By Duncan Steel 15/10/2019


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While many imagine that countries like the USA and Europe dominate space activities, in fact India is now a major player on this stage. It launches satellites for its own purposes and also commercially, and has constellations orbiting our planet and returning data of vital importance to that nation in many ways. 

Yesterday I was really pleased to give a short presentation at the annual Summit of the India New Zealand Business Council, in Auckland. The poster for the Summit, as below, shows something important: that agriculture and technological progress are linked with our activities in space (note the rocket launch). In the present-day space game, India is a major player.

Many prominent Indian and New Zealand dignitaries were present, including MPs and the Leader of the Opposition, Simon Bridges, gave a pictorial account of a recent visit he had made to India to discuss trade and cooperation.

For the event I made a short (six-and-a-half-minute) movie, to show the attendees that India has 59 satellites in Earth orbit (plus one circuiting the Moon, and another around Mars) … and also that these satellites come frequently across New Zealand’s skies, and so in principle might be able to deliver useful Earth observation imagery that we could use. If you’d like to watch that movie, click here (it’s a 578 MB download).

Of course, it would not all be one-way: there would be situations in which we could assist India in a variety of ways in terms of space activities, for example providing radio dishes for download, through joint scientific research, and shared educational efforts, to mention but a few.

If you take another look at the header graphic above this blog post you will see a pass near NZ that was made by India’s Oceansat-2 satellite on Monday 14th, the day of the INZBC Summit. The bright green area is my depiction of its sensor coverage, a sweep as the satellite passes from north to south, scanning almost all of NZ’s coastal region plus the continental shelf out beyond the Chatham Islands. This particular satellite is used to monitor such things as the ocean colour, which can give us information about river sediment outflows, chlorophyll washing out to sea seasonally as plants thrive and then die back, blooms of cyanobacteria, and all manner of other matters pertaining to the health of our local seas. That is, NZ scientists could do this, were we able to have imagery collected and downloaded as this and other satellites pass close to our shores.

What I suggested – and was enthusiastically endorsed by the High Commissioner of India, Mr Muktesh K. Pardeshi – was that some sort of teaming agreement might be arranged between the NZ Government and the Indian Space Research Organisation, which operates these satellites. One could give many arguments about how this could benefit both nations.

Just to show you what is possible, in the following graphic I show the orbital paths of the many Indian satellites in low-Earth orbit (below altitudes of about 1,000 km). Some of these are used for astronomical research, or are technology demonstrators, or designed specifically for passes over India… but note that the majority (which I have coloured in the saffron hue of the Indian national flag) are Earth observation satellites in near-polar orbits.

The grouping of those satellites is obvious. By choosing a specific orbital tilt that depends on the altitude, it is possible for the Earth’s asymmetric gravitational field to ‘automatically’ make their orbital planes swivel around at just the right rate to match against the rate at which our planet orbits the Sun. In this way they repeatedly cross the land below at a consistent local time of day, and so we term these “Sun-synchronous” orbits. As can be seen, most often the chosen time-of-day is mid-morning. I set up the above simulation to show the orbits as at 11:00 NZDT on Monday October 14th; these satellites mostly pass over NZ at between 10:00 and noon every day.

Obviously-enough, there are many different satellites to think about, each of them capable of returning data of use to us in NZ if  they actually collected and downloaded imagery during such passes over NZ. Would that not be a wonderful thing for NZ scientists and technologists to have? As I wrote earlier, there is much that NZ could gain from suitable teaming with India – a world-leader in space research – and I would like to think that there is much that NZ might provide in return.

Just to finish off, I note that India also operates several other types of satellite. In geostationary orbit 35,800 km above the equator it has a batch of communications satellites spaced in longitude (making it possible for us in NZ to see the Black Caps playing Test Matches against the Indian team in Mumbai or Kolkata). Also in geostationary orbit India has a handful of meteorological satellites, continuously imaging the Indian Ocean region for weather forecasts and the like, as in the next graphic.

New Zealand has no such satellites: we rely largely on the Japanese Himawari-8 satellite for our weather maps, although the US GOES-17 satellite over the central Pacific can also assist as its coverage encompasses NZ; for information about these satellites, see here.

Another type of satellite constellation operated by India is its own suite of navigation transmitters. Most of the world currently relies on the US military GPS (Global Positioning System) satellites, though new GNSS (Global Navigation Satellite System) constellations are now being operated by the European Union (Galileo), Russia (GLONASS), and China (Beidou). I wrote about such systems here and here.

India, instead, operates a regional system (RNSS), at a higher altitude. The GPS/GNSS constellations are mostly in orbits taking around 12 hours to circuit the Earth. India’s RNSS constellation members are instead in geosynchronous orbits: they are at an altitude of 35,800 km, and so orbit once per sidereal day, but they do not necessarily remain above the equator because their orbits are tilted. In this way India has developed its own independent system for obtaining navigational data and timing synchronisation throughout the sub-continent. For a recent news item about this, see here.

As my post’s title says, India is now a major player in Earth observation from low-Earth orbit – but also has satellites and ambitions far deeper into space.