Results from these joint SAMSO/ACIC ICBM G&G investigations were used collectively to form the first Minuteman G&G Error Budget*. The error budget with its numerical values had a National Security Classification of Secret and, therefore, is not included here. However, the format of the Minuteman G&G Error Budget, presented in the enclosed Table, was (is) Unclassified. The CEP value in the Minuteman G&G Error Budget reflects at a given time the predicted Minuteman target impact error due solely to the uncertainties present in the in-use supporting G&G data. This error budget was the Standard Minuteman G&G Error Budget kept by SAMSO for the Air Force, with a copy maintained at ACIC. Two additional error sources, missile hardware (principally the inertial guidance system) and software also degrade Minuteman target impact accuracy. Somewhere within the Air Force, the missile CEPs resulting from these two error sources were combined with the G&G CEP to obtain the (total) CEP for the field deployed Minuteman Force. As a result of the security dictum, it is believed that no one within ACIC ever knew the predicted Total Error Budget CEP Value for Minuteman. Note: Irrespective of the Minuteman G&G Error Budget discussions in this paper, it is assumed that the Air Force maintains (has) a Minuteman Error Budget with a Total CEP Value reflective of the target impact scoring of actual test range flights. As time progressed, it became possible to develop a more accurate Minuteman ICBM. This was due to the technological advances made in many For example, improvements in: +Inertial guidance systems – They became smaller in size, lighter in weight, and more accurate. ____________________ *No G&G Error Budgets are believed to have been generated for earlier Air Force ICBMs: the Atlas D, E, and F; and Titan I and II. An excellent discussion of the development, deployment, and deactivation of these ICBMs is provided in [8]. The earlier Atlases (A, B, and C) were ICBM “proof of concept configurations” [8; p. 8], flight tested near the end of the 1950s. Therefore, as prototypes, these three systems were not part of any field deployment plans.
During the 1988 time period, AFGL made gravimeter measurements at intervals along a tall tower [13][14]. Unfortunately, it appears that the surface gravity data representing ground truth in this endeavor was woefully inadequate in both density and geographic coverage. This ground truth deficiency is believed to have led AFGL investigators to arrive at a conclusion that may be viewed as too-hasty. (This investigation should be reinitiated, but with adequate ground truth data available.) Perhaps a dirigible or an aerial hovercraft would also be a good platform for making at-altitude gravity observations. The genesis of one of the more interesting ACIC G&G studies in support of Minuteman was a telephone call from a Minuteman Wing Air Force Officer to the Center’s Geosciences Branch. A coal company was contemplating the surface excavation of coal not far distant from a Minuteman silo. Some mining site particulars were verbally conveyed. The basic question arising from this situation was: If this surface coal mining operation were to occur, would it modify the Earth’s gravity field near the silo enough to require any missile gravity-related corrective action? The verbal preliminary response by ACIC to this question was: - Any effect on the missile would be negligible since gravity is a weak force*. -A G&G study is needed to obtain numerical values and verify the preliminary conclusion. -A letter be needed from the caller to ACIC requesting the G&G study be made and providing salient excavation area data such as size, depth, silo distance, etc.. The appropriate letter was received by ACIC and the G&G study was performed. Results from the study showed that the change in the local gravity field due to the coal removal would be negligible, and thus have no discernible effect on the deployed Minuteman. These findings from the ACIC Study were forwarded to the Minuteman Wing. ____________________ *As an aside, recall from physics that there are four fundamental forces: electromagnetism, the strong nuclear force, the weak nuclear force, and gravitation. Particles of gravitation, gravitons, unlike particles of light, photons, have not yet been detected. However, astronomers have recently detected gravitational waves deep in the Universe.