Near the turning of this millennium (1996–2004) it was detected that Prometheus and Pandora were not in their angular positions as predicted from their discoveries by the Voyager spacecrafts (1980). This is known as the problem of the lags of Prometheus and Pandora. The explanation for the origin of these lags is the chaotic motion associated with 121:118 mean motion resonance between the satellites. In the present work we revisit this problem and adopting the most extensive set of lags data, given by [R.G. French et al., Icarus 162, 143 (2003)], to show the need of unaccounted effects to produce the measured lags. By the analysis of conservation of angular momentum it can be verified that the mutual interaction between Prometheus and Pandora should be inversely proportional to the ratio of their masses. In this way, only the gravitational interaction between the two satellites does not explain such values. Consequently, the ratio between the lags of Prometheus and Pandora, Q, should be constant, and approximately the value of the inverse ratio between their masses (0.56, from [R.G. French et al., Icarus 162, 143 (2003)]). However, the values of Q from the measured lags are much higher, ranging from 48% up to 68% larger. Beyond that, the values increase over time in a rate given by the equation Q(t = 0.067 + 0.013t). Therefore, this analysis clearly shows the need of other mechanisms beyond the mutual interaction between Prometheus and Pandora in order to produce such values of lags. We estimate that at least one effect that produces an additional variation of mean motion of about 0.45°/year in one of the satellites for about 20 years would be necessary.

中文翻译：

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普罗米修斯和潘朵拉偏角位置上的不明分量

在这个千禧年（1996-2004年）临近之际，人们发现普罗米修斯和潘多拉卫星并不处在旅行者号探测器（1980年）发现的角度位置。这就是普罗米修斯和潘多拉的滞后问题。这些滞后的起源的解释是与卫星之间的平均运动共振121：118相关的混沌运动。在当前的工作中，我们将重新审视此问题，并采用[RG French等人，Icarus 162提供的最广泛的滞后数据集。（第143页，2003年）]，以显示出产生测得的滞后时需要不加说明的效果。通过角动量守恒的分析，可以证明普罗米修斯和潘多拉之间的相互作用应与它们的质量比成反比。这样，只有两个卫星之间的引力相互作用不能解释这样的值。因此，普罗米修斯和潘多拉，Q，的滞后之间的比率应当是恒定的，并且它们的质量之间的反比的大约值（0.56，从[RG法语等人，伊卡洛斯162，143（2003）]）。但是，测量到的滞后的Q值要高得多，范围从48％到68％更大。除此之外，这些值会随时间以方程Q（t= 0.067 + 0.013 t）。因此，该分析清楚地表明，除了产生普罗米修斯和潘多拉之间的相互作用之外，还需要其他机制来产生这种滞后值。我们估计，至少有一种效应会导致其中一颗卫星在大约20年内产生平均运动约0.45°/年的额外变化。