June 18, 2018

Instruments

The 2 Sentinel-2 satellites are each carrying a single scientific instrument called MSI (MultiSpectral Instrument) weighing 290 kg and conceived by Airbus Defence & Space in France.

MSI comprises a set of passive optical sensors that capture light reflected by Earth’s surface and atmosphere. The instrument covers a ground swath of 290 km and the average period of observation over land and coastal areas is 17 minutes (maximum 32 minutes, until the internal processing memory is saturated), generating ‘strips’ of imagery.

The instrument works like a camera, with some features specific to the Sentinel-2 mission:

  • 3 silicon carbide mirrors with very high optical stability collect light and transfer it to two focal plane assemblies (FPAs).
  • Each FPA is designed for a specific frequency range. Of the 13 frequencies observed by MSI, 10 are in the visible and near-infrared (VNIR) and 3 in the shortwave infrared (SWIR).
  • On each FPA, MSI receives light through 12 detectors staggered in two horizontal rows.
  • The signals at each frequency are separated by stripe filters on the detectors and then refined by digital filters.

To protect its sensors from possible solar glare, MSI has a shutter mechanism that is also used for calibration.

As light is acquired through a single channel, the swath is identical for each detector but the spatial resolution varies according to the frequency.

Spatial resolution

Band n°

Sentinel-2A

Sentinel-2B

Wavelength

(nm)

Bandwidth (nm)

Wavelength

(nm)

Bandwidth (nm)

10m

2

496.6

98

492.1

98

3

560.0

45

559

46

4

664.5

38

665

39

8

835.1

145

833

133

20m

5

703.9

19

703.8

20

6

740.2

18

739.1

18

7

782.5

28

779.7

28

8a

864.8

33

864

32

11

1613.7

143

1610.4

141

12

2202.4

242

2185.7

238

60m

1

443.9

27

442.3

45

9

945.0

26

943.2

27

10

1373.5

75

1376.9

76