Small, Nano, Cube SAR Satellite Constellation Advantages
We will start our first blog post talking about a topic we find fascinating. The launch of numerous backpack-sized SAR satellites by various companies and even governments. We are featuring in the banner above, Estonia’s second nano-sat, which we are proud to be sponsoring. You can learn more here.
What are the advantages to small sat constellations in the SAR business?
Monetization for small sat providers: what do investors see in it?
How can this industry revolution impact Ovela’s product offerings?
Advantages to small sat constellations in the SAR business
To understand the advantages to small sats from the sensor perspective we need to first take a high-level look at the way SAR (Synthetic Aperture Radar) functions. Assuming all sensors are doing very roughly the same thing, their highest variation is in orbital dynamics. NASA has an excellent look at orbital types we feature here.
Does the spacecraft sit on top of the same site (geosynchronous) and observe it consistently?
If so, the data is typically more costly as you are paying for both thruster time to move the satellite, and the opportunity cost of observing your site and not someone else’s. The advantage here is that you have more real-time observation (when you are observing) and very high resolution, but very low accuracy. Resolution is the size of the pixel, and accuracy is the ability to determine motion within that pixel over time. TerraSar-X is the first satellite that comes to mind in this profile. All military application SAR spacecraft are also in this profile.
If the spacecraft is in another orbit, what are the characteristics of that orbit? What is the global re-visit frequency?
Sentinel 1 a/b were the first spacecraft to be polar orbital with constant 6-day revisit frequency. While the S1 data is not globally available on that frequency, due to budget, that is the orbit speed. Other spacecraft such as ALOS and RadarSAT are also in LEO or MEO orbits where they revisit the rest of the planet in a frequency not possible from high earth orbit (geosynchronous). They simply have unique eccentricity of their orbits. This allows them to spend more time observing the arctic areas they were meant to study and less time observing other areas of the Earth. RadarSat was largely built for the Canadian Government to monitor its Arctic North, not provide commercial data on the Caribbean.
How will these small satellite constellations orbit?
As you can see in this illustration by Audacy / ICEYE above, they will have higher revisit frequency and resolution by increasing the number of satellites that are in a group orbiting the Earth. This dramatic increase in number gives them the advantage that larger spacecraft don’t have. They can make up for their sensor size by having many sensors in high speed orbits. As their revisit numbers increase, so will their accuracy. That is, IF, they can assure they are aligned perfectly to observe the exact same pixel each time they orbit.
Special Note: What is the role of reflectivity and phase data separation in the small sat constellation model?
Reflectivity (above) is the synthetic optical'esque image many of us are familiar with. It is a black and white (or other colour scale) picture based on the radar echoes the space craft gets back from its signal. There’s a huge business in this data set, just as there is in optical sensors - only without the issues of cloud cover. Here they are able to observe maritime domain awareness (ships moving around) and all sorts of other data on the motion of large objects - quickly.
Phase (above) is the area where Ovela is a specialist. This is what allows you to observe the deformation of the objects detected in the reflectivity image. It is not possible to make use of phase data unless the spacecraft operator can guarantee the spacecraft senses exactly the same pixel every overflight for many years. This requires extensive calibration, maintenance and ground station work. We are predicting the small sat operators will stay on the reflectivity business in the beginning but will eventually start to serve phase data. Phase interpretation and processing is an intense and fascinating process. Something that we are experts with and what we simplify in our platform. With phase data and high revisit, we can offer 1mm of accuracy on deformation targets.
Monetization for the small sat providers.
For human history launching things into space has been the work of governments and massive corporations, not start-ups. Now, with the small sat revolution comes the ability for a start-up to get a light payload onto a launch vehicle quickly, iterate products based on that tech, and (hopefully) see excellent returns. This is based on the idea that the SAR market currently only has one source that is open, Sentinel 1. S1 has its limitations and doesn’t make its data readily available to companies outside the EU. RadarSat 3, the Canadian government constellation, will be operated by behemoth MDA. In theory, part of it will be open… then again MDA monetizes RadarSat 2 so don’t expect that to be easy access either. NiSAR, the NASA/Indian space agency program will be open to American companies. This may be a real addition in the S1 class of sensor and availability … but again, will be limited to who can access it. There is a real market opportunity for providers who can leverage an affordable reflectivity offering without geo-restrictions.
The challenges these operators like ICEYE face are more in the business model and delivery. The remote sensing industry is old and slow. It has large players who aren’t happy to move their model away from providing costly data to large organisations. It is yet to be seen how quickly the data delivery and processing models catch up.
One thing is for sure, nano sat / small sat constellations and solo missions are bursting onto the scene in a big way!
How do small satellite SAR constellations affect Ovela products?
We are thrilled to have more SAR sensors available! Without a doubt, it will be a fantastic leap for our industry to have more sources available to choose from. The particularly exciting part of this is the injection of risk capital and new thinking. Our clients need access to affordable data we can add to their offering. As as SAR processor the best thing we can have is more material to work from! Onwards and upwards, we are cheering for all the SAR operators out there and will be patiently waiting for that phase data! See you there !