If you think of an artificial satellite, you generally imagine a huge device made of resistant material and weighing tons. However, not all of them are like this: at the Faculty of Engineering of the National University of La Plata (UNLP) they are making one that is the size of a lactal bread and that will be able to make atmospheric and soil observations. What is it about? Its name is USAT I and it is the first satellite of the UNLP “University Satellite” program.
“It weighs about 4 kilos and its measurements are 10 by 10 by 34 cm, similar to the size of a lactal bread,” he says. Sonia Botta, engineer at the Aerospace Technology Center (CTA) of the Faculty, in charge of coordinating the project.
Designed and manufactured by the CTA, together with the group of Electronic Navigation and Telecommunications Systems (SENyT), both from the Faculty of Engineering, this little satellite of the type CubeSat aims to demonstrate the operation of the GNSS system, a tool intended for use in navigation and orbital determination, and for measurements using the radio-occultation technique.
Botta explains that GNSS is a generic way of calling all the satellite constellations that are intended for use in navigation. A popularly known example is GPS. “With our GNSS receiver we will be able to detect GPS signals that travel through the atmosphere and the earth”. In this sense, it seeks to prove three things. The first will be to demonstrate its use in navigation, but once the positive result is obtained, two scientific techniques will be tested: radio occultation and reflectometry.
The function of the satellite, under this premise, is related to the technological demonstration of scientific techniques for Earth observation. “We aim for it to be able to make atmospheric and ground observations in Argentine territory, but since it is an orbit that covers the whole world, collaboration with other countries is open“, details the coordinator. And adds: “Once the satellite is in orbit, the mission will be a technological demonstration and its payload will be a GNSS receiver developed by the SENyT group.”
What are the measurement techniques?
The reflectometría GNSS o GNSS-R makes use of GNSS signals reflected from the Earth’s surface. It’s a type of scientific technique that began to be demonstrated on satellites a little over a decade ago. It can be used in measurements of soil characteristics, such as moisture, vegetation cover, or altimetry. In this mode, the receiver and the transmitting GNSS satellite work as a bi-static radar. “It is possible to measure how bouncing off the ground influences the GPS signal. If we can detect changes in this signal, we will be able to find out, for example, soil characteristics, such as moisture, vegetation cover, soil types, and even surface winds in oceans”, the specialist describes.
scientific technique radio concealment GNSS or GNSS-RO it indirectly measures the refraction of the signal emitted by GNSS satellites in the atmosphere. Depending on the position of the receiver, it can be used to study features of the upper layers of the atmosphere (for example, the ionosphere) or of the lower layers (such as the troposphere). “We can detect atmospheric variables, such as pressure, temperature and electron content,” he says.
What will come
In September of last year, the USAT I successfully went through the Critical Design Review (CDR), a fundamental step to start its construction. At present, the purchases are being completed to start the construction of the flight model.
“We are in a fairly advanced state where we hope that soon we will be able to have a complete flight model to start doing all the final tests that are required to go into space”, says Botta. And he concludes: “The launch date depends on when we finish the satellite and when launch opportunities arise, but We hope to do it before the end of the year, between October and November”.