  The Sun Watcher with Active Pixel System detector and Image Processing (SWAP)
telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological
mission and has acquired images of the solar corona every one - two minutes for
more than two years. The most important technological developments included in
SWAP are a radiation-resistant CMOS-APS detector and a novel onboard
data-prioritization scheme. Although such detectors have been used previously
in space, they have never been used for long-term scientific observations on
orbit. Thus SWAP requires a careful calibration to guarantee the science return
of the instrument. Since launch we have regularly monitored the evolution of
SWAP detector response in-flight to characterize both its performance and
degradation over the course of the mission. These measurements are also used to
reduce detector noise in calibrated images (by subtracting dark-current). Since
accurate measurements of detector dark-current require large telescope
off-points, we have also monitored straylight levels in the instrument to
ensure that these calibration measurements are not contaminated by residual
signal from the Sun. Here we present the results of these tests, and examine
the variation of instrumental response and noise as a function of both time and
temperature throughout the mission.
