G.5 Atmosphere model uncertainties and limitations

For mean activity conditions, the estimated uncertainty of the NRLMSISE-00 species density is 15%. For short term and local-scale variations, the estimated uncertainty of the NRLMSISE-00 species density is 100%_. Within the homosphere (below 90 km), the uncertainty is below 5% [RD.40]_.

For mean activity conditions, the estimated uncertainty of the JB-2006 total density within the thermosphere is 10-15% (depending on altitude).For extreme conditions (very high solar or geomagnetic activities), this uncertainty can considerably increase due to the lack of corresponding measurement data. The total density can have +/- 100% variation at 400-500 km for some activities and locations.

It should be noted that the NRLMSISE-00 model’s accuracy of prediction of atmospheric density and other parameters is limited by the complex behaviour of the atmosphere, and the causes of variability. While certain aspects of atmospheric variability are more or less deterministic, meteorological variations of the homosphere are difficult to predict more than 3 – 5 days in advance, and yet have effects on higher regions of the atmosphere (thermosphere). In the thermosphere, the response to varying solar and geomagnetic activity is complex, particularly in respect of the latter. Upper atmosphere density models can be used for prediction of future orbital lifetime, either to determine the orbital altitude insertions to ensure a given lifetime, or to estimate energy requirements for maintaining a particular orbit, for a particular spacecraft/satellite_. The primary influence on accuracy of the model’s density output is the accuracy of the future predictions of solar and geomagnetic activity used as inputs, rather than the accuracy of the specific model in representing the density as a function of solar and geomagnetic activity.