TY - JOUR

T1 - Residual Patterns in GRACE Follow-On Laser Ranging Interferometry Post-Fit Range Rate Residuals

AU - Duwe, Mathias

AU - Koch, Igor

AU - Flury, Jakob

N1 - Funding Information: The GRACE Follow-On monthly gravity field coefficients and the obtained residuals are calculated with our in–house gravity field recovery program GRACE-SIGMA (Koch et al. 2021). All data (excluding post-fit residuals and LRI gravity field coefficients) are available at NASA's PO.DAAC (https://podaac.jpl.nasa.gov), and GFZ's ISDC (https://isdc.gfz-potsdam.de/grace-fo-isdc/). The background model is GOCO06s (Kvas et al. 2021). Computations were made on a UNIX based machine. The position of the Sun is calculated with the Aerospace Toolbox in MATLAB including Ephemeris Data for Aerospace Toolbox. Parts of the figures and results have already been presented on GRACE Follow-On Science Team Meeting (GSTM) 2023. More information about GRACE and GRACE-FO can be obtained from https://gracefo.jpl.nasa.gov and at https://www.gfzpotsdam.de/en/grace-fo.

PY - 2024/3/19

Y1 - 2024/3/19

N2 - The novel laser ranging interferometer (LRI) on GRACE Follow-On (GRACE-FO) provides range and range rate measurements for more than 4 years now. Since the launch of the GRACE-FO mission there were few investigations about this measurement system on the level of gravity field recovery and analysis of post-fit residuals. We applied techniques such as along-orbit-analysis or time-argument of latitude diagrams (TAL) to analyse the post-fit range rate residuals as well as the post-fit range acceleration residuals to identify unknown characteristics and systematic effects. The effects are the range rate effect, the panel effect, the Carrier-To-Noise Ratio (CNR) effect and the polar effect. The range rate effect occurs, when the range rate observation ρ̇ of the LRI is around 0 m/s. In the TAL diagram the effect appears as a mesh pattern. The panel effect shows patterns of increased residuals when a specific satellite panel starts or stops being illuminated by the Sun. Increased residuals appear when the laser beam is aligned with the Sun. A CNR drop as well as a fluctuation of the yaw and pitch pointing angles obtained from the LRI steering mirrors is observable. Additionally, when the satellites flying into or out of the Earth shadow this effect coincides with the shadow transition effect. Another effect is the CNR effect which appears as an elliptic shape in the TAL diagram. This pattern occurs when the CNR values drop below the LRI requirements of 70 dB-Hz. All these effects have not been detected in the residuals of the GRACE-FO K-band ranging system (KBR) and therefore further investigation and studies will improve the understanding and applications of LRI technology.

AB - The novel laser ranging interferometer (LRI) on GRACE Follow-On (GRACE-FO) provides range and range rate measurements for more than 4 years now. Since the launch of the GRACE-FO mission there were few investigations about this measurement system on the level of gravity field recovery and analysis of post-fit residuals. We applied techniques such as along-orbit-analysis or time-argument of latitude diagrams (TAL) to analyse the post-fit range rate residuals as well as the post-fit range acceleration residuals to identify unknown characteristics and systematic effects. The effects are the range rate effect, the panel effect, the Carrier-To-Noise Ratio (CNR) effect and the polar effect. The range rate effect occurs, when the range rate observation ρ̇ of the LRI is around 0 m/s. In the TAL diagram the effect appears as a mesh pattern. The panel effect shows patterns of increased residuals when a specific satellite panel starts or stops being illuminated by the Sun. Increased residuals appear when the laser beam is aligned with the Sun. A CNR drop as well as a fluctuation of the yaw and pitch pointing angles obtained from the LRI steering mirrors is observable. Additionally, when the satellites flying into or out of the Earth shadow this effect coincides with the shadow transition effect. Another effect is the CNR effect which appears as an elliptic shape in the TAL diagram. This pattern occurs when the CNR values drop below the LRI requirements of 70 dB-Hz. All these effects have not been detected in the residuals of the GRACE-FO K-band ranging system (KBR) and therefore further investigation and studies will improve the understanding and applications of LRI technology.

KW - GRACE Follow-On

KW - Gravity field

KW - Laser ranging

KW - LRI

KW - Post-fit residuals

UR - http://www.scopus.com/inward/record.url?scp=85189169820&partnerID=8YFLogxK

U2 - 10.1016/j.asr.2024.03.035

DO - 10.1016/j.asr.2024.03.035

M3 - Article

AN - SCOPUS:85189169820

VL - 73

SP - 5769

EP - 5782

JO - Advances in space research

JF - Advances in space research

SN - 0273-1177

IS - 12

ER -