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INSAT-3D Payloads

The satellite has 3 payloads:

  • Meteorological (MET) - IMAGER and SOUNDER
  • Data Relay Transponder (DRT)
  • Satellite Aided Search and Rescue (SAS&R)

Meteorological Payload

The INSAT-3D spacecraft incorporates advanced Imager and Sounder instruments.

IMAGER

The INSAT-3D imager provides imaging capability of the earth disc from geostationary altitude in one visible (0.52 - 0.72 micrometers) and five infrared; 1.55 - 1.70(SWIR), 3.80 - 4.00(MIR), 6.50 - 7.00 (water vapour), 10.2 - 11.2 (TIR-1) and 11.5 - 12.5 (TIR-2) bands. The ground resolution at the sub-satellite point is nominally 1km x 1km for visible and SWIR bands, 4km x 4km for one MIR and both TIR bands and 8km x 8km for WV band.

SOUNDER

The INSAT-3D sounder has 18 infrared channels distributed over longwave and shortwave bands. A visible channel provides synoptic view of the clouds and the earth to aid in generating three dimensional map of temperature and moisture structure of the atmosphere.

The Sounder is a first time instrument of the geostationary INSAT series designed and developed at ISRO. The overall objective is to measure the temperature and humidity profiles (vertical distributions) to obtain a three-dimensional representation of the atmosphere. The instrument requirements call for soundings at 10 km ground resolution every 3 hours for a full frame scan. This enables the derivation of vertical profiles of temperature and humidity. These vertical profiles can then be used to derive various atmospheric stability indices and other parameters such as atmospheric water vapor content and total column ozone amount.

Telescope aperture 310 mm diameter
Number of bands (6) 18 Infrared + 1 Visible
Band definition Filter wheel with interference filters
IFOV (Instantaneous Field of View) 280 µrad x 280 rad, corresponding to 10 km x 10 km on the surface
Sampling interval 280 µrad E-W / N-S
No of simultaneous soundings 4 per band
Scan step angle 10 km E-W, every 0.1 s, and 40 km N-S after completion of E-W scan, 150 µR rms
Step and dwell time 0.1, 0.2 and 0.4 s
Turnaround time 0.1 s per scan
In-flight calibration Full aperture blackbody and space view
Scan modes Options provided to cater to quick dynamic environmental phenomena
Frame time 160 minutes for 6000 km x 6000 km area sounding
Signal quantization 13 bit/sample
Downlink data rate 40 kbit/s
Frame time 90 kg, (without cooler), 100 W
Band No. Center wavelength µm (cm-1) Bandwidth µm (cm-1) NEDT at 300 K (typical) K
1 14.71 (680) 0.281 (13) 1.5
2 14.37 (696) 0.268 (13) 1
3 14.06 (711) 0.256 (13) 0.5
4 13.96 (733) 0.298 (16) 0.5
5 13.37 (749) 0.286 (16) 0.5
6 12.66 (790) 0.481 (30) 0.3
7 12.02 (832) 0.723 (50) 0.15
8 11.03 (907) 0.608 (50) 0.15
9 9.71 (1030) 0.235 (25) 0.2
10 7.43 (1425) 0.304 (55) 0.2
11 7.02 (1425) 0.394 (80) 0.2
12 6.51 (1535) 0.255 (60) 0.2
13 4.57 (2188) 0.048 (23) 0.2
14 4.52 (2210) 0.047 (23) 0.15
15 4.45 (2245) 0.045 (23) 0.15
16 4.13 (2420) 0.0683 (40) 0.15
17 3.98 (2513) 0.0683 (40) 0.15
18 3.74 (2671) 0.140 (100) 0.15
19 0.695 (14367) 0.05 (1000) (0.67-0.72)   0.1% albedo

 

Communication Payload

 

Communication transponders are required to be configured to provide continuity of some of the INSAT services. A total satellite mass of 2000kg is considered for the launch compatibility, and 70 kg (approximately) of mass apportionment is done for the communication payload components. The communication payload components are - Meteorological Transmitter, Data Relay Transponder, Satellite Aided Search and Rescue (SAS&R) Transponder & S-band Broadcast Satellite Services Transponder.