Off-Nadir Pointing Attitude Law

[misanthrope]

Hi there,

I am trying to model an off-nadir attitude law.

I have tried to use the LofOffset attitude, by trying to tweak it this way:

LofOffset(inertialFrame, LOFType.TNW, RotationOrder.XYZ, radians(33.0), radians(0.0), radians(0.0))

So, basically, I’m trying to rotate the +z (body axis, pointing towards the Earth) by 33°, about the T axis (i.e. directed along track, according to the description); using the TNW frame, by setting up the attitude as I described, it should fulfill my request. However, something doesn’t add up in the results.

Could you please tell me if I’m in the right direction and how I can properly address the problem?

Thank you in advance.

P.S./Rant
As an intense Orekit user, I would like to let you know how I appreciate your hard work and how helpful it is to our community. However, I would also like to express a feedback developed over months of usage of your tool: the documentation lacks of a clear physical meaning for a lot of parameters used in some classes/methods. It is really hard to try to make a sense of what one is doing sometimes, ending up in doing trial & error and developing parallel cross-validation tools to see if it is actually executing what the tool suggests; you should really try to focus more on giving an intuitive understanding of what a function/class/method is actually doing, instead of just writing a confusing and (often) misleading description (just to give you an example, under the CelestialBodyPointed - Constructor Detail, what do you mean by “phasingCel, phasingSat”? Phasing of what and with respect to what?). Please take it with no offense, it is just a personal feedback after months of intense usage of Orekit. If needed, I would be more than willing to contribute to build a more clear and meaningful documentation.

[bcazabonne]

Hi @misanthrope

I think you will find some interesting information on the following post:

Attempting to point off-nadir using LofOffsetPointing

Thanks Luc! I appreciate the clarification. Yes, I plan on exploring rugged after I have a bit more familiarity with the Orekit.

@misanthrope

As an intense Orekit user, I would like to let you know how I appreciate your hard work and how helpful it is to our community. However, I would also like to express a feedback developed over months of usage of your tool: the documentation lacks of a clear physical meaning for a lot of parameters used in some classes/methods. It is really hard to try to make a sense of what one is doing sometimes, ending up in doing trial & error and developing parallel cross-validation tools to see if it is actually executing what the tool suggests; you should really try to focus more on giving an intuitive understanding of what a function/class/method is actually doing, instead of just writing a confusing and (often) misleading description (just to give you an example, under the CelestialBodyPointed - Constructor Detail, what do you mean by “phasingCel, phasingSat”? Phasing of what and with respect to what?). Please take it with no offense, it is just a personal feedback after months of intense usage of Orekit. If needed, I would be more than willing to contribute to build a more clear and meaningful documentation.

I understand your remark and I know that we have to improve the documentation. We try to write an understandable documentation for each class and method of Orekit. Also, we try to make class diagrams and documentation on the Maven site as understandable as possible. But sometimes it is a hard work to go into details and contribution are always welcome