From the website of the company ‘Planet’, published the same day the ISRO satellites were launched:

Today Planet successfully launched 88 Dove satellites to orbit — the largest satellite constellation ever to reach orbit. This is not just a launch (or a world record, for that matter!); for our team this is a major milestone. With these satellites in orbit, Planet will reach its Mission 1: the ability to image all of Earth’s landmass every day.

This constellation therefore formed the majority (88 of 104 satellites launched) of the payload carried by the last ISRO launch. As of this launch, Planet is operating 149 satellites in Earth orbit — this is no mean feat.

Also, an interesting side note: ISRO’s previous largest payload that I referred to in my last post — 20 satellites launched in June 2016 — also seems to be for this same company:

This is our 15th launch of Dove satellites and second aboard India’s PSLV. The launch of Flock 3p comes off the successful launch of Flock 2p on the PSLV in June 2016

Indian Space Research Organisation (ISRO) scripted history today by successfully launching a record 104 satellites, including India’s earth [sic] observation satellite, on a single rocket from the spaceport in Sriharikota. This is the highest number of satellites ever launched in a single mission.

The previous record was held by Russia, with 37 satellites launched at one go. The 104 satellites include 3 of India’s own and 101 of ISRO’s international customers, including 96 from USA. (The article states ISRO’s previous record as 23 satellites launched together in June 2015, but I can’t find a record for that. The closest I could find was this: 20 satellites launched in June 2016.)

As much as this is making news, and as much as ISRO should be proud, this should come as no surprise for space enthusiasts— ISRO has been quite a force in space technology, especially using its PSLV launch system, for quite some time now.

The four stage Polar Satellite Launch Vehicle (PSLV), used for this launch, was developed by ISRO in the 1990s to launch satellites into Sun-synchronous orbits for its own remote sensing satellites. (Other than ISRO, only Russia commercially launches satellites into Sun-synchronous orbits.) PSLV was also used by ISRO for Chandrayaan 1, its lunar probe, and Mangalyaan, its Mars orbiter, becoming only the fourth space agency to reach Mars orbit.

As an aside, the Sun-synchronous orbit is a very interesting concept: it is an orbit where the satellite passes over any given point on Earth’s surface at the same local solar time. This allows the satellite to be in constant sunlight as it passes over particular regions— which is great for imaging, remote sensing, spying and weather applications. The technicalities of such an orbit are very involved and very interesting: look up the Wikipedia page I’ve linked to above.

Fun fact: due to the mechanics of the orbit, a sun-synchronous orbit is stable without external thrust only on oblate spheroid planets. This means that such orbits work on Earth and will work on Mars, but on almost spherical planets such as Venus, it will require external thrust to maintain its orbit.

Must watch. Worth every second of the 7 minutes you will invest.

I know this can be hard to picture in your head, but the beauty of it is that once you do, this map sings. You can instantly see what’s what: the motion of the gas, where it’s more dense than other locations, how it’s distributed. It also shows our location in the galaxy! All those changing velocities depend on the Sun’s velocity, the velocity of the gas, but also the direction of the Sun’s motion and its position in the Milky Way’s disk. That’s a stunning amount of information.

This is fascinating.

If you like card tricks, you’ll love this.