Most space launch vehicles require accurate, high resolution measurements of the vertical profile of horizontal winds in the launch area immediately prior to launch. The measured wind profiles are used to adjust the launch vehicle trajectory to maximize vehicle performance while ensuring the dynamic loads encountered by the vehicle remain within design margins.
Despite the long history of upper air measurements for space launch operations there is still no standard definition of the accuracy of these measurements or an accepted protocol for testing upper air measurement systems to quantify accuracy.
This is not an inconsequential problem since the launch vehicle operators include measurement error budgets in their trajectory optimization programs. Small errors in these budgets can impact launch availability. Also, the space launch range operators must sustain the measurement systems, and this requires understanding the accuracy requirements of the range customers. If these requirements are not precisely specified and tested, the ranges may implement measurement systems with either inadequate or excess capability.
We have developed a set of accuracy metrics for balloon-borne upper air measurement systems used for space launch operations at the United States Eastern Range.
The accuracy of each quantity is decomposed into both random and systematic components. Random components are derived from differences between simultaneous measurements of two identical systems in flight. Systematic components are derived by comparisons with reference systems. For wind velocity we use the radar tracked Jimsphere as the reference system. Overall accuracy is then taken to be the root sum square of the random and systematic error components.
This paper describes these metrics and test protocols along with representative results from existing operational systems.
The 8th Conference on Aviation, Range, and Aerospace Meteorology