There are a few different ways that you can go about this, but the easiest way is to use the GoogleStaticMaps package. With this package, you can either use the getGoogleStaticMap function or the getBoundingBox function to grab the satellite tiles that you need.
Once you have your tiles, you can then use the addTiles function in Leaflet to add them to your map. For example:
library(leaflet)
Get the satellite tiles
tiles <- getGoogleStaticMap(center = c(lon = -122.4194, lat = 37.7749),
zoom = 10,
maptype = "satellite",
sensor = FALSE,
scale = 2)
Add the tiles to the map
leaflet() %>%
setView(lng = -122.4194, lat = 37.7749, zoom = 10) %>%
addTiles(tiles)
You can find more information on the GoogleStaticMaps package here: https://cran.r-project.org/web/packages/GoogleStaticMaps/index.html