Engineering Calculate angle between spacecraft & Sun vectors

AI Thread Summary
To calculate the angle between the spacecraft and Sun vectors, the dot product method is suggested, using the formula cos(θ) = RSC⋅RSun / |RSC|⋅|RSun|. The spacecraft's position vector (RSC) and the Sun's position vector (RSun) are essential for this calculation. To obtain RSun, the vector from the Earth's center to the Sun for the specific Julian date must be determined. Resources for finding the Sun's Earth-Centered Inertial (ECI) coordinates from the Julian date are recommended. This approach is considered valid for solving the problem.
Kovac
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Homework Statement
Compute angle between space craft & sun vector
Relevant Equations
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Hi, so I have no clue how to solve this problem but I started off by rewriting the issue as a dot product to find the angle. So;

cos(θ)= RSC⋅RSun / ∣RSC∣⋅∣RSun∣

Where Rsc = space crafts position vector.
Rsun is the Suns position vector.
∣RSC∣ is the length of the spacecrafts position vector.
∣RSun∣ is the length of the Suns position vector.

So in order to get the angle I planned to take arccosine.
But how do I get Rsun?

Is this a correct approach?
Am I doing something wrong or maybe theres a better approach to the problem?

sun_angle_task.png
 
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It looks to me that you'll have to find the vector between the Earth's center and the Sun for the Julian date given (JD = 2460157.5). Perhaps your book will have a procedure to find this?

By the way, what is the book you're studying?
 
Kovac said:
Hi, so I have no clue how to solve this problem but I started off by rewriting the issue as a dot product to find the angle. So;

cos(θ)= RSC⋅RSun / ∣RSC∣⋅∣RSun∣

Where Rsc = space crafts position vector.
Rsun is the Suns position vector.
∣RSC∣ is the length of the spacecrafts position vector.
∣RSun∣ is the length of the Suns position vector.

So in order to get the angle I planned to take arccosine.
But how do I get Rsun?

Is this a correct approach?
Hi. Not my area but I'd say it's a (the?) correct approach.

A search for "find sun's ECI coordinates from Julian date epoch" gives some potentially useful results.
 
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