By Martyn Herman RIO DE JANEIRO, Aug 15 (Reuters) - Australian track cycling great Anna Meares will be a spectator when the Olympic sprint gold is decided on Tuesday after failing to qualify for the quarter-finals. Reigning sprint champion Meares, who claimed a sixth Olympic medal when she finished third in the keirin on Saturday, was narrowly beaten by Hong Kong's Lee Wai Sze in the Rio velodrome on Monday. It means Meares, 32, will be battling for ninth place later on Monday, rather than a medal 24 hours later. More...