High Altitude Balloon

     The launch of the NASA high altitude OMS (Observations of the Middle
Stratosphere) balloon payload from Fairbanks, Alaska on 30 June 1997.  The helium bubble of this balloon will expand to a size of 4.3 million cubic feet (200 ft diameter) at its peak altitude of about 100,000 feet (30 km).  The weight of this payload (instrument and gondola) is approximately 1200 lbs.  The balloon, made of 0.8 mil plastic (about the thickness of a sandwich bag), adds an additional 1000 lbs weight.
    This photograph captures the helium bubble moments after it has been released from its moorings, as it ascends over a crane from which the instrument payload is suspended.  These are very tense moments during a launch of a high altitude balloon payload.  The bubble must rise in the proper direction so that it floats right above the crane.  Once the bubble is above the crane, the instrument payload is released, and its ascent to the stratosphere begins.  The layout direction of the balloon relative to the crane is critical to the success of the operation.  The proper direction is determined by real-time analysis of local weather conditions provided by meteorologists of the National Scientific Balloon Facility, which manages high-altitude balloon launches for NASA.  Click here for pictures of this launch that show the release of the payload.      
    After the scientific data has been collected, the flight is terminated by the detonation of a small charge that initiates separation of the parachute (and payload) from the balloon.  A ripcord on the balloon causes it to tear, releasing the helium.  The command to terminate is issued by the pilot of a chase airplane, who has assured the payload will descend over a safe landing area.  Once the package descends to the lower atmosphere, air pressure is sufficient for the parachute (red unit approximately mid-way between the payload and the helium bubble) to open.  The instruments are retrieved for subsequent flights (the balloon is also retrieved and is disposed).  Click here for a remarkable set of pictures documenting termination, descent, and landing from another balloon flight also from Fairbanks, Alaska during the summer of 1997.
    Engineers at JPL design and maintain the electrical and mechanical infrastructure of the balloon gondola.  Scientists at JPL have built and operate numerous balloon-borne instruments including ALIAS II, MkIV, UV-ozone, SLS, and FILOS.  The balloon-borne instruments measure composition at heights that can not be reached by aircraft.  These observations have been used to study, on fine spatial scales, the detailed chemical and dynamical processes that affect ozone, during field campaigns such as STRAT (New Mexico and Brazil), POLARIS (Alaska), and SOLVE (Sweden), and serve as an important link to global observations from satellite instruments.


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Author: Ross J. Salawitch
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