[bertylicious]

The SIFT algorithm discards low contrast keypoints. In the beginning the surface looks quite blurry (it seems the camera is auto-focusing the heat shield) which probably causes only low quality keypoints to be found on the surface. Additionally, if the algorithm also capped the maximum number of keypoints per image, the situation gets even worse, because strong keypoints on the heat shield (which had to be discarded "manually" later) compete against weak keypoints on the surface.