Bad news about SBI (12/29/2006)

Williams Field (Antarctica) The latest instrument remaining to be launched aboard an stratospheric balloon as part of the 2006/2007 Antarctic Summer campaign, had a shortest than anticipated flight time.

After being declared "flight ready" on the first days of December and waited his turn to flight, the SBI (Solar Bolometric Imager) instrument was launched on December 24 at 3:55 UTC time from the base located in Williams Field, near the McMurdo northamerican base.

According to the report of the scientific team "...the launch went flawlessly and after a perfect release SBI started to quickly gain altitude. Approximately 3 hours into the flight, when the payload was at 24000 meters (about 79000 feet) altitude we had a major malfunction of the control computer which for reasons still to be determined shut down abruptly. The control computer is responsible to command the telescope pointing system. Without that computer it was impossible to take images of the Sun. We still had good communications to the gondola via the command computer that was still alive and well. After two hours of unsuccessful attempts to bring the control computer back online we decided to order a premature termination of the mission..."

So, at 8:34 UTC the payload was separated from the balloon. The termination signal was transmited using the line-of-sight system (the balloon being still over the horizon from the view pint of the base) and the landing occurred 55 nautic miles southeast of Williams Field.

Without being near the landing site, a so called "blind" parachute release was performed once the instrument was in the ground.

On December 26 started the search of the payload using a Twin Otter twin engine turboprop aircraft. Due to the bad conditions it was impossible to land, but a member of the team aboard was able to see the gondola from the air, wich after touch down tipped over on its back as expected, looking in good condition. Initially was tought that will exist a possibility to re-fly the payload before the close of the season but the delays on the recovery, finally led to a cancellation for this year.

A few days after, the first Twin Otter mission to the landing site was completed. The recovery crew stripped the gondola down to helicopter lift weight limits, and returned the major portions of the flight train to McMurdo Station. Two follow-on recovery missions were on the base's schedule for several days being cancelled almost daily due to bad weather or higher priority missions that would made use of the aircraft.

After a Twin Otter mission delivered a helicopter technician, and a CSBF recovery crew to the landing site, finally the SBI gondola was recovered on January 9th 2007. After rigging by the technician, an helicopter completed a successful pick up and returned to Williams Field meanwhile the recovery crew completed recovering all equipment remaining in the field, and returned it also to Williams Field.

As you may remember from past updates, the SBI (Solar Bolometric Imager) is an instrument composed by a 30 cm telescope designed to obtain the first solar imaging in total light. It would provide flat spectral response over a wide spectral range (300nm - 2micron) with a resolution sufficient to identify the basic magnetic structures (spots, faculae, enhanced network), and measure their separate contributions to total irradiance variation. This would lead to obtain very valuable information regarding the influence of the sun's irradiance in climate studies.

The instrument was developed by the Johns Hopkins University Applied Physics Laboratory. (see web site), based in an early experiment called Flare Genesis, flown in the past by the same team and wich was also devoted to do solar research.