Phoebe: Albedo Map and Photometric Properties
Phoebe: Albedo Map and Photometric Properties
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DOI：
10.1006/icar.1999.6077
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发表时间：
1999-04
期刊：
影响因子：
3.2
通讯作者：
D. Simonelli;J. Kay;D. Adinolfi;J. Veverka;P. Thomas;P. Helfenstein
中科院分区：
文献类型：
--
作者：
D. Simonelli;J. Kay;D. Adinolfi;J. Veverka;P. Thomas;P. Helfenstein
利用旅行者2号（有效波长0.48 μm）的清晰滤光片图像，我们构建了有史以来第一张土星卫星菲比的数字化地图。在这张新地图中，大多数正常反射率在0.07和0.11之间;卫星直方图基本上是双峰的，这表明卫星主要被两种不同类型的表面物质覆盖。最高的反射率仅限于直径40至100公里的孤立准圆形斑点，包括赤道以南的三个不同反射率的斑点，以及北纬60°的一个特别明亮的斑点（正常反射率高达0.13，比平均表面亮50%）。最亮的北方点和最亮的南方点大致在同一经度上，这一排列使得土卫九具有显著的自转光变曲线。旅行者号图像的低分辨率不允许解释亮点的起源。菲比的全球平均光度函数是通过结合卫星的望远镜近对置相位曲线（S。Kruseetal.1986，Icarus 68，168-175），其中绝对盘分辨反射率是从旅行者图像测量的（假设半径为115、110和105 km的三轴椭圆体形状）。建模的望远镜观测支持存在一个显着的反对派激增，虽然分散的数据不允许明确确定激增的确切强度。派生的光度功能是一致的想法，菲比是一个C-型对象可能是一个原始的，捕获的身体有关凯龙，Pholus，和居民的柯伊伯带。卡西尼号的星图和光度信息将有助于我们计划拍摄高分辨率的菲比图像，这将是我们第一次近距离观察这类原始的太阳系外天体。
Using clear-filter images from Voyager 2 (effective wavelength 0.48 μm), we have constructed the first-ever digital albedo map of Saturn's moon Phoebe. Most normal reflectances in this new map are between 0.07 and 0.11; the albedo histogram is largely bimodal, suggesting that the satellite is covered predominantly by two different types of surface materials. The highest albedos are confined to isolated, quasi-circular spots 40 to 100 km across, including three spots of varying albedo in a band immediately south of the equator and one especially bright spot at latitude 60°N (normal reflectance as high as 0.13, ≈50% brighter than the average surface). The bright northern spot and the brightest of the southern spots occur at approximately the same longitude, an alignment that gives Phoebe its significant rotational lightcurve. The low resolution of the Voyager images does not permit interpretation of the bright spots' origin. Phoebe's global-average photometric function was determined by combining the satellite's telescopic near-opposition phase curve (S. Kruseet al.1986,Icarus68, 168–175) with absolute disk-resolved reflectances measured from the Voyager images (triaxial-ellipsoid shape assumed with radii 115, 110, and 105 km). Modeling of the telescopic observations supports the presence of a significant opposition surge, although scatter in the data does not allow unambiguous determination of the surge's exact strength. The derived photometric function is consistent with the idea that Phoebe is a C-type object—probably a primitive, captured body related to Chiron, Pholus, and the inhabitants of the Kuiper Belt. The albedo map and photometric information will aid in the planning of high-resolution Cassini images of Phoebe, which will represent our first close look at this class of primitive outer Solar-System object.