Sentry series satellite introduction and download tutorial

brief introduction

Copernicus is the European Union's earth observation program , The sentry satellites were part of the Copernicus project .

Copernicus plan

For decades, , European countries have done a lot of research and development in the field of earth observation , But it is repetitive and lacks service continuity .1998 year , Europe has established the global environmental security monitoring GMES It is used to coordinate the earth observation systems of various countries .2012 year , After the EU is directly involved in financing and development , The system was later renamed Copernicus . About the details of the Copernicus plan , Please watch this video ：

video

The Copernicus plan consists of three parts ：

Space part （ Sentinel series Space missions and other space agency missions ）;

Measurement part （ Provide ocean 、 Land based and airborne data collection networks for continental surface and atmospheric information ）;

Data management and global sharing ;

Sentinel satellite chronology

Satellite name	Launch time ( Specific date )	End time	Satellite positioning
Sentinel-1A	2014.4.3	Running , Life expectancy 7 year	radar
Sentinel-1B	2016.4.25	Running , Life expectancy 7 year	radar
Sentinel-2A	2015.6.23	Running , Life expectancy 7 year	High resolution optics
Sentinel-2B	2017.3.7	Running , Life expectancy 7 year	High resolution optics
Sentinel-3A	2016.2.16	Running , Life expectancy 7 year	Including radar 、 Optical imaging spectrometer 、 Positioning, etc 7 Class a sensors
Sentinel-3B	2018.4.25	Running , Life expectancy 7 year	Including radar 、 Optical imaging spectrometer 、 Positioning, etc 7 Class a sensors
Sentinel-4	expect 2023 launch	Life expectancy 8.5 year	meteorological
Sentinel-5P	2017.10.13	Running , Life expectancy 7 year	Air pollution observation
Sentinel-5	expect 2021-2022 launch	Life expectancy 7.5 year	Atmospheric monitoring
Sentinel-6A	2020.11.21	Running , Life expectancy 5.5 year	Global ocean topography survey
Sentinel-6B	expect 2025 year 12 Monthly launch	Life expectancy 5.5 year	Global ocean topography survey
Sentinel-7	There is no time for this	no	Anthropogenic carbon dioxide emission monitoring
Sentinel-8	There is no time for this	no	High space-time surface temperature monitoring
Sentinel-9	There is no time for this	no	Polar snow and ice terrain altimeter
Sentinel-10	There is no time for this	no	Environmental hyperspectral imaging
Sentinel-11	There is no time for this	no	Polar imaging microwave radiometer
Sentinel-12	There is no time for this	no	European radar observation system -L Band SAR

Sentry one

brief introduction

Sentinel-1 The mission consists of two polar orbiting satellites Sentinel-1A And Sentinel-1B Make up a constellation , Day and night operation , perform C Band SAR imaging . Available to users Level-0、Level-1 and Level-2 Data products .

sensor

SENTINEL-1 Carry one C-SAR sensor , Working in 5.405 GHz The center frequency of . It includes a right view active phased array antenna , Support fast elevation and azimuth scanning .C-SAR The sensor is in dual polarization （HH + HV,VV + VH） Through a launch chain （ You can switch to H or V） And two parallel supports to realize the operation receiving pair H and V Polarization chain . Dual polarization data can be used for land cover classification and sea ice application .

Sentinel-1 There are four acquisition modes ：

• Strip chart (Stripmap,SM)
• Interference width (Interferometric Wide swath,IW)
• Ultra wide (Extra-Wide swath,EW)
• Wave mode (Wave mode,WV).

Strip chart (SM) Pattern :

The narrow width of this mode is 80 km , Provide 5 m x 5 m Resolution image .Sentinel-1 By changing the beam incidence angle and elevation beam width , The user can select one of the six imaging strips .

Interference width （IW） Pattern :

The model is Sentinel-1 Default acquisition mode on land , The narrow width is 250 km , Provide 5 m x 20 m Resolution image .

Sentinel-1 In this mode , Use TOPSAR technology . Except image SCANSAR Control out of beam in range , The beam can also be electronically controlled from back to front in the azimuth direction of each pulse train , Avoid flaring and produce higher quality images . Doppler spectrum （ In the azimuth domain ） And wavenumber spectrum （ In the elevation domain ） The sufficient overlap of ensures the interferometry .

Ultra wide （EW） Pattern ：

This mode is mainly used for offshore and polar region operation services , Meet the requirements of wide coverage , Short revisit time requirements .

EW The mode works like IW Pattern , use TOPSAR technology , Use five subbands instead of three , Resulting in low resolution （20 m x 40 m）.EW Patterns and IW Similar model , It can also be used in interferometry .

The waves （WV） Pattern

SENTINEL-1 Of WV The model is combined with the global wave model , To determine the direction of waves on the ocean 、 Wavelength and height .

The wave pattern consists of 20 km x 20 The strip image of kilometers consists of , The sensor alternately collects data at two different incident angles . Every time 100 Km acquisition of primary wave image , Images with the same incident angle are separated 200 km .

Product introduction

Currently available on the ESA website 4 Product data download , It's the raw data RAW、SLC、GRD and OCN.

The processing steps involved in generating primary data products include preprocessing 、 Doppler centroid estimation 、 Single view multifocus 、 Generate SLC product 、 Generate GRD product 、 Image post-processing and mode specific processing for assembling multiple sub images . The specific generation process is as follows :

1 Level data can be processed into single view complex numbers (SLC) and / Or ground range detection (GRD) product .

SLC The product retains the phase information and processes it with natural pixel spacing .

GRD The product contains the detected amplitude and performs multi view to reduce the effect of speckle .

OCN Is aimed at Wave Mode To launch the 2 Class a products .

Data download

Only what I know now , There are four ways to download ：

• ESA official website (https://scihub.copernicus.eu/)
• Geospatial data cloud (http://www.gscloud.cn/)
• Google Earth Engine (https://code.earthengine.google.com/)
• PIE Engine (https://engine.piesat.cn/engine/home)

I recommend you to use Geospatial data cloud Download , There are two main reasons ： The data is updated in time ; Domestic download Fast .

Geospatial data cloud operation is relatively simple , No more introductions . Here is the download tutorial on the official website ：

Enter the official website of ESA （https://scihub.copernicus.eu/）：

Click to enter Open Hub, If you have an account, log in directly , No account click Sign up：

Fill in personal data as required , Click when finished Register：

Then a window will pop up , You need to go to your mailbox to activate your account , Go to your mailbox and jump to the activation link ：

After the account is activated , Log in to the main page , Click the left mouse button to check the image of the area to be downloaded ：

Click on the data bar , Data filtering ：

In the data filter column , Selection time （ Two hours sensing period and ingestion period, Personal understanding is the sampling time and warehousing time , No relevant information was found , Generally speaking, choose sensing period That's it ）、 Polarization mode 、 satellite 、 Product type, etc ：

Click the search button , The corresponding image will pop up , Click download ：

Sentry two

Sentinel-2 The mission consists of two polar orbiting satellites Sentinel-2A（2015 year 6 month 23 Launch Sunday ） and Sentinel-2B（ 2017 year 3 month 7 Launch Sunday ） form , Distributed in the same solar synchronous orbit , Each other becomes 180° phase , Width is 290 km .

Band introduction

each Sentinel-2 Satellites carry a multispectral instrument (MSI), In visible light 、 Near infrared and short wave infrared spectral ranges are common 13 Band .

Band	Central wavelength (µm)	Spatial resolution (m)
Band 1 - Coastal aerosols	0.443	60
Band 2 – blue	0.490	10
Band 3 – green	0.560	10
Band 4 – red	0.665	10
Band 5 – Red edge of vegetation	0.705	20
Band 6 - Red edge of vegetation	0.740	20
Band 7 - Red edge of vegetation	0.783	20
Band 8 – The near infrared	0.842	10
Band 8A - Red edge of vegetation	0.865	20
Band 9 – Steam	0.945	60
Band 10 – Shortwave infrared － Cirrus clouds	1.375	60
Band 11 - Shortwave infrared	1.610	20
Band 12 - Shortwave infrared	2.190	20

Product introduction

at present Sentinel-2 It mainly provides two kinds of product data ：L1C and L2A.

L1C： The product has been ortho corrected and sub-pixel geometric precision corrected , Is the zenith apparent reflectance data , Each image is 100 km x 100 km , It's about the size of 500 MB.

L2A： The product is provided by ESA Sen2cor Tools , Yes L1C Surface reflectance data products are obtained by atmospheric correction . from 2016 year 10 Data for the whole of Europe are available from January , from 2017 year 1 Global data available since January .

Data download

Data download method

According to the information found by the author , At present, you can download Sentinel-2 Video websites have 5 individual , Respectively ：

Website	website	remarks
ESA official website	https://scihub.copernicus.eu	Official website
Geospatial data cloud	http://www.gscloud.cn	Update one week later
Google Earth Engine	https://earthengine.google.com	The most reliable cloud computing platform , Timely and comprehensive data
PIE Engine	https://engine.piesat.cn/engine/home	defect 2017 Years ago
Microsoft Planetary Computer	https://planetarycomputer.microsoft.com	Only L2A Level data

Download method on the official website

We use the official website to download data ：

Reference sentry 1 Data download mode of satellite No , Register your account and enter the main page , And check the study area , Selection time ：

Sentry two has 4 Parameter selection , Select the satellite 、 Product category 、 Relative orbit book 、 Cloud coverage , Generally speaking, only the product level and cloud coverage are selected . We need to pay attention to , Cloud coverage is selected in brackets with conditions , such as [0 TO 10] Means that only cloud coverage is selected in 0-10% The image of ：

After filtering, you can click download ：

If you are downloading images from years ago , It is possible that the image has been taken off the shelf , You need to submit an application , You can download it in about a day . For example, I want to download 2019 In the Beijing area Sentinel-2 L2A data ,

At this time, it shows that the data has been removed from the shelf , You need to add to the shopping cart , Click download again and the data will pop up and be put on the shelf again , One week at the latest , The shortest 1 The data can be downloaded within days .

GEE Download data

The data download method of the official website also needs to do band synthesis locally 、 Crop and inlay , Even when the data has been taken off the shelf . Therefore, the author generally does not like downloading from the official website .

If you just want to download sentinel data for an area , No research , You can consider directly GEE download , Convenient and quick . Here is a simple data download script , For reference only ：

// Study area visualization 
Map.addLayer(roi)
Map.centerObject(roi,9)

// Time 
var startDate = ee.Date('2021-5-27'); 
var endDate = ee.Date('2021-8-31');  

var collection = SENTINEL
                  .filterDate(startDate, endDate)// Time to filter 
                  .filterBounds(roi)// Location filtering 
                  .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE',10))// Cloud cover filtering ,
                  .sort('CLOUDY_PIXEL_PERCENTAGE')// Cloud sort 
                  .first()                  ;// Select the image with the lowest cloud cover 
// Crop the study area 
var image=collection.clip(roi);
// Select the exported band 
image=image.select([ "B2", "B3", "B4", "B8"]);
// Load false color image 
Map.addLayer(image, imageVisParam, "image- False color ");
// Load true color image 
Map.addLayer(image, imageVisParam2, "image- True color ");
// export 
Export.image.toDrive({
    
  image: image,
  description: 'ROI',
  scale: 10,
  region: roi,
  maxPixels:1e13
});

A runnable link to the complete code ：

https://code.earthengine.google.com/2af1e4b4d6ce7eeb6a2e029c29266748

Sentry three

By 2021 year 12 month ,Sentinel-3 from 2 Satellites make up ：Sentinel-3A and Sentinel-3B. ESA plans to launch the project in 2024 Years and 2028 launch Sentinel-3C and Sentinel-3D satellite , In order to ensure that Sentinel-3 Continuity of tasks .Sentinel-3 It is also currently equipped with Sensors up to A satellite of , total 7 Class a sensors .

sensor

Here's the difference Sentinel-3 Can you introduce the sensor of ：

• Land sea surface temperature radiometer （SLSTR）： To determine the global sea surface temperature . It is measured in nine spectral channels and two additional bands , To optimize fire monitoring . The first six spectral bands cover visible light 、 Near infrared spectroscopy and short wave infrared spectroscopy ;VNIR Applicable to frequency band 1 to 3,SWIR Applicable to frequency band 4 to 6. this 6 The spatial resolution of frequency bands is 500 m, Frequency band 7 to 9 And the spatial resolution of the other two frequency bands is 1 km .

• Ocean and land color instruments （OLCI）： A medium resolution imaging spectrometer , It uses five cameras to provide a wide view .OLCI Yes 21 A spectral band , Wavelength ranges from optical to near infrared . The band width ranges from 400 nm To 1020 nm Unequal , It can be used to measure water vapor absorption 、 Aerosol levels and chlorophyll uptake .SLSTR and OLCI Is an optical instrument with overlapping paths , Allow new combined apps . Due to climate change , Inland coastal areas have become more and more concerned areas , from 2002 Year to 2012 year , Medium resolution imaging spectrometer (MERIS) Provides high quality observations for analysis .OLCI Yes MERIS Improved , Because it adds six spectral bands 、 Higher signal-to-noise ratio (SNR)、 Reduced sun glare 、 Maximum 300 m Spatial resolution and increased ground coverage , This is currently in space The only way to detect cyanobacteria Sensor .

• Synthetic aperture radar altimeter （SRAL）： Topographic instruments , But in the sea ice 、 ice sheet 、 Provide accurate topographic survey on rivers and lakes . It uses dual frequency Ku and C Band , Microwave radiometer calibrated by atmosphere (MWR) And orbital positioning DORIS The receiver supports .

• Satellite integrated Doppler orbit map and radio positioning (DORIS) ： A receiver for track positioning .

• Microwave radiometer （MWR）： Measure water vapor 、 The amount of water in the clouds and the thermal radiation from the earth .MWR The radiation accuracy of the sensor is 3.0 K.

• Laser retroreflector （LRR）： It is used to accurately locate on orbit satellites using laser ranging system . When and SRAL、DORIS、MWR When used in combination , They will obtain detailed topographic survey results of the ocean and inland waters .

• GNSS （GNSS）： Provide accurate orbit determination and can track multiple satellites at the same time .

Product type introduction

SLSTR：

Level-1 After quality control 、 Orthophoto positioning （ Latitude and longitude coordinates 、 Height ）、 Landmarks and preliminary pixel classification （ Land, for example / water / Cloud mask ）.

Level-2 It's from Level-1 Geophysical quantities are derived from the measurement data provided in the product , Dedicated to marine and land applications .

**OLCI **：

Level-1 Including the atmospheric roof (TOA) Radiation measurement 、 Radiometric correction 、 Calibration and spectral characterization .

Level-2 It's from Level-1 Geophysical quantities are derived from the measurement data provided in the product .

**Synergy **:

SYN Level-1 Handle OLCI and SLSTR Radiance and brightness temperature , Its associated comments are calculated in the same way . Also calculate OLCI Reference channels and all others OLCI and SLSTR The corresponding grid between channels .
SYN Level-2 Processing comes from OLCI and SLSTR Instrument information , Provide improved data for surface analysis .

Altimetry ：

Level-1 yes Level-0 Data after instrument calibration .
Level-2 yes Level-1 Data after geophysical correction .

Data download method

According to the information found by the author , Now you can download all Sentinel-3 Video website Only the ESA website （https://scihub.copernicus.eu）,GEE Can only download OLCI EFR image , Therefore, the download method of the official website is adopted ：

Reference sentry 1 Data download mode of satellite No , Register your account and enter the main page , And check the study area , Selection time ：

Select the corresponding sentinel 3 product data （ Due to product type options and sensors 、 Level data is irrelevant , It is only recommended to check the condition in the product type or the corresponding sensor ）：

Choose the right data , Download data ：

Sentry four

Sentry four No launch yet , The main objective of the satellite is to monitor Over Europe Air quality and aerosols , Support Copernicus atmosphere monitoring service with high spatial resolution and fast revisit time (CAMS). The satellite will be developed by the European Union 、 European space agency (ESA) With the European Environment Agency (EEA) Co operation .

Sentry five

The satellite No launch yet , expect 2021-2022 launch .Sentinel-5 Will focus on air quality and composition - Climate interaction , The main data products are O₃、NO ₂、SO₂、HCHO And aerosols . Besides ,Sentinel-5 It will also provide CO、CH₄ The stratosphere O₃ Quality parameters of , Cover the global climate every day 、 Air quality 、 ozone 、 Surface ultraviolet image .

sentry 5p

sentry 5p On 2017 year 10 month 13 Japan successfully launched from Russia's Plesetsk space launch site , Have a portable tropospheric monitoring instrument (TROPOMI) sensor , The main objective is to perform atmospheric measurements with high spatial and temporal resolution , For air quality 、 Ozone and ultraviolet radiation and climate monitoring and prediction .

[ Failed to transfer the external chain picture , The origin station may have anti-theft chain mechanism , It is suggested to save the pictures and upload them directly (img-CnZbrAlQ-1639768610373)(C:\Users\CR\AppData\Roaming\Typora\typora-user-images\image-20211218023923296.png)]

sensor

Tropomi（TROPO spheric Monitoring Instrument, Tropospheric monitor ） It can sense ultraviolet （UV）、 Visible light （VIS）、 near （NIR） And short wave infrared （SWIR）, To monitor ozone in the atmosphere 、 methane 、 formaldehyde 、 Aerosol 、 carbon monoxide 、NO₂ and SO₂ .

Tropomi One measurement per second , Cover about 2600 Kilometers wide and 7 Kilometer long area , A resolution of 7 x 7 km . The sensor is separated into different wavelengths by a grating spectrometer , Then four different detectors are used to measure the respective spectral bands .UV The spectral range of the spectrometer is 270-320 nm, The range of visible light spectrometer is 310-500 nm,NIR For the range of 675-775 nm,SWIR For the range of 2305-2385 nm.

Data download

The official website does not provide Sentinel-5P Data download , But it can be used GEE and PIE Download data .

stay GEE in , A total of 18 Kind of Sentinel-5P Download of product data , Readers can choose to download according to their needs .

For data download methods, please refer to sentry 2 The no. GEE Data download method , Simple code , I will not elaborate here .

Sentry six

Sentinel-6 The first satellite of 2020 year 11 month 21 Launch Sunday , It is mainly used for global ocean monitoring . In addition, the satellite is equipped with sensors to collect atmospheric data , For improved weather forecasting and hurricane tracking .

sensor ：

Sentinel-6 The satellite carries three kinds of sensors , Namely ：

Poseidon-4：Ku/C Band sky bottom pointing synthetic aperture radar （SAR, Limited to Ku Band ） altimeter ;

AMR-C： Multi frequency advanced microwave radiometer for climate ;

HRMR： An experimental high-resolution microwave radiometer for enhancing the measurement of atmospheric parameters in coastal areas

Data download

Although the satellite has been launched , But the author The download method of relevant data is not found .

You can try NASA released 27 view Sentinel-6 Of Sample data , Download at ：https://podaac.jpl.nasa.gov/Sentinel-6?sections=data.

Sentry seven - Sentry twelve

At present, ESA has not disclosed any more details , Follow up satellites have made progress , Will be in “ Geoscience remote sensing data collection ” Website （www.gisrsdata.com） Update on ：

Sentry tools

For the processing and use of sentry series data , ESA has developed numerous toolkits in conjunction with a range of agencies , Specific for ：

SNAP

SNAP Is applicable to all Sentinel The general architecture of the toolkit , Is currently the most widely used Sentinel Tools .

SNAP It is very suitable for earth observation processing and analysis .

Download at ：http://step.esa.int/main/download/snap-download/

S1TBX

S1TBX Is dealing with Sentinel-1 Data toolbox , For calibration 、 Speckle filtering 、 Registration 、 Orthorectification 、 set 、 Data conversion 、 Polarization measurement and interferometry .

Download at ：http://step.esa.int/main/download/

Atmospheric Toolbox

Atmospheric Toolbox It is used for ingestion 、 Tools for processing and analyzing atmospheric remote sensing data . The tool box is made up of CODA、HARP、VISAN and QDOAS Four-part composition .

Download at ：https://atmospherictoolbox.org/

Broadview

ESA and CNES Jointly developed open source tools for height measurement Broadview.

The tool can read all altimetry data from the official data center （ERS -1 、ERS -12、Topex/Poseidon、Geosat Follow-on、Jason-1、Envisat、Jason-2、CryoSat and Sentinel-3）, And conduct high-level data processing and visualization .

PolSARpro

PolSARpro Used to develop polarization SAR data .

Download at ：https://step.esa.int/main/toolboxes/polsarpro-v6-0-biomass-edition-toolbox/

CFI

Earth Observation CFI Software is used for timing 、 Coordinate transformation 、 Orbital propagation 、 Precompiling of satellite pointing calculation and target visibility calculation C Library collection .

Download at ：https://eop-cfi.esa.int/index.php/mission-cfi-software/eocfi-software/branch-4-x

ESOV NG

The tool is used as all ESA A tool for strip visualization of satellite instruments , And help users understand the time and place of satellite measurement .

https://earth.esa.int/eogateway/tools/esov-software-tools-esov-ng-

There are many other official and third-party sentinel data related tools , There will be no more detailed description here , Those who are interested can go Google once .

Reference resources

https://scihub.copernicus.eu/

https://docs.sentinel-hub.com/

https://www.mdpi.com/2072-4292/11/17/1969/htm

https://en.wikipedia.org/wiki/Copernicus_Programme

https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1/instrument-payload

At the end

1.Sentinel There are many satellite data products , From sentinel two, which has been widely recognized , To sentinel 12, which is still under planning , Let me smell the local tyrant of ESA .

2. Almost all the information listed in this article comes from ESA's official website and Wikipedia , Ensure the reliability of information .

3. Limited by the author's knowledge level and English ability , The tutorial may not be entirely accurate . If in doubt , It is recommended to find the answer in the reference website I listed . Try not to trust the information on the Chinese Internet , Including my tutorial , Because translation will inevitably lead to inaccuracy of information .

4. There are new updates to the follow-up sentry images , I will be in time “ Geoscience remote sensing data collection ” Add, delete, modify and query on , Welcome to your attention （www.gisrsdata.com）.