STREAMLINING SPACE LAUNCH RANGE SAFETY by National Research Council

Author:National Research Council
Language: eng
Format: epub
Tags: Space and Aeronautics: Space Systems and Hardware
Publisher: NATIONAL ACADEMY PRESS
Published: 2000-03-14T16:00:00+00:00

Accuracy Requirements

Tracking systems must be accurate, timely, and reliable enough to enable the ranges to calculate accurate IIPs. EWR 127-1 (Paragraph 2.5.4.1.1) establishes different IIP error standards for the WR and ER. The ER believes that the current limits are overly restrictive and has proposed relaxing them in the next version of EWR 127-1 (Campbell, 1999). For the ER, crossrange and downrange error in IIP must be no more than 100 feet (three sigma)1 until IIP clears the launch area (as currently authorized) or no more than 300 feet (per the proposed change). The proposed change also requires that error in vehicle position not exceed 140 feet in the vicinity of the launch area. At the WR, the allowable error is 1,000 feet. Once the vehicle clears the launch area, IIP crossrange error at the ER must not exceed 0.5 percent of the IIP range, and downrange error may not exceed 5 percent of the IIP range. At the WR, crossrange and downrange errors must not exceed 1 percent of the IIP range. The ER bases estimates of IIP error on static error sources, excluding time lags caused by data transfer and processing delays. The WR incorporates lag errors in its methodology. This may explain the large differences in accuracy requirements between the ranges.

1Sigma is a measure of statistical fluctuation. Three sigma means that the probability that the outcome will fall within expected limits (in this case, the probability of having an IIP error of 100 feet or less) should be at least 99.7 percent. The equivalent values for one and two sigma are 68 and 95 percent.

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