Aim and Objectives

The aim of SKIM is to measure directly and simultaneously the ocean Total Surface Current Velocity (TSCV - an Essential Climate Variable) and its component Stokes drift with the directional wave spectrum. SKIM will also provide a conventional nadir altimeter capability, enabling a unique and detailed exploration of the TSCV and Stokes drift relative to geostrophic currents – therefore going beyond geostrophy.

The following primary mission objectives have been established:

Over the global sea ice and precipitation-free ocean and inland seas from 82°S to 82°N:

  1. Measure and investigate the TSCV with a combined standard uncertainty in the across-track direction, UAC, and along-track direction, UAL, ≤0.15 m/s (goal: UAC and UAL ≤0.1 m/s) or 15% of the TSCV (whichever is greater) at a gridded resolution of 30 km with a mean revisit of ≤10 days at the equator a for at least 70% of the ocean surface (accounting for rain and gaps in coverage).
  2. Measure and investigate the TSCV with a combined standard uncertainty in the across-track direction, UAC, and along-track direction, UAL, ≤0.15 m/s (goal: UAC and UAL ≤0.1 m/s) or 15% of the TSCV (whichever is greater) at a gridded resolution of 30 km with a mean revisit of ≤10 days at the equator a for at least 70% of the ocean surface (accounting for rain and gaps in coverage).
  3. Measure and investigate Stokes Drift with a combined standard uncertainty ≤0.02 m/s (goal: ≤0.01 m/s) or 15% of the Stokes drift (whichever is greater) at a gridded resolution of 70 km with a mean revisit of ≤10 days at the equator a for at least 70% of the ocean surface (accounting for rain and gaps in coverage). The Stokes drift has larger spatial scales compared to TSCV as a result of atmospheric forcing.

SKIM is planned to fly in loose formation (same orbit about 1 minute away) with Metop SG B operational meteorological satellite, carrying a wind scatterometer (SCA) and a microwave imaging radiometer (MWI)