Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_31681 ( "Flight" text, "Launch date/time (UTC)" text, "Variant" text, "Launch Pad" text, "Payload" text, "Payload Mass" text )

### Question ###
Tell me the launch date/time for payload of gsat-4

### Accurate SQL ###

SELECT "Launch date/time (UTC)" FROM table_31681 WHERE "Payload" = 'gsat-4'