The satellite will fly over the same point on the globe at the same angle of view every eight days. However, with a field of view of 34° on either side of the ground track, it will be able to observe points roughly every three days from different angles, covering the entire globe in the same time. Trishna’s cameras have a resolution of 57 metres for observing land surfaces and coasts, and 1 kilometre for the open ocean. The multisensor satellite will observe simultaneously in the thermal and visible domains. This unprecedented combination of spatial and temporal resolution will enable global observation of thermal phenomena at fine scales, notably to aid land planning. Not much will escape the satellite’s beady eye compared to previous missions.
The bus accommodating the instrument payload will supply propulsion, power and orientation to control the satellite’s trajectory. It will be built by ISRO from an existing IRS-1k model adapted to the requirements of the Trishna mission.
- Mass: 770 kg (out of a total satellite mass of approximately 1 tonne)
- Mass storage: 1.4 Tbits of data
- Telemetry data rate: 640 Mbps (satellite-to-ground X-band link)
- Solar panels: 2 kW
The payload will comprise three instruments:
1) Thermal InfraRed (TIR)
Developed by CNES, the TIR telescope will feature four thermal infrared cameras currently in the design phase at Airbus. They will measure Earth’s surface temperatures.
- Mass: 195 kg
- Range: –20°C to +30°C
- Precision: 0.3°C
- Optics: three-mirror anastigmat telescope
- Coverage: four thermal bands (8.6 µm, 9.1 µm, 10.4 µm, 11.6 µm)
2) Visible and Near InfraRed/Short Wave InfraRed (VNIR/SWIR)
Developed by ISRO, this instrument will contain six visible cameras for identifying crop patterns and growth status. For example, amounts of vegetation and its growth status will be visible in each pixel.
- Mass: 90 kg
- Coverage: four visible bands (B1: Blue (485 nm), B2: Green (555 nm), B3: Red (670 nm), B4: NIR (860 nm)) + 2 SWIR bands (B5: Cirrus (1,380 nm), B6: SWIR (1,610 nm)
The VNIR/SWIR instrument will operate in pushbroom mode, building up images line by line in the satellite’s direction of motion. The +34° field of view is obtained by three visible cameras and three SWIR cameras.
3) Millimetre Wave Atmospheric Temperature & Humidity Sounder (MATHS)
This ISRO instrument is not part of the Trishna mission but will be taking advantage of a free berth on the satellite.