Optical bench of the laser ranging interferometer on grace follow-on

High reproducible Co2 laser spliced fiber-collimator for a space borne laser system

“…The monolithic fiber-collimator presented here provides excellent optical and thermal and mechanical performance. It is a part of the LRI and located on the Optical Bench Assembly (OBA) which has already been described in [1,3].…”

Laser ranging interferometer on Grace follow-on

“…Thus S/C 2 sends out a frequency shifted copy of the TX laser beam from S/C 1 back towards S/C 1. The heterodyne signal of the superposition of the LO beam on the master S/C and the received TX beam signal from the slave S/C yields two times the Doppler shift of the relative motion of the two S/C [6,7,8]. This heterodyne signal also contains the main science signal from which the distance variations will be derived to ultimately reconstruct the gravity field.…”

“…The key requirements of the FSM part of the OBE are to realize a small signal bandwidth of at least 1 kHz and an optical pointing noise of less than 2 µrad/√Hz. The key requirements of the QPR are to realize an equivalent input current noise of less than 5 pA/√Hz for frequencies up to 16 MHz and differential phase offsets between any 2 of the 4 AC channels of less than 100 mrad; see [6,7,8] for more details on the design of the OBS. …”

The absolute frequency reference unit for the methane-sensing lidar mission Merlin

“…As beam collimator, a fiber injector using an aspheric lens with the fiber directly spliced to the lens is employed. It follows the design of a fiber injector developed by SpaceTech used in the laser ranging interferometer (LRI) for the GRACE follow-on mission [4]. In order to keep the collimator as compact as possible, a high NA fiber is used which allows for a short focal length of the asphere.…”