The influence of atmosphere density variations, caused by geomagnetic activity, on accuracy of the forecast of ISS motion

We investigate the influence of variations of the geomagnetic activity index on accuracy of the forecast of uncontroled motion of the International Space Station in a time interval not more than 15 hours. The investigation is carried out in the framework of the atmosphere density model of GOST 25645.115-84. The forecast is considered to be acceptable if the absolute value of an error in the predicted station position do not exceed 400 m. From possible sources of errors, we take into account only inaccuracy in assignment of the atmosphere density, caused by variations of geomagnetic activity. A forecast error is estimated by the method of statistical modeling using the real data about the index of geomagnetic activity for five years (1998–2002). It is shown that the error in a predicted station position at the end of an interval of forecasting essentially depends on a level of solar activity. In case of long intervals this dependence can appear critical. For a 15-hour interval the probability of the unsuccessful forecast makes some percent at low solar activity and surpasses 30% at high. On shorter intervals the probability of the unsuccessful forecast is reduced. On intervals with a length less than 7.5 hours this probability does not surpass 1%. On intervals less than 4.5 hours unsuccessful forecasts do not occure.