Speaker
Description
The GRACE-Continuity mission (a joint U.S.-German partnership) is expected to launch in 2028 and will continue the legacy of the GRACE missions by providing critical measurements of Earth mass change over time. The spacecraft use interferometry to sense the changes in satellite separation, which can be used to infer the local gravity field. This science data underpins knowledge of large-scale mass transport, and particularly global movement of water and ice.
GRACE-C will rely on a laser ranging instrument as the primary instrument used to sense the spacecraft separation. This necessitates the inclusion of a Scale Factor measurement to provide a correction for any changes in the laser frequency over the 5 year mission lifetime.
The Scale Factor Unit (SFU) uses a nested phase modulation scheme to track changes to the optical cavity free spectral range which can be related to the laser absolute frequency by the cavity mode number (nu = N x FSR). The mission demands laser frequency knowledge to 25 ppb at 1064nm, with performance of better than 5ppb demonstrated.
This talk will discuss the progress towards the development of a flight ready Scale Factor Unit, including long-term performance of the technique as well as a discussion of key errors and limitations including spurious etalons, residual amplitude modulation and calibration errors.
| I am the presenting author | Yes |
|---|