Why MSS or SPOT-HRV does not have the "blue band"

[lybinhan1]

Somebody please help me. I have a question that why the "blue band" was not included in SPOT-HRV sensor? 

On Landsat 4 - TM sensor which have "blue band" from 1982. Why SPOT-1 (1986) and even SPOT-6 (2004) does not have "blue band". The bue band is important which is used to monitor sediment in water, mapping coral reefs, and water depth. So why they did not make that band in SPOT? Is it difficult to make or something? Please help me. Thank you.

[Lurker]

Spot 6 has blue :

http://www.satimagingcorp.com/satellite-sensors/spot-6/

maybe because SPOT aimed for object on land, so they dont need blue   

[Art409]

Landsat-1 (Originally named ERTS-A  for Earth Resources Technology Satellite); Landsat-2 (called  ERTS-B until few time prior to launch, and Landsat 3; and also Spot (Satellite Pour l’Observation de la Terre: Sattellite for Earth observation) prime focus was in terrestrial natural resurces (soils, crops, etc) Landsat was aimed to for geology an Spot for agriculture)

 

Due communication limitations at that time (we talk about hundreds of megabytes by minute in the ’70s) they chose limitated number of bands to survey different spectral signatures, and due just few things got differences in blue band (beyond water) they chose to carry a more usefull close infrared band than the blue one.

 

Regards.
Art

Edited September 15, 2016 by Art409

[lybinhan1]

Thank you Luker and Art409 very much. Now i understand . Have you all a nice day

[Art409]