pyephem - 计算太阳/国际空间站与地球上的观察者之间的相位角

Question

为了帮助我计算国际空间站的视觉星等，我需要能够计算相位角。

谁能帮我算一下吗？

在任何时刻我都会生成 Obs对象和ISS对象使用 PyEphem 。对于观察者我有 Alt/Az到ISS和Alt/Az到太阳...当然我有 ISS.range距观察者的距离(以公里为单位)。所以在我看来，我应该能够用“简单”的几何形状来计算相位角。不幸的是，这个简单的几何图形有点超出了我自信地计算出的能力(我猜自从我上次这样做以来已经太久了)。

答案:我想通了(在古老的互联网的帮助下)这是部分代码片段(由 Leandro Guedes 将 ephem.earth_radius 更新为 Km)

 # SSA Triangle.  We have side a and b and angle C.  Need to solve to find side c 
 a = sun.earth_distance * au - ephem.earth_radius/1000 #distance sun from observer (Km)
 b = iss.range / 1000 # distance to ISS from observer (Km)
 angle_c = ephem.separation( (iss.az, iss.alt), ( sun.az, sun.alt) ) 
 c = math.sqrt( math.pow(a,2) + math.pow(b,2) - 2*a*b*math.cos( angle_c) )
 # now we find the "missing" angles (of which angle A is the one we need)
 angle_a = math.acos((math.pow(b,2) + math.pow( c,2) - math.pow(a,2)) / (2 * b * c)) 
 angle_b = math.pi - angle_a - angle_c #note: this is basically ZERO - not a big surprise really - and I don't need this anyway.
 phase_angle = angle_a # This is the angle we need.  BINGO!!

Answer 1

答案:我想通了(在古老的互联网的帮助下)这是部分代码片段(由 Leandro Guedes 将 ephem.earth_radius 更新为 Km)

 # SSA Triangle.  We have side a and b and angle C.  Need to solve to find side c 
 a = sun.earth_distance * au - ephem.earth_radius/1000 #distance sun from observer (Km)
 b = iss.range / 1000 # distance to ISS from observer (Km)
 angle_c = ephem.separation( (iss.az, iss.alt), ( sun.az, sun.alt) ) 
 c = math.sqrt( math.pow(a,2) + math.pow(b,2) - 2*a*b*math.cos( angle_c) )
 # now we find the "missing" angles (of which angle A is the one we need)
 angle_a = math.acos((math.pow(b,2) + math.pow( c,2) - math.pow(a,2)) / (2 * b * c)) 
 angle_b = math.pi - angle_a - angle_c #note: this is basically ZERO - not a big surprise really - and I don't need this anyway.
 phase_angle = angle_a # This is the angle we need.  BINGO!!

(正式将我的答案作为实际答案发布 - 是的 - 我花了一段时间才弄清楚这就是我应该一直做的事情)。