Builder Journal · Mars Environmental Dynamics Analyzer (MEDA) Virtual Sensor Recovery
Every Kaggle competition page carries the same line of small print under the standings. This leaderboard is calculated with approximately 50% of the test data. The final results will be based on the other 50%. Everybody reads it. Everybody nods. Almost nobody asks which 50%.
I asked, and then I measured it, and it is not a random sample. It is the first 1,974,995 rows in spacecraft clock order, which is to say in time order, exactly half of the file, and the boundary falls inside sol 253.
That one fact rewrote six weeks of this project.
Where the competition stood
