Our constellation will soon be lifting-off
TECHNO FLASH #4
Exchanging IoT data between a ground terminal and a satellite at an altitude of 650 km is one thing. Creating and installing a space network with uniform global coverage is another!
1/3 The Kinéis constellation
We imagined – well, calculated for months – that to reduce the maximum interval between two satellite passes (or “revisit times” in space jargon), the best configuration would involve positioning the 25 nanosatellites on five equally spaced orbital planes, i.e., five satellites per plane. These planes were not chosen by chance but as having two very specific characteristics that are particularly useful for our constellation:
- The satellites pass over the Earth’s North and South poles, where they cross each other’s paths. Their rotational motions (in their respective orbits) coupled with those of the Earth, allow each of our 25 satellites to cover the entire surface of the globe, twice a day.
The orbits maintain a constant angle to the Sun, allowing the satellites to be illuminated regularly each day and throughout the year. This optimizes the charging of the batteries by the solar panels… batteries that are needed when the satellites are in the shadow of the Earth!
The orbits maintain a constant angle to the Sun, allowing the satellites to be illuminated regularly each day and throughout the year. This optimizes the charging of the batteries by the solar panels… batteries that are needed when the satellites are in the shadow of the Earth!These orbits are called “Sun-Synchronous Orbits” or “SSOs”.
To correctly position each of the 25 nanosatellites directly into the desired configuration of the constellation, a flexible and tailor-made micro-launcher solution is best. Firstly, since our satellites are the only ones carried by each launcher, we can choose our launch dates and keep full control of our very tight schedule. Secondly, it means we can inject our satellites directly into their final orbit plane, so that we don’t spend unnecessary time and fuel maneuvering them into their final positions. Finally, by using the same launcher, the industrial development and production of the 25 satellites is greatly simplified in terms of design (they have to fit under the same fairing) and testing (they have to withstand the same launch environments).
To put our entire constellation into orbit on five planes, we will thus need five launches of five satellites each!
What is a Kinéis nanosatellite?
It weighs 30 kg, has the shape of a parallelogram with a square base and sides of about 20 to 40 cm (about 16 U), and a total span with antennas extended of about 1.5 m.
Here is an artist’s view of the Kinéis satellite in flight:
In order to take up as little space as possible under the launcher’s fairing, our satellites’ antennas and solar panels are folded away during the launch, they are said to be ‘stowed’.
Here is an image showing the Kinéis satellite in its stacked configuration:
2/3 It’s nearly time for lift-off…
The launch is a very sensitive and stressful phase in the life of a satellite (any way you look at it!). And in our case, the 5 launches will be spread over only a few months.
Our satellites are designed and manufactured in “clean rooms” in cozy and protected environments by our manufacturers in France. After final testing and validation, they are prepared for transport in containers to the Rocket Lab launch pad in New Zealand. Throughout the trip, data on temperature, humidity and impacts inside the container are meticulously recorded.
On arrival, once customs formalities have been completed, they are transported by road to Rocket Lab’s clean rooms. The satellites are inspected, the batteries are given a topping-up charge and final adjustments are made before the flight. These operations take about 2 weeks for 5 satellites.
This is when the combined satellite and launch vehicle operations begin, during which Rocket Lab and Kinéis will work together. This involves integrating the 5 satellites on the launcher dispenser, itself installed on the 3rd stage of Electron, the famous “Kick Stage” propelled by Rocket Lab. Once the final checks have been carried out, the kick stage and the satellites are placed under the fairing. This upper composite is then integrated with the other two stages of the launcher, which is then transported to the launch pad and erected vertically: our satellites are ready for their final journey!
Electron from Rocket Lab
Kinéis chose Rocket Lab’s Electron launcher, which will lift off from New Zealand.
Electron belongs to the category of micro-launchers. It has a carbon structure that is 18 meters high and 1.2 meters in diameter. Its mass at lift-off is 13 metric tons. It has three stages capable of placing a payload of 170kg in SSO orbit at 650km of altitude.
The first stage is powered by 9 Rutherford engines each with a thrust of 24 kN, i.e., each of them can lift a 2.4 metric ton object. It is a bi-propellant, liquid oxygen/kerosene engine fueled by electric turbo pumps.
The second stage is propelled by the same Rutherford engine adapted to the space vacuum with 24.8 kN of thrust.
Finally, the Kick Stage, placed under the fairing, is propelled by a Curie engine, specially developed by Rocket Lab.
Each Kinéis launch will involve the following steps, taking less than an hour in all:
- H0: lift-off
- H0+155s: cut-off of 1st stage
- H0+158s (altitude 78km): separation 1st stage
- H0+162s (altitude 82km): ignition 2nd stage
- H0+184s (altitude 126km): fairing separation
- H0+535s (8 min 90 s): cut-off of 2nd stage
- H0+539s: separation 2nd stage
- Timing selon besoin mission: 3rd stage ignition (Kick Stage)
- Timing selon besoin mission: cut-off of 3rd stage (Kick Stage)
- Timing selon besoin mission: satellite separation
3/3 Once up there, it’s still not over!
Rocket Lab’s mission is completed when all five satellites are injected into the correct orbit, a few seconds apart to minimize the risk of collision. Each satellite then triggers an automatic sequence lasting a few hours in which the on-board computer is switched on, the solar panels and antennas are deployed and the satellite’s attitude is adjusted to point the solar panels towards the Sun. We can then make the first contact with the satellite from the control center.
The 5 satellites launched at the same time are always grouped together. All that remains to be done is to distribute them evenly along the orbit. In fact, the injection altitude is lower than the final constellation altitude (635 km vs. 650 km), which means they are flying on the final orbital plane at a higher velocity than desired. By remote control from our ground stations, we trigger the increase in altitude, one by one, as their respective angular position on the orbital plane is reached. It takes 4 to 5 weeks to complete the positioning using the electric propulsion system.
Before commissioning, all that remains is to check that all the instruments.
All these steps will be repeated 5 times for the launches and 25 times for the satellites at a hectic pace in 2023, but it will be well worth the effort, because the entire constellation will be ready to connect your objects all over the world, within a few weeks of the last launch, and for at least 8 years!