Iodine Frequency Reference on a Sounding Rocket

We build a self-contained optical absolute frequency reference at 1064 nm based on the rovibronic transition R(56)32-0 in molecular iodine and operate this instrument in space on a sounding rocket mission. The frequency reference uses a microintegrated extended cavity diode laser and a quasimonolithic spectroscopy module for modulation transfer spectroscopy, providing frequency instability of 2x10^-13 for averaging times of 100 s. To demonstrate the autonomous operation of our reference, we perform an absolute frequency measurement using a chip-scale atomic clock and an optical frequency comb during a 6-min-long space fight.