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Humboldt-Universität zu Berlin - Faculty of Mathematics and Natural Sciences - Optical Metrology

Optical frequency standard based on molecular iodine for sounding rockets (JOKARUS)

K. Döringshoff, V. Schkolnik, F. B. Gutsch, M. Krutzik, and A. Peters


jokarus logo

Spaceborne laser-based frequency references have the potential to outperform state-of-the-art RF clock sources for space and may be used in future precision experiments such as satellite-based gravimetry (GRACE) or gravitational wave detection (eLISA).
As absolute frequency reference, iodine stabilized laser systems are further envisioned as 'clocks' in space missions aiming at tests of the gravitational redshift and tests of special relativity.

JOKARUS project

In the JOKARUS project (german acronym: Jod Kamm Resonator unter Schwerelosigkeit) we miniaturize a Doppler-free MTS frequency reference where a micro-integrated ECDL laser is stabilized to hyperfine transitions in molecular iodine at 532 nm. We optimize this optical absolute frequency reference for autonomous operation onboard a TEXUS sounding rocket starting May 2018. The frequency of the iodine reference will be compared to an optical frequency comb flying as a seperate payload bulid by Menlo System.

JOKARUS payload

The laser system for JOKARUS is based on a micro-integrated ECDL MOPA, provided by our joint lab at the Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik FBH. Fiber optical modulators at 1064 nm prepare the pump and probe beam for modulation transfer spectroscopy. The spectroscopy module is realized by the Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM) Bremen and the electronics are provided by Menlo Systems.


jokarus payload
JOKARUS payload: The height and diameter of JOKARUS are
less than 400 mm and 344 mm. The mass of JOKARUS is
estimated to less than 25 kg. Design: V. Schkolnik


jokarus payload
CAD drawing of the JOKARUS laser system and spectroscopy module.
Design: V. Schkolnik, M. Oswald (Spectroscopy module, ZARM).


Current status

The JOKARUS Payload was recently successfully tested with respect to vibrational load with about 8 grms. The frequency stability of the iodine reference is currently investigated and shows white frequency noise at a level of about 2 10-13 / √τ.


jokarus payload
Allan deviation of the JOKARUS instrument.



This work is supported by the German Space Agency DLR with funds provided by the Federal Ministry for Economic Affairs and Energy under grant numbers DLR  50 WM 1646