Hi Ragu,

One of the major issues is the time lag. The rovers have to have a significant amount of autonomy to decide their own paths, or else disaster would strike very quickly - by the time the edge of the cliff has approached and Earth knows, its too late to stop you falling off. The Sojourner moved at a very very slow pace for this reason. The new rovers can navigate themselves from designated point to point.

The rovers "cheat" a little. They broadcast up to something like Mars Observer and THAT is relayed down to Earth.

Just last week I chatted to the lead communications engineer on the Beagle 2 project when I was on the BBC programme "All night Star Party",and the baudrates are pretty low on the uplink to Mars observer, but I think the downlink to Earth can be done at up to 500 Kbaud these days.

In the Voyager days, the ERP from Jupiter was around 10W, by the time it came down here it was 210 db down - If you gatherered all the energy received for a billion years it wouldn't light a flashlight for a 10th of a second.

Steve