ISRO’s most useful satellite is pointed not at the Moon but at the water, telling a fisherman where not to waste diesel – and it cannot see a single fish.
In brief
- India parked a satellite roughly 800 kilometres up to help nearly four million people catch fish, and it never sees one. It reads the colour of water. Colour points to plankton. Plankton points to dinner.
- The resulting advisories carry coordinates, depth and bearing to 586 fish-landing centres in regional languages. The hardware has reached the boat. The software largely has not: in one survey of 420 fishermen, 90% used no fishing app at all.
- The half of the space programme nobody photographs is the half that pays for itself – in diesel not burned, and in the 20,000-plus distress terminals that tell a boat when to turn back.
At four in the morning, a fisherman loads nets, ice, diesel and a day’s food, and pushes off into the only workplace on earth with no signage. Roads have boards. Airports have boards. Runways are practically over-signed. The sea has nothing – no arrow reading mackerel, 40 km ahead. He can steam for six hours and come home having burned fuel to catch water.
This is not a fringe hardship. Close to four million Indians work this unmarked ocean for a living, along a coastline of some 7,500 kilometres that stubbornly refuses to label itself.
So India built the signboard anyway. It sits about 800 kilometres up, moves at roughly seven kilometres a second, and – here is the joke at the centre of the whole enterprise – it cannot see a single fish.
The board that does not exist. What an INCOIS advisory actually contains: coordinates, depth, direction and distance from a landmark the crew already knows.
Illustrative values in the advisory format issued daily. Source: INCOIS, Ministry of Earth Sciences
The satellite does not find the fish
ISRO’s EOS-06, the third satellite in the Oceansat series, observes ocean colour, sea-surface temperature and wind. Its Ocean Colour Monitor watches for small shifts in the shade of seawater – shifts that betray the presence of chlorophyll.
Chlorophyll means phytoplankton. Phytoplankton means small fish. Small fish mean bigger fish arriving for dinner. So ISRO does not spot a pomfret from orbit. It finds the restaurant.
How does colour become a catch? Tap a step
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The Indian National Centre for Ocean Information Services, or INCOIS, turns those readings into Potential Fishing Zone advisories: coordinates, depth, direction and distance from a landmark the crew already knows. Daily information goes out to 586 fish-landing centres, in regional languages.
The division of labour is elegant. ISRO reads the ocean. INCOIS interprets it. Navigation and communication gear lets the fisherman act on it. India has effectively built Google Maps for a road that moves every day.
The fisherman is more digital than we imagine
The stereotype of the Indian fisherman navigating by instinct alone is out of date. A survey of 420 fishermen, largely from coastal Karnataka, found that 44.5% routinely travelled between 100 and 500 kilometres to fish, and a further 3% went beyond 500. Nearly three-quarters used GPS, wireless sets or fish-finders to measure distance.
That is a very long way to go looking for something that keeps moving. The same survey then turned up a wonderfully Indian contradiction. The hardware had reached the boat. The software had not.
A satellite in the sky. A GPS on the boat. And sometimes, a rope over the side.
This is not evidence that traditional knowledge has failed. It is evidence of the opposite: technology works best where it supports experience rather than pretending to replace it. The satellite suggests where the water looks promising. The fisherman still decides whether the sea feels right.
Sometimes the signboard says: turn back
Finding fish is only half the job. ISRO’s second-generation Distress Alert Terminal lets a crew in trouble send an emergency message by satellite. The alert carries the boat’s identity and position to a control centre and onward to the Coast Guard’s rescue coordination system. More than 20,000 first-generation terminals were already at sea when the upgraded service went live in 2024.
The new version can send an acknowledgement back to the boat. That small feature matters enormously.
What happens after the button is pressed? Send an alert
In the middle of an ocean, your distress alert has been received may be the most reassuring sentence a person can read. The same channel carries cyclone and tsunami warnings and fishing-zone information, routed to a mobile phone and read in the fisherman’s own language.
Space technology stops being impressive the moment it leaves the laboratory. It becomes valuable when it reaches the person who needs it.
A signboard, not a guarantee
A Potential Fishing Zone is exactly that – potential. The ocean moves. Wind shifts the zone. Cloud blocks optical observation for days at a stretch. Fish do not sign contracts promising to stay where the satellite last saw favourable conditions. INCOIS says as much itself, which is why wind speed and direction ride along in the advisory.
And efficiency has to be matched by management. Technology can cut wasted diesel; it cannot manufacture more fish. Pointing crews faster at a shrinking stock is not a triumph. That caveat does not weaken the achievement. It makes it honest.
India’s Moon and Mars missions produce spectacular photographs. This one produces coordinates, warnings and quieter engines. No countdown. No cheering control room. Just a boat changing direction before it wastes another tank of fuel.
The glamorous half of the space programme looks upward. The half that quietly pays for itself looks down – and points a fisherman towards his catch, or back towards home.
A version of this article first appeared in BusinessWorld.