From a question recently asked on MichaelWhelan.com:

In 1994, Michael Whelan produced a series of three digital prints through Mithril Publishing called PASSAGE TO SANCTUARY. The artwork was created entirely on the computer. After printing, the all digital source files were destroyed.

The run was limited to 555 of each print, but Mithril went out of business before the prints were fully distributed. These prints occasionally reach the secondary art market, but they are even scarcer than the advertised print run would indicate as many were never distributed.

Interestingly, Michael later produced an alternate version of LANDING, but as a traditional painting (acrylic on panel).