Sentinel-1

Sentinel-1 spacecraft

Sentinel-1 spacecraft, © Copernicus, ESA

Mission and sensor parameters

Sentinel-1 is an operational C-band radar earth observation satellite which is part of Copernicus: the Earth observation component of the European Union's Space programme¹. The Sentinel-1 mission comprises a constellation of two polar-orbiting satellites, operating day and night performing C-band synthetic aperture radar imaging, enabling them to acquire imagery regardless of the weather.

Mission parameters

Sentinel-1A was launched on 3 April 2014 and Sentinel-1B on 25 April 2016. Each satellite carries a single C-band SAR instrument (5.405 GHz centre frequency) which provides imagery in dual polarisation (HH+HV, VV+VH). Once launched, the European Commission assumes ownership of the satellites, and the European Space Agency the role of operator. In the Charter Governance ESA acts as mission owner of Sentinel-1.

Table 1 provides a summary of the Sentinel-1 mission.

Parameter	Specifications
EO Mission	Sentinel-1
Charter Owner Agency	ESA
Providing Agency	Copernicus, ESA
Date of launch	2014-04-03
Temporal coverage	2015-04-12 - present
Mission status	Operational
Mission Life Expected	>10 years
Orbit Type	Sun-synchronous
Local Time	18:00 ascending node
Orbit Height	693 km
Orbit Period	98.6 min
Repeat Cycle	12 days at Equator with one satellite
Ref. tube deviation	+/- 100m

Table 1 - Sentinel-1 mission parameters.

Note

On 23 December 2021, the Sentinel-1B spacecraft experienced an anomaly which resulted in a loss of data transmission.

Sensor specifications

Table 2 provides specifications of the C-SAR instrument, an active phased array antenna, on board the Sentinel-1 platform.

Parameter	Specifications
Center frequency	5.405 GHz (C-band)
Bandwidth	0-100 MHz
Look direction	Right
Incidence angle range	20-46°
Polarization	HH+HV, VV+VH, VV, HH
Imaging Modes	SM, IW, EW, WV imaging modes
Resolution	Low Resolution - S-LR (10 - 35m)
Swath width	Up to 410 km

Table 2: Sentinel-1 C-SAR sensor parameters.

Acquisitions modes and polarizations

Sentinel-1 SAR acquistion imaging modes are:

Stripmap (SM)
Interferometric Wide Swath (IW)
Extra Wide Swath (EW)
Wave (WV).

C-SAR imaging modes

Figure 1 - Sentinel-1 imaging modes (image credit: Copernicus, ESA).

The SM, IW, and EW modes support operation in selectable single polarisation (HH or VV) and dual polarisation (HH+HV, VV+VH).

Table 3 provides the characteristics of Sentinel-1 acquisition modes.

Acquisitions mode	Swath width	Incidence angle	Spatial resolution
SM	80 km	18.3-46.8°	5x5m
IW	250 km	9.1-46°	5x20m
EW	410 km	18.9-47°	20x40m
WV	20x20 km	21.6-25.1°, 34.8-38.0°	5x5m

Table 3 - Characteristics of Sentinel-1 C-SAR acquisitions modes.

Polarisation options are: Dual HH+HV, VV+VH Single HH, VV. Maximum Noise Equivalent Sigma Zero (NESZ) is of -22 dB. Subswath for IW and EW are respectively, 3 and 5.

Note

Sentinel-1 products received in the Charter are mostly given IW mode.

Processing levels

Sentinel-1 EO data are distributed at three levels of processing: L0, L1, L2. In the charter Sentinel-1 products are given at L1 in the following 2 product types:

Single Look Complex (SLC) L1 data: complex images with phase and amplitude of specified areas
Ground Range Detected (GRD) L1 data: only systematically distributed multi-looked intensity

SLC

Level-1 SLC products are images in the slant range by azimuth imaging plane, in the image plane of satellite data acquisition. Each image pixel is represented by a complex (I and Q) magnitude value and therefore contains both amplitude and phase information. Each I and Q value is 16 bits per pixel. SLC products are generated for all acquisition modes.

Characteristic	Value
Pixel value	Complex
Coordinate system	Slant range
Bits per pixel	16 I and 16 Q
Polarisation options	Single (HH or VV) or Dual (HH+HV or VV+VH)
ENL	1
Number of looks (rg x az)	1 x 1

Table 4 - Characteristics of Sentinel-1 SLC products.

Note

Sentinel-1 SLC products received in the Charter are mostly given in IW mode.

GRD

Level-1 GRD products are available in one of three spatial resolutions:

Full Resolution (FR) for SM mode
High Resolution (HR) for SM, IW and EW modes
Medium Resolution (MR) for SM, IW, EW and WV modes.

Resolution, pixel spacing, number of looks, ENL for Sentinel-1 SLC/GRD products can be found in Table 5 for each resolution class.

<

Acq. Mode	Product Type	Resolution Class	Resolution Rg x Az [m]	Pixel Spacing Rg x Az [m]	Num Looks Rg x Az	ENL
SM	SLC	-	1.7x4.3 to 3.6x4.9	1.5x3.6 to 3.1x4.1	1x1	1
	GRD	FR	9x9	3.5x3.5	2x2	3.7
		HR	23x23	10x10	6x6	29.7
		MR	84x84	40x40	22x22	398.4
IW	SLC	-	2.7x22 to 3.5x22	2.3x14.1	1x1	1
	GRD	HR	20x22	10x10	5x1	4.4
	GRD	MR	88x87	40x40	22x5	81.8
EW	SLC	-	7.9x43 to 15x43	5.9x19.9	1x1	1
	GRD	HR	50x50	25x25	3x1	2.8
	GRD	MR	93x87	40x40	6x2	10.7
WV	SLC	-	2.0x4.8 to 3.1x4.8	1.7x4.1 to 2.7x4.1	1x1	1
WV	GRD	MR	52x51	25x25	13x13	123.7

Table 5 - Characteristics of Sentinel-1 L1 products.

Note

Sentinel-1 GRD products received in the Charter are mostly given at High Resolution.

Ingested format

Information extracted from product annotation included in the STAC item of a Sentinel-1 GRD dataset are listed below.

Properties

STAC item content about properties for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "properties": {
    "datetime": "2022-10-11T11:29:01.526969Z",
    "start_datetime": "2022-10-11T11:29:01.526969Z",
    "end_datetime": "2022-10-11T11:29:26.525849Z",
    "created": "2022-10-12T10:05:46.5746468Z",
    "updated": "2023-08-23T15:57:26.8630676Z",
    "platform": "sentinel-1a",
    "constellation": "sentinel-1",
    "mission": "sentinel-1",
    "instruments": [
      "c-sar"
    ],
    "sensor_type": "radar",
    "gsd": 22,
    "title": "SENTINEL-1A GRD VV/VH 172 2022-10-11 11:29:01",
    "providers": [
      {
        "name": "ESA",
        "roles": [
          "licensor"
        ]
      }
    ],
    "license": "CC-BY-SA-3.0-IGO",
    "disaster:call_ids": [
      903
    ],
    "disaster:resolution_class": "LR",    
    "cpe:cos2_id": "903-ESA-SENTINEL_1A-S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE.zip",
  }

Satellite

STAC item content about Satellite for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "properties": {
    "sat:orbit_state": "ascending",
    "sat:anx_datetime": "2022-10-11T09:47:06.522627Z",
    "sat:absolute_orbit": 45394,
    "sat:relative_orbit": 172,
    "sat:platform_international_designator": "2014-016A"
}

SAR

STAC item content about SAR for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "properties": {
    "sar:instrument_mode": "IW",
    "sar:frequency_band": "C",
    "sar:polarizations": [
      "VV",
      "VH"
    ],
    "sar:product_type": "GRD"
}

Processing

STAC item content about Processing for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "properties": {
    "processing:level": "L1",
    "processing:lineage": "GRD Post Processing",
    "processing:facility": "Copernicus Ground Segment",
    "processing:software": {
      "Sentinel-1 IPF": "003.52"
    },
  }

Projection

STAC item content about Projection for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "properties": {
      "proj:shape": [
        25689,
        16764
      ]
  }

Geometry

STAC item content about Geometry for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [
          99.434959,
          13.719059
        ],
        [
          99.74543,
          12.207163
        ],
        [
          102.063171,
          12.657678
        ],
        [
          101.767723,
          14.165735
        ],
        [
          99.434959,
          13.719059
        ]
      ]
    ]
  },
  "bbox": [
    99.434959,
    12.207163,
    102.063171,
    14.165735
  ]

Assets

STAC item content about assets (annotation, quicklooks and spectral bands files harvested from the source product) for a Sentinel-1 GRD HR IW VV/VH Dataset is the following:

  "assets": {
    "amplitude-vh-iw-002": {
      "type": "image/x.geotiff",
      "roles": [
        "amplitude",
        "data"
      ],
      "title": "IW VH Amplitude pixel values",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/amplitude-vh-iw-002.tiff",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/measurement/s1a-iw-grd-vh-20221011t112901-20221011t112926-045394-056d8c-002.tiff",
      "file:size": 861579876,
      "sar:polarizations": [
        "VH"
      ],
      "proj:epsg": null,
      "proj:shape": [
        25689,
        16764
      ]
    },
    "annotation-vh-iw-002": {
      "type": "text/xml",
      "roles": [
        "metadata"
      ],
      "title": "Annotation VH IW 002",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/annotation-vh-iw-002.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/s1a-iw-grd-vh-20221011t112901-20221011t112926-045394-056d8c-002.xml",
      "file:size": 1910546,
      "sar:polarizations": [
        "VH"
      ]
    },
    "amplitude-vv-iw-001": {
      "type": "image/x.geotiff",
      "roles": [
        "amplitude",
        "data"
      ],
      "title": "IW VV Amplitude pixel values",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/amplitude-vv-iw-001.tiff",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/measurement/s1a-iw-grd-vv-20221011t112901-20221011t112926-045394-056d8c-001.tiff",
      "file:size": 861579876,
      "sar:polarizations": [
        "VV"
      ],
      "proj:epsg": null,
      "proj:shape": [
        25689,
        16764
      ]
    },
    "annotation-vv-iw-001": {
      "type": "text/xml",
      "roles": [
        "metadata"
      ],
      "title": "Annotation VV IW 001",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/annotation-vv-iw-001.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/s1a-iw-grd-vv-20221011t112901-20221011t112926-045394-056d8c-001.xml",
      "file:size": 1910546,
      "sar:polarizations": [
        "VV"
      ]
    },
    "calibration-vh-iw-002": {
      "type": "text/xml",
      "roles": [
        "calibration",
        "data"
      ],
      "title": "Calibration VH IW",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/calibration-vh-iw-002.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/calibration/calibration-s1a-iw-grd-vh-20221011t112901-20221011t112926-045394-056d8c-002.xml",
      "file:size": 1010137,
      "sar:polarizations": [
        "VH"
      ]
    },
    "calibration-vv-iw-001": {
      "type": "text/xml",
      "roles": [
        "calibration",
        "data"
      ],
      "title": "Calibration VV IW",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/calibration-vv-iw-001.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/calibration/calibration-s1a-iw-grd-vv-20221011t112901-20221011t112926-045394-056d8c-001.xml",
      "file:size": 1010137,
      "sar:polarizations": [
        "VV"
      ]
    },
    "noise-vh-iw-002": {
      "type": "text/xml",
      "roles": [
        "data",
        "noise"
      ],
      "title": "Noise VH IW",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/noise-vh-iw-002.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/calibration/noise-s1a-iw-grd-vh-20221011t112901-20221011t112926-045394-056d8c-002.xml",
      "file:size": 412712,
      "sar:polarizations": [
        "VH"
      ]
    },
    "noise-vv-iw-001": {
      "type": "text/xml",
      "roles": [
        "data",
        "noise"
      ],
      "title": "Noise VV IW",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/noise-vv-iw-001.xml",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/annotation/calibration/noise-s1a-iw-grd-vv-20221011t112901-20221011t112926-045394-056d8c-001.xml",
      "file:size": 412712,
      "sar:polarizations": [
        "VV"
      ]
    },
    "manifest": {
      "type": "text/xml",
      "roles": [
        "metadata"
      ],
      "title": "SAFE Manifest",
      "href": "https://.../S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7/manifest.safe",
      "filename": "S1A_IW_GRDH_1SDV_20221011T112901_20221011T112926_045394_056D8C_1BE7.SAFE/manifest.safe",
      "file:size": 24005
    }
  }

Product Calibration

For Sentinel-1 products calibration refer to the Radar Products Calibration (SAR-Calib) service and the calibration sheet available here.

ESA, Sentinel Online, Sentinel-1 Mission Guide. Available at: sentinel.esa.int ↩