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Soil Moisture Active Passive (SMAP) Satellite
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The Soil Moisture Active Passive (SMAP) satellite is a planned NASA satellite mission to monitor soil moisture around the globe. It is planned for launch in 2014.
As its name implies, the Soil Moisture Active Passive (SMAP) satellite uses active and passive radio systems to measure soil moisture around the globe. The spacecraft is in a sun-syncronous orbit that passes overhead of its target areas around 6 AM and 6 PM, approximately every 3 days at the equator and every 2 days at high latitudes.
SMAP's sensors can determine soil moisture down to a depth of approximately 5-10 cm. The active radar provides approximately 3 km resolution on the ground, using a 6 m antenna and measuring reflections in HH, VV, and HV polarization modes. The radar works in frequency hopping mode to avoid interference to and from aviation radars that operate in the same band. The instantaneous signal from the radar consists of two separate signals each of ~1.4 MHz bandwidth, separated by 5 MHz. It pulses every ~354 microseconds, for a duration of ~10-20 microseconds per pulse. The radar transmit power (not EIRP) is a few hundred watts.
SMAP will operate in a circular orbit of 670 km altitude. The ground footprint of the radar is approximately 1000 km. Resolution of the radar in low-resolution mode is approximately 40 km, and in high-resolution mode the resolution is approximately 3 km.
Soil moisture data can be used for improving numerical weather prediction, including seasonal climate prediction and rainfall prediction.
Like the European SMOS satellite, it is anticipated that SMAP's passive sensor will be subject to illegal RFI in the passive-only 1400-1427 MHz band.
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Frequency Bands |
| Band | Use | Service11 | Table |
| 1200 - 1300 MHz | SMAP active radar | Earth Exploration-satellite | F |
| 1400 - 1427 MHz | SMAP passive radiometer | Earth Exploration-satellite | F |
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