# 帮助了解泰坦，埃皮米修斯和土星环的令人不安的形象吗？

19

《纽约时报》的文章《土星的指环是由一群微型月亮雕刻而成》确实很有趣，并且链接到《科学杂志关闭卡西尼号飞越土星的环月卫星Pan，Daphnis，Atlas，Pandora和Epimetheus的最新付费专栏文章。

1. 土星环的后面，但是
2. 相对的环间距很大，但是
3. 当戒指和Epimetheus 对准焦点时，似乎没有对准焦点。

2

DarthFennec

1
@DarthFennec是的，此评论中的第二个链接显示此照片的FOV仅约为0.35度。
uhoh

2

Mazura

1

13

JPL 太阳系模拟器没有显示Epimetheus，但是在2006-04-28 08:12 UTC确实显示了Titan在Encke差距之后。

1

uhoh

30

uhoh

uhoh

1

Ingolifs

uhoh

2

Ingolifs

6

``````class Body(object):
def __init__(self, name):
self.name = name

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

fnames = ['Titan photo Cassini horizons_results.txt',
'Titan photo Titan horizons_results.txt',
'Titan photo Epimetheus horizons_results.txt' ]

names  = ['Cassini', 'Titan', 'Epimetheus']

bodies = []

for name, fname in zip(names, fnames):

with open(fname, 'r') as infile:

iSOE = [i for i, line in enumerate(lines) if "$$SOE" in line][0] iEOE = [i for i, line in enumerate(lines) if "$$EOE" in line][0]

print iSOE, iEOE, lines[iSOE], lines[iEOE]

lines = zip(*[line.split(',') for line in lines[iSOE+1:iEOE]])

JD  = np.array([float(x) for x in lines[0]])
pos = np.array([[float(x) for x in lines[i]] for i in 2, 3, 4])
vel = np.array([[float(x) for x in lines[i]] for i in 5, 6, 7])

body = Body(name)
bodies.append(body)
body.JD  = JD
body.pos = pos
body.vel = vel

Cassini, Titan, Epimetheus = bodies

r_Titan      = np.sqrt(((Cassini.pos - Titan.pos     )**2).sum(axis=0))
r_Epimetheus = np.sqrt(((Cassini.pos - Epimetheus.pos)**2).sum(axis=0))

hours = 24 * (JD - JD[0])

r_Titan_target      = 1.8E+06
r_Epimetheus_target = 6.67E+05

hours_Titan      = hours[np.argmax(r_Titan < r_Titan_target)]
hours_Epimetheus = hours[np.argmax(r_Epimetheus[30:] > r_Epimetheus_target)+30]

print hours_Titan, hours_Epimetheus
if True:
fig = plt.figure()

plt.subplot(2, 1, 1)
plt.plot(hours, r_Titan)
plt.plot(hours, 1.8E+06 * np.ones_like(r_Titan), '-k')
plt.ylabel('Cassini-Titan distance (km)', fontsize=16)

plt.subplot(2, 1, 2)
plt.plot(hours, r_Epimetheus)
plt.plot(hours, 6.67E+05 * np.ones_like(r_Epimetheus), '-k')
plt.ylabel('Cassini-Epimetheus distance (km)', fontsize=16)
plt.xlabel('2006-Apr-28 hours', fontsize=16)

plt.show()
``````

2

Mike G

@MikeG这是个好消息！您可以通过屏幕截图添加答案吗？
uhoh