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Thanks.

The Nadir vector moved more “right to left” than “down to up” in that video, but the velocity vector is very clearly pointing just “downwards”.

Is this mostly because of the velocity of the camera bearing satellite w.r.t the imaged satellite and earth?

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The satellite taking the picture had to slew to be pointing at Landsat-8 for a couple of frames. It is the relative positions between the satellites that changes, the vectors themselves don’t move that much in a short period of time- the nadir and velocity vectors rotate 360 degrees in one revolution around the Earth (relative to an earth center inertial reference frame). The Maxar satellite and Landsat-8 are in different orbits. It appears from the video that the Maxar satellite passed under Landsat-8, as evidenced by the nadir vector pointing straight at the screen toward the end of the video, and because we got a broadside view of the white Earth shield for the thermal imager.

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