### Requirements for a Successful Write Operation

When writing a FrameSetFrameSet in which the WCS FrameFrame is a SkyFrameSkyFrame to a FitsChanFitsChan, success depends on the following conditions being met:

1. The MappingMapping from pixel coordinates (the base Frame in the FrameSet) to the WCS SkyFrame includes a WcsMapWcsMap.
2. The Mapping prior to the WcsMap (i.e. from pixel to IWC) is linear.
3. The Mapping after the WcsMap (i.e. from native spherical to celestial coordinates) is a spherical rotation for the celestial axes, and linear for any other axes.
4. The TabOKTabOK attribute is set to a non-zero positive value in the FitsChan, and the longitude and latitude axes are separable. In this case the Mapping will be described by a pair of 1-dimensional look-up tables, using the “-TAB” algorithm described in FITS-WCS paper III.

If none of the above conditions hold, the write operation will be unsuccessful.