Prepared by: MORE Team MORE Relativity Meeting February 16-17, 2009 Rome Simulation of the solar conjunction experiment with BepiColombo.

Prepared by:

MORE Team

MORE Relativity Meeting

February 16-17, 2009

Rome

Simulation of the solar conjunction experiment with BepiColombo

MORE Relativity Meeting, February 16-17 2009, Rome

Introduction

being r1 and r2, respectively, the Sun-S/C and Sun-Earth distances, and b the

impact parameter.

221

3

4ln)1(

b

rr

c

GMt SUN

A solar conjunction experiment in cruise is foreseen for April 2016.

In principle, the accuracy of the measurement of the post-Newtonian

parameter γ should be higher in cruise rather than in orbit, due to the absence of

gravity gradient

An electromagnetic wave passing near the Sun is affected by a relativistic

delay, expressed as:

MORE Relativity Meeting, February 16-17 2009, Rome

Goals of the simulation

Goals:

Simulating the solar conjunction experiment occurring in 2016; a best case will be presented (upper limit to the accuracy in the estimation of γ);

Comparing the results to what we can achieve doing the experiment in 2017; Determining the effect of uncalibrated non-gravitational acceleration noise on the

measurement.

S/C

SEP

Geometry:

b

Sun

Earth

MORE Relativity Meeting, February 16-17 2009, Rome

Relativistic delay variation

Sun–Earth–Probe angle variation

Relativistic delay variation

MORE Relativity Meeting, February 16-17 2009, Rome

Simulation setup

Dynamic model:

Model for solar pressure: flat plate of 55 m2 area, average thermo-optical coefficients, always pointing toward the Sun (in order to maintain a constant sun-aspect-angle)

Absence of orbital and attitude maneuvers

Observables:

Observables: range, one measurement every 20 sec (the range rate does not give a significant contribution), for 20 days

Two DSN stations, providing a coverage of 15 hours per day Observables under 8 solar radii have not been considered Gaussian noise added (we have supposed to cancel the plasma noise, by

using the multi-frequency link), with a standard deviation of 20 cm

MORE Relativity Meeting, February 16-17 2009, Rome

Estimation - 2016

Estimation:

Estimation of the state vector of BepiColombo and γ The starting value of γ has been set to that obtained with the Cassini

mission γ = 1 + (2.1 ± 2.3)x10-5

γ = 1 – (8.5 ± 8.7)x10-6

Above the goal of the experiment!

MORE Relativity Meeting, February 16-17 2009, Rome

Estimation - 2017

γ = 1 + (1.5 ± 2.6)x10-6

Compatible with the goal of the experiment

MORE Relativity Meeting, February 16-17 2009, Rome

Conclusions

In conclusion:

The geometry of the solar conjunction in 2016 seems not to meet the scientific objective of MORE. In particular, the accuracy is more than 3 times worse wrt what we would like to achieve;

On the contrary, the solar conjunction in 2017 could allow a very precise measurement.