Narrative:

There are always false targets on the asde (airport surface detection equipment). When the WX is good, it's not a bother because we can visually scan the runways. When the WX is bad, we consistently ignore the false target. There's no way to discern if it's a vehicle, aircraft, or a lost aircraft. We do not send aircraft on final around and one day, this could prove fatal. Callback conversation with reporter revealed the following information: reporter advised that false targets have been a noted problem since 1995 without resolution. The poorer the WX, the more the false alerts. Reporter stated that controllers 'generally ignore' all asde alarms. The controller is aware of a near midair collision last year between an issued go around and an IFR departure due to a false asde alert. Attempts at 'radar filtering' have not helped. The controller advised that primary targets are barely visible. Supplemental information: tower specialist advised that controllers are required to evaluate each alarm. Since there are many false alerts targets not at known/published intersection crossing points 'can be ignored.' what is causing the false multipath reflection alerts is not exactly known. Consideration are the closeness of the asde antenna to the terminal, the software program and/or antenna angle. Implementation of amass had been delayed due to its own software problems as well as being unable to filter out false asde alerts.

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Original NASA ASRS Text

Title: MSP CTLR CONCERNED WITH CONSTANT ASDE (ARPT SFC DETECTION EQUIP) FALSE TARGETS WHICH ARE CONSISTENTLY IGNORED.

Narrative: THERE ARE ALWAYS FALSE TARGETS ON THE ASDE (ARPT SURFACE DETECTION EQUIP). WHEN THE WX IS GOOD, IT'S NOT A BOTHER BECAUSE WE CAN VISUALLY SCAN THE RWYS. WHEN THE WX IS BAD, WE CONSISTENTLY IGNORE THE FALSE TARGET. THERE'S NO WAY TO DISCERN IF IT'S A VEHICLE, ACFT, OR A LOST ACFT. WE DO NOT SEND ACFT ON FINAL AROUND AND ONE DAY, THIS COULD PROVE FATAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT FALSE TARGETS HAVE BEEN A NOTED PROB SINCE 1995 WITHOUT RESOLUTION. THE POORER THE WX, THE MORE THE FALSE ALERTS. RPTR STATED THAT CTLRS 'GENERALLY IGNORE' ALL ASDE ALARMS. THE CTLR IS AWARE OF A NMAC LAST YEAR BETWEEN AN ISSUED GAR AND AN IFR DEP DUE TO A FALSE ASDE ALERT. ATTEMPTS AT 'RADAR FILTERING' HAVE NOT HELPED. THE CTLR ADVISED THAT PRIMARY TARGETS ARE BARELY VISIBLE. SUPPLEMENTAL INFO: TWR SPECIALIST ADVISED THAT CTLRS ARE REQUIRED TO EVALUATE EACH ALARM. SINCE THERE ARE MANY FALSE ALERTS TARGETS NOT AT KNOWN/PUBLISHED INTXN CROSSING POINTS 'CAN BE IGNORED.' WHAT IS CAUSING THE FALSE MULTIPATH REFLECTION ALERTS IS NOT EXACTLY KNOWN. CONSIDERATION ARE THE CLOSENESS OF THE ASDE ANTENNA TO THE TERMINAL, THE SOFTWARE PROGRAM AND/OR ANTENNA ANGLE. IMPLEMENTATION OF AMASS HAD BEEN DELAYED DUE TO ITS OWN SOFTWARE PROBS AS WELL AS BEING UNABLE TO FILTER OUT FALSE ASDE ALERTS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.