There were 6 periods :

proto-Mother Gong #1 -1978 - band assembled to promote the Mother album
Members : Gilli Smyth, Jerry C. Hart (drums), George Bishop (sax), Paul Sanchez (bass), François Bessac (guitar), Jean-Paul Vivini (synth), Janno (percussion), Patrick Meadows (keyboards) and Ax Genrich (guitar).
They briefly toured in Spain and UK in the second half of 1978.

Mother Gong #2 -1978-79 in USA.
Members: Gilli Smyth, Harry Williamson, George Bishop, Bill Laswell, Bill Bacon, Kramer.
Participated to the first New-York Manifestival in Oct.1978 and toured the US in Spring 1979. This was really Gilli and Harry backed by members of New York Gong. Period documented on [r=5782231].

Mother Gong #3 -1979-80
Members : Gilli Smyth, Harry Williamson, Didier Malherbe, Trevor Darks, Mo Vicarage, Ermano Ghisio Erba and Eduardo Niebla.
Recorded the album Fairy Tales, and played at Glastonbury festival 1979 on the new Pyramid Stage.

Mother Gong #4 - 1981-83
Members : Gilli Smyth, Harry Williamson, Didier Malherbe, [a270816], [a388530] and Guy Evans.
This is the Robot Woman Trilogy period. Played festivals in Norway and UK, and headlined at Glastonbury 81, where Robot Woman was partly recorded. Harry and Gilli emigrated to Australia in 1982. The last part of the Robot Woman trilogy was recorded in Australia, with different (local) musicians.

Mother Gong #5 - 1986-1992 in Australia and UK
Members : Gilli Smyth, Harry Williamson, Robert Calvert, Conrad Henderson and [a345560].
This period ended when Harry and Gilli parted ways. Concerts in Australia and a stripped down tour of USA in '91.

Mother Gong #6 - 2005-2006
Members : Gilli Smyth, Didier Malherbe, [a353823], Orlando Allen, [a7399160] and Graham Clark.
Final resurrection of the band at the occasion of Gong's conventions in 2005 and 2006. They did also a few other gigs in UK and Norway.