You've probably read about the NASA Ultra-Long Duration Balloon (ULDB) project in the news lately. Most of the articles I've seen don't give much detail on the ULDB vehicle itself so I decided to do a little research. Ever wonder what kind computer they used or what software it runs? This article gives a few details and provides links to some of the NASA design documents for those who want even more info.

The ULDB test flight on March 11 was successful in-spite of an early termination shortly after 24 hours. The early termination of the test mission was due to unexpected pressure readings within the balloon. The balloon was landed safely and the data gathered during the test flight should prove useful in preparing for additional test flights and the launch of the first mission in September.

The ULDB vehicle is designed to support missions in an environment above 99% of the Earth's atmosphere for durations of up to 100 days. The pumpkin-shaped balloon is 128 meters in diameter and 78 meters tall. It is made of a multi-layer composite material with layers of polyester, mylar, and polyethylene film. The first mission for the ULDB is to carry TIGER, the Trans-Iron Galactic Element Recorder. TIGER is a cosmic-ray telescope composed of four plastic scintillation counters, two Cherenkov lightboxes, and a scintillating fiber hodoscope. The whole package weighs 540kgs and produces telemetry at a rate of about 5kbps.

A PC104 system with redundant Intel 133mhz 486DX4 CPUs and a redundant bus controls the ULDB. VxWorks was chosen as the OS. The system has a SCSI hard drive and 11 UARTS used for RS-232 communication with the TIGER instrument as well as various sensors and controls on the vehicle. In addition to the 5kbps telemetry stream from TIGER the system must also manage data coming in from the attitude control system, from a variety of sensors, including GPS, atmospheric pressure, balloon pressure, air temperature, component temperatures, and a radiometer. The system controls all communications between the ULDB and the ground through a 50kbps TRDSS data link. Commands to the ULDB are issued by a ground team and relayed by the computer to the appropriate instrument package or balloon control system.

Power for the vehicle is provided by 3 photo voltaic panels. Each panel has 73 square feet of surface area and the combined power output provides 500 watts of power during daylight hours. Batteries provide 200 watts of power when daylight is unavailable.

For more information try these URLs:

Main ULDB Project Page
http://www.wff.nasa.gov/~uldb/

Photos from the Australian Test Flight
http://www.wff.nasa.gov/~uldb/australia2001images.html

ULDB Flight Processor Hardware
http://www.wff/nasa.gov/~uldb/fltprochardware/index.html

ULDB Flight Software
http://www.wff.nasa.gov/~code584/ULDBFlightSoftware/index.html

TIGER (first misssion payload)
http://cosray2.wustl.edu/tiger/index.html