Coincidence, or clever Korean timing?

Coincidence, or clever timing by the North Koreans? When North Korea conducted its alledged atomic bomb test last Monday at 01:36 UTC, it almost seems as if they waited untill the test area was just outside the footprint of the Japanese IGS 1B, detonating it within minutes of it passing by.

IGS 1B (03-009B, #27699) is a Japanese high resolution radar reconnaissance satellite, one of the primary purposes of which is to keep an eye on North Korea.