Milky Way open clusters are very diverse in terms of age , chemical composition , and kinematic properties .
Intermediate-age and old open clusters are less common , and it is even harder to find them inside the solar Galactocentric radius , due to the high mortality rate and strong extinction inside this region .
NGC 6802 is one of the inner disk open clusters ( IOCs ) observed by the Gaia -ESO survey ( GES ) .
This cluster is an important target for calibrating the abundances derived in the survey due to the kinematic and chemical homogeneity of the members in open clusters .
Using the measurements from Gaia -ESO internal data release 4 ( iDR4 ) , we identify 95 main-sequence dwarfs as cluster members from the GIRAFFE target list , and eight giants as cluster members from the UVES target list .
The dwarf cluster members have a median radial velocity of 13.6 \pm 1.9 km s ^ { -1 } , while the giant cluster members have a median radial velocity of 12.0 \pm 0.9 km s ^ { -1 } and a median [ Fe/H ] of 0.10 \pm 0.02 dex .
The color-magnitude diagram of these cluster members suggests an age of 0.9 \pm 0.1 Gyr , with ( m - M ) _ { 0 } = 11.4 and E ( B - V ) = 0.86 .
We perform the first detailed chemical abundance analysis of NGC 6802 , including 27 elemental species .
To gain a more general picture about IOCs , the measurements of NGC 6802 are compared with those of other IOCs previously studied by GES , that is , NGC 4815 , Trumpler 20 , NGC 6705 , and Berkeley 81 .
NGC 6802 shows similar C , N , Na , and Al abundances as other IOCs .
These elements are compared with nucleosynthetic models as a function of cluster turn-off mass .
The \alpha , iron-peak , and neutron-capture elements are also explored in a self-consistent way .