The Lincoln Labs CCID-80 detectors are 4096x4096 pixels, 
each 15 microns on a side.  As described in

   http://www.imagesensors.org/Past%20Workshops/2015%20Workshop/2015%20Papers/Sessions/Session_10/10-01_Suntharalingam_IISW2015.pdf

the full-well capacity of each pixel is about 200,000 electrons.

  So, we need to keep the number of photons striking each pixel
below (roughly) 200,000 to prevent saturation.

  Each camera has a diameter D = 10.5 cm, which yields 
a collecting area A = 86.6 sq.cm.  If we compute the number
of photons collected by the camera per second, we find (VERY roughly)


      V = 0  ->      10^6   photons / sq.cm. / sec      for V-band

                 3 x 10^6   photons / sq.cm. / sec      for wide TESS band


  The number of photons collected from a V = 0 star will be (VERY roughly)

      N  =       (3 x 10^6   photons / sq.cm. / sec)  x  (86.6 sq.cm.)  

                 2.6 x 10^8  photons / sec    for V = 0

                 2.6 x 10^6  photons / sec    for V = 5

                   1 x 10^6  photons / sec    for V = 6


  These calculations ignore many real-life factors, but it's clear that
the device will collect enough photons in a short 1-sec or 2-sec
exposure that it comes close to saturating a V=6 star.