We have carried out a multi-site campaign to measure oscillations in the F5 star Procyon A .
We obtained high-precision velocity observations over more than three weeks with eleven telescopes , with almost continuous coverage for the central ten days .
This represents the most extensive campaign so far organized on any solar-type oscillator .
We describe in detail the methods we used for processing and combining the data .
These involved calculating weights for the velocity time series from the measurement uncertainties and adjusting them in order to minimize the noise level of the combined data .
The time series of velocities for Procyon shows the clear signature of oscillations , with a plateau of excess power that is centred at 0.9 mHz and is broader than has been seen for other stars .
The mean amplitude of the radial modes is 38.1 \pm 1.3 cm s ^ { -1 } ( 2.0 times solar ) , which is consistent with previous detections from the ground and by the WIRE spacecraft , and also with the upper limit set by the MOST spacecraft .
The variation of the amplitude during the observing campaign allows us to estimate the mode lifetime to be 1.5 _ { -0.8 } ^ { +1.9 } d. We also find a slow variation in the radial velocity of Procyon , with good agreement between different telescopes .
These variations are remarkably similar to those seen in the Sun , and we interpret them as being due to rotational modulation from active regions on the stellar surface .
The variations appear to have a period of about 10 days , which presumably equals the stellar rotation period or , perhaps , half of it .
The amount of power in these slow variations indicates that the fractional area of Procyon covered by active regions is slightly higher than for the Sun .