What are the differences between SMAP Near-Real-Time and Standard products?

When utilizing the SMAP Near-Real-Time (NRT) data products (SPL2SMP_NRT and SPL1BTB_NRT) it is important to understand how they differ from standard SMAP data products and their limitations. Below we outline the main differences in each NRT data product.


  • Water/land TB correction is performed with coarser sampling within the antenna beam pattern to speed up the integration process.
  • Antenna azimuth data, which directly impact geolocation, were sometimes extrapolated from the last known values when the more rigorous data were unavailable within the 3-hour latency NRT window.
  • Spacecraft’s roll, pitch, and yaw are all assumed to be zero, directly impacting geolocation.


  • Dynamic ancillary GMAO modeled surface/soil temperatures may be substituted with those acquired the previous day(s) when the concurrent temperature data were unavailable within the 3-hour latency NRT window. Normally, this would not cause many problems, but whenever and wherever precipitation occurred, this substitution could incur significant additional uncertainties to L2 soil moisture retrievals.
  • Surface flags are also skipped in NRT L2, meaning that soil moisture retrievals under less-than-optimal ambient surface conditions (thus higher uncertainties) could have been attempted and ended up showing up in the final NRT L2 product
  • Surface flags are not used in the NRT L2 processing, so retrievals may be attempted in the NRT product when they would not have been in the standard product.

More information on the NASA LANCE group and NRT data can be found here: https://forum.earthdata.nasa.gov/viewtopic.php?t=5201