Figure 2: Astrometric residuals of the astrometry until end of April 2015 against solution 102, described in Sec. 3.4. The left column is for the observations included in the fit, the central column for the observations replaced by our remeasuremen ts, and the right column for the observations filtered out by our selection process. The vertical dashed line corresp onds to the Mars encounter. 2013 2014 2015 −2 −1 0 1 2 RA cos(DEC) res. ["] Included 2013 2014 2015 −2 −1 0 1 2 DEC res. ["] Year 2013 2014 2015 −2 −1 0 1 2 Replaced 2013 2014 2015 −2 −1 0 1 2 Year 2013 2014 2015 −5 0 5 Excluded 2013 2014 2015 −5 0 5 Year 8