DESCENDING ACR LGT NEARLY COLLIDED WITH A BALLOON AT FL266.

Narrative

WHILE WORKING LGT X TO SFO ON THE MOD 9 ARR; THE FLT CREW ADVISED THEY HAD PASSED WITHIN 4' OF WHAT APPEARED TO BE A WX BALLOON AT FL266. I ADVISED THAT I HAD NO NOTICES OR RPTS ON BALLOON ACTIVITY. I WAS UNABLE TO ADVISE THE PLT OF THE POSSIBILITY OF BALLOON TFC BECAUSE I HAD NOT RECEIVED ANY PRIOR NOTICE OF THE RELEASE. NORMALLY; THIS IS THE ONLY WAY WE HAVE OF KNOWING IT COULD BE THERE. THE RETURN FROM THE BALLOON IS USUALLY INADEQUATE FOR RADAR TRACKING OR IT IS MOVING TOO SLOWLY AND IS SCREENED OUT BY MTI. ADEQUATE NOTICE OF A RELEASE SHOULD BE DISSEMINATED TO THE SECTOR PRIOR TO LAUNCH TO FACILITATE ADVISORIES TO THE ACFT INVOLVED. ADDITIONALLY; PLTS SHOULD BE AWARE OF ATC LIMITATIONS IN PROVIDING TRACKING OF THESE BALLOONS AND THE FACT THEY ASCEND THROUGH THE PCA DURING THEIR FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE CTLR RPTR GAVE THE INFO CONCERNING THE CLOSE CALL WITH THE BALLOON TO HIS SUPVR. HE LATER FOUND OUT THAT THE CENTER HAD NOT HAD PRIOR INFO ABOUT THE BALLOON LAUNCH. RPTR ALSO STATED THAT WHEN A BALLOON IS LAUNCHED THAT WILL PENETRATE THE PCA; IT USUALLY HAS A BATTERY OPERATED TRANSPONDER ABOARD. SUCH WAS NOT THE CASE IN THIS INCIDENT. NOBODY KNOWS WHERE THE BALLOON WAS LAUNCHED OR WHY NOTIFICATION WAS NOT GIVEN.