Calculate angle between spacecraft & Sun vectors

[Kovac]

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?

 

[gneill]

Welcome to Physics Forums!

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?

 

[Steve4Physics]

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.