Limiting Performance of Generalized Sign Test Detector

The limiting performance of the generalized sign test detector as the number M of target returns becomes infinite has been derived by Hansen and Olsen [1]. Simple expressions are derived herein for the limiting performance for finite M as K, the number of noise samples in the reference set, becomes infinite. Curves are presented which indicate how this limiting performance is approached as K is increased for both constant target returns and fluctuating target returns.     

Signatures of troposphere-stratosphere momentum coupling: Implications for global atmospheric angular momentum and earth rotation budgets

During January–August 1978, the global atmospheric angular momentum (M) exhibits distinct patterns of short term momentum interchange across latitudes. In the northern hemisphere winter-spring season, 30–50 day modulations of M are present in which momentum $\text{enhancements}$ at mid-latitudes (20–30°) are closely matched by momentum $\text{depressions}$ at high latitudes (50–60°). During the same interval there are no corresponding variations in M evident in the southern hemisphere. Conversely, during southern hemisphere fall-winter, similar anticorrelations in monthly scale momentum excursions are evident between mid and high latitudes. In the northern hemisphere, the winter-spring momentum signatures are detected throughout the atmosphere, from the lower troposphere to the stratosphere. During the southern hemisphere fall-winter, the modulation patterns are not evident at the higher altitudes. Structural details of the momentum signatures indicate that the coupling is sometimes effective on very short time scales, e.g. 1–2 days, or less. The evidence of distinct anti-correlation between large regions has interesting implications for studies of global atmospheric circulation, and also for studies of the excitation of variations in earth rotation in response to short term modulations of M.     

Dust environment models for comet P/Halley: Support for targeting of the GIOTTO S/C

In March 1985 ESA's GIOTTO spacecraft will fly by P/Halley's nucleus at a distance of a few hundred kilometres. The near nucleus dust environment the probe will traverse poses a hazard with respect to physical damage as well as to attitude disturbance with the possible loss of ground station contact. To predict S/C survivability and dust impact rates for the experiments, a model of the spatial distribution of the dust in the nucleus' vicinity is required. In the ‘dynamic’ model, the local spatial dust density is derived from exact expressions for the dust particle dynamic motion. The model has been implemented in a software system which allows for fast simulations of a cometary fly-by.     

Results on thermal conditions of crystal growth processes in space and on earth

A special measurement technique allows to determine the stationary and dynamic temperature profiles, acting on a material sample during a Bridgman crystal growth process. It turns out that the thermal field of the furnaces at the place of the sample is modified by a number of device-related factors and by regular correlations. The investigations refer to the execution of experiments in the field of materials sciences in space in furnaces on board Salyut-stations.     

Status of space science and technology — An Australian perspective

The “Tyranny of Distance” has had a profound influence on Australian history and reaction to it has been an important factor in determining national scientific and technological goals. Because of its size and geographical remoteness, Australia is one of the countries to have gained substantially from the applications of space technology particularly in the fields of communications, meteorology and remote sensing. Australia is the fifth largest investor in INTELSAT which carries a major fraction of the nation's overseas telecommunications. A domestic satellite system, AUSSAT, is being acquired to improve telecommunications within the country. Australia is heavily dependent on satellite data for routine meteorological forecasting. Data from the Australian Landsat Station are in strong demand, particularly for mineral exploration. In the field of space science, Australia is collaborating with Canada and the United States in feasibility studies for STARLAB, a free-flying UV-optical one metre telescope proposed for launch by the US Space Shuttle beginning in 1989. These scientific and technological programs in which Australia is participating are all dependent upon the space programs of other nations and in describing the status of space science and technology from an Australian perspective some comments will be made on particular aspects of the space programs of the United States and Japan.     

Experiences of the GDR in space sciences and technology

Following a historical review of the first activities of GDR scientists in the fields of space research, especially on astronomical and geodetical satellite-observations and in atmospheric and magnetospheric research, the growing scientific and increasingly efficient technological and economic benefits of the cooperation of the Academy of sciences and other scientific and technological institutions of the GDR within the Intercosmos-programme are described. Especially, the experiences in connection with remote sensing, of the cooperation with countries as Cuba and the Peoples Republic of Vietnam and of the common USSR - GDR manned spaceflight are discussed under the viewpoint of the mutual interests of developing and developed countries in the fields of space science and technology.     

Cometary habitats for primitive life.

Comet Halley studies indicate most of the nucleus is covered by an insulating crust, presumed of pyrolysed organic material. The subcrust is warmed and percolated by gases within 2AU, so provides one habitat for primitive replicating organisms. Cracks and crevices within contaminated ice in the craters provides a habitat for photosynthesising organisms. Subsurface lakes on the Europa model, though insulated by some metres of ice, would require a trigger (perhaps meteorite impact and energy source (chemical or metabolic energy) to initiate and maintain a suitable-habitat on short period comets. Constraints on transfer between comets and other planetary bodies implies that radiation-resistant species with lengthy hibernation potential would be expected.     

Prebiotic synthesis and reactions of nucleosides and nucleotides.

Diiminosuccinonitrile (DISN) has been investigated as a potential prebiotic phosphorylating agent. It is formed readily by the oxidation of diaminomaleonitrile (DAMN), a tetramer of HCN. DISN effects the cyclization of 3'-adenosine monophosphate to adenosine 2',3'-cyclic phosphace in up to 40% yield. The DISN-mediated phosphorylation of uridine to uridine mono-phosphate does not proceed efficiently in aqueous solution. The reaction of DISN and BrCN with uridine-5'-phosphate and uridine results in the formation of 2,2'-anhydronucleotides and 2,2'-anhydronucleosides respectively, and other reaction products resulting from an initial reaction at the 2'- and 3'-hydroxyl groups. The clay mineral catalysis of the cyclization of adenosine-3'-phosphate was investigated using homoionic montmorillonites.     

The Infrared Space Observatory (ISO)

The Infrared Space Observatory (ISO), a fully approved and funded project of ESA, will operate at wavelengths from 3–200 microns. The satellite essentially consists of a large cryostat containing about 2300 litres of superfluid helium to maintain the telescope (primary mirror diameter of 60 cm) and the scientific instruments at temperatures between 2K and 8K. A pointing accuracy of a few arc seconds is provided by a three-axis-stabilisation system. ISO's instrument complement consists of four instruments, namely: an imaging photo-polarimeter (3–200 microns), a camera (3–17 microns), a short wavelength spectrometer (3–45 microns) and a long wavelength spectrometer (45–180 microns). ISO's scheduled launch date is May 1993 and it will be operational for at least 18 months. In keeping with ISO's role as an observatory, two-thirds of its observing time will be made available to the general astronomical community via several Calls for Observing Proposals.     

Measurements of the earth radiation budget from satellites during the first garp global experiment

Two special measurements of the energy exchange between earth and space were made in connection with the FGGE. A global monitoring program using wide-field-of-view and scanner detectors from NASA's NIMBUS-7 satellite successfully returned measurements during the entire FGGE. This experiment system also used a black cavity detector to measure the total energy output of the sun to very high precision. A second set of high frequency time and space estimates of the radiation budget were determined from selected geostationary satellite data. Preliminary results from both radiation budget data sets and the solar “constant” measurements will be presented.