Impacts of frequency-dependent instrument noise for next-generation gravimetric mission on determining temporal gravity field model

The Bender-type constellation has become a feasible option of the next-generation gravimetric mission (NGGM) for improving the quality of temporal gravity field solutions. In the context of Bender-type NGGM, the payload requirement is limited to approximately 20 nm/Hz^1/2 at the measurement bandwidth (MBW) of 0.01–1 Hz for laser ranging instrument (LRI), and 10^–11 m/s² at 0.001–0.1 Hz for accelerometer (ACC). Low-frequency noise is also, respectively, limited to 1/f and 1/f² for LRI and ACCs due to unavoidable electronic noise. However, due to the complex payload manufacture procedures and volatile space observation environment, in reality, LRI or ACCs noise may not be rigorously consistent with the designed noise models in frequency domain. Frequency-dependent noise in in situ observations always results in different MBW boundaries or different low-frequency features. In this study, the potential impacts of this unaccounted frequency-dependent instrument noise are analyzed via various detailed simulations, and the conclusions are summarized as follows. (1) In the instrument noise only scenarios, a similar behavior is shown between the frequency spectrum of instrument’s frequency-dependent noise in terms of amplitude spectral density and the corresponding gravity solution in terms of geoid height error. (2) The ACC MBWs seriously affect the quality of gravity solution, while the impacts of low-frequency features (e.g., 1/f^3/2 and 1/f² behavior of LRI noise, 1/f⁵ and 1/f⁶ behavior of ACC noise) are quite minor. (3) Frequency-dependent instrument noise plays less role when the background force model errors are included, and significant improvement is observed when the atmospheric- and oceanic-induced aliasing error is excluded, indicating the necessity of accurate background force models as well as proper de-aliasing strategy. (4) In the full noise contaminated scenarios, to achieve the scientific goal of Bender-type NGGM, it is feasible to shift the low MBW boundary from 0.001 to 0.004 Hz for ACC, and from 0.01 to 0.1 Hz for LRI. The results are helpful to specify the requirement of manufacturing key payloads for the Bender-type NGGM.