I asked Dr. Ellis Miner from JPL about the batteries, this was his reply: The 153-minute lifetime of the Huygens batteries is a worst-case scenario. The battery capacity is several hundred Watt hours, even with the assumption of complete failure of one of the five batteries. The 153 minutes assumes a worst cast energy consumption during the descent phase (2.5 hours descent + 0.5 hour on the surface) of 326 Watt hours. More careful analysis of the actual expected consumption during that 3-hour descent phase is 235 Watt hours. While on the surface of Titan the consumption will be something on the order of 100 Watts. Furthermore, the 2.5-hour descent time is also a worst case number, and every minute earlier than that provides an additional minute of surface data. In fact, the limiting factor on the amount of surface data collected is likely to be the disappearance of the Cassini orbiter over the horizon of the Huygens Probe transmitters. That occurs nominally just under an hour after nominal landing. The present plans are too keep the probe transmitting for the full 210 minutes. Ken