A near-earth optical communications terminal with a corevolving planetary sun shield

The umbra of a planet may serve as a sun shield for a space based optical communications terminal or for a space based astronomical observatory. An orbit that keeps the terminal or observatory within the umbra is desirable. There is a corevolution point behind every planet. A small body stabilized at the planet corevolution point will revolve about the sun at the same angular velocity as the planet, always keeping the planet between itself and the sun. This corevolution point is within the umbra of Mars but beyond the end of the umbra for Mercury, Venus, and earth. The Mars corevolution point is an ideal location for an astronomical observatory. There Mars obstruct less than 0.00024 percent of the sky at any time, and it shades the observatory completely from the sun. At the earth corevolution point, between 51 and 84 percent of the solar disk area is blocked, as is up to 92 percent of the sunlight. This provides a reduction from 3 dB to 11 dB in sunlight that could interfere with optical communications if scattered directly into the detectors. The variations is caused by revolution of the earth about the earth-moon barycenter

Fraunhofer filters to reduce solar background for optical communications

A wavelength that lies within a spectral interval of reduced solar emission (a Fraunhofer line) can carry optical communications with reduced interference from direct or reflected background sunlight. Suitable Fraunhofer lines are located within the tuning range of good candidate lasers. The laser should be tunable dynamically to track Doppler shifts in the sunlight incident on any solar system body that may appear in the background as viewed by the receiver. A Fraunhofer filter used with a direct-detection receiver should be tuned to match the Doppler shifts of the source and background. The required tuning calculated here for various situations is also required if, instead, one uses a heterodyne receiver with limited post-detection bandwidth

Shutters and slats for the integral sunshade of an optical reception antenna

Optical reception antennas used at a small Sun-Earth-probe angle (small solar elongation E) require sunshading to prevent intolerable scattering of light from the surface of the primary mirror. An integral sunshade consisting of hexagonal tubes aligned with the segmentation of a large mirror was proposed for use down to E = 12 degrees. For smaller angles, asterisk-shaped vanes inserted into the length of the hexagonal tubes would allow operation down to about 6 degrees with a fixed obscuration of 3.6 percent. Two alternative methods are investigated to extend the usefulness of the integral sunshade to smaller angles by adding either variable-area shutters to block the tube corners that admit off-axis sunlight or by inserting slats (partial vanes) down the full length of some tubes. Slats are effective for most operations down to 6 degrees, and obscure only 1.2 percent. For E between 10.75 and 12 degrees, shutters cause even less obscuration

Chemical weed control in small grains

"Federal regulations on herbicide usage are frequently changed. So dealers and growers must stay informed on the status of label clearance. Read labels carefully and understand them before the herbicide is applied. Labels include application instructions as well as limitations and restrictions for a particular herbicide."--First page.L.E. Anderson, O. Hale Fletchall, and Harold Kerr (Department of Agronomy, College of Agriculture)Revised 2/83/8

Vine weeds in soybeans

"Vine weeds not only vigorously compete with crops, but they also plug up the combine and contribute to serious lodging. Once they are entangled in the soybean canopy, any attempt at cultivation strips foliage from the soybean plants. Severe infestations may cause 40 percent yield reduction. High moisture at harvest can also be a problem."--First page.Steve Livingston, L.E. Anderson, and Harold D. Kerr (Department of Agronomy, College of Agriculture)New 4/83/10

Herbicides for conservation tillage cropping systems

"Reliable weed control is necessary for successful reduced tillage cropping. In the future, energy sources for farm power may be in short supply and surely will become more costly in relation to the variable costs of other materials put into crop production."--First page.L.E. Anderson, O. Hale Fletchall and Harold D. Kerr (Department of Agronomy, College of Agriculture)Revised 9/83/12

Habitat and sex effects on behaviour in fawn-footed mosaic-tailed rats (Melomys cervinipes)

Habitat complexity reflects resource availability and predation pressure - both factors that influence behaviour. We investigated whether exploratory behaviour and activity varied in fawn-footed mosaic-tailed rats (Melomys cervinipes) from two habitats that were categorised differently based on vegetation. We conducted vegetation surveys to determine structural complexity and vegetation cover, confirming that an abandoned hoop-pine (Araucaria cunninghami) plantation forest was structurally less complex, with lower vegetation cover than a variable secondary rainforest. We then tested mosaic-tailed rats from both sites in four behavioural tests designed to assess exploratory and activity behaviours (open field, novel object, light-dark box, acoustic startle), predicting that rats from the less structurally complex habitat would be less exploratory, and show lower activity. Our results provide some evidence for a contextspecific trade-off between exploratory behaviour and predation risk in rats from the abandoned hoop pine plantation, as rats were less active, and showed a freezing strategy in the light-dark box. We also found context-specific sex differences in behaviour in response to a novel object and sound. Our results suggest that small-scale variation in habitat structure and complexity, as well as sex differences, is associated with variation in behaviour, most likely through effects on resource availability and/or predation risk

Chemical weed control in field corn for 1983, Part 2. Pre-emergence and postemergence

"Because the concentration of herbicides in commercial products may vary, herbicide rates are given on the basis of active ingredient (called acid equivalent for some herbicides) or per surface acre that will actually be treated."--First page.L.E. Anderson, O. Hale Fletchall, David Guethle, and Harold Kerr (Department of Agronomy, College of Agriculture)Revised 12/82/15

The economics of rabbit control in Central Otago: A preliminary analysis

With contributions by J.M. Williams, J. Bell and T.M. Broad, Agricultural Research Division, Ministry of Agriculture and Fisheries. Prepared under contract for Agricultural Research Division Ministry of Agriculture and Fisheries, WellingtonThis paper reports a preliminary examination of the economic efficiency and equity implications of recent rabbit control policies and programmes. The Alexandra Pest Destruction Board in Central Otago was used as a case study. Public and private expenditure data on rabbit control were collected and analysed for the period 1974-75 through 1981-82. Control programme benefits were estimated using data obtained in a survey of runholders and from historical production records. Programme costs were developed from actual expenditure data on control operations and administration based on Board records. While the estimated benefits are much less precise in comparison to programme costs, the results of the cost-benefit analysis suggest that significant cost savings can be achieved in meeting the stated objectives of current pest management policies. In particular, the level of annual expenditure in recent years on those lands which can be regarded as good natural habitat for the feral rabbit does not appear to be warranted, since such land types have an inherently low productive capacity and could not sustain the present level of control input on a 'user pays' basis. Although certain public benefits (e.g., land and water conservation) were not estimated, such benefits would have to be quite large to justify recent levels of annual taxpayer input into APDB control operations. The incidence of programme costs under present policy shows that most of the burden is borne by the tax-paying public. The report concludes with some suggestions to appraise these implications more accurately for regional and national public policy