FLC OF B757-200 SIGHTS UNUSUAL OBJECTS IN CLOSE ENOUGH PROX TO CONCERN THEM FOR POSSIBLE COLLISION. OBJECTS SIGHTED ABOVE AND BELOW THE ACFT.

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NEAR MISS WITH UNIDENTED OBJECTS; SLC. OBSERVATION: WHILE ON L DOWNWIND FOR RWY 34L SLC; I OBSERVED SOMETHING WHIZ PAST US ON THE L. ESTIMATING ITS SIZE IS DIFFICULT AS I HAVE NOTHING IN MEMORY WITH WHICH TO COMPARE; BUT I ESTIMATE IT AT 4-6 FT HIGH. INITIALLY; I THOUGHT IT WAS A LIGHT ACFT; THEN I THOUGHT IT WAS A BIRD. I THEN OBSERVED SUNLIGHT GLINTING OFF THE LOWER PORTION OF THE OBJECT. AS I OBSERVED IT PASS; I REALIZED HOW CLOSE WE HAD COME TO IT. MY FO AND THE ACM ASKED WHAT I SAW. BEFORE I COULD REPLY; I OBSERVED ANOTHER SIMILAR OBJECT WHIZ BY ON OUR R. THE FIRST OBJECT WAS APPROX 10-20 FT BELOW OUR FLT PATH. I CALLED OUT AND POINTED. THIS TIME I COULD CLRLY SEE THAT IT WAS A METAL OBJECT SUSPENDED BY A CLUSTER OF 2 OR 3 BALLOONS. THEY WERE NEARLY THE SAME COLOR AS THE SETTING SUN -- A PINKISH FLESH COLOR. MY FO AND THE ACM CALLED THEM OUT ALSO; BUT WHEN I LOOKED; THEY WERE LOOKING SLIGHTLY BELOW OUR FLT PATH. THEY OBSERVED 2 ADDITIONAL BALLOON OBJECTS. WE ALL AGREED THEY WERE OBSERVING DIFFERENT OBJECTS THAN I. BTWN MY CREW; AND MYSELF WE OBSERVED 4 OBJECTS IN CLOSE PROX TO OUR ACFT. A DEFINITE HAZARD TO AIR NAV! POS: WE HAD JUST BEEN CLRED OUT OF 10000 FT (TO 8000 FT I BELIEVE) WHEN WE ENCOUNTERED THE OBJECTS. I ESTIMATE 9900 FT MSL. WE WERE ON AN ASSIGNED HDG OF 165 DEGS AND WERE ABOUT 1 1/2 MI S OF A POINT ABEAM THE TOUCHDOWN END OF RWY 34L. CONCLUSION: I ASSISTED A FSS (MANY YRS AGO) LAUNCH WX BALLOONS. I DO NOT BELIEVE THESE OBJECTS TO BE FSS WX BALLOONS. A HIGH SCHOOL SCIENCE PROJECT GONE AWRY; PERHAPS?