Satellite technology for tracking birds and sea mammals
Burgeoning world communication networks indicate a period of intense investment in space technology, this makes it a good point in time to pose the question: Is there a satellite location system capable of remotely recording the track of an electronics package made small enough for a bird to carry? Clearly a solution for birds will considerably advance the possibility of tracking other wildlife and indeed almost any artefact. The laws of nature give a finite working lifetime to all earth satellites. This and the steady advance of technology means that satellite systems are deployed and fade from use over a single decade. While replacements for those that malfunction or become exhausted can be launched, improved concepts consistently make periodic system replacement more worthwhile. Among the currently available satellite systems capable of positioning, the Argos data collection and location system is the most suitable for wildlife tracking. A short explanation of Doppler positioning is given and examples of data from remote sensing satellites show some of the background data available. I have briefly cited early studies on Elk, Polar bears, Dolphins, Turtles, Basking shark and Humpback whales. Design work for the bird location package begins in section 3. An experimental harness is tested together with a lightweight pure nickel case for the electronic assembly. Environment effects are considered and wind tunnel tests are made to determine drag and heat loss. Sub-sections 3-1 to 3- 8 complete the work as follows:- High stability oscillator. A circuit with acceptable performance and minimal power input is evolved by investigation of each component. RF power circuits and phase modulator designed for minimal part count are described. Digital encoder, required to generate the PTT identity code etc is described, it uses microminiature components and a CMOS field programmable ROM. A developed version for sensor data input is also described. Antenna, this is designed using a model bird filled with a fluid having similar permittivity and conductivity to living tissue. Impedance and field patterns are measured using a signal source, vector voltmeter, reflectometer, spectrum analyser and specialised test equipment. Power is derived from lithium cells as a result of pulse testing to identify the best type; solar arrays are also investigated. Possible behavioural aberrations due to RF emissions are considered as the RF pulse power is 30 dBs (1000 times) higher than conventional equipment at VHF. It is shown that avian heart-rate is not affected by the RF pulse. Results and conclusions Solutions to engineering problems encountered in applying the design to birds, seals and whales are shown to be successful by the results of field trials. Appendices outline supporting work.