From Sensor to Space: how Saft batteries support Satellite IoT connectivity to ensure continuous communication everywhere on earth

Do you know how many satellites you are using in just one single day? 
About 50 on average! Many of the daily services you are probably using, from your TV, Internet, phone, video games, music streaming services, weather reports, to your car GPS, are all using satellites, directly or indirectly. Not no mention the many IoT applications used for the farming, manufacturing, retail, car or health markets. Indeed, it’s estimated that only 10% of the world’s surface has terrestrial connectivity. Satellite IoT connectivity extends the reach of terrestrial network coverage and allows continuous connectivity everywhere on the planet.

Since the launch of the world’s first Commercial Satellite Communications in 1962, the market has expanded at an exponential rate, bringing with it wider bandwidth, increased consumer expectations and a growing competitor market. 
Demands from 5G means cheaper satellites are needed to perform multiple satcoms functions and to ensure that there will be no holes in the 5G coverage map. This is how many IoT connectivity providers such as Deutsche Telekom, Semtech or Sigfox are partnering with space companies to accelerate Internet of Things (IoT) adoption with a more affordable and simplified satellite connectivity. 

By 2027 it is expected that more than 1700 satellites will be launched on average each year for government agencies and commercial organizations worldwide; a threefold increase on the past decade.* (source Satellite Market Research Report – Feb 21)

Saft has been contributing to this development by powering many satellites over the last 57 years with reliable batteries. In space, our batteries are subjected to extremely demanding conditions. Over the years, we have pushed the limits of our batteries to their maximum to meet these constraints. Follow us to discover how satellites are used for communication and how the IoT is benefitting from our space experience… 

How do satellites work? 

Look up, can you see the thousands of stars in the sky? If you are lucky, you might even see some moving and twinkling mainly during summer time. Hold on… They aren’t stars! Satellites orbit the earth by the thousands high above your head. So high, you are unlikely to see them all. They move in precisely calculated loops, circular or elliptical, at varying distances from Earth, usually well outside its atmosphere.

Satellites are placed in space to overcome the various limitations of Earth's geography. They can capture more data more quickly due to their height above the earth. Satellites are used for 3 main purposes: 

• Communication satellites are being used like mirrors: a signal is beamed into space, it then bounces back off the satellite, and is sent back down again to Earth and its destination. 
• Photography, imaging, and scientific surveying satellites gather visual images, or other kinds of data over vast areas of the globe to help us interpret the changes the earth is undergoing or weather patterns including Universe survey using telescopes or radar satellites. 
• Navigation satellites act like sky compasses. 

The function of a satellite influences how far away from Earth it needs to be, how fast it must fly, and the orbit it has to follow. Some turn at the same rotational rate as Earth so they're effectively fixed in one position above our heads (Geostationnary satellites); others go much faster. This is how Thomas Pesquet saw the sun rise 16 times each day from his low orbit spatial station, the ISS. 

Satellites come in low, medium, and high orbit—short, medium, elliptical and long distances above Earth.

Low Earth Orbit (LEO) are the closest ones to earth, just a few hundred kilometers up. They rotate fast as they have to overcome Earth's gravity and can therefore cover large areas of the planet rapidly. LEO satellites are used for applications requiring close proximity such as observation, communication (including the IoT), or exploration. They can transfer signals to ground stations or local antenna very fast —a few tenth of microseconds latency. 1,500 of these satellites are currently launched every year… but this is set to change.

Medium Earth Orbit (MEO) satellites are launched about 10 times higher up than a LEO, roughly 20,000 km above our heads. They can take up to 12 hours to circle the planet. These satellites are used for communication and Global Positioning Systems (GPS). 

Geostationary Orbit (GEO) and Geosynchronous Orbit (GSO) satellites are based at an altitude of roughly 36,000 km in the equatorial plan. They orbit approximately at the same rate as earth which allows them to stay above a fixed point of the earth. They are being used for voice and data communication, Internet, Broadcasting cable TV and radio signals but also for weather forecasting and reports, and spy networks. Since they operate further away from earth, their latency is higher, around 1 second. Have you ever noticed how the answer comes with a slight delay during TV interviews? This is why. Approximately 25 of these satellites are launched every year.
 

How are satellites powered? 

Satellites are big, expensive technological devices. To perform their duty and allow the scientific instruments, on-board computer, navigation sensors and communication systems to function, they need power. An autonomous, maintenance free, reliable power supply. A failing power supply could result in the loss of the satellite in space —something unacceptable. So how do you power a satellite in space to enable it to perform its functions without failing? 

Satellites work with solar panels that supply them with electricity. When the satellite passes in the shadow of the earth, a battery takes over… That’s where Saft’s batteries come into the picture. 

Saft has been unfailingly powering space since 1966. 
We employ the most rigorous standards in terms of quality, testing and documentation to make sure that our batteries do not in any way jeopardize a mission. 

Our solutions are used on extremely demanding missions such as GEO telecommunication and MEO global-positioning satellites and support specific applications from high-power telecommunications to observation and defense LEO satellites. Other applications served by Saft’s space qualified batteries include space experiments, launchers, space transfer vehicles, rovers, planetary landers, astronaut tools, space object study, and deep space probes. 

Batteries that work in the most demanding conditions

Space is very demanding environment for batteries: 

• They must be small and light: every extra pound adds to the cost when it comes to firing a rocket into space. 
   
• They need to withstand severe shocks and vibrations and are subject to a lot of pressure due to gravitational forces. The rocket must be launched at 25,000 km/h which creates an incredible levels of vibrations. On average, the physical and mechanical constraints are x 1,000 times higher than terrestrial conditions.
   
• Satellites evolve in extreme temperature conditions. The skin of a satellite can reach 300°C on the side facing the Sun and -170°C on the side facing away which can impact the capacity and efficiency of the battery if not properly managed. The battery is shielded from these extremes by thermal insulation, but still must be able to be charged and discharged in temperatures ranging from 0°C to 40°C. 
   
• Satellites, particularly MEO’s, are subject to radiation which can damage satellites’ electronic systems without special shielding. 
   
• They need to offer long shelf life to power up successfully after being on standby for long durations during the voyage from Earth.
   
• The energy that needs to be delivered by the battery to ensure continuity of services is high, up to 20-30 kW for the largest satellites. 80% of this energy is used for data transfer, 20% for internal operation of the satellite. 
   
• Some satellites like radars do not work continuously. To activate them, the battery needs to be delivering high pulses. 
   
• If the satellite is knocked out of its intended orbit, the orientation may no longer be correct for the solar panels to perform their function. In this case, the battery needs to take over and must be able to provide power for longer periods of time to allow the scientific crew to recover the satellite. This happened on the SoHo mission. Saft batteries were the only reason why the satellite could finally be recovered after more than 3 months lost in space. 
   
• Satellites can be in use for more than 20 years. This means that the battery needs to offer robustness in terms of cyclability. LEO satellites can circle the planet in 90 minutes, of which 30 min are in the dark. The rechargeable battery therefore needs to be able to perform many cycles, up to 5,500 cycles a year for 10 to 12 years or more. That’s about 80,000 cycles altogether! To give you a comparison point, a normal laptop usually performs 1,000 cycles. Airbus's first Eurostar geostationary telecommunications satellite, the W3A, has been orbiting for 18 years. It is equipped with Saft Li-ion batteries which, after all this time, are still going strong, with only a few percent power loss (less than 5 %) since the start of the mission.

Nowhere on earth is a battery subjected to such conditions. 

A trustworthy battery technology, operating at the highest standards

Technologies used in space need to be tried and tested. New technologies are therefore used with caution and subjected to lengthy phases of tests. Despite this, battery technologies have evolved over the years. In 1979, Saft equipped all of Arianespace’s satellite launchers, with Nickel Cadmium (Ni-Cd) batteries. From 1986 to 1990, Saft developed highly reliable and resistant Nickel-Hydrogen (Ni-H2) batteries, some of which are still operating today. In the early 2000s, Saft started using lithium-ion (Li-ion) technology for space applications. This technology significantly reduces the weight of the equipment and therefore its cost. The whole system is coordinated by an on-board computer which allows to follow the battery parameters and make sure that it is in good health.
The battery technology used in space nowadays is the same as the one we provide for IoT applications even if the battery construction might differ. So, we are not saying it lightly when we tell you our rechargeable batteries are reliable, can perform many cycles, offer a long lifetime and can withstand extreme conditions. 
 

To extend your journey with the stars, visit our website for more stories of how Saft is powering space and the IoT.