インドのNavICナビゲーションシステムは、搭載されたルビジウム時計の相次ぐ故障や後継衛星の打ち上げ失敗が重なり、稼働衛星が最低運用数を下回ったためサービスを停止した。

ISRO Spaceflight

🚨 India's indigenous navigation system (NavIC) has officially gone out of service!

As of 13 March 2026, the number of active satellites in the NavIC constellation has fallen to just 3, below the min. requirement of 4 satellites. 🛰

Here is a full timeline of events that caused an entire satellite constellation to go defunct:

After being denied permission by the US to avail navigation services via America's GPS for the Indian Armed Forces during the Indo-Pak war of 1999, India decided to build their own indigenous navigation system, which would come to be known as NavIC.

The first satellite of this system - IRNSS-1A, would be launched in 2013, followed by 8 more satellites (IRNSS-1B to 1I) by 2018 comprising the first generation of NavIC satellites.
One of these satellites (IRNSS-1H) would fail when the payload fairing on its launcher PSLV-C39 failed to separate.

One of the major requirements for navigation satellites is to be able to make extremely precise measurements of time, hence each of the satellites in the first generation of NavIC used three imported Rubidium atomic clocks sourced from a Swiss company called SpectraTime.

However, starting around 2016, a large number of SpectraTime's atomic clocks on ISRO's IRNSS satellites as well as ESA's Galileo satellites began to fail unpredictably.
Within a short span of time, 5 of the IRNSS satellites had become completely defunct as a result of all atomic clocks on them failing.

Taking the lessons from the first generation of NavIC, ISRO developed a second generation which used indigenously developed atomic clocks along with some imported ones.
The first satellite in the second generation (NVS-01) would launch successfully in 2023.

At that point of time, the active satellites in the NavIC constellation were IRNSS-1B, IRNSS-1F, IRNSS-1I and NVS-01 i.e., 4 satellites - equal to the minimum requirement for a navigation constellation to function.

In one of these 4 satellites - IRNSS-1F, two out of its three atomic clocks had already failed.
This meant that if the last clock on that satellite were to fail, IRNSS-1F would go offline, the no. of active NavIC sats would fall to 3, and the whole constellation would go defunct.

In 2025, ISRO would launch NVS-02 to try to ease the burden on a system that was already hanging by a thread. But despite a successful launch into Geostationary Transfer Orbit on GSLV-F15, the satellite failed to reach its target Geostationary Orbit due to a failure in the pyro channel in a main thruster valve of the satellite's propulsion system.

During the initial investigation, ISRO announced that they were unable to pinpoint the exact cause of the valve failure.
Recently, they revealed that the failure was due to at least one of the pins in every single redundant connector on the valve getting disconnected.

As a result, NavIC continued to remain in a precarious situation and ISRO were in a race against time make the necessary corrections and launch NVS-03.

However, this would be followed by repeated failures of ISRO's workhorse PSLV rocket, leading to ISRO suspending all rocket launch activities for a duration of 3 months.

And it was then that on 13 March 2026, the last functioning atomic clock on IRNSS-1F finally failed. The satellite immediately lost the ability to provide positioning and navigation services, bringing the total number of active sats to 3, and hence the entire NavIC constellation now stands defunct.

・2026年3月13日、稼働衛星が3機となり最低運用数4機を下回り、NavICはサービスを停止しました。・初代衛星でSpectraTime製ルビジウム時計が多数故障しました。
・2代目で国産時計を導入し、NVS-01は成功でしたがIRNSS-1Fの最後の時計が停止しました。・NVS-02はGTO到達に失敗（弁のコネクタピン離脱）、PSLVの連続失敗で打上げが停止しました。・これらが重なったぽい。
・画像: 'NavIC'の文字とインド上空をカバーする衛星の図が示されています。

インド NavICナビゲーションシステムのサービス停止

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