Description of the payload

This telescope is the culmination of a great cooperative effort between Italian and American teams. It was designed to have the angular resolution and sensitivity necessary to measure the angular power spectrum of anisotropy in the cosmic microwave background at sub-degree scales, a region where there is a wealth of cosmological information.

The telescope consists of a 1.3m off-axis paraboloidal mirror feeding a pair of cold (1.5 K) ellipsoidal mirrors which reimage the prime focus onto an array of feed horns. These concentrate the incoming radiation onto bolometric detectors, cooled to 0.3 Kelvin by a helium refrigerator.

The pointing system consists of a pair of flywheels which torque the telescope against the flight train of the balloon. The rotation rate is adjusted via feedback from rate gyroscopes, a magnetometer, and tilt sensors. The telescope is fully pointable in azimuth, and can tip between 35 and 55 degrees in elevation. An on-board optical star-tracking camera allows accurate post-flight reconstruction of pointing.

Details of the balloon flight and scientific outcome

Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven 28X - 800.000 m3 - SF3-29.47-.8/.8/.8-NA
Balloon serial number: W29.47-2X-24
Flight identification number: 1555P
Payload weight: 4539 lbs

The balloon was launched on August 12 by dynamic method. Initially the ascent was smooth but balloon stopped ascending at 81.000 ft so decision was made to stop the flight early. Apparently ingested air after the launch thus float altitude was not reached.

The payload landed in a pond about 70 miles west of Palestine. Due to early termination at low altitude which reduced the shock of the parachute opening and a soft landing in mud, the payload was in remarkably good condition so the scientific experience was succesfully reflown on August 30 (flight 1559P)

This flight was intended as a test in preparation for a Antarctic long duration flight, but due to the balloon failure no scientific data was obtained.

External references and bibliographical sources