30th Weather Squadron, Vandenberg AFB CA, supports spacelift and ballistic missile launches on Western Range by evaluating numerous weather launch commit criteria. Additionally, the Squadron provides upper air data to Range Safety and the Launch Agency flight engineers for risk mitigation and vehicle performance evaluation.
Weather launch commit criteria are in place largely to avoid natural and triggered lightning strikes to the launch vehicle, which may disable the flight termination system. Upper air data are used to model flight performance, catastrophic abort effects (such as toxic dispersion and debris impact location), and "nominal" (successful) launch hazards (such as solid rocket motor and stage impact locations). Other Launch Agency weather launch commit criteria serve to ensure vehicle performance and mission success.
Launch Go/No-go decision is made by the Launch Decision Authority, based on inputs and concurrence from the Mission Director, Mission Flight Control Officer (Safety), Launch Weather Officer, and others. The decision may be to hold launch until conditions are "green", or reschedule the launch attempt.
Data are available for 139 launches since February 1988. Analysis shows 22% of all launch attempts from Western Range resulted in a scrub due to weather (or weather-related) constraint violation. Of all weather scrubs, 25% were due to violation of natural and triggered lightning criteria, 30% due Safety constraints, and 45% due Launch Agency constraints. Between December 1997 and May 1998, weather impacted over 70% of the missions at Vandenberg AFB.
This paper is informative in nature, illustrating affects of the El Nino enhanced Winter/Spring of 1998, compared to historical data over the previous 10 years. Statistics will show frequency of launch scrubs, countdown holds, occurrences of "red" weather conditions, and the distribution by constraint category. Although El Nino 1998 played a significant role in the unfavorable weather at Vandenberg AFB, other factors, such as operations tempo, contributed to the high number of launch scrubs and holds.
The 8th Conference on Aviation, Range, and Aerospace Meteorology