Ven Sujato translates Sati as ‘Mindfulness’ and Sampajanna as ‘Situational Awareness’… see this thread for Sampajanna and this thread for Sati and here for the relationship.
Here is a story that Ajahn Sumedho once told about the relationship between the two…
If I just follow the view that I’ve got to be mindful, I can be quite heedless.
One example of this is when I was at Wat Pah Pong. I would
go on almsround to Bahn Gor, which is a three kilometer walk.
One day it looked like it was going to rain and we thought it
advisable to take our umbrellas. So I took my umbrella and
started off. But then it didn’t rain and so we put our umbrellas
outside the village so we wouldn’t have to take them into the
village. I said to myself: “You must be mindful, Sumedho, and
when you come back from your almsround you must remember
your umbrella. Remember where it is so that you can take it
back to the monastery.” So I went on almsround being very
mindful of each step, got back to the monastery and realized
I’d forgotten my umbrella.