Error generating chart: No features contain non-null values of "system:time_start" from Landsat 8 image

Question

I am getting Error generating chart: No features contain non-null values of "system:time_start" building a monthly landsat LST:

var geometry = 
    /* color: #d63000 */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[-75.35023860347604, 41.76108398613208],
          [-75.35023860347604, 39.69663659517741],
          [-71.98842219722604, 39.69663659517741],
          [-71.98842219722604, 41.76108398613208]]], null, false),
    imageCollection = ee.ImageCollection("LANDSAT/LC08/C02/T1_L2"),
    imageCollection2 = ee.ImageCollection("LANDSAT/LC09/C02/T1_L2");


Map.centerObject(geometry);

var time_start= '2023' , time_end='2024'

var landsat8 = imageCollection
.filterDate(time_start,time_end)
.filterBounds(geometry)
.filter(ee.Filter.lt('CLOUD_COVER',45));

//print(landsat8)

var landsat9 = imageCollection2
.filterDate(time_start,time_end)
.filterBounds(geometry)
.filter(ee.Filter.lt('CLOUD_COVER',45));

//print(landsat9)

var landsat_collection= landsat8.merge(landsat9)
.sort('system:time_start');

//print(landsat_collection)

function temporal_collection(collection, start, count, interval, unit){
  var seq = ee.List.sequence(0,ee.Number(count).subtract(1));
  var origin_date= ee.Date(start);
  return ee.ImageCollection(seq.map(function(i){
    var start_date = origin_date.advance(ee.Number(interval).multiply(i),unit);
    var end_date = origin_date.advance(ee.Number(interval).multiply(ee.Number(i).add(1)),unit);
    return collection.filterDate(start_date,end_date).median()
    .set('system:time_start', start_date.millis())
    .set('system:time_start', end_date.millis())
  }))
}

var landsat_monthly = temporal_collection(landsat_collection, time_start,12,1,'month')
//print(landsat_monthly)

var temp = landsat_monthly.select('ST_B10').map(function(img){
  var kel = img.multiply(0.00341802).add(149);
  var cel = kel.subtract(273.15);
  return cel
  .copyProperties(img, ['system: time_start', 'system: time_end'])
});
//print(temp)

print(ui.Chart.image.series(temp, geometry, ee.Reducer.mean(), 100,'system:time_start'));

// print(
//   ui.Chart.image.series({
//     imageCollection: temp, 
//     region: geometry, 
//     reducer: ee.Reducer.mean(),
//     scale: 100, 
//     xProperty: 'system:time_start'
//   }))

Map.addLayer(temp.toBands().clip(geometry),[],'temp',false)

I have tried several ways using print ui chart time series but the error is still the same.

What is wrong here?

Answer 1

You've got a typo in your code that's affecting the .copyProperties function. It should be written as 'system:time_start' and 'system:time_end'.

Instead, you've written 'system: time_start' and 'system: time_end'.

The spaces inside the property names in your original code are causing issues with identifying the correct properties to copy. Removing these spaces should fix the issue.