The MATS satellite mission studies atmospheric gravity waves, crucial for momentum transport between atmospheric layers. Launched in November 2022, MATS uses a limb-viewing telescope to capture high-resolution images of noctilucent clouds and airglow, visualising wave patterns in the high atmosphere. This paper accompanies the public release of the Level 1b dataset, i.e. calibrated limb images. Later products will provide global maps of gravity wave properties, airglow, and noctilucent clouds.