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Asset Resolver

Asset Resolver API

Resolve download URLs for specific spectral bands and output formats. The asset resolver handles COG routing, band selection, and format conversion so you always get consistent, analysis-ready data.

Endpoint

GET/api/v1/assets

Requires authentication via Bearer token.

Query Parameters

Parameter	Type	Required	Description
scene_id	string	Required	The provider-scoped scene ID (e.g., `sentinel-2:S2B_MSIL2A_20250115T184929`). See Scene Details for ID format.
bands	string	Optional	Comma-separated list of band names to include. Accepts both native names (`B04,B08`) and common names (`red,nir`). Omit to return all available bands.
format	string	Optional	Output format. One of: `cog` (default), `geotiff`, `png`, `jpeg`. COG is recommended for analysis workflows.

COG Routing Logic

The asset resolver intelligently routes requests to the most efficient data source based on the scene provider and requested format. This is handled transparently so you always get a direct download URL.

How it works

Scene lookup -- The resolver identifies the upstream provider and original asset catalog for the given scene ID.

Band mapping -- Common band names (e.g., nir) are translated to provider-specific names (e.g., Sentinel-2 B08, Landsat B05).

COG preference -- If the provider already serves COGs (e.g., Planetary Computer), the resolver returns the direct URL. If the source format is not COG, it routes through the ASTRA conversion pipeline.

Signed URLs -- All returned URLs are pre-signed with a 1-hour expiry. No additional authentication is needed to download the assets.

Example Request

cURL

terminal

curl "https:"color: #6b7280">//astraos.cloud/api/v1/assets?\
  scene_id=sentinel-2:S2B_MSIL2A_20250115T184929&\
  bands=red,nir&\
  format=cog" \
  -H "Authorization: Bearer astra_sk_live_your_key_here"

Python

assets_example.py

import requests
response = requests.get(
    "https://astraos.cloud/api/v1/assets",
    params={
        "scene_id": "sentinel-2:S2B_MSIL2A_20250115T184929",
        "bands": "red,nir",
        "format": "cog",
    },
    headers={"Authorization": "Bearer astra_sk_live_your_key_here"},
)
assets = response.json()
for band_name, asset in assets["assets"].items():
    print(f"{band_name}: {asset[&"color: #6b7280">#39;href&#39;]}")
"color: #6b7280"># Download the red band COG
import urllib.request
red_url = assets["assets"]["B04"]["href"]
urllib.request.urlretrieve(red_url, "red_band.tif")

JavaScript

assets_example.js

const params = new URLSearchParams({
  scene_id: "sentinel-2:S2B_MSIL2A_20250115T184929",
  bands: "red,nir",
  format: "cog",
});
const res = await fetch(`https:"color: #6b7280">//astraos.cloud/api/v1/assets?${params}`, {
  headers: { Authorization: "Bearer astra_sk_live_your_key_here" },
});
const data = await res.json();
Object.entries(data.assets).forEach(([band, asset]) => {
  console.log(`${band}: ${asset.href}`);
});

Response Format

response.json

1{
2  "scene_id": "sentinel-2:S2B_MSIL2A_20250115T184929",
3  "format": "cog",
4  "assets": {
5    "B04": {
6      "href": "https://storage.astraos.cloud/assets/abc123/B04.tif?sig=...",
7      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
8      "title": "Red (B04) - 10m",
9      "file:size": 52428800,
10      "eo:bands": [{ "name": "B04", "common_name": "red", "center_wavelength": 0.665 }],
11      "expires_at": "2025-01-15T20:00:00Z"
12    },
13    "B08": {
14      "href": "https://storage.astraos.cloud/assets/abc123/B08.tif?sig=...",
15      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
16      "title": "NIR (B08) - 10m",
17      "file:size": 52428800,
18      "eo:bands": [{ "name": "B08", "common_name": "nir", "center_wavelength": 0.842 }],
19      "expires_at": "2025-01-15T20:00:00Z"
20    }
21  },
22  "metadata": {
23    "crs": "EPSG:32610",
24    "resolution": 10,
25    "source_provider": "copernicus",
26    "routing": "direct"
27  }
28}

Field	Description
assets[].href	Pre-signed download URL. Valid for 1 hour. No additional auth required.
assets[].file:size	File size in bytes for the resolved asset.
assets[].expires_at	ISO 8601 timestamp when the signed URL expires.
metadata.routing	`direct` if the provider natively serves COGs; `converted` if ASTRA ran a format conversion.
metadata.resolution	Ground sample distance in meters for the resolved bands.

Common Band Names

You can use either provider-native band names or STAC common names. The resolver maps common names to the correct provider band automatically.

Common Name	Sentinel-2	Landsat 8/9
blue	B02	B02
green	B03	B03
red	B04	B04
nir	B08	B05
swir16	B11	B06
swir22	B12	B07

← Scene Details Processing →

Query Parameters

Parameter	Type	Required	Description
scene_id	string	Required	The provider-scoped scene ID (e.g., `sentinel-2:S2B_MSIL2A_20250115T184929`). See Scene Details for ID format.
bands	string	Optional	Comma-separated list of band names to include. Accepts both native names (`B04,B08`) and common names (`red,nir`). Omit to return all available bands.
format	string	Optional	Output format. One of: `cog` (default), `geotiff`, `png`, `jpeg`. COG is recommended for analysis workflows.

COG Routing Logic

How it works

Scene lookup -- The resolver identifies the upstream provider and original asset catalog for the given scene ID.

Band mapping -- Common band names (e.g., nir) are translated to provider-specific names (e.g., Sentinel-2 B08, Landsat B05).

Signed URLs -- All returned URLs are pre-signed with a 1-hour expiry. No additional authentication is needed to download the assets.

Example Request

cURL

terminal

curl "https:"color: #6b7280">//astraos.cloud/api/v1/assets?\
  scene_id=sentinel-2:S2B_MSIL2A_20250115T184929&\
  bands=red,nir&\
  format=cog" \
  -H "Authorization: Bearer astra_sk_live_your_key_here"

Python

assets_example.py

import requests
response = requests.get(
    "https://astraos.cloud/api/v1/assets",
    params={
        "scene_id": "sentinel-2:S2B_MSIL2A_20250115T184929",
        "bands": "red,nir",
        "format": "cog",
    },
    headers={"Authorization": "Bearer astra_sk_live_your_key_here"},
)
assets = response.json()
for band_name, asset in assets["assets"].items():
    print(f"{band_name}: {asset[&"color: #6b7280">#39;href&#39;]}")
"color: #6b7280"># Download the red band COG
import urllib.request
red_url = assets["assets"]["B04"]["href"]
urllib.request.urlretrieve(red_url, "red_band.tif")

JavaScript

assets_example.js

const params = new URLSearchParams({
  scene_id: "sentinel-2:S2B_MSIL2A_20250115T184929",
  bands: "red,nir",
  format: "cog",
});
const res = await fetch(`https:"color: #6b7280">//astraos.cloud/api/v1/assets?${params}`, {
  headers: { Authorization: "Bearer astra_sk_live_your_key_here" },
});
const data = await res.json();
Object.entries(data.assets).forEach(([band, asset]) => {
  console.log(`${band}: ${asset.href}`);
});

Response Format

response.json

1{
2  "scene_id": "sentinel-2:S2B_MSIL2A_20250115T184929",
3  "format": "cog",
4  "assets": {
5    "B04": {
6      "href": "https://storage.astraos.cloud/assets/abc123/B04.tif?sig=...",
7      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
8      "title": "Red (B04) - 10m",
9      "file:size": 52428800,
10      "eo:bands": [{ "name": "B04", "common_name": "red", "center_wavelength": 0.665 }],
11      "expires_at": "2025-01-15T20:00:00Z"
12    },
13    "B08": {
14      "href": "https://storage.astraos.cloud/assets/abc123/B08.tif?sig=...",
15      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
16      "title": "NIR (B08) - 10m",
17      "file:size": 52428800,
18      "eo:bands": [{ "name": "B08", "common_name": "nir", "center_wavelength": 0.842 }],
19      "expires_at": "2025-01-15T20:00:00Z"
20    }
21  },
22  "metadata": {
23    "crs": "EPSG:32610",
24    "resolution": 10,
25    "source_provider": "copernicus",
26    "routing": "direct"
27  }
28}

Field	Description
assets[].href	Pre-signed download URL. Valid for 1 hour. No additional auth required.
assets[].file:size	File size in bytes for the resolved asset.
assets[].expires_at	ISO 8601 timestamp when the signed URL expires.
metadata.routing	`direct` if the provider natively serves COGs; `converted` if ASTRA ran a format conversion.
metadata.resolution	Ground sample distance in meters for the resolved bands.

Common Name

Sentinel-2

Landsat 8/9

blue

B02

green

B03

red

B04

nir

B08

B05

swir16

B11

B06

swir22

B12

B07