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-28
Flight identification number: 1559P
Payload weight: 4517 lbs
The balloon was launched by dynamic method, around 7:30 local time on August 29, after which the balloon took two and a half hours to reach its float altitude of 38.5 km when it started to flight to the west.
After a flight of 5 hours and before the package moves out of telemetry range of the base, was decided to terminate it. The payload landed safely near Fort Stockton, Texas.
This flight was the second try after a failed flight on August 12.
This test flight -in preparation for a Antarctic long duration flight- proved the robustness of the pointing and data acquisition systems, the feasibility of the scan strategy, and the performance of the cryogenic systems at float altitude, as well as yielding important scientific data.
External references and bibliographical sources