Sen. McCain is on the committee that oversees NASA. He recently said that the basic problem is poor management. IMHOP he's right. lou
At 02:41 PM 3/30/2000 -0500, you wrote: > >>Tony, >I don't think it was actually EMC. The report I saw on CNN said the legs >opened with a "jolt", fooling the sensors which were supposed to cut the >retro rockets when they detected the shock of landing. >Scott Lacey< > >It looks like Scott Lacey is right, thank you! I made the assumption that >"spurious signal" was electrically generated. It appears it was >mechanically or magnetically generated! Is a Hall effect sensor >"microphonic"? >Well, I guess another lesson for me not to jump to conclusions before all >the data is available! >Tony >Colorado > >Below is an excerpt from the complete NASA report. > ><<Premature shutdown of descent engines. >PLAUSIBLE. A magnetic sensor is provided in each of the three landing legs >to sense touchdown when the lander contacts the surface, initiating the >shutdown of the descent engines. Data from MPL engineering development unit >deployment tests, MPL flight unit deployment tests, and Mars 2001 >deployment tests showed that a spurious touchdown indication occurs in the >Hall Effect touchdown sensor during landing leg deployment (while the >lander is connected to the parachute). The software logic accepts this >transient signal as a valid touchdown event if it persists for two >consecutive readings of the sensor. The tests showed that most of the >transient signals at leg deployment are indeed long enough to be accepted >as valid events, therefore, it is almost a certainty that at least one of >the three would have generated a spurious touchdown indication that the >software accepted as valid. The software - intended to ignore touchdown >indications prior to the enabling of the touchdown sensing logic - was not >properly implemented, and the spurious touchdown indication was retained. >The touchdown sensing logic is enabled at 40 meters altitude, and the >software would have issued a descent engine thrust termination at this time >in response to a (spurious) touchdown indication. >MOST PROBABLE CAUSE OF LOSS OF MISSION>> > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > >To cancel your subscription, send mail to: > [email protected] >with the single line: > unsubscribe emc-pstc > >For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > >For policy questions, send mail to: > Richard Nute: [email protected] > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
