Overview of the Satellites used for capturing TERN’s RS data

Landsat

   The Landsat program is the longest-running initiative for the acquisition of satellite imagery. So far, eight Landsat satellites have been launched. The first one was launched in 1972, although this first mission was not originally called Landsat (but ‘Earth Resources Technology Satellite’). There are currently two active Landsat satellites, Landsat 7 (launched in 1999) and Landsat 8 (launched in 2013). Landsats 7 and 8 are part of NASA’s Earth Observing System (EOS) program. Landsat 9 is expected to be launched in December 2020.

   Landsat 7 and 8 sensors capture data in 8 (from 450 to 900 nm) and 11 (from 435 to 12,510 nm) spectral bands respectively (see Tables 1 and 2). Landsat spectral bands have a moderate spatial resolution (15-60m in Landsat 7 and 30-100m in Landsat 8) and low temporal resolution (16 days for Landsats 7 & 8, both Landsats offset 8 days). For easy downloading Landsat images are often divided into ‘scenes’, each scene measuring 100 x 100 nautical miles (i..e. 185 x 185 kms).

   In the nearly 50 years since the first launch, Landsat satellites have acquired and transmitted to receiving stations around the world millions of images. These images have been used for multiple applications, including: cartography, regional planning, geology, agriculture, forestry, natural resources management, and education.


Table 1. Landsat 7 bands. NIR = Near Infrared. SWIR = Short-Wave Infrared.

Band

Wavelenght (nm)

Resolution (m)

Band Spectrum

1

450 – 520

30

Blue

2

520 – 600

30

Green

3

630 – 690

30

Red

4

770 – 900

30

NIR

5

1,550 – 1,750

30

SWIR 1

6

10,400 – 12,500

60* (30m pixels)

Thermal

7

2,090 – 2,350

30

SWIR 2

8

520 – 900

15

Panchromatic

* Band 6: acquired at 60m resolution, but resampled to 30m pixels in data product.


Table 2. Landsat 8 bands. NIR = Near Infrared. SWIR = Short-Wave Infrared.

Band

Wavelenght (nm)

Resolution (m)

Band Spectrum

1

435 – 451

30

Ultra Blue (coastal/aerosol)

2

452 – 512

30

Blue

3

533 – 590

30

Green

4

636 – 673

30

Red

5

851 – 879

30

NIR

6

1,566 -1,651

30

SWIR 1

7

2,107 – 2,294

30

SWIR 2

8

503 – 676

15

Panchromatic

9

1,363 – 1,384

30

Cirrus

10

10,600 – 11,190

100* (30m pixels)

Thermal 1

11

11,500 – 12,510

100* (30m pixels)

Thermal 2

* Band 10 & 11 (Thermal IRs): acquired at 100m resolution, but resampled to 30m pixels in data product.



Moderate Resolution Imaging Spectroradiometer (MODIS)

   The Moderate Resolution Imaging Spectroradiometer (MODIS) is a payload imaging sensor currently on board of two satellites of NASA’s Earth Observing System (EOS) program (see above), Terra (launched on 1999) and Aqua (launched on 2002). MODIS has now been succeeded by the Visible Infrared Imaging Radiometer Suite (VIIRS). The VIIRS sensor was launched on board the Suomi National Polar-orbiting Partnership (Suomi NPP) in 2011 and will be launched on board the Joint Polar Satellite System, the latest generation of U.S. polar-orbiting environmental satellites and a collaborative effort between NOAA and NASA. 

   The MODIS sensors capture data in 36 spectral bands (from 400 to 14,00 nm) (see Table 3). MODIS spectral bands have a low spatial resolution (2 bands at 250 m, 5 bands at 500 m and 29 bands at 1 km), and a high temporal resolution (together the sensors on board Terra and Aqua image the Earth every 1 to 2 days). 

   MODIS low spatial resolution but high temporal resolution were selected to facilitate the monitoring of large-scale dynamics on land, the oceans, lower atmosphere. Therefore, MODIS can provide substantial aid for tracking changes of ecosystem state and health in space and time. Some specific examples of the use of MODIS derived data in the management of ecosystems include: monitoring vegetation cover (e.g. deforestation), computation of vegetation indices (e.g. NDIV and EVI), identifying large and/or fast snow cover changes, estimating water level changes (e.g. flooding in riverine, lake or coastal areas), as well as the detection and mapping of wildfires.


Table 3. MODIS bands. NIR = Near Infrared. SWIR = Short-Wave Infrared.

Band

Wavelenght (nm)

Resolution (m)

Primary Use

1

620 – 670

250

Land/Cloud/Aerosols Boundaries

2

841 – 876

250

3

459 – 479

500




Land/Cloud/Aerosols Properties

4

545 – 565

500

5

1,230 – 1,250

500

6

1,628 – 1,642

500

7

2,105 – 2,155

500

8

405 – 420

1,000





Ocean Color / Phytoplankton / Biogeochemistry


9

438 – 448

1,000

10

483 – 493

1,000

11

526 – 535

1,000

12

545 – 556

1,000

13

662 – 672

1,000

14

673 – 683

1,000

15

743 – 753

1,000

16

862 – 87

1,000

17

890 – 920

1,000


Atmospheric Water Vapour

18

931 – 941

1,000

19

915 – 965

1,000

20

3,660 – 3,840

1,000



Surface/Cloud Temperature

21

3,929 – 3,989

1,000

22

3,929 – 3,989

1,000

23

4,020 – 4,080

1,000

24

4,433 – 4,498

1,000

Atmospheric Temperature

25

4,482 – 4,549

1,000

26

1,360 – 1,390

1,000


Cirrus Clouds

Water Vapour

27

6,535 – 6,895

1,000

28

7,175 – 7,475

1,000

29

8,400 – 8,700

1,000

Cloud Properties

30

9,580 – 9,880

1,000

Ozone

31

10,780 – 11,280

1,000

Surface/Cloud Temperature

32

11,770 – 12,270

1,000

33

13,185 – 13,485

1,000


Cloud Top Altitude

34

13,484 – 13,785

1,000

35

13,785 – 14,085

1,000

36

14,085 – 14,385

1,000



Satellite Pour l’Observation de la Terre (SPOT)

   The Satellite Pour l’Observation de la Terre (SPOT) is a family of commercial high-resolution optical imaging satellites. So far, seven SPOT satellites have been launched, with the last two-launched remaining active (SPOT 6 launched in 2012 and SPOT 7 launched in 2014). The architecture of the SPOT 6 and SPOT 7 satellites is very similar to that of the Pleiades satellites. SPOT 6, SPOT 7, Pleiades 1A, and Pleiades 1B share the same orbit and altitude placed 900 apart from each other.

   The sensors in SPOT 6 and SPOT 7 capture data in four multi-spectral bands and panchromatic band (see Table 4). SPOT 6 and SPOT 7 spectral bands have a high spatial resolution (1.5 – 6 m).

   Since their release, the SPOT family of satellites has captured and transmitted over 10 milling high quality images. These images have been used to monitor natural phenomena and human activities, as well as to help detect and forecast climatologic and oceanic events.


Table 4. SPOT 6 and 7 bands. NIR = Near Infrared.

Wavelenght (nm)

Resolution (m)

Band Spectrum

450 – 745

1.5

Panchromatic

450 – 525

6

Multi-spectral: Blue

530 – 590

6

Multi-spectral: Green

625 – 695

6

Multi-spectral: Red

760 – 890

6

Multi-spectral: NIR