I learn from listening to Material World on Radio 4 that the digital camera on the Cassini and Huygens probes have lower mega-pixel ratings than the average mobile phone (Cassini is 1 mega-pixel and Huygens, much smaller) – and of course they’re black and white. Obviously this is a combination of things like data rates and available time to transmit (in the case of Huygens), as well as what was available to put on a probe in 1997.