- 1Sapienza University of Rome, Aerospace engineering, Rome, Italy (fabrizio.demarchi@uniroma1.it)
- 2NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
- 3NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA
The VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) mission is a future NASA Discovery mission that aims to improve our understanding of Venus' evolution, structure, and geological processes. Its gravity science experiment will produce a uniform, high-resolution gravity map of Venus, providing unprecedented constraints on the planet’s crustal and interior structure. The radio tracking relies on a dual-frequency transponder in X and Ka bands. This advanced multi-frequency system achieves Doppler measurement accuracy of about 18 μm/s (for most of the mission duration) at 10-second integration time and can correct 75% of the plasma noise, particularly important at low Sun-Probe-Earth (SPE) angles (<15-20°).
Numerical simulations of the VERITAS gravity experiment were carried out using JPL’s MONTE software, considering detailed dynamical and noise models. The noise model accounts for 1) media propagation effects, i.e., troposphere, ionosphere, and plasma, where troposphere has a seasonal variation and plasma noise depends on SPE angle, and 2) spacecraft and ground station instrumentation. While many noise sources have a white noise spectral profile, significant contributors such as the frequency and timing system (FTS) and plasma introduce colored noise, i.e., whose magnitude varies with frequency.
A colored-noise results in a non-diagonal correlation matrix which can bias (with respect to a white-noise case) the best-fit estimated parameters and lead to an underestimation of their uncertainties.
Therefore, the main objective of this work is to evaluate the impact of colored noise on the estimation of the parameters related to the Venus’ gravity field (i.e., the spherical harmonic coefficients).
To this aim, we simulated the Doppler observables and the gravity recovery for both the white-noise and colored-noise cases. Colored noise was simulated with the algorithm described by [1] and we developed a method to incorporate these correlations into the sequential filtering process used for orbit determination. We will present the results of these simulations.
[1] Timmer, J. and Koenig, M. (1995). On generating power law noise. Astronomy and Astrophysics, 300:707.
How to cite: De Marchi, F., Giuliani, F., Durante, D., Cascioli, G., Iess, L., Mazarico, E., and Smrekar, S.: VERITAS Gravity Science Experiment: Impact of Colored Noise on Parameter Estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12405, https://doi.org/10.5194/egusphere-egu25-12405, 2025.
