Recall that the depth of a transit by Earth, in front of the Sun,
  would be

                                            -5
          depth of Earth transit  =   8 x 10     =  0.008 percent

                                                 =  80 parts per million


  So if TESS can make measurements at the level of 60 parts per million,
  then there is some hope of finding an Earth-like transit.
  But it will not be easy.