  Absorption by carbon monoxide in the spectrum of quasar SDSS
J000015.16+004833.2 is investigated in order to derive a constraint on the
temporal variation of the proton-to-electron mass ratio, mu. The spectrum was
recorded using VLT/UVES, and it was partially corrected for long-range
wavelength scale distortions using the supercalibration technique. Eight
vibrational CO singlet-singlet bands belonging to the A-X electronic absorption
system, and the perturbing d3-X(5, 0) singlet-triplet band are detected in the
damped Lyman-alpha system at z =2.52. The spectra are modelled using a
comprehensive fitting technique, resulting in a final value of Dmu/mu=(1.8 +/-
2.2 +/- 0.4)x10e(-5), which is consistent with no variation over a look-back
time of 11.2 Gyrs.
