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January 9, 2008 Vol. 1, Issue 1


In the summer of 2003, Rex Geveden, Program Manager for Gravity Probe B at Marshall Space Flight Center, was eager to ship the spacecraft to Vandenberg Air Force Base for integration and testing and then launch.

In April the Gravity Probe B (GP-B) program had undergone a termination review, which in Geveden’s estimation, had been a close call. Getting the spacecraft to the launch pad would remove the threat of imminent cancellation. “We have to ship this thing to Vandenberg as fast as we can possibly ship it, because nobody will ‘un-ship’ us,” Geveden thought.

GP-B was no stranger to the threat of cancellation. By this point, it was in the home stretch of its development after earning the distinction of being NASA’s longest-running project in the history of the agency. Its scientific experiment was originally conceived in 1959, just a year after NASA’s founding, and it first received funding from the agency in 1964. During its nearly 40-year history, the program had faced cancellation numerous times, only to have its funding restored, often as a direct result of the personal lobbying efforts of Principal Investigator Dr. Francis Everitt of Stanford University. Even after the spacecraft had been shipped to Vandenberg, the possibility of cancellation due to a delay still loomed large for all parties involved.

Cancellation wasn’t the only dark cloud on the horizon; other issues cast long shadows at NASA that year as well. The Space Shuttle Columbia was lost on February 1, 2003 during its return to Earth, and in the aftermath the agency endured intense scrutiny. An accident investigation took place throughout the spring and summer, culminating in the release of the Columbia Accident Investigation Board (CAIB) Final Report in late August. The report was highly critical of NASA, faulting its approach to risk management and safety as well as its organizational culture. In this heated political context, everyone working with or for NASA was keenly aware that all eyes were on the agency.

GP-B arrived at Vandenberg in July. As NASA and its contractor teams from Stanford and Lockheed Martin checked out the spacecraft and its various systems in preparation for its Flight Readiness Review, engineers reviewing the data from functional tests of the satellite’s payload turned their attention to a problem with the Experimental Control Unit (ECU), a box on the spacecraft that housed a number of electronic components. The ECU, which had been slated for testing months before, created significant signal interference (“noise”) in the Superconducting Quantum Interference Device (SQUID), the highly sensitive magnetic field detector that would provide measurements critical for the mission’s science objectives.

An official anomaly report from Stanford University, the prime contractor for GP-B, described the findings: “…then the Experiment Control Unit (ECU) electronics box is powered on, the SQUID signals show various degrees of DC-coupled sensitivity to the spacecraft bus voltage level.”

Once engineers discovered that the interference originated in the ECU, they constructed a massive fault tree to determine the possible causes of the problem. Engineers from Stanford and Lockheed Martin, the contractor that had built the box, agreed that it was a grounding issue, and that the ECU power supply was the likely culprit.

Fixing the ECU would not prove easy. The resolution of this very specific technical problem would ultimately require a significant management decision involving all the key organizations with responsibility for the development of GP-B.


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