The brightening of Saturn's F ring
The brightening of Saturn's F ring
复制标题
DOI：
10.1016/j.icarus.2012.02.020
复制
发表时间：
2012-05-01
期刊：
影响因子：
3.2
通讯作者：
Nicholson, Philip D.
中科院分区：
文献类型：
--
作者：
French, Robert S.;Showalter, Mark R.;Nicholson, Philip D.
图像光度测定显示，在卡西尼号巡行期间，F环的亮度大约是旅行者号1980年和1981年飞掠时的两倍。它的宽度是原来的三倍，具有更高的综合光学深度。我们用卡西尼号的窄角相机对5年间拍摄的4800多张土星F环的照片进行了光度测量。我们表明，在许多观测几何形状中，环不是光学薄的，并应用基于阴影和遮挡存在的单散射的光度模型，推导出平均有效光学深度τ近似于0.033。来自旅行者PPS和卡西尼VIMS的恒星掩星数据验证了光学深度和宽度测量结果。与这种几十年尺度的变化相反，F环的基线性质从2004年到2009年没有显著变化。然而，我们已经研究了2006年末出现在环上的一个主要的明亮特征。这种瞬态特征使环的总体平均亮度增加了84%，半衰期为91天。(c) 2012 Elsevier Inc.版权所有。
Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4800 images of Saturn's F ring taken over a 5-year period with Cassini's Narrow Angle Camera. We show that the ring is not optically thin in many observing geometries and apply a photometric model based on single-scattering in the presence of shadowing and obscuration, deriving a mean effective optical depth tau approximate to 0.033. Stellar occultation data from Voyager PPS and Cassini VIMS validate both the optical depth and the width measurements. In contrast to this decades-scale change, the baseline properties of the F ring have not changed significantly from 2004 to 2009. However, we have investigated one major, bright feature that appeared in the ring in late 2006. This transient feature increased the ring's overall mean brightness by 84% and decayed with a half-life of 91 days. (c) 2012 Elsevier Inc. All rights reserved.