Implementing the VAHIRR Launch Commit Criteria using existing radar products

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Wednesday, 1 February 2006: 4:30 PM
Implementing the VAHIRR Launch Commit Criteria using existing radar products
A301 (Georgia World Congress Center)
Francis J. Merceret, NASA, Kennedy Space Center, FL; and M. McAleenan, T. M. McNamara, J. W. Weems, and W. P. Roeder

Presentation PDF (202.6 kB)

Lightning Launch Commit Criteria (LLCC) are rules designed to prevent launching vehicles into environments conducive to natural or triggered lightning. Even ranges located in areas where natural lightning is rare may be subject to cloud electric fields that can trigger lightning. To assure avoidance of a triggered lightning event like that which destroyed an Atlas Centuar (AC-67) at the Eastern Range in 1987, the LLCC are extremely conservative. Some of these rules have had such high safety margins that they prohibited flight under conditions that are now known to be safe 90% of the time.

The introduction of Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) has permitted improvements to the LLCC for anvil clouds that maintains their current level of safety but increases launch availability. The increased launch availability comes from VAHIRR-based LLCC that permit flight under conditions where it was previously forbidden. Unfortunately, VAHIRR is not a product currently generated by any of the operational range radar systems including the WSR-88D used at most American ranges and the WSR-74C used at the Eastern Range. Before VAHIRR can be used to its fullest advantage, software must be written and certified for these radar systems to generate the product. It will be several years until an operational VAHIRR product is available. There is, however, an immediately available work-around.

This paper compares the VAHIRR-based LLCC with the pre-VAHIRR version and specifically identifies those conditions under which relief from flight restrictions is provided. It also describes a procedure for interim implementation of the VAHIRR LLCC using currently available standard radar products. This interim procedure is slightly more restrictive than the full implementation with dedicated software will be, but it does allow a large part of the benefit of the new rules to be realized now. The only required radar products are a MAX product over a user-selected layer and some method of determining cloud thickness such as vertical cross sections or a combination of CAPPI and ECHO TOP products. The specific methodology used at the Eastern Range will be described in detail.