Progress should be "Fraction" 0-1 or "Percentage" 0-100.
Progress should be normalized to the full set of tiles, not just the tiles observed to date. i.e. 200 days into the survey we shouldn't be at "1" yet.
Add light gray progress line for what we would have achieved if we were perfectly on schedule to finish in 5 years (i.e. a straight line from (startdate,0) to (startdate+5years, 1).
on-schedule trend lines for the #tiles vs. time would be normalized to the total number of tiles in each program
Suggestions for survey progress plots: