I have to admit it’s doubly amusing finding articles like Mars ate my spacecraft!, once for the content and once for the amusing title:
The investigation board made the not-terribly-earth-shaking observation that tired people make mistakes. The contractor used excessive overtime to meet an ambitious schedule. Mars is tough on schedules. Slip by just one day past the end of the launch window and the mission must idle for two years. In some businesses we can dicker with the boss over the due date, but you just can’t negotiate with planetary geometries.
[. . .]
NASA’s mantra is to test like you fly, fly what you tested. Yet no impact test of a running, powered, DS2 system ever occurred. Though planned, these were deleted midway through the project due to schedule considerations. Two possible reasons were found for Deep Space 2’s twin flops: electronics failure in the high-g impact, and ionization around the antenna after the impacts. Strangely, the antenna was never tested in a simulation of Mar’s 6 torr atmosphere.
While the DS2 probes were slamming into the Red Planet things weren’t going much better on MPL. The investigation board believes the landing legs deployed when the spacecraft was 1,500 meters high, as designed. Three sensors, one per leg, signal a successful touchdown, causing the code to turn the descent engine off. Engineers knew that when the legs deployed these sensors could experience a transient, giving a false “down” reading… but somehow forgot to inform the firmware people. The glitch was latched; at 40 meters altitude the code started looking at the data, saw the false readings, and faithfully switched off the engine.
A pre-launch system test failed to detect the problem because the sensors were miswired. After correcting the wiring error the test was never repeated.
H/T to Paula Lieberman for the link.
