and major issues affecting human productivity and discusses some selected factors which might not be sufficiently identified and/or considered from the Bioastronautics point of view at the present stage of planning Space Station design and operation.     

Coronal interconnection of two active regions observed in 3.5–5.5 keV X-rays

Using HXIS data, we have studied further development of the coronal arch extending towards SE above the active region (AR) No.17255 in November 1980. The disappearance of that arch was followed by the appearance of another arch-like structure towards SW. We have studied the development of the new structure and classified it as an arch interconnecting AR 17255 with AR 17251, which was ～30° to the west. We estimate physical characteristics of this interconnection and compare them with Skylab data and the earlier arches.     

Implementation of a semianalytic satellite theory with recovery of short period terms

First order averaging is applied to the artificial satellite problem to obtain the averaged orbit which includes the secular, long and medium period effects of the oblateness of the Earth and the third body perturbations of the moon and sun. Perturbation theory is then used to recover the short period effects due to J₂, the moon, and sun. The perturbation analysis is carried out by means of Lie series and is developed through the first order. Optimization of the resulting short period series was then accomplished in several steps: first all separate algebraic coefficients were precalculated and stored; then all redundant SIN/COS calls were eliminated; next all repetition of numeric and algebraic coefficients were precalculated in pairs; application of the distributive principle allowed a significant reduction in additions and multiplications; finally trigonometric identities were used to further reduce the SIN/COS computations. The result of this optimization along with an interpolator for the averaged equations of motion results in a computer program which requires only $\text{1}\text{6}$ the CPU time (with no loss in accuracy) of the original non-optimized test program.