Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2
Troubleshooting; Confusion; Training / Qualification; Communication Breakdown; Distraction
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
ATC Equipment / Nav Facility / Buildings; Procedure
The Automated Radar Terminal System [ARTS] System went out and we were using primary targets for separation. Aircraft X came over from ZLC15 with multiple coordinations on descent and position due to the outage. Coordination was performed by the Tower for a departing [Aircraft Y] on course through the final approach course for the active runway.  Aircraft X was cleared for the visual and the VFR Aircraft Y was misidentified through position correlation between the Tower and Radar controllers.  The VFR Aircraft Y was never in communication with the Radar Controller. Instructions for collision avoidance were given to the wrong aircraft.  The problem is we are always doing this type of maintenance during normal business hours and we should be doing it overnight when traffic volumes are lowest and the margin of safety would be higher.  This was an unsafe situation and would not have taken place had we not given up the ARTS system.We should be giving different shift assignments to maintenance personnel when monthly/yearly PMs [Preventative Maintenance] are due.  Trying to accomplish these things during normal business hours introduces risk into the system unnecessarily.  No overtime would be needed if they were just assigned a 1600 to midnight shift once or twice a month to accomplish these PMs.
Controller describes operational error due to lack of Automated Radar Terminal System [ARTS]; which had been released to Maintenance for preventative maintenance.