user: Question: Tell me the launch date/time for payload of GSAT-4
Columns: ['Flight', 'Launch date/time (UTC)', 'Variant', 'Launch Pad', 'Payload', 'Payload Mass']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['D1', '18 April 2001 10:13', 'Mk I(a)', 'First', 'GSAT-1', '1,540kg']
SQL:

assistant: SELECT "Launch date/time (UTC)" FROM "Table" WHERE "Payload" = 'GSAT-4';