SELECT aqs."TimeStamp",
    array_to_json(
        array_agg(
            row_to_json(
                (SELECT d
                    FROM
                        (SELECT "SensorID_1" SensorID, "SensorID_1_Temp" SensorIDTemp UNION ALL SELECT "SensorID_3" SensorID, "SensorID_3_Temp" SensorIDTemp)
                        d
                )
            )
        )
    )
    AS data
FROM  stats."AQSTemperatures" aqs
GROUP BY aqs."TimeStamp";

TIMESTAMP  |                                   data
------------+---------------------------------------------------------------------------
 1489175568 | [{"sensorid":1,"sensoridtemp":16.125,"sensorid":3,"sensoridtemp":28.062}]
 1489014070 | [{"sensorid":1,"sensoridtemp":15.437,"sensorid":3,"sensoridtemp":51.437}]
 1489010909 | [{"sensorid":1,"sensoridtemp":15.562,"sensorid":3,"sensoridtemp":48.375}]
 1489428353 | [{"sensorid":1,"sensoridtemp":15.437,"sensorid":3,"sensoridtemp":44.75}]
 1489176230 | [{"sensorid":1,"sensoridtemp":16.187,"sensorid":3,"sensoridtemp":28.062}]
 1489011301 | [{"sensorid":1,"sensoridtemp":15.625,"sensorid":3,"sensoridtemp":48.875}]
 1489015597 | [{"sensorid":1,"sensoridtemp":15.5,"sensorid":3,"sensoridtemp":52.75}]
 1489174910 | [{"sensorid":1,"sensoridtemp":16.062,"sensorid":3,"sensoridtemp":29.25}]
 1489014728 | [{"sensorid":1,"sensoridtemp":15.5,"sensorid":3,"sensoridtemp":52.0}]
 1489174251 | [{"sensorid":1,"sensoridtemp":15.937,"sensorid":3,"sensoridtemp":36.187}]
 1489173924 | [{"sensorid":1,"sensoridtemp":15.812,"sensorid":3,"sensoridtemp":42.062}]
 1489011633 | [{"sensorid":1,"sensoridtemp":15.625,"sensorid":3,"sensoridtemp":49.187}]