Iridium satellite constellation is about:

Iridium communication owned Iridium satellite constellation provides voice and data coverage to satellite phones, pagers, and integrated transreceiver over the entire earth surface, the idea of this concept was to cover every surface of Earth at every moment, the constellation consists of 66 active satellites in orbit(low Earth orbit) to provide global coverage(+ additional satellites in case of failure). With K-a band inter satellite communicate the satellites communicate with one another. The link among these satellites is designed in a way that each satellite has four inter-satellite links, one each to the fore and aft in the same orbital plane and one each to satellite in neighboring plane to either side , this ensure excellent service coverage in N and S poles, the pole to pole orbital velocity is about 100 minutes. Thus the network consists of 6 orbital planes with 11 satellites in each orbit (excluding the spare satellites).

Falcon 9 at  Vandenberg Air Force Base, California (courtesy : twitter @SpaceX)

Special about Iridium satellite constellation:

1.     4 inter-satellite links (2 in the same orbital plane and 1 each in the adjacent plane) this allows network handoff traffic among the satellites to deliver the signals with lower latency, redundancies, and a continuous connection.

2.      Low earth orbiting satellites completing each orbital revolution in 100 minutes (@ 27360 km/hr ), shorter registration time than the Geostationary earth orbits.

3.     48 spot beams per satellites – each spot comprises of 250 miles in diameter and total 48 beams will form around 2800 miles in diameter, allowing the overlapping and minimizing missed and dropped the connection.

Iridium is now developing its next generation of a worldwide network of telecommunication, Iridium Next.

Iridium NEXT – next-gen satellite network

Iridium has signed a contract with SpaceX to replace it's existing 75 Iridium NEXT satellites (including 9 on-orbit backup satellites) into space on a Falcon 9 rocket over 8 different  

launches, which will be launched at Vandenberg Air Force Base in California. The American aerospace manufacturer and space transport company have made their 14th successful

launch this year – releasing 10 satellites to low Earth orbit, this was the 3rd of 8 planned launches for establishing the Iridium NEXT.

Main engine cutoff and stage separation confirmed. Second stage engine burns underway. Source: twitter @SpaceX

For every space launch by SpaceX, there is a two-stage step. One to release the satellite to the destined orbit and another stage is a recovery run for recovering the Rocket booster that was used during the uplift using a drone-ship. The second stage for recovering the rocket booster used for the launch of Iridium Next satellite was successfully completed and the rocket booster was recovered at the Pacific Ocean marked as ‘Just Read The Instruction’. The next launch at Vandenberg Air Force Base in California. SpaceX is now targeting five subsequent Iridium NEXT launches approximately every two months thereafter. SpaceX hs now planned Iridium NEXT satellite launch fourth launch in late November.