BackForwardInstrument:  MERSI-LL 

Instrument details
Acronym MERSI-LL
Full name Medium Resolution Spectral Imager - Low-Light
Purpose Multi-purpose imagery with low-level light capability
Short description
  • 7-channel VIS/IR spectro-radiometer, with one VIS operable with low-level illumination and 6 MWIR/TIR [see details in table below]
  • Calibration monitoring here
Background

Derivative of the 25-channel MERSI-2 flown on FY-3D, replacing the 19 SW channel by a Low-light VIS channel, for use in a dawn-dusk orbit
Scanning Technique

Cross-track: 2048 samples for channels at 1000 m resolution at nadir, or 8192 samples for channels at 250 m resolution, swath 2900 km - Along-track: ten 1-km lines every 1.5 s.
Resolution 500 m or 1.0 km at s.s.p.
Coverage / Cycle Global coverage twice/day (including VIS).
Mass Power Data Rate

 

Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: 2021 to 2034
Last update: 2024-09-09
Detailed characteristics

Center wavelength

Bandwidth

SNR or NEΔT @ specified input

IFOV at s.s.p.

0.70 μm

0.5-0.9 μm

7.0 @ 4.0e-5 W m-2 sr-1 μ-1(LowLight)

200 @ 50.0e-5 W m-2 sr-1 μ-1 (daytime)

1000 m

3.80 μm

0.18 μm

0.25 K @ 300 K

1000 m

4.05 μm

0.155 μm

0.25 K @ 300 K

1000 m

7.20 μm

0.50 μm

0.30 K @ 270 K

1000 m

8.55 μm

0.30 μm

0.25 K @ 270 K

1000 m

10.8 μm

1.0 μm

0.3 K @ 300 K

250 m

12.0 μm

1.0 μm

0.3 K @ 300 K

250 m
Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • Moderate resolution optical imager
WIGOS Subcomponents
  • Subcomponent 1
  • VIS/IR imagery; realisation of a Day/Night band [in SSO]
  • VIS/IR imager [in SSO]
  • VIS/IR imager with day/night capability [in SSO]]
Mission objectives
Primary mission objectives
  • Cloud cover
  • Cloud top height
  • Cloud top temperature
  • Fire fractional cover
  • Sea surface temperature
Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
Note: * Primary mission objective.
VariableRelevance for measuring this variableOperational limitationsExplanation
Cloud cover*3 - highNo specific limitation.VIS, MWIR and TIR channels
Cloud top height*3 - highNo specific limitation.TIR channels in window and water vapour band (for emissivity) to estimate cloud top height from its temperature
Cloud top temperature*2 - very highNo specific limitation.TIR channels in window and water vapour band (for emissivity)
Cloud type3 - highNo specific limitation.VIS, MWIR and TIR channels
Downward long-wave irradiance at Earth surface4 - fairCloud sensitive.. Highly indirect.MWIR and TIR channels including the water vapour band
Fire fractional cover*4 - fairCloud sensitive.. Coarse spatial resolution.VIS, MWIR and TIR channels
Fire radiative power2 - very highCloud sensitive.. Coarse spatial resolution.MWIR and TIR channels
Fire temperature2 - very highCloud sensitive.. Coarse spatial resolution.MWIR and TIR channels
Land surface temperature3 - highCloud sensitive.MWIR and TIR window channels (high sensitivity to high temperature, cloud impact reduction, water vapour correction)
Sea surface temperature*2 - very highCloud sensitive.MWIR and TIR window channels around 3.7 and 11 micrometers (cloud impact reduction, water vapour correction)
Sea-ice cover4 - fairCloud sensitive.VIS, MWIR and TIR channels
Snow cover5 - marginalCloud sensitive.. Daylight only.VIS channel(s)
Soil moisture at surface4 - fairCloud sensitive.. Index only.VIS and TIR window channels. Soil moisture inferred from thermal inertia
Integrated Water Vapour (IWV)2 - very highCloud sensitive.TIR channels around 6.3 micrometers and in the 11 micrometers split window
Upward long-wave irradiance at TOA5 - marginalSpectral interpolation needed.MWIR and TIR channels in windows around 3.7 and 11 micrometers, and in the water vapour band around 6.3 micrometers
Upward long-wave irradiance at Earth surface4 - fairCloud sensitive.. Highly indirect.MWIR and TIR channels in windows around 3.7 and 11 micrometers, and in the water vapour band around 6.3 micrometers
Wind (horizontal)4 - fairLimited to high latitudes.. Cloud or water vapour tracers needed.TIR channels in the 11 micrometers window and the 6.3 micrometers water vapour band