The acid test: These earliest temperature profiles from COSMIC (2006) were taken from two spacecraft looking at the same occulting signal while the spacecraft were still very close together. The occultation tangent points are only 1.5 km apart. No calibration or bias adjustment has been made. As the true temperature difference between the two is negligible, this comparison provides a pure test of measurement precision. Above about 23 km we see the curves diverge slightly owing to declining precision in the thinning upper atmosphere. Below that altitude the curves are nearly indistinguishable. No other sensing technique, including weather balloons, comes within a factor of ten of this precision. A model profile from NOAA/NCEP (National Centers for Environmental Predictions) is shown for comparison. (COSMIC retrievals by UCAR, 2006)