Sentinel-1-Level-1-Detailed-Algorithm-Definition.pdf "Section 5.1: Absolute DC Calculation (from Orbit & Attitude)" defines a series of steps to calculate the value u0 (a spacecraft-centric orientation in ECEF) based on having the ECEF position, ECEF velocity, and a set of quaternions. Implementation of equations 5-9 through 5-15 is easy, if not very straightforward. My problem is that when I plug in numbers provided in the Level-0 data (defined in Sentinel-1-SAR-Space-Packet-Protocol-Data-Unit.pdf, "Sub-commutation Ancillary Data Service" for ECEF position, ECEF velocity, and quaternions) I get a rubbish resulting u0 vector. u0 is supposed to be of a similar orientation to the velocity vector and the cross of u0 and the position vector should yield the start of the look/target vector.

Does anyone know what steps one should take with Level-0 data (additional rotation?) to get the appropriate results using this algorithm?