Satellite

thirteen years to four satellites in your sky. lift each one to where it stays.

a story: raise India's navigation satellites to the one height where they stay, across thirteen years of launches, failed clocks, a rocket that never opened and a valve that never did, until the fourth is in your sky

NavIC is India's own satellite navigation. GPS satellites circle at 20,200 km, twice a day, so each one rises and sets across your sky; ISRO parks NavIC's at 36,000 km, where an orbit takes exactly one day, so they turn with the ground and stay over India. There is only one such height: lower, a satellite runs ahead of the ground; higher, it falls behind. A position needs four in view at once. The story is NavIC's as Wikipedia's IRNSS article lists it (fetched 4 November 2026): IRNSS-1A on 1 July 2013 and six more by April 2016; 1A's three clocks failing from July 2016; 1H lost on 31 August 2017 when the rocket's heat shield failed to separate; 1I in April 2018; NVS-01 in May 2023; NVS-02 on 29 January 2025, left in its transfer orbit because the valves admitting oxidiser to the thrusters did not open (ISRO, February 2025; its Apex Committee of February 2026 found the drive signal was not reaching the pyro valve); and NVS-03 on 30 October 2026, raising its orbit now. As of 2026 three satellites (1B, 1I, NVS-01) could give a position, one short of a fix. This is a toy model: the one under your thumb is a circle at one height, the drag is the burn, the transfer orbit is drawn as the lowest circle, and the years are compressed; every other orbit is a real satellite's from CelesTrak's elements of 2 November 2026, drawn for every year because the slots are the same. 1D, 1F, 1H and NVS-02 are not in today's elements and are not drawn as real orbits. The article dates only 1A's clock failures (and counts nine of twenty-four clocks failed by May 2018, unnamed); the card lets 1C's clocks fail by 2018 and 1E's by 2023, so that three give a position by 2025, which is where the record stands. The Earth is drawn at twice its true size so India can be seen; the heights above it are to scale with each other. At the end, tap another city to read the same sky from there: a satellite parked over India is high in Nairobi's sky and below Tokyo's horizon.

Concepts: orbits, time, navigation.

An interactive you play with one thumb, on Wundr.