Jikiken(EXOS-B) observation of siple transmissions

A Japanese magnetospheric satellite Jikiken (EXOS-B) was used to observe Siple transmissions and VLF emissions triggered by the Siple signals. Energetic particle fluxes were also observed at the same time. The first experiments were made during July, August and September in 1979 and the second experiments were made during December in 1979 and January in 1980. The Siple triggered emissions were observed in August. This report reviews the preliminary results.     

Propagation of upstream protons in the near-earth solar wind

The propagation of energetic protons (35–1600 keV) from the Earth's magnetosphere to the ISEE-3 spacecraft located about 240 earth radii (R_E) upstream in the solar wind is used as a tool to study the interaction between these protons and the solar wind. In this preliminary study we present proton pitch angle distributions seen at different times during the development of upstream events that occur in relatively quiet interplanetary conditions. In general a highly anisotropic sunward flow is seen at the beginning of the events. During the course of the events pitch angle distributions may vary between streaming along the field lines (peaked around 0° pitch angle), a uniform intensity between 0° and 90°, and a peaked distribution around a preferred pitch angle that is often near 90°.     

Optical Calibration of Geostationary Satellite Tracking Systems

A precise calibration method for range and angle observation has been developed for eliminating the systematic error of tracking systems, thus improving the accuracy of orbit determination for geostationary satellites. The principle of calibration is based on an orbit determination employing a point of optical angle observation in addition to radio tracking observation, in which we estimate observation bias parameters simultaneously with orbital elements, including the effects of geodetic mismodelings. As shown by an actual calibration experiment in our ground station, orbit determinations is sufficiently accurate that the error of predicting satellite range falls within a few meters at four days after the day of orbit determination.     

Heterodyne spectroscopy of astronomical and laboratory sources at 8.5 μm using diode laser local oscillators

The first 8.5m infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N₂O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 × 10^–6 m) and the minimum detectable (black-body) power was 1 × 10^–16 W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.We wish to thank Dr Jack Butler and Craig Simpson (Arthur D. Little, Inc.) for their continuing (and successful) efforts to grow better diode lasers during the course of this experiment. We thank the National Radio Astronomy Observatory for the loan of a 40-channel filter bank and associated mini-computer.We thank en masse the dozens of people who loaned equipment to us for the duration of this experiment, and the commercial firms (especially Harshaw, Inc.) which expedited orders for crucial equipment. We thank Dr Bertram Donn, Dr Norman Ness, and Dr George Pieper for administrative, scientific, and financial support; and we thank Mr James Faris for technical assistance and Dr Sol Glicker for preparation of sample gas cells. We thank Dr Thomas Clark for providing the Kohoutek ephemeris, sighting printout, and predicted molecular line positions and for advice and the loan of some equipment. Finally, we wish to acknowledge the strong support accorded us by our wives and families who scarcely saw us during this period.     

Validation of aerosol measurements by the satellite sensors SAM II and SAGE

The satellite sensors SAM II and SAGE have been developing a global data base on stratospheric aerosols since they were launched in October 1978 and February 1979, respectively. The validity of this data base has been tested by numerous comparisons with other measurements made by lidars, balloon-borne particle counters, and aircraft-borne impactors and filters. Because the satellite sensors measure extinction and the correlative sensors measure other properties (e.g., backscatter, number, mass), special techniques are required to convert each measured property to other properties and to quantify conversion uncertainties and measurement uncertainties. Use of these techniques in two major comparative experiments shows that the SAM II and SAGE extinction measurements agree with each other and with values derived from dustsonde, lidar, and filter measurements. In addition, the comparative experiments have highlighted the uncertainties of each type of sensor and stimulated further efforts to reduce these uncertainties.     

Performance limits for processor networks with divisible jobs

Ultimate performance limits to the aggregate processing speed of networks of processors that are processing a divisible job are described. These take the form of either closed-form expressions or numerical procedures to calculate the equivalent processing speed of an infinite number of processors. These processors are interconnected in either a linear daisy chain with load origination from the network interior or a tree topology. The tree topology is particularly general as a natural way to perform load distribution in a professor network topology with cycles (e.g., hypercube, toroidal network) is to use an embedded spanning tree. Such limits on performance are important as they provide an ideal baseline against which to compare the performance of finite configurations of processors.     

14.5-14.8 GHz Frequency Sharing by Data Relay Satellite Uplinks and Broadcasting-Satellite Uplinks

Data relay satellites are being developed to provide real-time data links between research satellites in low earth orbits and central data acquisition and processing facilities. Frequency assignments for data relay satellite links will be made in bands allocated internationally to the space research service. One of the bands which will be used lies between 14.5 and 15.35 GHz, where the space research service has had a frequency allocation as a secondary service since 1971. During the General World Administrative Radio Conference of the International Telecommunication Union, held in Geneva in 1979, a primary frequency allocation was made in the band 14.5-14.8 GHz to the fixed-satellite service, specifically for use by earth-to-space links of the broadcasting satellite service. The feasibility of shared band operation is evaluated between data relay satellite uplinks and broadcasting-satellite feeder links in the band 14.5-14.8 GHz. Relationships for predicting interference power levels are formulated, as functions of satellite separation and of earth station separation. Tradeoffs between satellite separation angle and earth station separation are explored, and conclusions are drawn regarding the feasibility of band sharing. Co-channel operation is demonstrated to be technically feasible for typical systems, provided appropriate separations are maintained.     

Recent SETI observations at Arecibo

During 1980 and 1981, the 305-m radio telescope at the Arecibo Observatory in Puerto Rico was used to conduct a high resolution search for narrowband signals from the direction of 210 nearby solar type stars and 5 OH masers. For each star at least 4 MHz of bandwidth surrounding the 21-cm HI line and/or the 18-cm OH lines was studied with a spectral resolution of 5.5 Hz in both right and left circular polarization. The formal limit of sensitivity achieved during the course of this search varied depending upon the particular receivers available. In all cases the search could have detected a narrowband transmitter of power comparable to the Arecibo planetary radar, had any such been transmitting on the frequencies searched during the time of observation out to the distance of the farthest target star. As in previous searches, the number of "false alarms" encountered was far greater than predicted on the basis of Gaussian noise statistics. A small number of stars have exhibited signals which cannot immediately be explained in terms of astrophysical or man-made sources and deserve reobservation. This is typical of the results of previous non-real-time searches and does not yet constitute the detection of an ETI.     

Daily variations of the geomagnetic field

The atmospheric dynamo theory of the daily magnetic variations (S) has received substantial support from recent observational and theoretical work. In particular, several features of the variations, such as their remarkable enhancement close to the dip equator and other effects indicating a strong control by the main geomagnetic field, are well explained by the dynamo theory. Also the detection of ionospheric currents by instrumental rockets has confirmed an essential part of the theory.Considerable impetus was given to their study by the acquirement of much new data on magnetic variations during the IGY-IQSY period. Additional observations in the Pacific area were obtained during the IQSY by the establishment of four island stations equipped with newly developed magnetometers. A major advance at other stations was the development of automatic standard observatories using nuclear magnetometers.Several methods for the world-wide analysis of the S-field have been developed. A possibility now being studied is the completely automatic evaluation and construction by computers of ionospheric current charts for any day and any epoch UT.Some theoretical and statistical papers are briefly reviewed. These include discussions of the day-to-day variability of S, seasonal changes of the S-field, the nature of the equatorial electrojet, the possibility of solar wind effects contributing to the daily variations, and the modification of the dynamo theory to take account of the possible flow of electric current from the ionosphere along magnetic lines of force in the magnetosphere.Finally, an attempt to extend the dynamo theory of S by treating the ionosphere as a three-dimensional medium, instead of regarding it as a thin shell, has revealed that, although the relations between the horizontal components of electric field and current density in the dynamo layer are given with reasonable accuracy by the well-known layer equations, the assumption, implicit in the thin shell treatment, that the horizontal currents are non-divergent is not in fact true. Hence a revision of some earlier theoretical work on S appears necessary.