Abstract: AT ABOUT 7:45 PM ON APRIL 30, 1987, EMPLOYEE #1, AN ASTRONOMER, WAS USING THE MAYALL 4 METER TELESCOPE AT KITT PEAK NATIONAL OBSERVATORY. THE BUILDING HOUSING THE TELESCOPE IS 105 FEET IN DIAMETER AND 18 STORIES HIGH. THE FIVE UPPER STORIES COMPRISE A DOME THAT HOUSES THE TELESCOPE. THE TELESCOPE CAN ROTATE 360 DEGREES AND WEIGHS 500 TONS. A CATWALK CIRCLES THE INTERIOR OF THE BUILDING AND IS FIXED TO THE STATIONARY PORTION JUST BELOW THE ROTATING DOME. TWO ACCESS DOORS LEAD TO THE CATWALK. ONE IS ON THE WEST SIDE AND ONE IS ON THE SOUTH. A FIXED LADDER, PART OF THE LOWER DOME TRACK, AND A STOP REST ARE MOUNTED ON THE ROTATING DOME IN SUCH A MANNER THAT THEY EXTEND 1/3 OF THE WAY OVER THE DOOR OPENINGS. WHEN THESE FIXTURES ARE ROTATED BY OR STOPPED IN FRONT OF AN ACCESS DOOR, THE DOOR WILL OPEN NO MORE THAN 3 INCHES. BOTH DOORS HAVE AN ELECTRICAL INTERLOCK SWITCH THAT STOPS MOVEMENT IF OPENED. DUE TO THE WEIGHT OF THE DOME, IT TAKES FROM 5 TO 6 SECONDS AND TRAVELS A MINIMUM OF TEN FEET BEFORE STOPPING. MOVEMENT IS CONTROLLED BY THE TELESCOPE OPERATOR WHO ENTERS THE NECESSARY INFORMATION INTO A COMPUTER. THE COMPUTER MAKES THE NECESSARY ADJUSTMENTS AUTOMATICALLY. EMPLOYEE #1 & A GRADUATE STUDENT LEFT THE CONTROL ROOM FOR THE CATWALK TO CHECK THE WEATHER. WITH THE DOME TURNING, EMPLOYEE #1 OPENED THE WEST CATWALK DOOR AND ATTEMPTED TO STEP OUT. HIS HEAD, RIGHT ARM AND LEG HAD PARTIALLY PASSED THROUGH THE DOOR OPENING WHEN THE DOOR WAS STRUCK BY THE FIXED LADDER ON THE MOVING DOME. AS IT PASSED, THE DOOR WAS PUSHED SHUT TO WITHIN 3 INCHES OF THE SILL. AS THE DOOR CLOSED, EMPLOYEE #1'S HEAD WAS COMPLETELY CRUSHED BETWEEN THE DOOR AND THE DOOR EDGE. THE GRADUATE STUDENT AND THE OPERATOR ATTEMPTED RESCUE, BUT EMPLOYEE #1 WAS PRONOUNCED DEAD ON THE SCENE BY AIR RESCUE AT ABOUT 8:20 PM.