Global Problem
- Many biological and technical processes involve long-distance (cross-continental) dispersal/migration of small propagules.
- Smallest PTT (satellite) tags are ca. 9 grams, thus the smallest animal tracked globally is ~250 grams.
- Many ecologically and economically important species are smaller than 250 grams, such as bats, birds, and insects.
- Biologists need a system to track disease transmission (e.g. West Nile virus), and pests (locust plaugues), and identify migration routes and wintering areas (conservation).

Our solution
We propose a satellite that has
- global coverage,
- tracks as precise as 10km,
- locates animal ~ every day,
- has a lifetime of 10 years,
- can track 1000+ transmitters simultaneously,
- can distinguish between dead and live animals and
- is highly adaptable for multiple types of low-power transmitters.

Why a new animal-tracking satellite when such satellites already exist and have had considerable success?
Existing systems require relatively massive and bulky transmitters on the animal. A small passerine bird (average weight: ~25 grams) can carry a payload which is only a small fraction of its body mass, say 3%, without seriously inhibiting its behavior.

Currently, transmitter modules are available which weight one gram or less, including antenna and battery, which deliver peak pulse power of one milliwatt, and which can emit 20 millisecond pulses at one second itervals for durations of one month or more. Such a transmitter is inadequate for tracking by existing satellite systems.

Signal strength requirements for detection of a single, short pulse of a conventional radio transmitter from a low orbit satellite
Assumptions
Receiver system noise temperature 50 Kelvin
- Satellite height 400 Km.
- Earth is a black body at 300 K, which completely occults the antenna beam.
- Receiver bandwidth B=10 KHz. Limits noise power and data rate. Precludes pulse length < 0.1 millisecond.
- Earth (animal) antenna is isotropic, gain 0 dB; efficiency 10%.
- Satellite receiving antenna gain 15 dBi. At 150 MHz the effective are is 10 m².
- Required signal to noise power ratio at detector 10 dB.
- Boltzmann's constant k=1.38x10-23 Watt/K/Hz.

Required Ground Transmitter Power:
1 milliwatt