<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_satellite_tile(self, x_tile, y_tile, z_tile):
 """Load up a single satellite image tile."""

        cache_file = "mapscache/{}.{}.{}.jpg".format(z_tile, x_tile, y_tile)
        if cache_file not in self._tiles:
            if not os.path.isfile(cache_file):
                url = _IMAGE_URL.format(z_tile, x_tile, y_tile, _KEY)
                data = requests.get(url).content
                with open(cache_file, 'wb') as f:
                    f.write(data)
            self._tiles[cache_file] = [
                x_tile, y_tile, z_tile,
                ColourImageFile(self._screen, cache_file, height=_START_SIZE, dither=True,
                                uni=self._screen.unicode_aware),
                True]
            if len(self._tiles) > _CACHE_SIZE:
                self._tiles.popitem(False)
            self._screen.force_update()