1、Lessons Learned Entry: 1529Lesson Info:a71 Lesson Number: 1529a71 Lesson Date: 2004-10-11a71 Submitting Organization: JPLa71 Submitted by: David J. OberhettingerSubject: Ensure Test Monitoring Software Imposes Limits to Prevent Overtest (2003) Abstract: When a GSE power meter registered zero due to
2、an AC power glitch, the test monitoring and control software interpreted this as a loss of power and increased the test level past the maximum rating of the test article. This ground test error could have damaged flight hardware. Perform FMEA on test equipment to identify all potential GSE-induced f
3、ailure modes. Either program the test control software or insert a limiting hardware device to prevent overtest.Description of Driving Event: Vacuum testing of the Mars Reconnaissance Orbiter (MRO) telecommunications subsystem at JPL included a multipaction test of the diplexer, which is conducted w
4、ith the equipment powered. (“Multipaction” is a phenomenon that occurs when radio frequency (RF) transmit power accelerates electrons in a vacuum, causing a corona discharge and possible RF system failure.) During this test, an accurate indication of the power output of the test equipment was not pr
5、ovided to the test monitoring software. This caused the test monitoring software to command the test equipment to increase the transmitter output to a potentially harmful level. Analysis showed that the GSE power meter stopped taking measurements, possibly due to an AC power anomaly. The test monito
6、ring software then interpreted the zero reading from the power meter as a loss of power, and responded by increasing the drive level of the X-Band Synthesizer to a level sufficient to drive the Traveling Wave Tube Amplifier (TWTA) to maximum output power. To prevent a recurrence, an attenuator or li
7、miter was inserted to maintain the RF output below a specified level, preventing the TWTA from providing more power than the maximum rating of the test article should the power measurements fail. References: (1) Jet Propulsion Laboratory Problem/Failure Report No. Z82462, November 12, 2003. (2) LLIS
8、 #0573, “Power Bus/GSE Sneak Paths May Energize Spacecraft in the Ground Test Environment“ (3) LLIS #0583, “Test Contingency Planning Should Consider Facility Power Interruptions,” February 19, 1998. Additional Key Words: facility power, test failure, test-induced Provided by IHSNot for ResaleNo rep
9、roduction or networking permitted without license from IHS-,-,-failure, power limits, test software, fault protection, RF breakdown, RF test, test overstress, High Power RF Breakdown FacilityLesson(s) Learned: GSE failures can negate the test limits programmed into commercial test monitoring and con
10、trol software applications.Recommendation(s): 1. Before it is used with flight hardware, perform a Failure Mode and Effects Analysis (FMEA) on GSE test equipment to identify failure modes that could cause test monitoring and control software to initiate an overtest.2. Prior to test, under the test p
11、rinciple of “First, Do No Harm“ to flight equipment, assure that test monitoring and control software is programmed or a limiting hardware device is inserted to prevent overtest under all conditions, including GSE failure.3. Evidence of Recurrence Control Effectiveness: Preventive Action Notice No.
12、Z87420 was opened by JPL on September 6, 2005 to initiate and document appropriate Laboratory-wide corrective action on the above recommendation.Documents Related to Lesson: Principle No. 4.12.5.1, JPL Design, Verification/Validation and Operations Principles for Flight Systems (D-17868), Rev. 2, Ma
13、rch 3, 2003.Mission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Flight Operationsa71 Ground Equipmenta71 Hardwarea71 Payloadsa71 SoftwareProvided by IHSNot for ResaleNo reproduction or networking permitted without licens
14、e from IHS-,-,-a71 Spacecrafta71 Test & Verificationa71 Test ArticleAdditional Info: Approval Info: a71 Approval Date: 2005-08-29a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
