Hi,

I have tried this mission again (with the camera on the back), and there are still issues. I can get close enough for the APXS to start irradiating this time, but after it gets to about 1/4 of the way through the measurement, the measurement stops, and when I start it again I get the same error message "No target in range". I have to reverse the rover into the rock again, which results in the same bug stopping the measurement. This happened about 4 times before I reported it.

Some rechargeable AAs have them, maybe it's not as common as I thought. Even electricity bills (here in Ireland anyway) electrical bills are quoted as (kilo) watt-hours.
The robots will charge at a rate of some amount of charge per time, so it would be watt-hours per hour i.e. watt times hours divided by hours, so it would just reduce to watts.
I know I'm being very pedantic about this, but it would be a bit silly for an awesome simulator like this to be let down by details like that!

If you look at the side of a typical battery the capacity is given as milliwatt-hours. Perhaps capacity was a bad choice of words on my part, but it should still be watts (i.e. joules per second - energy per time) for a rate of energy usage.
https://en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours_and_watts_per_hour