Encyclopedia Astronautica
1970.04.15 - Apollo 13 swings behind the moon


At 00:21:35 GMT Apollo 13 passed behind the moon, out of radio contact with earth. Flying high above the lunar surface, the crew reached a distance of 401,056 km from the center of the earth, an all-time altitude record. At 02:40:39 GMT the cold, exhausted, and ailing crew conducted a completely manual 4 minute 23 second burn of the LM descent engine to reduce the coast time back to earth and moved the landing point from the Indian Ocean to the South Pacific.

Meanwhile the S-IVB/IU stage had impacted the lunar surface at 01:10 GMT at a speed of 2579 meters per second. Impact was 137.1 kilometers from the Apollo 12 seismometer. The seismic signal generated by the impact lasted 3 hours 20 minutes and was so strong that a ground command was necessary to reduce seismometer gain and keep the recording on the scale. The suprathermal ion detector experiment, also deployed by the Apollo 12 crew, recorded a jump in the number of ions from zero at the time of impact up to 2,500 shortly thereafter and then back to a zero count. Scientists theorized that ionization had been produced by 6,300 K to 10,300 K (6,000 degrees C to 10,000 degrees C) temperature generated by the impact or that particles had reached an altitude of 60 kilometers from the lunar surface and had been ionized by sunlight.

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