Free linear drift in a new source removes over 99% of added period change information in 88 of 115 four-year quadratic transit designs with three times and 30-second errors

We tested three future transit times in 115 fixed quadratic transit designs. The old data contain 4,378 published times from a fixed 2022 catalog. Each new time has an independent 30-second standard error. The interval has calendar labels 2027 to 2031. Each old source has a free offset and zero drift. The new source has a free offset and linear drift. Its best three dates are the first, middle, and last permitted transits. We compare these dates with zero new drift. Free new drift removes more than 99% of the added period change information in 88 designs. The old information remains. The median formal error reduction falls from 85.74% to 12.95%. An independent Gaussian drift calibration can restore the gain from comparing old and new slopes. Its median standard error must be at most 4.86 seconds per Julian year to retain 90% of that gain. We give exact formulas, ideal span and visit bounds, and all system results. Full matrix projections, 60-digit arithmetic, simulations, and a clean reproduction check support the calculations. This is a formal design test with fixed independent errors. It does not establish real source drift or orbital decay. No new transit was measured. The package preserves raw tables, source history, code, the proof, selection records, figures, and reproduction instructions.

transit timing · orbital decay · linear drift · observation design · Fisher information · timing calibration · public astronomical data