Cosmic ray neutron scattering for estimation of soil moisture with the following requirements.

1. Neutron detectors - we require two detectors (bare and moderated) that measure fast neutrons resulting from scattered cosmic rays (passive or ambient).

2. Auxiliary sensors (barometric pressure, air temperature and relative humidity) - we require shielded sensors to measure atmospheric temperature (+/- 0.2 degree Celcius) and relative humidity (+/- 2%), and an integrated sensor to measure barometric pressure (+/- 1 hPa).

3. Sensitivity and resolution - we require high sensitivity such that soil moisture (volumetric water content in percent) can be inferred at precisions of 2% in under 4 hours of cosmic ray sensor integration. It is understood that shorter time periods can be measured with higher uncertainty. The approximate radius of influence for 85% of the signal must be 200 m or more, with depth sensitivities of 0.3 m or more under typical soil moisture and agronomic or rangeland conditions.

4. Remote data access - raw and processed sensor data and diagnosics (e.g., battery voltage) must be transmitted at time intervals as low as 30 minutes, then posted to an open web service within 4 hours. Factory installed, tested and configured satellite modem (Iridium or equivalent) with Short Burst Data (SBD) service must transmit messages up to 340 bytes and receive messages up to 270 bytes in size in real time. Satellite telemetry is required, rather than a cellular modem, due to data coverage issues at remote sites.

5. Power requirements - the system must operate continuously and transmit data at intervals of 30 minutes or more. Remote locations require a solar panel and battery (not included with the instrument purchase) of no more than a 50 Watt panel charging a 35 Amp-hour battery (purchased separately). Furthermore the provided instrument enclosure for the datalogger and satellite modem must allow space for the battery.

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