The WIRE anomaly report was completed June 8th. Here is the official press release:
Douglas Isbell
Headquarters, Washington, DC June 25, 1999
(Phone: 202/358-1547)
Lynn Jenner
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-8982)
RELEASE: 99-74
INVESTIGATION FINDS DESIGN ERRORS CAUSED WIRE SPACECRAFT FAILURE
NASA's Wide-Field Infrared Explorer (WIRE) failed because of an incorrectly designed electronics box that prematurely fired explosive devices, causing early ejection of the instrument's telescope cover, a NASA board has found.
The WIRE Mishap Investigation Board found that the design of the instrument's electronics box did not take into account subtle, but known, start-up characteristics of one component within the box. Electrical power created at the start-up of this component reached explosive devices, called pyrotechnics, meant to eject the telescope's cover later in the mission. The power reached the pyrotechnics within a fraction of a second after the box was turned on, and the cover was ejected.
With the premature loss of the telescope's cover, the frozen hydrogen used to cool the telescope's sensitive infrared detectors was exposed to the Sun. As the telescope warmed, the hydrogen converted into a gas and vented entirely into space within 48 hours of launch. Without the frozen hydrogen, the instrument could not conduct its scientific mission.
"There was no component failure," said Darrell Branscome, chairman of the eight-member WIRE Mishap Board and Deputy Associate Administrator (Enterprise Development) for NASA's Office of Space Flight, Washington, DC. "This was simply a case of a design error that allowed power to get to the explosive charges before it should have. The system operated the way it was designed. Unfortunately, the design was flawed."
The report added that simulators and other support equipment used for design and verification tests lacked the fidelity required to detect this potential failure.
"A significant contributing cause of the anomaly was the failure to identify, understand, and correct the electronic design of the pyro electronics box," the report said. "Design errors in the circuitry, which controlled pyro functions, were not identified. The pyro electronics box design was not peer reviewed, and other system reviews conducted by the instrument design team did not focus on the electronics box."
WIRE was launched from Vandenberg Air Force Base, CA, March 4 aboard a Pegasus XL launch vehicle. WIRE's mission was to detect infrared light in the background cosmos to learn more about the formation of stars, galaxies and the current state of the universe.
NASA has already taken additional steps to ensure that design engineers are aware of this condition. A NASA Parts Advisory was issued on May 27 at the request of the Mishap Board informing design engineers of the need to consider the startup behavior of electronic devices to prevent unwanted or unexpected power discharges.
The team's report also included recommendations for future spacecraft designers. These include the use of independent, separate inhibiting devices for pyrotechnics for mission-critical or irreversible events; additional testing for anomalous start-up behavior; detailed, independent reviews to assess the system design; and consideration of the design, location and mounting of external vent hardware in the event of a worst-case venting scenario.
The WIRE spacecraft is now in a stable orbit with its other systems and electronics in good working order. Ground controllers will proceed with tests on new flight-control technology aboard the spacecraft.
The WIRE mission was the latest in a series of Small Explorers, a project under the Explorers Program managed by NASA's Goddard Space Flight Center, Greenbelt, MD. Goddard also built the WIRE spacecraft. The Jet Propulsion Laboratory, Pasadena, CA, managed development of the WIRE instrument, which was constructed by the Space Dynamics Laboratory at Utah State University, North Logan, Utah.
The full text of the executive summary of the report is available
on the World Wide Web
at:
ftp://ftp.hq.nasa.gov/pub/pao/reports/1999/wire_summary.pdf
-end-
Previous updates:
August 18, 1997 Structure and Cryostat progress
October 20, 1997 Structure qual and harness
installation
October 31, 1997 First powerup
November 7, 1997 Transponder integration, power
long functional
November 14, 1997 WIE and pyro
box integration
November 21, 1997 RF and ACS
integration
December 5, 1997 ACS testing
December 23, 1997 Work under spacecraft
January 9, 1998 ACS testing, gyro phasing
January 16, 1998 Instrument thermal simulator
January 23, 1998 Wire tracker
January 30, 1998 Build up solar array
February 6, 1998 Ops testing, remove transponder
February 20, 1998 Move to Building 7
March 12, 1998 Cleaning and Solar Array Testing
March 23, 1998 Prep for Environmental and into EMI
April 3, 1998 EMI and Vibration
April 20, 1998 Vibration and Shock
April 25, 1998 Thermal Balance
May 29, 1998 Instrument integration and Thermal
Vacuum
June 3, 1998 Spin Balance
June 17, 1998 Astrotech Tour and Magnetic
Calibration
June 30, 1998 QD qual, fairing fit
check, comprehensive testing
July 29, 1998
Ready to ship, QD testing
August 13, 1998 Launch delay
November 23, 1998 New launch date
January 19, 1999 WIRE at launch site
January 21, 1999 WIRE turnover/on Byrd Mobile
January 26, 1999 Instrument cooling, electrical
mate
January 29, 1999 Spacecraft on the rocket
February 15, 1999 Hydrogen load in progress
February 19, 1999 Fairing installation
February 24, 1999 L-1011 arrival
February 25, 1999 Rollout to the hot pad
March 1, 1999 Launch day--first try
March 2, 1999 Launch abort
March 4, 1999 Launch day
March 4, 1999 Launch timeline
March 8, 1999 Despin underway
March 12, 1999 Under control