Does anyone know whether the orekit algorithm library can implement the function of the payload gazing to the ground? If the payload gaze function can be realized, what specific measures should be taken? I saw that there is an attitude library in the algorithm library, but it seems that this library is only designed for satellite platforms.
Hello everyone. Could you please give me some help!
I am not sure I understand your question.
Do you mean you want you payload to look at some specific point or region on ground as the satellite is flying roughly above it?
If this is the case, there are several different features you can use. You can use attitude providers to make you satellite exactly point to some target (look at AligneAndConstrained attitude mode for example). You can use field of views defined with respect to the satellite frame to compute when the target enters or leaves the field of view, i.e. when it is visible (look at FieldOfViewDetector for a point target and at FootprintOverlapDetector for an entire region target, taking care that this last event detector is very computer-intensive and not very accurate as it relies on sampling the region).
Hello. Thank you for replying to my question. English is not my native language, which makes it impossible for me to elaborate the problem accurately. I’m sorry for this. Next, I will describe my problem as clearly as possible. The background of the problem is to gaze at ground targets (including point targets and surface targets) in order to achieve the above function. Option one: We can choose the movement of the satellite payload to achieve the purpose of dynamically tracking and gazing at ground targets. Method Two: The installation position of the satellite payload and the Angle to the ground remain unchanged, while the satellite platform moves to achieve the purpose of dynamically tracking and gazing at ground targets. Since the movement of the satellite platform requires more energy and is not quite in line with practical applications, Method One is adopted. When using the orekit algorithm library, I couldn’t find the classes and keywords related to the payload attitude definition and controlling the changes of this part. Therefore, I would like to consult you whether this algorithm library can currently implement the functions for controlling the attitude changes of the payload. (For example, controlling the ground Angle of FOV to change over time). Hope to receive your reply.
Don’t worry about your English, many people on the forum are not native speakers (I am not, I am French), but we try to understand each other.
We don’t have a feature that would allow moving parts on satellite, so changing only the field of view orientation (i.e. the payload) without changing the attitude cannot be modeled directly in Orekit.
This is however not really a problem. Even if the real satellite would not change its attitude but only the payload would be re-oriented, you could model this with a fixed Field Of View and a target pointing attitude. I would really suggest to use AligneAndConstrained, with some specific point on ground from your area of interest (typically the center), it is the simplest attitude mode to use.
Then, as you propagate, you could try to extract the orientation angles between the LOF and this attitude, that would give you the orientation you would upload to move the paylod on board. I think there was a recent thread on the forum dealing with this angles computation.
Well. Thank you again for taking the time to reply to my question. I will consider your suggestion.