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Megha Tropiques Payloads

Megha-Tropiques carries the following four payloads:

  • Microwave Analysis and Detection of Rain and Atmospheric Structures (MADRAS), an Imaging Radiometer developed jointly by CNES and ISRO
  • Sounder for Probing Vertical Profiles of Humidity (SAPHIR), from CNES
  • Scanner for Radiation Budget (ScaRaB), from CNES
  • Radio Occultation Sensor for Vertical Profiling of Temperature and Humidity (ROSA), procured from Italy

MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Structures)

MADRAS system is a five channel, self calibrating, microwave radiometer system. The radiometer is designed to estimate atmospheric water parameters and wind speed in the equatorial belt. The choice of the channels has been driven by their potential contribution to the measurement of the parameters defined above.

Geophysical Parameters

  • Rainfall
  • Cloud Ice Content
  • Wind Speed
  • Total Precipitable Water
  • Cloud Liquid Water
Channel No. Frequency Pol NEΔT Spatial Resolution
M1 18.7 GHz H+V 0.5 K 40km
M2 23.8 GHz V 0.5 K 40km
M3 36.5 GHz H+V 0.5 K 40km
M4 89 GHz H+V 1.0 K 10km
M5 157 GHz H+V 1.0 K 6km


SAPHIR microwave humidity sounder and radiometer

Channel No. Centre Frequencies(GHz) Max. Passband (MHz) ΔT(K)Sensitivity at 300 K Absolute Calibration (K) Over 180 - 300K Pol.
S1 183.31 ± 0.2 200 <2 (TBC) ± 1 H
S2 183.31 ± 1.1 350 <2 (TBC) ± 1 H
S3 183.31 ± 2.8 500 <2 (TBC) ± 1 H
S4 183.31 ± 4.2 700 <2 (TBC) ± 1 H
S5 183.31 ± 6.8 1200 <2 (TBC) ± 1 H
S6 183.31 ± 11.0 2000 <2 (TBC) ± 1 H


ScaRaB- Broadband radiation measurement instrument

SCARAB is a four channel instrument mainly measuring in Visible (Sc1), InfraRed (Sc4) along with Solar Radiation (Sc2) and Total Radiation (Sc3). The long-wave irradiance is deduced from the difference between Sc3 and Sc2 measurements. Channels in Visible and IR window, Sc1 and Sc4 are used for scene identification (surface, clouds, partially covered) and for assuring compatibility and comparisons with the images from operational satellites.

Geophysical Parameters

  • Radiation Fluxes
Channel Wavelength Signal Dynamics Noise (Crest)
Sc1-Visible 0.5 to 0.7 µm 120 < 1
Sc2-Solar 0.2 to 4.0 µm 425 < 0.5
Sc3-Total 0.2 to 100 µm 500 < 0.5
Sc4-IR Window 10.5 to 12.5 µm 30 < 0.5


ROSA Radio Occultation Sensor

GPS Radio Occultation sensor enables measurement of water vapour and temperature profiles in the tropics. GPS ROS payload is there to supplement / complement the mission for the atmospheric studies. A GPS ROS payload, ROSA (GPS-ROS) provided by the Italian Space Agency (ASI), is configured as the fourth payload.

Parameter Specification
Frequency L1 1.56 to 1.59 GHz; L2 1.212 to 1.242 GHz
GPS code used C/A and P Code
GPS code used <300 km
Hor Res 0.3 km (Low Troposphere); 1-3 km (High Troposphere)
Vert Res <1 K Temperature; 10% or 0.2g/Kg Humidity