32 TESS Sector 77 files cannot cover half of each of three 2-hour transits at a 9.5-day period

Can a total coverage fraction describe the chance of observing repeated planet transits in data with long gaps? We test 128 public TESS light curves. We select two targets from each camera detector in Sectors 76-79 before we calculate the windows. We use exact interval integration over a uniform orbital phase. In all 32 tested Sector 77 files, no phase can give three usable 2-hour transits at periods from 9.36 to 9.94 days. A usable event has at least half of its duration covered by accepted cadence cells. A two-block geometric bound proves this result between grid points. At 9.5 days, an independent-event model gives a median three-event probability of 21.07%. It has the same baseline and mean usable event count as the exact model. The exact two-event probability has a median of 78.55%. The exact median three-event probability rises to 6.54% at 11 days. The common zero interval remains in seven tests of duration, coverage threshold, quality flags, and flux availability. We release the source subsets, hashes, interval tool, phase windows, figures, and independent checks. This is a data-coverage result for the tested files. It is not a planet detection or a measurement of search-pipeline completeness.

TESS · transit window function · data gaps · exoplanet search · orbital phase · survey completeness · reproducible astronomy