The purpose of this work is the analysis of the consequences that desaturation maneuvers can have in the precise orbit determination expected from the radio science experiments (MORE) of the BepiColombo mission to Mercury. This is an ESA/JAXA joint project with very challenging objectives regarding geodesy, geophysics and fundamental physics. Due to the intense radiation environment, the attitude of the Mercury Planetary Orbiter (MPO) has to be controlled by means of inertial wheels that absorb the solar radiation pressure torques acting on the spacecraft. In this way the overall angular momentum is conserved as long as the wheels reach their maximum rotation state. Then they have to be slowed down by a series of thruster pulses, which induces a residual acceleration on the probe and this is what we call a desaturation maneuver. Here, we will show how such maneuvers affect the orbit of the s/c and the radio science measurements and how we can include them in the orbit determination and parameter estimation procedure. The non linear least square differential correction fit we consider is applied on a set of observational arcs separated by intervals of time where the MPO is not visible. With the current baseline of two ground stations, two maneuvers are performed per day, one during the observing session, the other in the dark. To reach the scientific goals of the mission, they have to be treated as "solve for quantities". We have developed a specific methodology based on the deterministic propagation of the orbit, which is able to deal with these variables, by connecting subsequent observational arcs in a smooth way. The numerical simulations we will show demonstrate that, under given hypotheses, this constrained multi-arc strategy is able to determine the maneuvers together with the other parameters of interest at the level of accuracy required. The future development consists in including accelerometer readings and calibrations in the correction.
Desaturation maneuvers and precise orbit determination for the BepiColombo mission
MILANI COMPARETTI, ANDREA;TOMMEI, GIACOMO
2011-01-01
Abstract
The purpose of this work is the analysis of the consequences that desaturation maneuvers can have in the precise orbit determination expected from the radio science experiments (MORE) of the BepiColombo mission to Mercury. This is an ESA/JAXA joint project with very challenging objectives regarding geodesy, geophysics and fundamental physics. Due to the intense radiation environment, the attitude of the Mercury Planetary Orbiter (MPO) has to be controlled by means of inertial wheels that absorb the solar radiation pressure torques acting on the spacecraft. In this way the overall angular momentum is conserved as long as the wheels reach their maximum rotation state. Then they have to be slowed down by a series of thruster pulses, which induces a residual acceleration on the probe and this is what we call a desaturation maneuver. Here, we will show how such maneuvers affect the orbit of the s/c and the radio science measurements and how we can include them in the orbit determination and parameter estimation procedure. The non linear least square differential correction fit we consider is applied on a set of observational arcs separated by intervals of time where the MPO is not visible. With the current baseline of two ground stations, two maneuvers are performed per day, one during the observing session, the other in the dark. To reach the scientific goals of the mission, they have to be treated as "solve for quantities". We have developed a specific methodology based on the deterministic propagation of the orbit, which is able to deal with these variables, by connecting subsequent observational arcs in a smooth way. The numerical simulations we will show demonstrate that, under given hypotheses, this constrained multi-arc strategy is able to determine the maneuvers together with the other parameters of interest at the level of accuracy required. The future development consists in including accelerometer readings and calibrations in the correction.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
