Forage-diving behaviour of adult Japanese female loggerhead turtles (Caretta caretta) inferred from Argos location data

Adult female loggerhead sea turtles (Caretta caretta) nesting in Japan use different feeding habitats as a function of body size. The Argos location data of two females inhabiting either oceanic or neritic habitats were analysed to infer their foraging and diving behaviour. There were no significant differences in the number of transmissions received per satellite pass, the number of locations per day, and the frequency of location-accuracy classes between oceanic and neritic females, implying that there was little difference in the time these two turtles stayed at the sea surface. Two possible forage-diving behaviours are suggested for these turtles: (1) both dive duration and depth were not different between the two feeding habitats; or (2) although dive duration was not different between feeding habitats, dive depth was different.

Modeling and Analysis of the Control System of a Satellite Tracking Antenna

In this paper a model is developed for the 60-foot satellite tracking antenna at Vandenberg Tracking Station (VTS). The model includes the control system, the motors, and the antenna structure. The antenna performance is simulated, using MATRIXX/SystemBuild, for two kinds of inputs: step functions and satellite passes. The predicted antenna performance is then compared to real antenna data, that was recorded at VTS, in order to demonstrate the accuracy of the model. Finally, the model is used to predict the antenna performance on a satellite pass for which no real data is available. The model shows that the antenna is capable of performing this pass with tracking errors less than the specified 2 milliradians (0.114°).

Photometric studies of the great red aurora March 13 and 14, 1989

Extended photometric coverage of the great red aurora of March 13–14, 1989 was obtained at the Rabbit Lake observatory located in northern Saskatchewan, at an eccentric dipole latitude of 65.3°. The red aurora first appeared there about 0311 UT on March 13 and appeared to have run its course by about 0700 UT on March 14. During much of the two nights the observatory was near the poleward edge of the display; the aurora was active much of the time and its brightenings were accompanied by poleward expansions to as far north as the observatory. Combining these observations with those at low latitudes suggest a large auroral expanse from an equatorward edge of about 30° to a poleward edge of about 65° magnetic latitude. One key value of the optical data was the semicontinuous monitoring of major auroral emission intensities. The 01D emission at 630 nm reached 130 kR intensity shortly after onset, at about 0347 UT on March 13. Its intensity the following night was typically 35 kR or below. A HILAT satellite pass around 0415 UT March 14 indicated an electron influx of average energies varying between 150 and 800 eV. The excitation efficiency for the 630 nm emission, neglecting any collisional deactivation, was approximately 1 kR per erg cm−2 s−1 (1 erg = 10−7 J) of precipitating electron energy. These measurements along with related worldwide observations will assist in gaining a better understanding of the magnetospheric conditions producing such major widespread auroras.

Auroral influence on ionospheric electron content

A number of earlier investigations have established that regions of enhanced electron concentration in the ionosphere are often associated, both temporally and spatially, with optical auroral features. Attempts to determine whether these enhancements are completely accounted for by the same particle precipitation that causes the aurora have been only partially successful, largely because it is difficult to collect data over a sufficient time with sufficient spatial resolution to permit accurate modelling. This paper attempts to take one more step along this road by using photometer records, taken over a period of three quarters of an hour before a satellite pass, in a model computation to predict the total electron content of the ionosphere as observed during the satellite pass. The procedure is successful when the auroral activity is strong enough to dominate, but is unsuccessful when the aurora is weak and other ionospheric processes dominate.

NOAA satellite and air-borne sensing of a small-scale, coastal tidal jet

Koombana Bay, on the south-west coast of Australia, contains a tidal jet that emanates from Leschenault Inlet via a man-made channel 150 m wide. The tides are of mixed diurnal-semidiurnal character. The strongest jets are induced by the diurnal tide and flow at night in summer and during daytime in winter. The duration of the discharge is about 9 h, after which the maximum length of the jet is a few kilometres. Extensive field studies together with numerical and analytical modelling have recently been completed on the jet. These allowed predictions of optimum times for viewing the jet via an air-borne thermal scanner aboard the CSIRO Fokker F27 aircraft, and a NOAA7 satellite image. The air-borne image mapped the late-summer jet, which consisted of night-cooled water from the shallow Inlet. Because the satellite pass occurs in late afternoon, the seasonality of the tide limits visibility of the jet in the imagery to late winter. The NOAA7 image shows a jet composed of warm water that has been heated during the day inside the Inlet. These observations confirm the sea data and model results and are believed to be the first use of NOAA imagery to resolve a coastal oceanographic feature of this scale.

Using a Hand-held Calculator for Ship's Position Comparison

The author's personal experiences under operational conditions have been with the CBM (Commodore Business Machines) S.R. 4148R, which has proved quite adequate for position comparisons in a surface warship fitted with a Magnavox satellite navigation system primarily used as a DR recorder. It is fed with ship's course and speed, corrections to the positions found being up-dated from satellite passes. Occasionally the criteria for up-dating from a satellite pass are not met and the system may run on DR for several hours without up-dates. Since the system is unable to compensate automatically for tidal or current drift and set or for leeway, the accuracy of the DR will deteriorate with age. The possibility of component malfunction, albeit temporary, may also contribute to DR error. In such conditions a series of astronomical observations is made; the calculator is capable of finding the average of such a series if required.