Angularjs - multiple json array not working properly

I'm having this little app, requesting the json file which works fine when using one level json, below code that works:

service:

angular
    .module ('myApp')
    .factory('Summary', function ($resource) {
        return $resource('summary.json');
    });

controller:

angular
    .module ('myApp')
    .controller ('summaryCtrl', ['$scope', 'poller','Summary', function ($scope, poller,Summary) {

        var poller1;
        //using angular-poller 
        poller1 = poller.get(Summary, {delay: 2000});
        poller1.promise.then(null, null, function (data) {
            $scope.summary = data;
            console.log(data);
        });
    }]);

json:

[
    {"channel": "aaa", "value": 13256},
    {"channel": "bbb", "value": 6598},
    {"channel": "ccc", "value": 245 },
    {"channel": "ddd", "value": 123},
    { "channel": "eee", "value": 956},
    { "channel": "fff", "value": 142}
]

output in console:

[Resource, Resource, Resource, Resource, Resource, Resource, $promise: Object, $resolved: true]

All that above works fine as I'm getting 6x Resource, as soon as I introduce multilevel json and amend the controller it is not working properly, below is new code where I'm trying to retrieve uk:

new json:

[
    {
        "uk": [
            {"channel": "aaa", "value": 13256},
            {"channel": "bbb", "value": 6598},
            {"channel": "ccc", "value": 245 },
            {"channel": "ddd", "value": 123},
            { "channel": "eee", "value": 956},
            { "channel": "fff", "value": 142}
        ]
    },
    {
        "us": [
            {"channel": "aaa", "value": 457},
            {"channel": "bbb", "value": 364},
            {"channel": "ccc", "value": 457 },
            {"channel": "ddd", "value": 45},
            { "channel": "eee", "value": 3},
            { "channel": "fff", "value": 143562}
        ]

    }
]

controller:

angular
        .module ('myApp')
        .controller ('summaryCtrl', ['$scope', 'poller','Summary', function ($scope, poller,Summary) {

            var poller1;
            poller1 = poller.get(Summary, {delay: 2000});
            poller1.promise.then(null, null, function (data) {
                $scope.summary = data.uk; //here I need to get uk data
                console.log(data.uk);
            });
        }]);

output in console is undefined

What am I doing wrong here? Many thanks for your help.