operate the spacecraft in the planned pointing direction

14:17 Jun 25, 2019 

Thanks again for your explanation! I handed in my translation with a comment and will let you know once I get my client's feedback.

10:35 Jun 25, 2019 

the whole spacecraft keeps moving - its "position" in space is a moving point along its orbit.

If you mean by "its position" bringing the telescope to point in the desired direction, that must be using some energy, but we can not guess the technical details of how the energy collected by the solar panel is used. To which extant there is some fuel available and to which extent the energy from solar panel is used is impossible to know from the fragment of ST available.

We also can only guess if the whole spacecraft is monolithic or some part can move in relation to the rest of the spacecraft. The energy from the solar panel is for sure used to supply with power the electronics and instruments on board, but the rest is far from obvious.

But as far as what "operating" means, it's about keeping the telescope pointing in the desired direction, while slowly rotating it along its axis.

05:30 Jun 25, 2019 

Here's requirement for the Cheops spacecraft (found online) that maybe clarifies the question:
«A 3-axis stabilized spacecraft, keeping the telescope line of sight fixed in inertial reference frame with an APE (Absolute Performance Error) better than 8 arcsec for pointing accuracy (for 68% of the observation time), slowly rotating around the telescope line of sight for maintaining the focal plane radiator oriented towards cold space (i.e., at zenith of the subsatellite point), enabling a passive cooling of the CIS (Contact Image Sensor) detector to 233 K.»
My problem is to know if the energy from the solar panels is used to orientate the telescope to its pointing direction (which will probably change over time) or to operate the spacecraft once it's in its position.

15:42 Jun 24, 2019 

Thank you!

15:39 Jun 24, 2019 

Yes.

14:56 Jun 24, 2019 

Thank you! So this means that my second interpretation is correct (to operate the spacecraft after it is positioned in the planned pointing direction)?

14:52 Jun 24, 2019 

ie.

the spacecraft's pointing direction,

14:50 Jun 24, 2019 

It means that

the three solar panels are orientated in such a way to provide sufficient power to operate the spacecraft in the planned pointing direction