  Upflows at the edges of active regions (ARs) are studied by spatially and
temporally combining multi-instrument observations obtained with EIS/Hinode,
AIA and HMI/SDO and IBIS/NSO, to derive their plasma parameters. This
information is used for benchmarking data-driven modelling of the upflows
(Galsgaard et al., 2015). The studied AR upflow displays blueshifted emission
of 5-20 km/s in Fe XII and Fe XIII and its average electron density is 1.8x10^9
cm^3 at 1 MK. The time variation of the density shows no significant change (in
a 3sigma error). The plasma density along a single loop drops by 50% over a
distance of 20000 km. We find a second velocity component in the blue wing of
the Fe XII and Fe XIII lines at 105 km/s. This component is persistent during
the whole observing period of 3.5 hours with variations of only 15 km/s. We
also study the evolution of the photospheric magnetic field and find that
magnetic flux diffusion is responsible for the formation of the upflow region.
High cadence Halpha observations of the chromosphere at the footpoints of the
upflow region show no significant jet-like (spicule/rapid blue excursion)
activity to account for several hours/days of plasma upflow. Using an image
enhancement technique, we show that the coronal structures seen in the AIA 193A
channel is comparable to the EIS Fe XII images, while images in the AIA 171A
channel reveals additional loops that are a result of contribution from cooler
emission to this channel. Our results suggest that at chromospheric heights
there are no signatures that support the possible contribution of spicules to
AR upflows. We suggest that magnetic flux diffusion is responsible for the
formation of the coronal upflows. The existence of two velocity components
possibly indicate the presence of two different flows which are produced by two
different physical mechanisms, e.g. magnetic reconnection and pressure-driven.
