The benefits of remote sensing from space: Interview with Youssef Houali

Youssef Houali un de nos experts

The democratization of earth observation is one of our objectives, which also involves training and information. Youssef Houali, one of our GIS and remote sensing experts, answers our questions and explains all about spatial remote sensing.

Briefly, what is remote sensing from space?

Remote sensing refers to the set of technologies and skills used to observe the earth from space (hence the word “space”), and to analyze and interpret the various phenomena associated with it. This observation is carried out by sophisticated sensors on board satellites, using the properties of electromagnetic waves emitted or reflected by terrestrial objects.

In short, it’s the acquisition of information about the earth from space.

What are the different sensors used in remote sensing?

The 3 most commonly used types of sensor are optical, radar and thermal.

Optical sensors are passive sensors with several spectral bands that form part of the electromagnetic spectrum, e.g. red, green and blue.

Then there are radar sensors, which are active sensors, hence their ability to acquire data day and night, whatever the weather conditions.

The third sensor is thermal. The latter is based on the infrared waves emitted by warm bodies such as buildings, soil, water and even clouds (which is why it is so widely used in weather forecasting). Thermal sensors can capture images day and night, and are used to estimate the temperature of objects, hence their use in mapping water stress, drought, forest fires, etc. They can therefore be used to observe climate change by studying the temperature of oceans and continents, and the composition of the atmosphere.

What are the different types of sensors we'll be using on our satellites?

Our first satellite, Protométhée Earth Intelligence, scheduled for October 2023, will feature a multispectral sensor with 4 bands and a resolution of up to 1.5m.

Our second satellite, Hyperméthée, scheduled for 2024, will feature a 32-band hyperspectral sensor with 4.75 m resolution. Hyperméthée will provide additional information by characterizing the nature of the matter observed. Among other things, it can be used to classify soils, detect sites, assess water turbidity, etc.

In 2025, we will launch our future Japetus constellation, which will comprise twenty multispectral satellites with a resolution of 1m, enabling us to achieve an exceptional revisit rate and unprecedented responsiveness. For example, a site can be observed on average every 2 hours and up to every 45 minutes, offering a revisit capacity 10 times greater than that of existing systems.