BABY (BAckground BYpass)

The BABY experiment, short for BAckground BYpass, was a balloon-borne mission designed to measure the nighttime atmospheric UV background in the 300-400 nm wavelength range. The project was developed and executed primarily by the Istituto di Fisica Cosmica ed Applicazioni all'Informatica (IFCAI) in Palermo, Italy. The effort also involved collaboration with the University of New Mexico, Albuquerque, and the Electronics Engineering Department of the University of Palermo. BABY was part of a larger research initiative known as EUSO (Extreme Universe Space Observatory) devoted to the observation of the Extreme Energy Cosmic Rays from space, detecting the faint UV fluorescence light emitted by the atmosphere as a final result of the cosmic rays interacting with the Earth's atmosphere

The BABY instrument consisted of two collimated photomultipliers (PMTs) housed in a pressurized aluminum container as we can see in the scheme at left. These PMTs, manufactured by EMI, were designed to detect single photons using two different methodologies: single photon counting and charge integration. The container also housed electronic modules and high-voltage supplies and was hermetically sealed to maintain internal pressure. The PMTs were equipped with BG1 optical filters to isolate the 300-400 nm wavelength band and collimators that limited the field of view to approximately 3.1°. The signals from the PMTs were processed through custom-designed electronics that included a charge integration module and a fast discriminator. These modules allowed for the precise counting and integration of photon signals, enabling cross-verification of results.

Balloon launched on: 7/30/1998 at 00:55 local
Launch site: Base di Lancio Luigi Broglio, Trapani, Sicily, Italy  
Balloon launched by: Agenzia Spaziale Italiana (ASI)
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 7/31/1998 at ~ 6:00 local
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 5 h
Landing site: In the Mediterranean Sea, SW from Sicily, Italy

The balloon was launched on 30 July 1998 at 0.55 A.M. local time from the Italian base of Trapani-Milo in Sicily. The flight was carried out under moonless night condition as the moon was below the horizon. The BABY detector was positioned at the bottom of the stabilized platform with the collimators looking vertically down. The maximum altitude reached by the balloon was about 26 km: This implies a monitored earth surface of about 6:5 km2 shared by the two "eyes". The balloon ?ew, as shown in the map above, over the territory of West Sicily before gaining the open sea where, after a couple of hours, the payload was separated from the balloon and the flight ended.

The entire flight lasted about five hours, during which the instrument provided detailed measurements of the nightglow intensity, distinguishing between the ambient light over land, influenced by human activities, and the more stable conditions over the sea.

The results from the BABY experiment indicated nightglow brightness values of approximately 400-450 photons per square meter per steradian per nanosecond, consistent with earlier observations. The experiment successfully demonstrated the feasibility of using balloon-borne instruments to measure atmospheric UV backgrounds and validated the dual detection approach of photon counting and charge integration. These findings were instrumental in informing the design of future missions like AIRWATCH from SPACE, intended to detect cosmic ray-induced fluorescence from orbit.

• AIRWATCH from SPACE: preliminary results from lab. measurements and from balloon background observations  
• BaBy - The Background Bypass IASF Palermo website
• The atmospheric nightglow in the 300-400 nm wavelength. Results by the balloon-borne experiment BABY uclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 480(2-3), 547-554