Departments
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Week of 11 June 1999 |
Vol. II, No. 35 |
Feature
Article
Malfunction trips up satellite
Project managers for the Boston University terriers satellite are attempting to salvage its mission to explore Earth's upper atmosphere, despite a serious malfunction that led to a loss of power to the spacecraft.
Following its successful launch into space on May 18, the satellite has been orbiting Earth as planned, but has been unable to orient itself so that its solar panel fully faces the sun. The panel is designed to gather solar energy and continually recharge a set of batteries that run the craft and all of its instruments. Without power the satellite has gone into sleep mode, preventing the BU team from communicating with it to change its position.
Undergraduate students at BU's mission control center on campus, originally recruited to compile data from terriers as it passes over a radio dish mounted atop the University's Photonics Center building, are now attempting to transmit instructions from the ground to reposition the craft with the hope that sunlight will slowly recharge the batteries and reestablish communication.
"We remain hopeful," says Supriya Chakrabarti, chief scientist for the mission and director of BU's Center for Space Physics. "Despite our disappointment, all of the students working on the terriers project are working hard on the recovery effort. I'm very impressed with how well they have responded to the challenge. We are very gratified by the support we are receiving from the scientific community and the campus," he adds.
University scientists have been working with a NASA-appointed recovery team to analyze data the satellite sent down before its batteries ceased to function. Chakrabarti says they have discovered the source of the problem -- a flawed algorithm in the attitude-control software.
"If we can reestablish communication, we can send commands to override the algorithm and correctly orient the satellite," he says.
Terriers is a NASA-funded project led by CAS Assistant Research Professor Dan Cotton. He and the team of faculty members, graduate researchers, and students had planned to use data from the satellite to create a three-dimensional map of the ionosphere. Ultimately the map could help scientists predict space weather -- phenomena such as massive radiation storms that threaten power grids, satellites, and astronauts working outside their spacecraft.
BU students designed and built the instruments for measuring ionospheric conditions. A private company built the spacecraft bus, which includes the power, attitude control, and communication systems.
The recovery strategy includes the establishment of an additional ground station, this one in Alaska. On June 4, physics and astronomy major Kevin France (CAS'00) and Tim Cook, associate research professor of space physics, installed a new, larger radio dish at the Poker Flat Research Range, a facility located 30 miles north of Fairbanks and operated by the University of Alaska's Geophysical Institute.
According to Chakrabarti, the northern site provides BU with more frequent daily opportunities to establish contact. Another saving factor, he adds, might be seasonal variations in Earth's orientation toward the sun, which could afford Terriers an opportunity to recharge its batteries.